SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: H8Monday on May 21, 2014, 04:12:29 PM
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So I took the new combo to the lake today for some test and tune. I'm hugely disappointed in the performance. Maybe a few of you experts here can look at the details and tell me where I went wrong with my recipe for big power and better than stock speed.
I spent a couple hours on the lake today doing carb tuning. I swapped jets about 6 times. I've been from 86 squared to 80 squared with no change in max rpm. none. zero. When I got down into the 70's, 76 exactly, It started to ping, So I went back up from there.
Engine: 521 Ford - Eagle rotation assy 4.3 Steel crank Mahle pistons 38cc dish final CR approx 9.75:1
Heads :D0VE C , mild port work.
Cam: In 345 Exh 359 at cam duration Int 228 Exh 238 max lift at intake occurs at 109 degrees ATDC and at exhaust 119 degrees BTDC - Hydraulic roller
Comp gold roller rockers 1.7 ratio
Intake: Stealth
Carb: Holley 850 HP Ultra jetted at 84 square. 4.5 power valves front and rear.
Fuel system: Holley blue pump and regulator 6psi
Dist: Summit billet mechanical. Timing is set to 36 degrees all in at 3400
Exhaust: Harman Marine Long bolt logs.
Drive: Berkeley 12JG
Bowl: Dominator HD
Impeller: Dominator skirted AA cut
Place diverter
Boat: 21' Eliminator Sport Cruiser. No interior. 20 gallons of fuel. 2 people.
Performance: 4500 RPM and 58 mph @ 4100 feet altitude here.
According to the Berkely chart I'm making a whopping 325 HP. Sweet. I could have done that with a stock 460 and saved THOUSANDS.
Help? Advice? Suggestions?
Regards, -Todd-
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only 4500 rpm. is a single 850 enough carb for all those big cubes?
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The logs aren't helping, the carb is too small, that's a big impeller.
I'm betting that thing would wake up with a set of headers, a 1050 dominator, and an A cut.
Edit: I'm more of a cheby guy, but that seems like maybe a bit much timing. Fords generally don't have shitty chambers like BBCs and don't need huge domes on the pistons to get any compression, so you don't need to chase the flame around the dome for ever to make the piston move...Fords generally run less timing I think. Maybe try your smaller jetting and pull 3 or 4° out of to keep it from pinging. Ralph should be along shortly with the answer.
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I'm not a expert but I also have a 460 ford dove heads roller rockers big cam 850 dbl holley same long bolt logs I think I maxed out at 4400 rpm took the logs off went with lightning headers now she runs 5200 your motor needs to breath your probably creating back pressure in the motor so its doing the opposite affect your loosing power that's was my case yours could be different
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Get those logs off of there if you want to go fast. An engine is nothing more than an air pump you're all restricted on the exhaust side.
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Get those logs off of there if you want to go fast. An engine is nothing more than an air pump you're all restricted on the exhaust side.
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thats what my problem was I agree
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Did you degree in your camshaft? Sounds like a bad mis match of parts, carb, intake, exhaust are all too small. Stealth intake is not ideal for a jet boat, also you should lock the timing out, no need for mechanical advance as there is next to no load on the engine at low rpm. The impeller just compounds the problem, that motor wants to breathe and turn a little more rpm!
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It's a big cam to run a AA what is the power curve ? My buddy built a 460 ford dove heads logs a .484 lift hydraulic flat tapped tunnel ram duel 450 turned aluminum AA 4900 19 Rogers .. 76mph ... With the cam you have and logs ur killing the motor
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Here's a pic of the boat. I think it shows why I had to do logs.
(https://www.socaljetboats.com/proxy.php?request=http%3A%2F%2Fwww.credaroliimages.com%2FBoats%2FMy-21-Eliminator-Sport-Cruiser%2Fi-NpqJpG6%2F0%2FL%2FCI124736-L.jpg&hash=c8415239f2214a0f054fad014ce8130080126baf)
(https://www.socaljetboats.com/proxy.php?request=http%3A%2F%2Fwww.credaroliimages.com%2FBoats%2FMy-21-Eliminator-Sport-Cruiser%2Fi-wgn5Z57%2F0%2FL%2FCI124734-L.jpg&hash=61454d745a53abab7822e54abe82278aad599e67)
Maybe I was falsely led to believe that a big inch motor like this could easily make 500+ hp in current form and over 650 hp with proper exhaust, alum heads and single plane intake.
So, should I start carving on the impeller to get the RPM's up? This thing has a 7k rpm bottom end in it. Go to something like an A/B and see how it does? I'd be happy to see 5500 - 6000 at WOT. I've got a brand new A sitting here I could try. This carb and intake are good to 6500 on this size engine. Is this exhaust that big of a deal in this combo?
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You can go with better exhaust ...doesn't have to be over transom exhaust. Go check out options at cpperformance
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The motor can make plenty of power. You have some components fighting you though. Get some lightining through transom headers if you can and a bigger carb. Think there were some bigger carbs for sale earlier this week. Really clean boat man, just need to get it dialed in better.
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cut the impellor to an A your motor is making power higher up, yes logs suck but no way would i spend 2k or cut that pretty boat to fit exhaust.
my .02
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Look for a good set of used lightnings.. you can't run Bassett tt headers or rewarders with a engine hatch
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Jim Brock usually has great deals on used parts. Jim 1818-890-1867
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Your rpm and mph seem about right.....but those numbers are low for your cubic inches.
Center rise manifolds are probably gonna be your best bet.
Gonna have to modify the engine cover though.
-beerjet-
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Yeah beer jets right center rise manifolds
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Here's a pic of the boat. I think it shows why I had to do logs.
(https://www.socaljetboats.com/proxy.php?request=http%3A%2F%2Fwww.credaroliimages.com%2FBoats%2FMy-21-Eliminator-Sport-Cruiser%2Fi-NpqJpG6%2F0%2FL%2FCI124736-L.jpg&hash=c8415239f2214a0f054fad014ce8130080126baf)
(https://www.socaljetboats.com/proxy.php?request=http%3A%2F%2Fwww.credaroliimages.com%2FBoats%2FMy-21-Eliminator-Sport-Cruiser%2Fi-wgn5Z57%2F0%2FL%2FCI124734-L.jpg&hash=61454d745a53abab7822e54abe82278aad599e67)
Maybe I was falsely led to believe that a big inch motor like this could easily make 500+ hp in current form and over 650 hp with proper exhaust, alum heads and single plane intake.
So, should I start carving on the impeller to get the RPM's up? This thing has a 7k rpm bottom end in it. Go to something like an A/B and see how it does? I'd be happy to see 5500 - 6000 at WOT. I've got a brand new A sitting here I could try. This carb and intake are good to 6500 on this size engine. Is this exhaust that big of a deal in this combo?
Not even close to mechanically inclined, but I do have the exact same hull as yours. I'm running a mild BBC (350hp) and had a JC-A. (Dominator now) and I was running 57mph at 4500rpm.
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X10...she's suffocating. Let her breathe. Bigger carb/s bigger exhaust. More air + more fuel + more space + bigger exit = big bang! Simple.
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Btw sweet float forgot to mention that.
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X10...she's suffocating. Let her breathe. Bigger carb/s bigger exhaust. More air + more fuel + more space + bigger exit = big bang! Simple.
and when he spends all this money to do this and he still doesn't get what he wants then what? change the heads? :o there is now way in hell that motor is gunna spin that AA to 6k
you said you have an A impeller put it in. why the 1.7 rockers? timing should be fine, read your plugs.. did you degree the cam?
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Just my 2 cents but holley will take 7lbs so bump up n maybe add a second set of breathers to vavle cover along with impeller n exhaust adjustments
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I'm not sold on the fact that the exhaust is the problem.
You have too much pump. At that altitude, you should be able to pull 5K without much drama.
The camshaft is a selection I am not convinced is right for the combo, the altitude kills it for me. You really need to know how it was installed. I would have installed it 2* earlier than what the cam manufacturer says.
Do you have a vacuum number from the intake manifold?
36 degrees total timing is actually pretty tame for 4100 feet. May have a bit more there. Is it running fat? It should be.
What risers do you have? What is the engine temp running flat out?
Is the bowl stuffed? do you have a loader?
How certain are you that the throttle butterflies are opening 100%?
Sorry to have more questions than answers, but I could not make heads or tails of what you have going on.
Absolutely beautiful boat.
GT
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I'm not sold on the fact that the exhaust is the problem.
You have too much pump. At that altitude, you should be able to pull 5K without much drama.
The camshaft is a selection I am not convinced is right for the combo, the altitude kills it for me. You really need to know how it was installed. I would have installed it 2* earlier than what the cam manufacturer says.
Do you have a vacuum number from the intake manifold?
36 degrees total timing is actually pretty tame for 4100 feet. May have a bit more there. Is it running fat? It should be.
What risers do you have? What is the engine temp running flat out?
Is the bowl stuffed? do you have a loader?
How certain are you that the throttle butterflies are opening 100%?
Sorry to have more questions than answers, but I could not make heads or tails of what you have going on.
Absolutely beautiful boat.
GT
no doubt the cam is well, suspect to say the least, but, lets work with what we have
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no doubt the cam is well, suspect to say the least, but, lets work with what we have
While I agree Ralph, I was simply stating that I really don't think the "logs" are the problem... ;)
I would be really curious to see what the vacuum numbers are.. I'm thinking a 1" carb. spacer, while a little redneck, may help in this scenario...
I am thinking you are experiencing a reversion issue on a very small level, any way you can reduce the amount of water going through the risers on the VERY short term?
Also, are you running a flame arrestor or an air filter? How large is it. May help explain your jetting moving target.
GT
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So I took the new combo to the lake today for some test and tune. I'm hugely disappointed in the performance. Maybe a few of you experts here can look at the details and tell me where I went wrong with my recipe for big power and better than stock speed.
I spent a couple hours on the lake today doing carb tuning. I swapped jets about 6 times. I've been from 86 squared to 80 squared with no change in max rpm. none. zero. When I got down into the 70's, 76 exactly, It started to ping, So I went back up from there.
Engine: 521 Ford - Eagle rotation assy 4.3 Steel crank Mahle pistons 38cc dish final CR approx 9.75:1
Heads :D0VE C , mild port work.
Cam: In 345 Exh 359 at cam duration Int 228 Exh 238 max lift at intake occurs at 109 degrees ATDC and at exhaust 119 degrees BTDC - Hydraulic roller
Comp gold roller rockers 1.7 ratio
Intake: Stealth
Carb: Holley 850 HP Ultra jetted at 84 square. 4.5 power valves front and rear.
Fuel system: Holley blue pump and regulator 6psi
Dist: Summit billet mechanical. Timing is set to 36 degrees all in at 3400
Exhaust: Harman Marine Long bolt logs.
Drive: Berkeley 12JG
Bowl: Dominator HD
Impeller: Dominator skirted AA cut
Place diverter
Boat: 21' Eliminator Sport Cruiser. No interior. 20 gallons of fuel. 2 people.
Performance: 4500 RPM and 58 mph @ 4100 feet altitude here.
According to the Berkely chart I'm making a whopping 325 HP. Sweet. I could have done that with a stock 460 and saved THOUSANDS.
Help? Advice? Suggestions?
Regards, -Todd-
Somethings wrong with these numbers. If you only have approx .350 lift in a 500ci motor it can't make any power. These numbers can't be right.
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you said you have an A impeller put it in. why the 1.7 rockers? timing should be fine, read your plugs.. did you degree the cam?
I'm going to try to get the impeller installed tomorrow. I'm running REAL short on time now. Work is cutting into my boat wrenching time.
I used 1.7 rockers because thats what the cam specs said to run.
Plugs show fat at 84 squared. I'm now under a time constraint, so I'm going to leave it fat for the weekend. I'll be on Havazoo Sat and Parker on Sun.
Cam was degree'd It was installed straight up and matched the specs on the cam card.
Here is a copy of the cam specs:http://www.cranecams.com/product/cart.php?m=product_detail&p=24363 (http://www.cranecams.com/product/cart.php?m=product_detail&p=24363)
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You are trying to tune at 4100 feet if you going to be at less than 400?
GT
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Those numbers make more sense, 590 Int and 614 exh.
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I'm not sold on the fact that the exhaust is the problem.
You have too much pump. At that altitude, you should be able to pull 5K without much drama.
The camshaft is a selection I am not convinced is right for the combo, the altitude kills it for me. You really need to know how it was installed. I would have installed it 2* earlier than what the cam manufacturer says.
Do you have a vacuum number from the intake manifold?
36 degrees total timing is actually pretty tame for 4100 feet. May have a bit more there. Is it running fat? It should be.
What risers do you have? What is the engine temp running flat out?
Is the bowl stuffed? do you have a loader?
How certain are you that the throttle butterflies are opening 100%?
Sorry to have more questions than answers, but I could not make heads or tails of what you have going on.
Absolutely beautiful boat.
GT
I didn't pull a vacuum number yet
Its running fat. I'm back at the factory installed 84 squared jets. Going lean only made it ping. I didn't pick up a single RPM. I played with timing from 32 to over 45 degrees. No increase in RPM, No ping. BUT, when I started leaning it out, down around 78 size jets, it would pingwith over 32 degrees of timing.
also, I pumped the tanks dry, and did all of this tuning with 30 gallons of Chevron 92 Octane in it today.
Exhaust is Harman Marine long bolt logs with matching snails.
Flat out temp never got over 140. I'm not running a gate valve, I'm running a regulator on the water inlet. I'm running it at the lowest possible pressure.
The bowl is a brand new Dominator HP bowl set up for skirted Impellers. I'm running an AA Dominator skirted Impeller. For those that are reading and don't know what this is, the impeller has an extended 'skirt' that fits into an area in the bowl where the stuffer would be. It fits into the stuffer area, similar to how it fits inside the wear ring.
I have been running a loader for years. Its a pretty standard full ramp, open center type of loader. No shoe, no rideplate.
I'm 100% sure that the butterflies on both primary and secondary open 100%
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That's really not that big of a cam for 521 cubic inches
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While I agree Ralph, I was simply stating that I really don't think the "logs" are the problem... ;)
I am thinking you are experiencing a reversion issue on a very small level, any way you can reduce the amount of water going through the risers on the VERY short term?
Also, are you running a flame arrestor or an air filter? How large is it. May help explain your jetting moving target.
GT
shutting down the water isn't really possible for me right now. I removed my old gate valve and replaced it with a regulator setup
I was doing the tuning today with no rear seat, no hatch and open carb. No flame arrestor or air filter. Normally I run a 12"dia by 2" air filter
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I agree with the others that you may have too much impeller. I'd put the A in there and lean out the primary side of the carb a bit. I wouldn't give up on the logs either. They may be robbing some power, but as Ralph and GT told you they're not your problem. There's been plenty of guy's that make them work with blowers and turbos. If they take 20-30 hp away, you should still be in the 500 hp range. Just my thoughts.
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You are trying to tune at 4100 feet if you going to be at less than 400?
GT
The engine went in the boat yesterday. It was supposed to go in 2 weeks ago, but you know how some shops can be with deadlines. I'm headed to havasu for the weekend. I spent the day trying to find some expected performance out of this engine. I was trying to make sure nothing was 'wrong' with it, because I AM going to Havasu this weekend. Since I'm going to be near sea level, I decided to leave it plenty fat today.
My quest for getting the max performance out of this engine will have to be postponed until after the holiday. Right now the numbers just don't make me happy at all. The Berkeley chart says I'm making 368 hp. I'm not buying the 'its the logs' answers. Like some have said, I think the cam choice is a little suspect. I may have to get some suggestions from the peanut gallery on this subject.
Holley and other carb calculators say that a 521 turning 6000 rpm needs just over 800 cfm carb
Weiand says the stealth is good to 6800 RPM. LOTS of people are using them on big fords to make over 600 hp
I'm running an AA impeller at the recommendation of one of the advertisers here that I used to select all my pump parts from. I explained my engine combo and my hull, and he said AA impeller and Dom bowl.
I have no problem experimenting with impellers now. Its cheap, and relatively easy.
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One quick question I have it about the impeller style.
My A impeller is a stock Berkeley non-skirted style impeller. Will it simply bolt into Dominator bowl and just lose the slight stuffer effect that the skirt gives?
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shutting down the water isn't really possible for me right now. I removed my old gate valve and replaced it with a regulator setup
I was doing the tuning today with no rear seat, no hatch and open carb. No flame arrestor or air filter. Normally I run a 12"dia by 2" air filter
I was thinking more along the lines of bypassing some water from the snails to a dump.
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Are you going to try and change the impeller before Havasu? That would be the best move because worst case scenario is your RPM's are a little high at WOT. Plus it would give a good baseline since you'll be close to sea level.
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One quick question I have it about the impeller style.
My A impeller is a stock Berkeley non-skirted style impeller. Will it simply bolt into Dominator bowl and just lose the slight stuffer effect that the skirt gives?
Yes, and no...
Lets think about it this way, at as low of RPM you are getting now, the lack of stuffer effect will actually do you a bit of good.
GT
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One quick question I have it about the impeller style.
My A impeller is a stock Berkeley non-skirted style impeller. Will it simply bolt into Dominator bowl and just lose the slight stuffer effect that the skirt gives?
You'd need the right wear ring for the A impeller. Then just set the clearance.
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Lets think about it this way, at as low of RPM you are getting now, the lack of stuffer effect will actually do you a bit of good.
GT
Thats what I was thinking also. I was just curious about the fit. I was under the impression that I can run a Berkeley Impeller in this bowl with now clearance issues. I was just curious if anyone knew anything otherwise.
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Logs are costing you about 300 rpm .had close to the same combo in a ultra open bow change impeller and see what happens should get you close to where you want
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Also too, you can't use the Berkeley impeller chart with a Dominator impeller... It will be quite off..
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Your "corrected" HP should be closer to 490 HP. ;)
GT
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"Cam: In 345 Exh 359 at cam duration Int 228 Exh 238 max lift at intake occurs at 109 degrees ATDC and at exhaust 119 degrees BTDC - Hydraulic roller"
The duration is a lot "small" for an SBC, let alone a 521 BBF. (My 383 is 235*/235*)
You need 240*/250* easy to feed that 521.
I'm at 238*/246*, hyd. roller cam, in a 461 BBC, 750 Holley 3310, swings a "AA" American Turbine in a Berk JC at 4900-5K, 21' Eliminator Day Cruiser...Logs and snails
My $.02
Dan'l
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One quick question I have it about the impeller style.
My A impeller is a stock Berkeley non-skirted style impeller. Will it simply bolt into Dominator bowl and just lose the slight stuffer effect that the skirt gives?
If the impellers themselves haven't been modified to adjust front clearance and the diameters of the wear ring surface are the same, they will directly interchange. Make sure that any shims are retained and used with each impeller as currently installed so front clearance remains the same.
Without a stuffer, it just won't build bowl pressure quite as fast.
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Althouogh the manifolds do take some HP but thats not all your problem, my opinion,
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And don't start throwing good parts and wasting good hard money, there are smart people here someone will help. Again don't throw parts away .
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I agree a lot of it is the cam is to small the impeller is wrong and the logs are killing about 300 rpms all together and you get what you got. You'll work it out it will just take a little time.
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I'm hugely disappointed in the performance. Maybe a few of you experts here can look at the details and tell me where I went wrong with my recipe for big power and better than stock speed.
Engine: 521 Ford - Eagle rotation assy 4.3 Steel crank Mahle pistons 38cc dish final CR approx 9.75:1
Heads :D0VE C , mild port work.
Cam: In 345 Exh 359 at cam duration Int 228 Exh 238 max lift at intake occurs at 109 degrees ATDC and at exhaust 119 degrees BTDC - Hydraulic roller
Comp gold roller rockers 1.7 ratio
Intake: Stealth
Carb: Holley 850 HP Ultra jetted at 84 square. 4.5 power valves front and rear.
Fuel system: Holley blue pump and regulator 6psi
Dist: Summit billet mechanical. Timing is set to 36 degrees all in at 3400
Exhaust: Harman Marine Long bolt logs.
Drive: Berkeley 12JG
Bowl: Dominator HD
Impeller: Dominator skirted AA cut
Place diverter
Boat: 21' Eliminator Sport Cruiser. No interior. 20 gallons of fuel. 2 people.
Performance: 4500 RPM and 58 mph @ 4100 feet altitude here.
According to the Berkely chart I'm making a whopping 325 HP. Sweet. I could have done that with a stock 460 and saved THOUSANDS.
Help? Advice? Suggestions?
Regards, -Todd-
I'm seeing a major engine components/overall powerplant mismatch here, and on several levels (actual parts chosen, specific part type chosen, and I suspect part setup when installed). Looking at what you are working with, your unfortunate real world results seem about right to me relative to the overall combinaton.
You need to be willing to make some substantial component changes in order to see a dramatic improvement, including induction, exhaust, camshaft, I suspect cylinder head port work, and I bet valve train geometry (which significantly affects cam timing).
LO
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I'm seeing a major engine components/overall powerplant mismatch here, and on several levels (actual parts chosen, specific part type chosen, and I suspect part setup when installed). Looking at what you are working with, your unfortunate real world results seem about right to me relative to the overall combinaton.
You need to be willing to make some substantial component changes in order to see a dramatic improvement, including induction, exhaust, camshaft, I suspect cylinder head port work, and I bet valve train geometry (which significantly affects cam timing).
LO
LO give me your opinion on where to start then. If you're seeing something in my parts list that seems off I'm all ears.
I'll take a minute to explain the parts chosen, then I'd love for people to chime in and make me aware of the error of my selections, and their suggestions towards better parts.
Here we go.
The mission: Make the boat faster. (Isn't that what we all want?) ;)
Limitations: Full engine enclosure with a flat sundeck for the hunnies. So, no headers. Lightnings MIGHT fit, but man... the cost. Also, it has to be reliable. I want to get 5-8 seasons of use out of it before rebuild.
Engine Design: Jet boat performance is a result of torque. So, lets make lots of torque at lowish RPMS.
How to make Torque: First.... make it big. I went with the 521 because a 4.3" crank was a large as I was comfortable with for longevity. Same with the .030 overbore.
Next, a dual plane intake is known for its low-ish RPM torque building. I was already running the Stealth, so run it, and save a few $$.
Carby selection says that you go Huge for big RPM and big horsepower, and you go smallish for low RPM response and again, torque. I chose the 850 as it falls right in the middle of those 2 requirements.
I was also already running the D0VE C heads. There are thousands of builds out there making serious power with these heads. So, some mild port cleanup and a few more $$ saved instead of SCJ heads.
Cam selection. This is where I turned to my engine builder for his advice. He suggested this cam, as it was designed for strong midrange torque.
exhaust we covered, I understand these logs don't provide great scavenging like a well designed header, but they are a necessary evil.
I could have built a maximum effort, high horsepower, high RPM fire breathing monster, but it would have REQUIRED headers, SCJ heads, bigger cam, single plane manifold, and bigger carb. I tried to choose parts that would build a stump puller instead. Couple that with an AA impeller and the intended result was to get good performance at lower than typical RPM's.
So, I need help from the peanut gallery to help adjust my recipe. Something is clearly off. And now that you know my intent, I'm all ears as to how to get this boat to move faster. After all.... it was a 63 MPH boat with a 460, same intake, heads, 750DP and an aggressor 9 vane bowl with aggressor A impeller.
Lets hear those thoughts and ideas.
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Engine Design: Jet boat performance is a result of torque. So, lets make lots of torque at lowish RPMS.
How to make Torque: First.... make it big. I went with the 521 because a 4.3" crank was a large as I was comfortable with for longevity. Same with the .030 overbore.
Next, a dual plane intake is known for its low-ish RPM torque building. I was already running the Stealth, so run it, and save a few $$.
Carby selection says that you go Huge for big RPM and big horsepower, and you go smallish for low RPM response and again, torque. I chose the 850 as it falls right in the middle of those 2 requirements.
I was also already running the D0VE C heads. There are thousands of builds out there making serious power with these heads. So, some mild port cleanup and a few more $$ saved instead of SCJ heads.
Cam selection. This is where I turned to my engine builder for his advice. He suggested this cam, as it was designed for strong midrange torque.
exhaust we covered, I understand these logs don't provide great scavenging like a well designed header, but they are a necessary evil.
I could have built a maximum effort, high horsepower, high RPM fire breathing monster, but it would have REQUIRED headers, SCJ heads, bigger cam, single plane manifold, and bigger carb. I tried to choose parts that would build a stump puller instead. Couple that with an AA impeller and the intended result was to get good performance at lower than typical RPM's.
So, I need help from the peanut gallery to help adjust my recipe. Something is clearly off. And now that you know my intent, I'm all ears as to how to get this boat to move faster. After all.... it was a 63 MPH boat with a 460, same intake, heads, 750DP and an aggressor 9 vane bowl with aggressor A impeller.
Lets hear those thoughts and ideas.
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I am not LO, but everything in the above is correct but wrong.
Whoever told you you needed bottom end torque is fired.
A Jetboat cannot do anything with bottom end torque.
A jet pump takes almost ZERO torque to turn up to about 3500 rpm. After that the torque curve is LINEAR. Meaning the faster it turns the more toque is required.
That being said, you built a killer pull truck motor. That is what I was eluding to when I mentioned the cam shaft choice.
To make a jet run like it is scared, you need to make the torque way up high in the rpm range (like from 3500 and up) Everything you have in this build with the exception of the intake manifold reeks bottom end balls.
If I were in your situation I would first change the camshaft. This will net the biggest gains for the least about of money and work.
Do not worry about the exhaust for now, it will survive with what you have.
You really should consider a larger carburetor when you upgrade the cam.. I am actually thinking a Dominator is not out of the question but a really well prepped 850 double pumper will bring some fun to the show. Look into changing the venturis for improved velocity in the boosters.
The ignition system is fine, the rocker ratio is hurting you.
I have to go back to work now but just wanted to keep the conversation going.
GT
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i say cut the impellor and enjoy it for the season, the cam will need to be changed, hydrolic cam and bbf is very hard to set up correct, head work and a cam that works with the flow #s of the heads (custom cam) for starters...
i have a 502 bbf on pump gas 10.6-1 comp edelbrock heads turning an A 5800 rpm, yes custom cam matched to the heads via lakesonly..
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If I remember correctly bbf like the cam way advanced like 8 degrees or so
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Just came off the lake. Installed the A impeller.
It turned 4700 rpm and 59 mph.
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And for those interested, it was 72 degrees and 4100 feet altitude. Carb is still fat with a slight bottom end stumble.
I'll be on Havasu Saturday and Parker on Sunday. I'll let you guys know what it does with some air.
I've got an entire Holley jet kit with me. I intend to keep it fat and alive.
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Man that is a bit disappointing. Hope it shows a little more life at sea level.
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Just for a reference point, when we (compjet) run in Burley, ID (4,163ft elevation).....we are barely breaking into the 80's.
In Parker, AZ (423ft), the same boats are well in the high 90's. It was about a 10 to 15 mph loss at that altitude.
Also, another point of reference, I was running a 513ci ford, 12.5:1, 112oct and a 1250cfm quickfuel carb dyno'd at 745hp @ 6k. I run a B- impeller and its spinning around 6500rpms. Never GPS'd it much, but the best one I got was 94mph, but keep in mind, this is a much lighter/smaller boat than your cruiser.
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You concentrated the build on low end torque, and your now dissatisfied that it won't spin. That's why it sucks. Cut your impeller until you can see RPM where that thing makes peak HP...this is not linear...might require a dyno...that's the best it'll do.
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Based on what youre getting now at that altitude, I would assume once you get it dialed in at havasu, you will pick up 10mph or so....thats if you can find some smooth enough water on that lake this weekend. Good luck and keep us posted.
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Based on what youre getting now at that altitude, I would assume once you get it dialed in at havasu, you will pick up 10mph or so....thats if you can find some smooth enough water on that lake this weekend. Good luck and keep us posted.
You might be right, but betting closer to 6 MPH. :sly:
Speaking of Burley.. ???
GT
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Well I'm off to join the madness. I'll be on Havasu Sat and on Parker Sun. If you see me in my poser ride, come say 'hi'. Its always fun to meet new boat peeps.
-Todd-
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Well I'm off to join the madness. I'll be on Havasu Sat and on Parker Sun. If you see me in my poser ride, come say 'hi'. Its always fun to meet new boat peeps.
-Todd-
Just got done reading your whole thread. Ill be out there this weekend also. Will keep an eye out for your ride. Would love to see it in person. Ill be in this.
Chris
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Cam specs dont sound right not enough lift for duration, 850 carb is plenty with right jetting, dont lock out mechanical advance, timing should be 10 to 12 degrees with 36 to 38 total in by 2800 to 3000rpms. Logs at least should be port matched and opened up as far in as possible. Dont know much about stealth intake. Ive run bbf for years my new 502 runs a edelbrock rpm manifold, 750 vac. sec. holley, msd dist. & 6A box, ported dove heads, 10 to 1 comp, 270-280 dur. @ .513-.520 lift comp cam. My 21' charger runs 63mph @ 5200rpms thru a panther pump shooting 65-80' @ 10' high rooster.
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Cam specs dont sound right not enough lift for duration,
;)
850 carb is plenty with right jetting, dont lock out mechanical advance, timing should be 10 to 12 degrees with 36 to 38 total in by 2800 to 3000rpms. Logs at least should be port matched and opened up as far in as possible.
Not being a douche, just keeping it real. Nothing in this part of your post is actually accurate for this situation. An 850 is short on volume to be "perfect", it will "work", but theoretically short. Locking out the mechanical advance will work fine too, the jet drive does not require ANY low RPM grunt, which is why it works locked out. Locked out distributors also idle quite a bit better. The only benefit you gain from not being locked out is hot starting. I doubt seriously port matching a set of logs will do anything at all (not from the seat of the pants aspect anyways), the problem is the way they merge the different cylinders, the "timing is all wrong. The ports are plenty large, they just all merge at the same time, making them restricted because of pressure, not necessarily port size. It would actually run a little harder if the left side manifold was installed backwards, this actually improves the flows and equals the same flow as the right... It is just not practical. look up an animation for a Ford firing order and you will see why... The left side run sequentially... But backwards for good exhaust flow.
Not breaking beans, just maybe helping you improve your deal...
Dont know much about stealth intake. Ive run bbf for years my new 502 runs a edelbrock rpm manifold, 750 vac. sec. holley, msd dist. & 6A box, ported dove heads, 10 to 1 comp, 270-280 dur. @ .513-.520 lift comp cam. My 21' charger runs 63mph @ 5200rpms thru a panther pump shooting 65-80' @ 10' high rooster.
Just a hunch or an educated guess here, but if you switched to a larger carburetor with mechanical secondaries you may find the true weaknesses in the Panther Jet, Energizer kit the Panther and you will have a totally different boat. Likely well into the 70's. 8)
Just my humble opinions... 8)
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Nothing is accurate in this situation? His or mine? Look at the specs quoted for his situation, with mildly ported stock heads and no more cam and compression than he has a bigger carb does nothing worth spending big bucks on. Someone recommended a 1050 dominator, only with serious port work, bigger valves and more cam would this be feasable. Using Holley's CFM formula even 850 is to big. I run a 750 vac sec carb to help achive some economy as this motor drinks enough gas as it is much less pay $500.00 for a double pumper. The Panther logs i run had serious port match problems to the heads. I used gaskets and opened up head ports as well as log ports and could tell big difference in performance. I did extensive porting and polishing to this heads. My mini cruiser seats up to 8 passengers, holds 50 gallons gas and sometimes pulls 2 to 3 skiers, I need all the low end grunt I can get. Idle is just fine and boat launches like a rocket. I live where summers are 100-105 deg. at 1800' altitude. Just trying to help the guy out with what worked for me. JUST MY OPINION
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Nothing is accurate in this situation? His or mine? Look at the specs quoted for his situation, with mildly ported stock heads and no more cam and compression than he has a bigger carb does nothing worth spending big bucks on. Someone recommended a 1050 dominator, only with serious port work, bigger valves and more cam would this be feasable.
I had already said the cam is all wrong. I recommended a cam before all else. The carburetor was definitely going to be next in line..
Using Holley's CFM formula even 850 is to big. I run a 750 vac sec carb to help achive some economy as this motor drinks enough gas as it is much less pay $500.00 for a double pumper. The Panther logs i run had serious port match problems to the heads.
You can take the Holley carburetor formula and throw it in the trash on a jet. The formulas were calculated for variable torque like in a car or even a V-drive, the torque curve on a jet pump is completely linear, meaning as soon as the torque curve flattens out, so does the gain in RPM. (there is actually a slight gain, but not much). The vacuum secondary carburetor you have, even with the lightest secondary spring is keeping the rpm's limited and if it were not for the Panther jet pump being super inefficient you would not be pulling the revs that you are. Plain and simple fact is that you are comparing a pineapple to a plumb. Mean no offense at all.
I used gaskets and opened up head ports as well as log ports and could tell big difference in performance. I did extensive porting and polishing to this heads. My mini cruiser seats up to 8 passengers, holds 50 gallons gas and sometimes pulls 2 to 3 skiers, I need all the low end grunt I can get. Idle is just fine and boat launches like a rocket.
I will personally guarantee you are not using any of this "low end grunt". The pump does not eat ANY torque until it gets to approximately 3500 RPM, then from there it is linear all the way up until it blows apart or cavitates so bad it stops moving more water.
Again, comparing a pineapple. His logs are some of the best made, there is not a lot more to gain in that arena IMHO, more cam, potentially some carburetor work and it will wake up to smell the coffee.
I live where summers are 100-105 deg. at 1800' altitude. Just trying to help the guy out with what worked for me. JUST MY OPINION
He was at more than twice the altitude, making getting the required air into the cylinders more than twice as difficult. that is why I recommended more carburetor.
We had a house at Lake Tahoe until this last year, trust me when I say you simply cannot get enough air into the motor. On the cruiser, I had installed two bilge blowers to push air into the engine compartment, believe it or not, we picked up nearly 100 RPM, although I think it was because the air charge was cooler...
Don't be offended, just adding to what you are saying. You can't argue with real life. It is all fact.
GT
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Soooooooo, how'd she run with some air?
Bueller.... Bueller, anyone?
GT
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GT, the water on Havasu and Parker was shit this weekend. (Weird huh?)
I didn't bother with GPS but it did pull a solid 5k rpm.
Seat of the pants said we were finally moving, although it could have just been the chop. ;-)
Engine ran solid with some air but still not what I expected.
I'd like to start hearing suggestions for a proper cam. Or at least how I should go about selecting the next one.
Thanks guys.
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GT, the water on Havasu and Parker was shit this weekend. (Weird huh?)
I didn't bother with GPS but it did pull a solid 5k rpm.
Seat of the pants said we were finally moving, although it could have just been the chop. ;-)
Engine ran solid with some air but still not what I expected.
I'd like to start hearing suggestions for a proper cam. Or at least how I should go about selecting the next one.
Thanks guys.
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Sounds more gooder... :thumbup:
In all honesty, I will be giving you recommendations for a Big Chevy, Fords are elusive creatures...
Lakes Only or George at Clay Smith Cams would be whom I would reach out to. Ford valve train geometry always kicks my butt. There is a little too much math required for me to get it right being as I really don't see many big Fords.
If it were a Bow tie or a Bow tie clone, I could spill it in my sleep.
Good luck and if you need to change the exhaust, center riser would be your only choice, they will typically outflow your existing by about 15%, so not really dramatic, but it's something.
GT
When needing a set of stairs, call the stair people... (quote from Mike Holmes) ;)
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Thanks for the tips GT. I understand. :-)
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Since you are in the market for a new cam, might I suggest regrinding your existing cam. From Crane Cams, a new billet roller is $440 and a regrind is just $176.
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I love that idea a lot.
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In reviewing this thread, I see that I completely missed that you had a Dominator AA impeller in your pump. That's quite a big impeller (bigger than a Berkeley AA). With that in mind, your noted rpm with the Dominator AA (or any AA) doesn't seem as bad. And the increase in rpm that came with the change to the A impeller makes sense, as does the rpm increae that came with the altitude change.
Stealth intakes may be dual plane, but they are considered a "hgh rpm"dual plane," and are acceptable for a 5000 rpm stroker, generally speaking. The logs can be worked with.
Right now I think a cam change is what's most necessary. Proper valve train setup is important as well. And in a D0VE-headed stroker with logs that is going to run 5000 rpm sustained, very good port work is paramount. I can barely ball park a camshaft without personally viewing the port work in the heads and seeing any port mismatch at the logs, etc. that said, you definitely need more cam and could even gain power with a non-roller, flat tappet hydraulic camshaft that has bigger numbers on paper. A solid flat tappet or roller will do even better but I don't know what your willing to do in this regard.
Lastly, 70 mph is possible, but getting that big boat out of the water will play a big part of acheiving that goal.
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put in a A empeller, 108 lobe center cam, and a dominator carb, then you will have a runner