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-

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.

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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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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Here's a pic of the boat. I think it shows why I had to do logs.





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?

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.

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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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-

Here's a pic of the boat. I think it shows why I had to do logs.





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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Btw sweet float forgot to mention that.

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

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

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.