SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: metalmulisha5006 on June 01, 2015, 07:16:18 PM
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My combo JC split bowl bronze b impellor
454 std bore
10.5 compression 119 cc
Eddy tunnel ram 2 750 double pumpers
243 intake
249 exhaust
.640.640 lift
110 centerline
106 lobe sep
Hyd roller
Turned Impellor 5400 rpm with sum carb probs with the 781's 2.19 1.88 valves blended bowls and gasket match ports..my 990's have 2.30 1.88 valves intake runner cc is 337 and 117cc combustion chamber... My question if I switched to rectangle port with a victor port matched intake and a 1050 would I pick up or hurt the combo
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2.30" intake valve with 337cc port? Sounds excessively hogged out. Do you have any flow data on the 990 heads?
I think on a small 4.250" bore, 2.300 intakes will shroud the valves considerably. 337cc seems large for 990s. I fear that any increase in flow will be accompanied with a decrease in velocity.
I know the exhaust side is weak on the 990s. Assuming that the flow increased proportionally to the increase in valve size and volume (which I seriously doubt), you will need more lift on the exhaust side to get the exhaust valve to a point where it is flowing comparable to the intake.
Is this a planned purchase or you already have them?
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I alrdy own them I cc'd them ..the exhaust is cut pretty wild too very nice port job I'll post pics tomorrow.. I have all the parts jus didn't kno if it's worth the swap ..everyone I ask says swap but they don't kno much about jet boats..kinda disappointed with the set up I have thought I woulda went faster
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There is more to it than just horsepower.
Setup and hardware are everything!
Could you describe the rest of the boat or do you have a build thread?
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The typical crossover RPM between prepped ovals and squares is around 5800/6000. Below that ovals, above that squares make more power.
We built two identical 496s about 5 yrs ago for brothers. Comp solid roller cams: 246@.050 and .623 lift, performer airgap intakes, 850 holley dp, 9.6 compression, both sets pocket ported by me, 2.19/1.88 in both and unshrouded. 049s and 990s, its what they had. boats near identical 18 1/2 Kachina and Challenger, I built both pumps and did both set backs and set ups. both "A" impellers, both DPS inducers. both had Bassets and no mufflers. 049 boat: 73mph, 990 boat: 70, cut 990 impeller to "B" and they ran near identical, except it used more fuel, went BC on 990 boat and fuel was worse and gained only 1 mph. REMEMBER, these were 496s, we don't often bother with 454s. TIMINATOR
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The boat is 18 ft python
From what I was told on here it's a bubbledeck style I've only seen one other hull like mine...prob cause it's not a good hull.. 3/4 stringer. Pump is in stock location and built by tom at jet boat performance..I don't have a loader but I'm ordering one today...the boat runs 68-69 depending on water..my 355 spun 5-5100 rpm at 61 mph...
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Something is fundamentally wrong worth this set up.
5,400 rpm on a bronze B?
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Yea by all means any info I'm open too..
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Something is fundamentally wrong worth this set up.
5,400 rpm on a bronze B?
And heads won't fix it imo.
GT
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Wat will?
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Wat will?
Not sure.
Tied up for a bit, but I'll be back. I have a few questions.
GT
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Ok thanks
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I agree, the set up/ RPM seems wrong. The first thing I'd do is check the tach. MSD and others make a digital tach checker. We check them for free here, you can't tune unless you know the truth. Most of the boat tachs we see are off from 200 to as much as 500 RPM at around 5000 RPM, mostly they read high, just like most non-GPS speedos. About 3 or 4 times a year we have guys come in with similar readings and when we check the tach, we find that they are set to the 6 cylinder position! I can understand that because most car guys with big blocks can't believe that their engine only turns 4200 RPM wide open.
In your case, I don't believe that is a correct RPM reading unless your pump is worn out or assembled incorrectly. With your engine, I would expect more along the lines of 4600.
I also believe that a loader will slow your boat by a few MPH too. We have plenty of 70 and 80 MPH boats out there without loaders. If the boat doesn't unload going down the lake, it will probably slow it. The river guys use them to keep loaded in the rough water of the river(Parker/Havasu) After doing the jetting/ timing thing, we take top and bottom pump pressures to see if the shoe/loader setup is correct. For most loaders, we end up going back to a rock grate to see where we are, checking the speed and pressures as we change stuff. Also, just because an impeller is stamped "A" doesn't mean it still is, it may have been modified and not correctly, or where it should be, and not restamped.
Some of the things that affect RPM in the pump are in no particular order: brand of impeller(legends and Aggressors are "tight"), shouldered or old type wear ring, wide or narrow wear ring, side and end wear ring clearances, age of impeller (beat up / eroded leading and trailing edges, brand of bowl, stuffer or not, clearance from impeller to bowl, nozzle size, age/wear in bowl, blueprinted bowl and/or impeller, loader, shoe, shape of hull in front of suction, angle of suction installation, ride plate angle, droop and what brand/type and length, brand of suction housing, type and fitment of clean out cover(yup, really!), and I'm sure GT will add some more that I haven't thought of!
Back to the engine now. IMHO I would try an RPM Airgap intake or a Dart singleplane intake with an 850 to a HP 970 carb with your setup. Try to borrow one before you buy. Most of our big valved, unshrouded, bowl ported, factory oval port headed, solid roller cammed, 496s run fastest with one of those intakes. They usually run about 75-80 at our altitude and 115 degree heat. Check the tach and bowl pressures, top and bottom before spending any cash. TIMINATOR
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Wonder if the back halfs of the carbs would help at wot...smh
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Pretty easy way to smoke a motor. One of the questions I was going to ask was spark plug heat range and condition.
GT
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Boat was lean..when I check the plugs they look white lol motor is brand new
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Boat was lean..when I check the plugs they look white lol motor is brand new
I cannot stress enough how important it is to track the tune.
What water temperature, rpm, oil pressure, fuel pressure, idle speed etc... if something suddenly changes, find out why.
You should be pulling at least one plug after every day of boating.
You should also be watching header tube discoloration.
GT
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So do you think by the info given I should be able Togo in the 70's in proper working order
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So do you think by the info given I should be able Togo in the 70's in proper working order
What was the speed with it hurting?
GT
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68.4 gps
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68.4 gps
Yes.
In all honesty, I've you get the time dialed in you will have a much better idea of what to concentrate on next. Right now you would be throwing the poop at the toilet paper.
GT
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I agree, the set up/ RPM seems wrong. The first thing I'd do is check the tach. MSD and others make a digital tach checker. We check them for free here, you can't tune unless you know the truth. Most of the boat tachs we see are off from 200 to as much as 500 RPM at around 5000 RPM, mostly they read high, just like most non-GPS speedos. About 3 or 4 times a year we have guys come in with similar readings and when we check the tach, we find that they are set to the 6 cylinder position! I can understand that because most car guys with big blocks can't believe that their engine only turns 4200 RPM wide open.
In your case, I don't believe that is a correct RPM reading unless your pump is worn out or assembled incorrectly. With your engine, I would expect more along the lines of 4600.
I also believe that a loader will slow your boat by a few MPH too. We have plenty of 70 and 80 MPH boats out there without loaders. If the boat doesn't unload going down the lake, it will probably slow it. The river guys use them to keep loaded in the rough water of the river(Parker/Havasu) After doing the jetting/ timing thing, we take top and bottom pump pressures to see if the shoe/loader setup is correct. For most loaders, we end up going back to a rock grate to see where we are, checking the speed and pressures as we change stuff. Also, just because an impeller is stamped "A" doesn't mean it still is, it may have been modified and not correctly, or where it should be, and not restamped.
Some of the things that affect RPM in the pump are in no particular order: brand of impeller(legends and Aggressors are "tight"), shouldered or old type wear ring, wide or narrow wear ring, side and end wear ring clearances, age of impeller (beat up / eroded leading and trailing edges, brand of bowl, stuffer or not, clearance from impeller to bowl, nozzle size, age/wear in bowl, blueprinted bowl and/or impeller, loader, shoe, shape of hull in front of suction, angle of suction installation, ride plate angle, droop and what brand/type and length, brand of suction housing, type and fitment of clean out cover(yup, really!), and I'm sure GT will add some more that I haven't thought of!
Back to the engine now. IMHO I would try an RPM Airgap intake or a Dart singleplane intake with an 850 to a HP 970 carb with your setup. Try to borrow one before you buy. Most of our big valved, unshrouded, bowl ported, factory oval port headed, solid roller cammed, 496s run fastest with one of those intakes. They usually run about 75-80 at our altitude and 115 degree heat. Check the tach and bowl pressures, top and bottom before spending any cash. TIMINATOR
Paragraphs. Whew.
I'm thinking he should be spinning close to 5,600 rpm.
I think the TR is the way to go.
I also think a loader cannot hurt as long is set up correctly.
115 is pretty cold.
He said bronze B.
GT
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So today I've redone my throttle linkage full throttle now...re jetted the carbs and changed the squirters and brought the timing up to 38 degrees ...
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Interesting, you have a Dominator bowl and Place HPH on a Berkeley suction housing. I'm really curious to see what is inside that pump.
Could you take some pictures of the jet intake and surrounding fiberglass, from different angles, under the boat? Do you know the history of the impeller? Pictures of the impeller please.
Cheers,
Joe
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It's a JC split bowl conversion done by jet boat performance ... Impeller is made by tom at JBP ...suction housing is all stock ..I don't have any pics of the impeller I'll take some soon as I get home
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We don't set up our pumps that loose. TIMINATOR
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We don't set up our pumps that loose. TIMINATOR
Huh?
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didn't think that took any explanation, still don't
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didn't think that took any explanation, still don't
I don't see anything where a "loose" pump was indicated. You did however make me go back and read though.
Not being wise, just not understanding the comment. Sorry.
GT
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GT, we all know the factors that affect pump RPM at any HP level, and know that any boat speed probably can be attained by a wide range of RPMs. Our PREFERENCE (not shouting, just emphasis) is to build torque motors and keep the pump RPM down. Since we do all of our engine and pump machining and assembly in house, it is easier for us to match the engine to the pump and vice versa, than most shops. I.E. Motor guy lies about the HP and pump guy has to cut or change the impeller or loosen the pump to get the engine in its power band.
One of my best friends is a retired pump/ flow engineer and we spend lots of time and research on this subject. As a matter of fact he is the Comp jet guy that runs the small block, I'm sure you know who he is. His engine would be more reliable, except his philosophy is to use the lightest, smallest, cheapest, (yes cheapest) part that will JUST do the job, like Pro-Comp rods, no chit!. The last race in point, one of his injectors failed (totally) early in the second heat, and he finished the last heats all on 7 cylinders. Too cheap to carry a spare, really. I believe he ran second and third in those later races. Usually he just splits the block or cylinders. Again the "anybody can build it strong enough, it takes an Engineer to make it JUST strong enough" philosophy.
Back to us. He keeps harping on the fact that pump efficiency relates to output pressure VS input pressure, and even before his input we made our pumps "tighter"(more efficient) than most, and that complements my preference for torque engines. Given the choice, I will always make my power at a lower RPM than most. We prefer the results: less wear, less noise, less fuel consumption at cruise, and less expensive components, because its not the HP that hurts parts, its the RPMs. All of our 70 and 80+ MPH boats run single carb, dual plane intake manifolds at under or around 5000 RPM. Its how we roll, been doing it for 40 years and have it down pretty well. We use single plane intakes to over 100 MPH, and haven't put a tunnel ram on anything in about 10-12 years, except for two guys that had them and liked the "look". They pay for that in fuel and know it. As an example I ran a 21 Daytona for 4 years with thru transom exhaust, swim platforms, pump in STOCK location, American Turbine aluminum "A" impeller (untouched, out of the box), single plane Merlin intake, single stock 1050, AFR 320 heads, Comp roller cam, 10.6 compression, REGULAR pump gas and no additives. 102 MPH RADAR and GPS at 5700 RPM. Dave (Aggressor) sent me a high helix "A" stainless impeller for evaluation when he first started making them and with no changes it dropped the RPM to 5500 and it only ran 96/97 MPH. Since it was cammed for 6200 RPM, I did what anybody would do, I stuck a bottle on it and it ran 6100 RPM in the 100teens. Still on regular. A ton of folks in Phoenix rode in it, it was only a lake boat, with a bimini top. I used to ride around with the top up and smoke a lot of boats that way. Me, a smartass, but prepared and anal(short for analyze) TIMINATOR
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OK clarification time, pump not loose by normal standards, but ours. MY bad.
If anybody is interested I'll post pics and info on sparkplug "reading", or I'll look up the year and month of the HOTBOAT article on plugs and reading them and then all can find it online, I've got the article/issue around here someplace, (I wrote it). TIMINATOR
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I will have to agree with the fuel comsuption is kinda crazy with the tunnel ram..as far as reading plugs I've tuned nos cars before..I've built lots of engines but I was trying on this set up pump gas std bore 454 with 550-575 hp with iron heads...I meen I have a 14.1 496 it's well over 700hp I'm not trying to break any records jus wanna get the boat in the 70+ range and I'll be happy I've only had it out one time with the 454...but I do thank you guys for all the advise...
Gt so the keel of my boat is round...sooo wat does that mean to me?
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I will have to agree with the fuel comsuption is kinda crazy with the tunnel ram..as far as reading plugs I've tuned nos cars before..I've built lots of engines but I was trying on this set up pump gas std bore 454 with 550-575 hp with iron heads.
Gt so the keel of my boat is round...sooo wat does that mean to me?
I figured about 550 hp and the rounded keel means drive it like it's stolen.
GT
Sent from my SCH-I545 using SoCal Jet Boats mobile app
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GT, we all know the factors that affect pump RPM at any HP level, and know that any boat speed probably can be attained by a wide range of RPMs. Our PREFERENCE (not shouting, just emphasis) is to build torque motors and keep the pump RPM down. Since we do all of our engine and pump machining and assembly in house, it is easier for us to match the engine to the pump and vice versa, than most shops. I.E. Motor guy lies about the HP and pump guy has to cut or change the impeller or loosen the pump to get the engine in its power band.
One of my best friends is a retired pump/ flow engineer and we spend lots of time and research on this subject. As a matter of fact he is the Comp jet guy that runs the small block, I'm sure you know who he is. His engine would be more reliable, except his philosophy is to use the lightest, smallest, cheapest, (yes cheapest) part that will JUST do the job, like Pro-Comp rods, no chit!. The last race in point, one of his injectors failed (totally) early in the second heat, and he finished the last heats all on 7 cylinders. Too cheap to carry a spare, really. I believe he ran second and third in those later races. Usually he just splits the block or cylinders. Again the "anybody can build it strong enough, it takes an Engineer to make it JUST strong enough" philosophy.
Back to us. He keeps harping on the fact that pump efficiency relates to output pressure VS input pressure, and even before his input we made our pumps "tighter"(more efficient) than most, and that complements my preference for torque engines. Given the choice, I will always make my power at a lower RPM than most. We prefer the results: less wear, less noise, less fuel consumption at cruise, and less expensive components, because its not the HP that hurts parts, its the RPMs. All of our 70 and 80+ MPH boats run single carb, dual plane intake manifolds at under or around 5000 RPM. Its how we roll, been doing it for 40 years and have it down pretty well. We use single plane intakes to over 100 MPH, and haven't put a tunnel ram on anything in about 10-12 years, except for two guys that had them and liked the "look". They pay for that in fuel and know it. As an example I ran a 21 Daytona for 4 years with thru transom exhaust, swim platforms, pump in STOCK location, American Turbine aluminum "A" impeller (untouched, out of the box), single plane Merlin intake, single stock 1050, AFR 320 heads, Comp roller cam, 10.6 compression, REGULAR pump gas and no additives. 102 MPH RADAR and GPS at 5700 RPM. Dave (Aggressor) sent me a high helix "A" stainless impeller for evaluation when he first started making them and with no changes it dropped the RPM to 5500 and it only ran 96/97 MPH. Since it was cammed for 6200 RPM, I did what anybody would do, I stuck a bottle on it and it ran 6100 RPM in the 100teens. Still on regular. A ton of folks in Phoenix rode in it, it was only a lake boat, with a bimini top. I used to ride around with the top up and smoke a lot of boats that way. Me, a smartass, but prepared and anal(short for analyze) TIMINATOR
I wasn't trying to pee on your campfire. Just wanted to know what you meant by loose pump.
And your torque/lower rpm analogy is right up my road.
I feel anytime you need to pull now than about 6k is tone to rethink the whole deal.
Said it 100 times if I've said it one.
Thank you for taking the time.
GT
Sent from my SCH-I545 using SoCal Jet Boats mobile app
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Well my throttle linkage and base plates were junk so after a trip to jegs new linkage baseplates and bowls I'm gonna get this damn set up to work in the am...