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ok, so i got this thing running pretty good, and all the work i did to the motor gained me 200rpm. i assumed it just needed some tuning, but i havent been able to gain a thing, went from a 750 vac secondary, to a 650 double pumper and no change at all, other than it ran better with the mechanicals. now im back to the 750 with some way bigger jets, bigger squirters and a metering block instead of a plate. no change there either. i know there is more HP in this engine and i think it lies in the cam. i gained a total of 200rpm over a stock 460, i have more compression, bigger cam, ported heads and changed from logs to headers. compression is 10.5:1+, cam is a Lunati 280/292 .514/.543, i can post more details tommorow that is just off the top of my head. im thinking advancing the cam could help get the power band down a bit so i can use it.
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Put a 850DP on it and see if there is any change.
How many Rs are you turning and what impeller ???
From stock I gained 700rpm, 4600-5300.
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what do the plugs look like? that should help you with the carb, more isn't always better ;)
what is your top end rpm?
THIS A AMERICAN TURBINE IMPELLAR CHART:
H.P. 9.5 9.25 AA A B C
150 2900 3050 3200 3600 3800 4050
200 3200 3350 3500 4000 4200 4450
250 3450 3600 3700 4300 4500 4800
300 3800 3950 4050 4550 4800 5100
350 4050 4200 4300 4750 5100 5350
400 4250 4400 4500 5050 5300 5600
450 4450 4600 4700 5250 5500 5850
500 4650 4800 4950 5400 5700 6050
550 4800 4950 5100 5550 5850 N/A
*THESE RPM VALUES MAY VARY ACCORDING TO HOW YOUR BOAT ALLOWS THE PUMP TO LOAD
HORSE POWER REQUIREMENTS ARE AT THE PUMP SHAFT
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MOST jetboats like the camshaft installed 4 degrees advanced. If you didn't degree it when you put it in, now is the time to check it. For top performance it must be degreed. Budlight :idea:
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MOST jetboats like the camshaft installed 4 degrees advanced. If you didn't degree it when you put it in, now is the time to check it. For top performance it must be degreed. Budlight :idea:
does this apply to blown mtrs as well as normally aspirated mtrs?
fastrat
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not unless cam has too much duration and is bleeding off boost then advancing will help trap some of the charge by closing the intake early. blower motors have more torque than 2 gravitationally challenged dudes on a 12 ft cheater pipe :wink: so usually not needed.
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My motor has the cam 2 degrees advanced per George S. @ Clay Smiths Cams. The same as his personal jetboat, according to him. Budlight
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Theres a good chance that your bigger cam and head work has moved your power curve a little beyond your impeller cut and is hurting your overall performance. You might look into cutting a little off your impeller to get your new engine combo were it wants to run.
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i was spining 4600 rpm, now im spinning 4800. i think i remember reading on the cam card that its got something like 5 degrees advance ground into it, but i would have to double check. i have a 9 keyway timing set, so i may just try it at +2 and see what happens. for the carb, im going to get one of those proform main bodies for the 650DP and kick the vac. secondaries to the curb.
i was thinking about cutting the impeller down, but its not even been in there a year, so i will mess with the motor first.
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i was spining 4600 rpm, now im spinning 4800. i think i remember reading on the cam card that its got something like 5 degrees advance ground into it, but i would have to double check. i have a 9 keyway timing set, so i may just try it at +2 and see what happens. for the carb, im going to get one of those proform main bodies for the 650DP and kick the vac. secondaries to the curb.
i was thinking about cutting the impeller down, but its not even been in there a year, so i will mess with the motor first.
Put a 850DP on it and see if there is any change.
How many Rs are you turning and what impeller ???
From stock I gained 700rpm, 4600-5300.
Dave,
When I put my 750vac on I lost almost a full 300RPM !!!
Fords love carberation. Believe it or not on most BBF bigger is better. Dave on my Off-Road truck I run the 750 with no loss in rpm, it will turn 5800-6000K depending on elavation. In the boat it is lean with the 750 at 5000-5100. Don't waste your money on that 650.
Give me a call before you do anything Please !!!
1-928-704-1158