lake tested the new engine today

[WHATA SQUIRT]

so what rpm should a 496 turn? 850 carb, victor jr intake,10:1, 188 factory heads,comp cams .564 lift.. 234* 237*@.050, on a 112 ..12jg pump a impeller freash from MPD..just curious..I only saw 4800 rpm...is this right?

[RCB19]

Depends on the size of your impeller. AA maybee, A or B and I would say that you have some problems. Cam seems a little small for that motor.

[502 JET]

so what rpm should a 496 turn? 850 carb, victor jr intake,10:1, 188 factory heads,comp cams .564 lift.. 234* 237*@.050, on a 112 ..12jg pump a impeller freash from MPD..just curious..I only saw 4800 rpm...is this right?
How much total ignition timing are you running?With the engine off have someone push the gas pedal all the way open look inside the carb and make sure you are getting full throttle.

[GUGS102]

so what rpm should a 496 turn? 850 carb, victor jr intake,10:1, 188 factory heads,comp cams .564 lift.. 234* 237*@.050, on a 112 ..12jg pump a impeller freash from MPD..just curious..I only saw 4800 rpm...is this right?
What exhaust are you running? With my roller 496 with a 246 @50 .622 lift comp, 950HP, air gap, JG with "A" berk and logs I could only turn 5000. I put in TT headers and immediately turned 5500 with no tuning.
Gugs

[Duane HTP]

For one thing, you camshaft is too small by about .100" to make real power with that many cubic inches.

[WHATA SQUIRT]

ok, sorry I forgot some details..carb is all the way open, currently running log manifolds w/ small tips 2 7/8 ..Impeller is an "A" berkley alum....total timing this time out was 34*..cam setup is a hyd. flat tappet. cam claims 2000-6200..someone pls make it all better.....thanks guys..by the way its a 21 ft bahner closed deck

[Duane HTP]

Another thing you might do, is to check and make sure your tachometer is accurate.

[502 JET]

ok, sorry I forgot some details..carb is all the way open, currently running log manifolds w/ small tips 2 7/8 ..Impeller is an "A" berkley alum....total timing this time out was 34*..cam setup is a hyd. flat tappet. cam claims 2000-6200..someone pls make it all better.....thanks guys..by the way its a 21 ft bahner closed deck
With the rpms you are turning that impeller the JPC shows you are only making 350hp.
GUGS102 numbers on the JPC with logs shows 395hp to turn 5000rpms and with the increased rpms with the TT headers shows 525hp to turn the A berk impeller 5500rpms.A 130hp increase!!! According to the JPC.
I dont know how accurate the JPC is but when I run the numbers for my boat with a AT-B impeller at 5500rpms it shows 450hp to turn it and I was running a 450hp 502 crate motor.The JPC is 100% accurate with my setup not sure about others but I would bet it is very close.
SQUIRT I suggest you get a better exhaust system before you worry about the cam size being too small.It wont matter how large of a cam you run if you cant get the exhaust out of the motor.

[WHATA SQUIRT]

First off thanks for all the information guys,I really apreciate it..What is JPC that 502 jet is refering to?.And to HTP tach is going to the gauge shop monday for calibration just to be sure...Sorry still new to this boat engine thing.Im not to worried about cam size and I know that exhaust is my next investment ..just curious as to how much the pump/water load really affects the overall RPM of the Engine.I do know this the engine runs a hell of alot better than the old stock 454,it RPM'S very quickly and pulls real hard...I haven't stayed in it for a long time to see what it will do,still breaking it in for what thats worth..oh yeah how accurate are those water pick up speedo's? Theres one in the boat and it works just not sure how accorate it is..once again thanks for all the info....

[WHATA SQUIRT]

how much power should this 496 make..10.25:1 ,188 factory as cast heads, .564/.567 lift 234/237 @.050 on a 112 LC cam ,matching springs etc. 850 demon victor jr intake..4.250 stroke 6.385 rod..just curious never even asked the builder..

[YeLLowBoaT]

well I did some pluging in on desktop dyno and it can out To make about 370 hp at 5000 so if you have a "A" impeller your rpms are right on....

[kp216]

oh yeah how accurate are those water pick up speedo's? Theres one in the boat and it works just not sure how accorate it is.
Some are accurate, some are close, some are way off. How's that for a hedge-the-bet answer? :rollside:
The only way to tell for sure is check it against the "Great Humbler", a GPS. Mine was actually within 1 mph.

[MikeF]

and pulls real hard...
I can tell you that it is not the cause of the new engine. :)

[502 JET]

First off thanks for all the information guys,I really appreciate it..What is JPC that 502 jet is referring to?.And to HTP tach is going to the gauge shop monday for calibration just to be sure...Sorry still new to this boat engine thing.Im not to worried about cam size and I know that exhaust is my next investment ..just curious as to how much the pump/water load really affects the overall RPM of the Engine.I do know this the engine runs a hell of alot better than the old stock 454,it RPM'S very quickly and pulls real hard...I haven't stayed in it for a long time to see what it will do,still breaking it in for what thats worth..oh yeah how accurate are those water pick up speedo's? Theres one in the boat and it works just not sure how accurate it is..once again thanks for all the info....
The (JPC) Jet Boat Performance Calculator is a program that I believe was designed by LVJETBOY who is banned from the forum at this time.With the program you can select the manufacturer and impeller size and put in an rpm reading and it will tell you how much power you are making to turn that rpm or put in hp reading and it will tell you how many rpm you can turn with the selected impeller.If you have a speed reading and max rpms the JPC will also predict speed numbers when you add more hp or rpm or you can put in a speed number and it will give you the hp and rpm needed to get that speed.
The jet pump works like an engine dyno provided it stays loaded with no cavitation it holds the engine back at it max power.That is why if everything is correct with your set up your engine is only making enough power to turn that A impeller at 4800.
The water pressure speedos are good to fill the hole in the dash.If you want know your exact speed you need to use a gps.I use the hand held gps from my fishing boat.

[GUGS102]

With the rpms you are turning that impeller the JPC shows you are only making 350hp.
GUGS102 numbers on the JPC with logs shows 395hp to turn 5000rpms and with the increased rpms with the TT headers shows 525hp to turn the A berk impeller 5500rpms.A 130hp increase!!! According to the JPC.
I dont know how accurate the JPC is but when I run the numbers for my boat with a AT-B impeller at 5500rpms it shows 450hp to turn it and I was running a 450hp 502 crate motor.The JPC is 100% accurate with my setup not sure about others but I would bet it is very close.
SQUIRT I suggest you get a better exhaust system before you worry about the cam size being too small.It wont matter how large of a cam you run if you cant get the exhaust out of the motor.
Another option is to go to a larger snail. I was running the 3.5" logs when I turned the 5000. With a stock motor and the same pump, 4600 was all I could get. I've got a set of 3.5" logs and hose if you don't want the headers, they would work better than what you have, but not optimum. The 3.5" will flow ALMOST 40% more according to the flow bench. Just another option.
Gugs

[SmokinLowriderSS]

well I did some pluging in on desktop dyno and it can out To make about 370 hp at 5000 so if you have a "A" impeller your rpms are right on....
I did the same, dug up head flow data I found (stock), and wound up very close to your figures YB, as stock manifolds due to the small snails.
BAD NEWS: If you're running an A SQUIRT, you're dead on where you should be, it's all ya have.
GOOD NEWS: There's more available, it only costs $$$$$. :cry:
Now, the bigger snails MAY gain ya 20 or 30 HP, get you to 400, Spin ya 5-grand or a few turns more.
A set of headers (minimum 2-grand new (ASSuming jacketed TT ones, injected OT's much cheaper) with 4" outlets) could get you to 450HP, putting you over 5200 right in the meat off the HP production.
Now, just .100 cam lift change gets ya about 10 HP, maybe ... BUT I suspect this is as as 502 said, the exhaust is cramping it by then. About 20HP with the extra .100 AND a set of headers. That's not changing the duration, just the lift. By then, duration probably pretty short too. and ought to be a roller.
Changed to an Isky EE-392 I have on file, with .590 lift and 254* duration, I'm looking at an honest 500HP (headered) which would translate to 5400 RPM.
Damn, does it show I LOVE playing with this program? :) :) :)