How much pep

« **on:** September 24, 2007, 03:30:23 PM »

would i get out of adding a dual plane manifold an bigger carb?

i an running a stock 460 with stock manifold edelbrock 600cfm carm with a jacuzzi pump a impeller an a place diverter on a 21foot carrabean mini day cruzer
i dont want to sacrafice dependabilty im just looking a some more pep in my step with out breaking the bank an loosing dependabilty any thoughts are appreciated

thanx in advance squiggie

« **Reply #1 on:** September 24, 2007, 03:46:33 PM »

Some numbers as to what your boat is running now would be a good start .

GPS speed

RPM

When was the last time your pump was gone through . Your pump could be the culprit .

-beerjet-

« **Reply #2 on:** September 24, 2007, 03:48:12 PM »

I thought a 460 came with a dual plane intake, no?

« **Reply #3 on:** September 24, 2007, 04:45:39 PM »

It's probably a junk Torker manifold, that's what my boat came with...

Try a high-rise dual plane, Like a Weiand Stealth or an Eldebrock RPM Air Gap with a 750 holley and you will be able to feel a difference

« **Reply #4 on:** September 24, 2007, 04:56:41 PM »

What are you looking for? More ooph out of the hole? More top speed?

For bottom end (out of the hole), then adding a 4 hole spacer under the carb, using a dual plane, a smaller carb, and or a bigger acc pump shot will all help.

For top end, an open hole spacer, bigger air cleaner / inlet / screen, bigger carb, colder air will all help.

« **Reply #5 on:** September 24, 2007, 05:01:31 PM »

Can you post some pics of the intake on it now? Mine came with a factory ford Cobra-Jet intake on it . And it realy isnt that bad of an intake, just heavy.

« **Reply #6 on:** September 24, 2007, 07:37:18 PM »

running a 460 with stealth manifold and a 750 demon =works well with a stock setup

« **Reply #7 on:** September 24, 2007, 09:46:09 PM »

Dual Planes on big blocks tend to like more carb since only half the carb is working at any given time. A 750 CFM carb for example only allows the motor to see 375 CFM...way too small. I'd use an open hole spacer or increase the carb size to an 850 or 950. Sounds big, but properly jetted your motor will thank you.

« **Reply #8 on:** September 25, 2007, 11:38:10 AM »

as of right now i have a top speed of 42 with 5200 rpm
i had the pump rebuilt at the begining of the summer put a new impeller,bearing,seal,wearing, tortilla warmer the whole 9 yards
i will get some pic's together tonight im at work now an dont have them with me it gets up on plane pretty good im just looking for a little more u know who isnt
i should have something up here around 6ish thanx again guys

« **Reply #9 on:** September 25, 2007, 04:32:22 PM »

according to mr grant=you carb your motor to a formula they provide when considering a carb=i will look for this info=was considering a 850 but was told this was to much=this is before alum heads were put on maybe now it will handle it-gettin 77 on this set up now

« **Reply #10 on:** October 05, 2007, 07:14:52 AM »

Quote from: speedymopars on September 24, 2007, 04:56:41 PM

What are you looking for? More ooph out of the hole? More top speed?

For bottom end (out of the hole), then adding a 4 hole spacer under the carb, using a dual plane, a smaller carb, and or a bigger acc pump shot will all help.

For top end, an open hole spacer, bigger air cleaner / inlet / screen, bigger carb, colder air will all help.

Not dissin on you, but you just reminded me of this purple boat I've seen a lot locally. It's got a BB in it and the dude has probably 10" of spacers in between his manifold and carb....
Kinda hard not to laugh at that one. He's barely fast enough to keep up with my Supreme at 48MPH.

« **Reply #11 on:** October 05, 2007, 07:55:10 AM »

Quote from: UNDONE on October 05, 2007, 07:14:52 AM

Not dissin on you, but you just reminded me of this purple boat I've seen a lot locally. It's got a BB in it and the dude has probably 10" of spacers in between his manifold and carb....
Kinda hard not to laugh at that one. He's barely fast enough to keep up with my Supreme at 48MPH.

BUT it looks cool!

May be the only 10" the guy has.

« **Reply #12 on:** October 08, 2007, 10:04:29 AM »

The more spacers you have, the higher up in the band the RPM range is. Depending on the manifold, like on the edelbrock torker, 2-3 inches of spacer makes the manifold work, where in stock form the plenum is too small.

If it's a single plane, 10 inches of plenum spacers probably *starts* the RPM range of the manifold around 7500 RPM!

A 5500-10000RPM manifold will always work well in a jet boat

You can make a dual plane work a little higher RPM by adding an open spacer. I found on my engines the peeks go up about about 200-250 RPM per 1/2 inch.

So if you have a performer, and you needed a performer RPM, throw a 1/2 to 1 inch open spacer on it. It may get you a few more MPH/RPM without spending the bucks on a new manifold.

« **Reply #13 on:** October 08, 2007, 12:49:45 PM »

The purple boat I'm talking about pushes 4800RPM's if it's lucky. I think he just wanted his scoop sittin on top...

« **Reply #14 on:** October 08, 2007, 07:13:35 PM »

Fashion over function....I guess his friends wait for him when they go out...

« **Reply #15 on:** October 10, 2007, 03:03:19 PM »

Quote from: just squirtin on September 25, 2007, 04:32:22 PM

according to mr grant=you carb your motor to a formula they provide when considering a carb=i will look for this info=was considering a 850 but was told this was to much=this is before alum heads were put on maybe now it will handle it-gettin 77 on this set up now

The formula for determining carburetor sizing is simple and straightforward:

Multiply: Displacement X Max RPM's X Volumetric Effeciency. Then divide the result by 3456. The answer yields the required carburator size. Volumetric effeciency is rarely 100% in a normally aspirated engine. Using a volumetric effeciency of 90% is more than generous for a mildly modified engine.

Thus: 460 X 5000 X .90 divided by 3456 = 599 cfm (rounded off). You would do well with a 650 cfm carburator with vacuum secondaries.

So much for the belief a "750 double pumper" is the answer.

Quote from: Quickjet on September 24, 2007, 09:46:09 PM

Dual Planes on big blocks tend to like more carb since only half the carb is working at any given time. A 750 CFM carb for example only allows the motor to see 375 CFM...way too small. I'd use an open hole spacer or increase the carb size to an 850 or 950. Sounds big, but properly jetted your motor will thank you.

A dual plane manifold is FAR superior in low and mid-range performance than a single plane manifold. Plenum design in a dual plane enhances the velocity of the air/fuel mixture and that, in turn, assures maximum filling of the cylinders which is essential to throttle response.. Moreover, BOTH "halves" of the carburator are working all of the time. The suggestion they are not is absurd. Single plane manifolds are of benefit in the mid to upper rpm ranges...not the low to medium range. Do not use an "open hole spacer" and do your best to avoid the age-old temptation to over-carb your engine. You are operating in water, not on the dragstrip. Bigger is NOT better.

« **Reply #16 on:** October 10, 2007, 07:49:16 PM »

You should say bigger is not always better. Depends on the setup.

I had a 455 olds that turned 4400 RPM with a 750 vac secondary holley on a performer.

Converting to an 850 DP I was able to get 5200RPM out of it.

On my new motor,I will be directly comparing and measuring a stock dual plane, a torker, and a tunnel ram.

On those single carb manifolds, I will be comparing a 1.25 inch 4 hole and a 1.25 inch open spacer.

With the singles, I will have a 600 vac annular holley, a 750 vac, and an 850 dp.

With the tunnel ram, I have a pair of 450 CFM mechanicals.

I will take each combo and tune it for its max performance. At the end of the day I will know and have data (to post) what works the best.

I suspect the TR will smoke all the other manifold combos everywhere, with the torker 850 1.25 inch open spacer having the next most top end, and the 600 annular Dual Plane having the best mileage and holeshot.

I have my GPS and my Gtech for measurments, and those that know me on other boards, know I'll post some complete data, good or bad...

« **Reply #17 on:** October 10, 2007, 09:32:44 PM »

Awesome, I cant wait to find out the results. Any ideas on how a single carb tunnel ram might compare?

« **Reply #18 on:** October 10, 2007, 10:21:44 PM »

Quote from: bipolar4U on October 10, 2007, 03:03:19 PM

A dual plane manifold is FAR superior in low and mid-range performance than a single plane manifold. Plenum design in a dual plane enhances the velocity of the air/fuel mixture and that, in turn, assures maximum filling of the cylinders which is essential to throttle response.. Moreover, BOTH "halves" of the carburator are working all of the time. The suggestion they are not is absurd. Single plane manifolds are of benefit in the mid to upper rpm ranges...not the low to medium range. Do not use an "open hole spacer" and do your best to avoid the age-old temptation to over-carb your engine. You are operating in water, not on the dragstrip. Bigger is NOT better.

First things first, Welcome bipolar4U

Now, your information about dual plane manifolds is correct in the fact that they give better performance off idle through mid-range and into moderate high rpm. But a jet boat will go from idle to 3000+ rpm in a fraction of a second with no load just to get the pump spinning, than need good torque from 3000-6000 rpm. These requirements are better suited with a high rise single plane manifold.

As far as over-carburation (I'm sure you know this), an engine is nothing more than a big pump and most modified jet boat engines can use a lot of air flow, but the problem is most people will not take the time to jet a large carb down to the required fuel required to run its best.

But don't get me wrong, your information is excellent for a I/O or direct drive boat, but for a jet boat bigger is better.

« **Reply #19 on:** October 11, 2007, 05:13:27 AM »

Quote from: The Chaz on October 10, 2007, 09:32:44 PM

Awesome, I cant wait to find out the results. Any ideas on how a single carb tunnel ram might compare?

Tunnel rams work on the bottom end because of the long runners (modern EFI engines all have really long runners for low and mid RPM grunt).

Tunnel rams work on the mid and top becuase the runners are straight making the heads flow better than they should, and they have a huge plennum to really help on the top end.

Everytime I test a TR it picks up power everywhere.

The issue I have with a single carb TR is the fact that the outside cylinders tend to run lean, while the inside run rich. This is due to the turn the af has to make that is not present in the dual carb setup. That said, it wouldn't affect the low-mid range that much, so on a jet boat it may not be as big of an issue as it would on a drag car. The single carb TR with a Ford or HEMI port spacing would be affected more than the Chevy / OLDS spacing; and I suspect the high rpm HP numbers will not be as great but will still outperform a standard single plane (probably not the real high end jobs though).

SQUIGGIE

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