SB

iTrader: (1)

You will have no issue skiing and tubing, unless you put too much prop on it. You could put a 500hp 502 in your boat and overprop it and be a pig planing.

Listen, the 383 with any of those intakes will plane 5 million times faster than your old motor.

Nice thing when people in my area ask same question - sometimes they ask about intake, or carb , or cam, or etc but based off same planing speed/tubing/etc - I just take'm for a quick ride in a 5.7 that's been hopped up. The response when gunning from idle is - "wholly schit ! That answers that !" Followed by some laughing.

The notch in dividers help more when the engine doesn't have enough carb. If you have enough carb, you are going to use a 750 right ? The notch is not needed for top hp.

Again, notch or not, the 383 as I mentioned above, will be worlds better than what you have.

SB

iTrader: (1)

Btw, my memory says the RPM non airgap have fully divided plenums pre Vortec and Vortec. Some of the BBC's have the cut out.

Double check on this. but I truly think the cut out was part of the Air Gap rpm difference.

94sylvan

You are correct on the RPM performer, I looked it up again yesterday. Just the air gap has the cutout. I haven't bought a carb yet, was leaning toward 1409 edelbrock 600 cfm. Volumetrically its' plenty of carb under 5000 rpm and would idle / shift better than 750, plus help economy a little. This might be a case where the AirGap cutout helps extend the top end for me then with the small carb. The 305 has the quadrajet and I've rebuilt it twice already in the last year and just like in the past working with cars, I would like to throw it off a cliff. I didn't go real aggresive with cam as I stuck in the XM262 hydraulic flat tappet from Comp.

CC230

Sylvan, Bob did not spec the air gap, I told him that's what I thought I wanted to use, he didn't disagree. I had the thought the lines of what SB said, it may soften the low end blow to the outdrive (if even measurable), but I don't plan on hammering it out of the hole either. The cars I've used the air gap on I really liked the response also, so didn't really think to much about it.
Was it a good choice or not? Not sure. Carburetor I think I may go with a QF 750.

SB

iTrader: (1)

94 Sylvan,Take it from my experience with SB's in boats.

If you are not using a mechanical secondary carb, you want one that you can adjust the opening of the scondaries.

This rules out the Edelbrock Carbs.

Against theory and myth, a boat likes the secondaries to open soon. If you get a Holley VAc secondary, make sure to get one with quick change spring set up.

You will crap your pants with the performance gain as you try each step down softer spring. Don't be surprised if you end up at or near the softest spring.

A mechanical secondary carb will use more fuel because of the two accelerator pumps, but it is actually a better system since you have direct control over airflow.

CC230

SB that's what I'm shooting for is a mechanical secondary, and also with that, should be able to control the secondary's for some kind of cruising speed economy LOL!

minx163

I'm running a Performer duel plane Vortec and a single plane 1" thermal spacer with a mechanical 750 Ebelbrock I didn't fully understand why SB ruled them out. . It looks like your DCR is around 7.4 :1 It should be fine on pump gas. I used a lighter circle track flywheel also. It makes a huge difference in throttle response. Especially for those out of water experiences here's a couple videos of my setup at WOT
https://www.youtube.com/watch?v=pB_xViJUs0E

https://www.youtube.com/watch?v=fZ9g6vPaml8

SB

iTrader: (1)

Good running Donzi. Congrats.

The Edelbrock carbs use an 'air valve' for the air flow thru the secondaries. The AVS series feature an adjustable air valve. The Performer series don't have an adjustable system.

The air valve is located over the throttle blades (yes, the blades are connected by 'mechanical linkage) and under the boosters.

ACrooks69

iTrader: (1)

I have a nice Q-Jet the was built by JET that ran real well on my old 383 build. Started out redone for a hopped up 5.7 then the 425hp 383. That's about the most I would use it with, but it ran real nice and no Q-Jet bog. I really have no use for it anymore and it's no good for a car. If you'd be interested, I can dig it out.

ACrooks69

iTrader: (1)

Oh by the way, I tried a couple edelbrocks on those motors and they never ran as good as the Q-Jet.