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Discussion Starter #1
I have a ZZ4 clone engine. A 355 with the GM ZZ4 cam, flat top pistons @.025 deck height, and set of vortec heads that have been pocket ported.

I am running this in a 69 chevy truck with 373 gears and a 700r4 trans.

I am debating or either a holley 750 vac (3310) or a 650 vac (1850).

Which carb would be better performance and everyday driving?

Thanks, Litdave
 

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Im not sure of the power band of the ZZ4 cam, if you plan to stay within 6000 RPMs Id use the 650 out of those 2 choices.
If you plan to rev it closer to 7000 RPMS( I dont see that happening ) than Id use the 750.
 

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GPEAK, duration, lift, intake centerline, lobe seperation, etc. etc.

GPEAK LOL OOPs, Im sorry, I mis read that:spank:
 

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Discussion Starter #7
The cam specs are

Intake 210 duration @ .506 lift w/1.6 rocker
Exhaust 221 duration @ .509 lift w/1.5 rocker

I have a 750 on it now and it seems to come on really strong around 3500+ rpms but the throttle response seems kind of slow at lower rpms. I wasn't sure if it was too much carb or just the way the cam is.
 

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actually I show 208/221 @ .050 & .510/.510 with 1.6 & 1.5 rockers .
Anyway, no matter, out of those two choices Id use the 650 for sure. Id even go smaller, it looks to me like it probably peaks around 5000 RPMs.
 

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Come Home Safe Soldier
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I run an Road Demon on my 355.625cfm282 duration cam,9.5:1 compression,89 octane.I wanted to put that carb on my entertainment center cause it is so cool looking,my wife wont let me.That carb is great.Not too big,not too small
 

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Discussion Starter #11
Thanks guys, I'm sold on a 650.

Now I need to find a carb. I started looking on Ebay but I couldn't find any 650 vaccum squarebore Holleys. Did Holley make such a thing? I know they make a 650 spreadbore but that won't fit my RPM intake without and adapter.

Maybe I should go with a 600 but that seems like a little too small.
 

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Sumitt or Jeg's has a vacuum secondary 650 squarebore Holley. Also you could use a Demon, they even have one calibrated special for a zz4.
 

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Technical Support Barry Grant
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ZZ4 carburetor

On the ZZ4 engines we use a 650 Speed Demon that is calibrated to the engine. In performance testing we were able to produce more HP, and drivability than the larger Holley carburetor that GM had used in it's testing when the engine was originally designed.
 
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