ariba

Hello
I have a new 350/290 HP chevy and I bought Holley 600 CFM STREET WARRIOR CARBURETOR. The mechanic said it too much for the car

The engine
https://www.summitracing.com/parts/nal-12499529

The Carb
https://www.holley.com/products/fuel...parts/0-80457S

is it possible to adjust it?

he said it's just better buying a lower CFM rochester carb.

Q do I buy a 400 CFM? any suggestions??
I need a part number if one of you have something in mind.

Ryan Menzies

Ariba - Get a new mechanic.
600 CFM on a close to 300 HP SBC is a little low in my option but this could be a long, drawn out conversation.
BTW the "lower" cfm Rochester is 750CFM.

Barry's70LT1

I've see lesser engines work very well on a 650 Holley DP. A 650 would have been my choice.
A 600 would be too much carb for a lawn mower, not your engine. Can you tell I don't like a 600 cfm for a 350.

A 600 will work well, however you're not getting the full potential from that engine.

Priya

I disagree. A 600 cfm will be adequate for that motor. Its not too much carb either.

ariba

This is a speed shop but maybe he is wrong

cv67

Its fine

CanadaGrant

The carb you picked will handle quite a bit more than the 350/290 hp you have and the stock Rochester is 750 cfm with a few made in 800 cfm configuration. I have that same carb you picked on my wife's 78 with a ZZ4 crate 350, a cam and 1.6 roller rockers which ups the horsepower to around 390 and it has worked fine for the last ten years.
You might want to think about finding a new "speed shop" guy...

Street Rat

A 600 Holley will work great.

As others said, I would probably have gone somewhat bigger. You will probably need to change jets to maximize performance (if you want).

I have a 670 Holley Ultra vacuum secondary carb and I love it. My build is somewhat mild. I get great mileage and power when needed.

Sounds like the speed shop wants to sell you a carburetor. Stick with what you have and tune it to your engine.

ariba

Thanks
I really trust him he dos't have a carb and he asked me to buy from any palace even online.

ariba

Just updating
Called Holley and called summit and both gave me different opinions.
But there is a big possibility it's the fuel pump is sending more than 8 PSI
So I bought two thing so either one of them work

First: Fuel Pressure Regulator

https://www.summitracing.com/parts/sum-g3032b

If it didn't works
Second: Two different sizes of Holley Standard Main Jets

https://www.summitracing.com/parts/hly-122-60

https://www.summitracing.com/parts/hly-122-62

gasket
https://www.summitracing.com/parts/sce-358

BUT it's a big possibility it's THE Fuel Pressure Regulator

ariba

I think this video will help!..

ariba

It was the
the fuel pump sending to much FUEL

Solved it with a Fuel Pressure Regulator

https://www.summitracing.com/parts/sum-g3032b

The Vette is running Great ......

ariba

Update
It's a Shame that you rely on mechanic word, especially when he told me the fuel regulator solved the problem and its working fine. The body restoration just finished a few days ago so there wasn't time for me to check the Carb worked fine or not.

Now the problem
when you start the car you need to step on it and raise the RPM or it will shut down. You have to wait until it gets worm 2-3 min.

The fuel Regulator is 4.5 - 9 psi.

The13Bats

Your mech sounds like more ego than knowledge, sadly a lot are like that,

I 600 is kind of the plug and play out of box carb,
My mild buick 6 v ran great on it,

Im no fan of over carbing but a 600 on a v8 over 300 ci is marginal unless just a cruiser math might not say it but a dyno will......

TimAT

I fail to see a problem here. The choke needs to be adjusted properly so the fast idle system on the carb has a chance to do it's job.
My carb is not equipped with a choke in any fashion- I have to play with it until it gets warmed up a bit too.

Street Rat

Sounds like the floats aren't in adjustment. That's what I would check first. Possibly not enough fuel until the pump fills the bowls.

Then again a choke problem is possible. The Holleys need tweaking on fast idle speed.

And 600 cfm is fine.

ignatz

If the 600 is returnable I would do that and get a 650.

maj75

I ran a Holley 600 dual feed, dual pump on a 400/TH400 in a GTO. People said it was too small, wouldn’t work with an automatic. Ran well enough at the strip to throw a rod through the block at 5800 rpm... Best throttle response I ever had from a carbed car.

stingraymyway

If you can afford it. Look into the Holley Sniper EFI unit. Takes all the worry out of the situation.

ariba

Maybe this is my last plan