smacko

Hi,
I'm posting this for a fellow Vette owner with A C3; He has a 1980 model which as far as I know is standard with regards to engine and exhaust ect, except he replaced the original Rochester with a 600cfm HOLLEY.

TWO; Questions; Firstly, what is the consensus on the forum about optimal sized Holleys for this car with other gear standard.

Secondly; his main problem started recently on a club run all of a sudden when his car started running like a chaff cutter and blowing smoke (black) by the bucketful - REALLY BADLY.

This persisted although we had mild but temporary improvement in replacing an o-ring. Fuel had leaked everywhere around the valley cover.
This has started again all of a sudden even tho it was 'fixed' during the week!

Same probs; fuel everywhere and enormous smoke.

My initial thoughts were that it had to be either the float sinking, needle valve & seat sticking (Its a recoéd carb not new) or as I was pondering last night, perhaps even a cracked carby housing or split in a fuel hose??

Any thoughts?

Thanks!
:cheers:

smacko

ANYONE???

spokewrench

As Far as size goes- I believe the Quadrajet he replaced was 750 cfm and if properly setup, would work much better than this 600cfm Holley, and it is the size G.M. engineered into this engine. As far as black smoke billowing with this Holley- can mean only one thing! It is running way too rich! Check for blown power valve, then make sure the needle and seats are not damaged, and if not set your float level correctly and lastly make sure the floats are not sticking open- It is definately running with too much fuel getting to the engine-

Now, if you need some expert advice on how to set up this Holley carb. or if you want to get the original quadrajet rebuilt and restore that lost 150 cfm -contact this forums induction system and ultimate tuning expert- Lars- He knows more than most of us combined will ever know about induction systems
and he is a really cool guy! Contact him here- V8FastCars@msn.com

Ganey

600 for a basically stock 350. The 600 is said to be Holley's largest selling carb. 350, the largest selling perf. engine size since 68.
Basically what you want is velocity & capacity. With a square bore one should size it properly to the engine, so many sizes are offered.

The GM solution
Q-J- Small primarys w/ huge secondary.
With the spreadbore the small primarys allow velocity, response & fuel economy while the huge sec. provide capacity. Designed by RPD of GM w/ basically unlimited budget & then used on nearly all GM V8s w/ 4 bl. since.
From about 300 C.I. to 500 C.I., so the Q-J sizes itself to the engine & the 750 rating is not really relevant to your 350.
A modified 350 can use 750 for example. 750 minimum for 454.

Remember a carb is a responsive device.

KenSny

I agree with Ganey - The Holley 600 will work just fine on the stock 350 for it's rated HP. Go to the Holley site and use the formula to compute CFM. To compare the Holley to a Qjet and say he lost "150 cfm" does not compute and does not make sense.

He's got other problems......

smacko

THANKS GUYS!

Your response verifies the same conclusion that a mate and I discussed last night; I tend to believe the primary culprit, being that this happened suddenly, is a blown power valve.

Thanks again,
Steve

Matt Gruber

on my 72 it was always dirt on the needle, until i got a new gas tank/lines, now it never happens