budavid

Hi there,

I'm new to the vette field, I just bought a used 72 vette that used to run but after a very long paint job the carburetor is screwed, it keeps dripping in the barrels from the nozzels and overflowing from the vents, I tried to knock on the bowls and the valves once and it worked, but now after 2 weeks I ended up with opening the bowls with no use.. I'm thinking of replacing it.

after a long search in older threads and researches about carburetors, I'm confused about choosing the right carburetor to replace mine..

from what I read about ZZ4's, the ZZ4 comes with a 750cfm carb. mine has 600cfm holley whith part # 80450.

many suggest Demons and Edelbrocks, since I have no clue about american cars, I need help now with this, because I never worked with a carburetor before.

I need the car for street use, not a daily driver, maybe 3 times a week or less.


thanks.

MelWff

have you tried adjusting the float level?

budavid

I don't think that it is the issue, becaue when it worked last time it was fine and not dripping, looks like that the valves leak contineously and need to be replaced along with everything, it leaks from the throttle shaft or what it is called, I really don't know how to deal with carbs, thats why I'm thinking of buying a new one.

the float level is on top right?

avner

I remember this problem at my holey in yhe first time that I start my engine on my 68.
The problem was one of the 'C' clips on the plastic float was missing in the bowls, it took me several time to open the bowls to see it, put a new one and everything was good.
Good Luck
Avner

budavid

ok, but it is leaking from many places anyway, isn't it wiser to replace the whole thing in stead of fixing this and that and checking? besides, parts are not so available here in the gulf, maybe it is better to take this one off and buy a new one, I'm not a carburetor genius unfortunately.

I just need to know what carb size I should go for, same as the one I have or upgrade to 750 as recommended by GM for the ZZ4? I'm afraid that going for higher cfm's will give bad results for street use and idle.

MakoShark72

I run a Holley 670 SA on my ZZ4, it screams! But swap the #68 secondary jet into the primary side and pick up a #76 for the secondary (as per Lars' recommendation). Easy to do...

Alwyn678

DEMON 850 works well for me

69vettester

Thats some good info to your question.

budavid

OK, all that I understood is that 670 street avenger works well, but the #68 and #76 thing I didn't understand well..

and I see a Demon thing over here, but never heared about the 850!? isn't it too much for the street use?

MakoShark72

The 670 Street Avenger runs a little lean out of the box... The carb comes with 65 primary jets, and 68 secondary jets. You put the 68 jet in the PRIMARY, and go buy a 76 jet for the secondary. That richens up the carb enough...slightly bigger jets..

The jet costs less than $10 and it takes about 10 minutes to do the swap.

Email Lars..and ask him to send you his instructions on the Street Avenger stumble issues...

V8FastCars@msn.com

Rob

budavid

clear enough, thanks for the tip.

but your ZZ4 is stock? or upgraded? fuel consumption??? many told me that anything above 650 is a waste without modifications such as high flow intakes and headers + cam..

MakoShark72

Stock with Hooker sidepipes. Fuel consumption?? Tough to answer because I have a 200-4R overdrive trans and 3.08 gears, AND I keep my foot in it most of the time.

I'd say on the highway... low 20's, but that is based more on what other guys are getting, who have many more miles than I have...

bowtie racing

Why not leave all the guess work out of it??

http://www.barrygrant.com/demon/default.aspx?page=13


With manual trans go with mechanical secondaries and vacuum with automatic. You really dont need bigger carburator.

FKING1

I run a SA 670 on my ZZ4. Have played with several sets of jets.
Currently running 72 primary and 80 2nd.
May be a little rich but it runs great for Autocrossing.
May try 70's and 75's.
Problem is with 68's primary is an off idle stumble. 76 for 2nd's should be OK

MakoShark72

Mine actually has a slight stumble off idle as well, I may try bumping up to a 70/78 combo tomorrow...

ZZ71S

Gm puts Holley 770 sa on the turn key zz4.
I am using the 770 on my zz4 with no jet changes and the plugs are a nice brownish color and it runs very well

Dantana

Some of this info is surprising to me. I never would have guessed anything over the 670 SA that I have on mine (from previoius owner) would not be enough to get everything out of the ZZ4. Maybe I'll up jet mine and see what happens. I have always attributed the general lack of performance (opinion...) to the TH400 that is in there.

In any event, my 670 SA does pretty well. They are cheap and easy to come by so picking one up should be easy.

budavid

so I assume that GM recommendation for a 750 or 770 is to help with idle mixture?

as Makoshark72 mentioned, that 670 SA is lean at idle.

isn't it wiser to go for 750 or 770 for future projects, such as cam upgrade and maybe heads?

but why a 670 Demon is always enough for a 350? better flow?

in case of changing from Holley to Demon, are there things to be changed with it? or it is just a plug and play job?

and my car is manual, so I should go with mechanical secondaries for sure? I think mine has vaccum.

sorry for my many questions, but I have no clue about carburetors, I learned few things this week, but I still have to learn more.

thanks.

Aldo_45030

OK my turn can you guys post up what jet changes you made to you 670SA's i am in a place now where i need to dump the crossfire and select a carb for my ZZ4. I already have a performer rpm manifold the rest is stock.

nonracer

Try changing the discharge nozzle to a larger one they are usually a little small out of the boxplus if your plugs look good and it runs good at cruise and wide open I dont think you need a jet change.