4 barrel on a V6

[spyder_xlch]

I bought a Monza awhile ago and got it running but haven't played with it yet. I'm getting ready to do things like set the timing, tune the carb, set floats, blah, blah, blah. Before I go to far I'm wondering if the carb on it is the best for it. It's a 231CI with a Holley 600 vacuum secondary, Edelbrock intake, unknown headers, dual exhaust, unknown cam, unknown internals. Is the 600 alittle too big for this engine? Would a Q-jet be better? I always liked Q-jets. Never been a Holley fan. I thought about putting a Carter on and even have an old Rochester 4GC that I'd try if it fit the intake. I don't want to put an adaptor on to use a Q-jet and I don't really want to get rid of the Edelbroke intake. But if a Q-jet and stock intake would work better on a daily driver but still make good power I might consider swapping the Holley/Edelbrock for a stock 4 barrel set up. Anybody have words of wisdom?

[75Monzta]

Buick 4.1's came with 4bbl intakes and Q-jets. I happen to have an extra 4bbl intake off one of the few 4.1's i have had. They are pretty good intakes. Just port match up into the port about 1.5 inches.

[res0o7eb]

Quadrajet - use an adaptor on the Edelbrock.
Or send an email to Vic to make manifolds correctly.

[Astre-mutt]

Unless there is a good size cam in it, then a 600 would be a lot of carb for an engine that small. If the manifold has 2 sets of hole in it, then it will take a either a square or spread bore carb. That includes Rochester carb, but that is still a lot more carb then you need. A Carter 500 would be the biggest carb you should use. Even though you don't like Holley's, a Holley 390 would be perfect size for that engine. The Rochester would be a better choice then the 600 you have now.

[res0o7eb]

Unless there is a good size cam in it, then a 600 would be a lot of carb for an engine that small

You are using "Holley carburetor thinking". You need to qualify your statement thusly, "a Holley 600 would be a lot of carb for an engine that small."
Quadra-Jets aren't Holleys. Q-jets flow between 650-800 CFM, but can be put on small displacement engines. GM first used the Q-jet on the 1966 Pontiac OHC-6 Sprint - a hi-performance 230 cu. in six-cylinder engine. If it worked flawlessly on a 230 L-6 (I know, I have a 1969 Pontiac Firebird with an OHC-6 Sprint and Quadrajet), it should work flawlessly on a 231 V-6.

Good idea, Matt. I think I will convert my Skyhawk over to a Q-Jet.

[Astre-mutt]

The quadrajet meters air, which lets one carb work on a variety of engine sizes. The Holley has to be the right size for each application. That's why there is only a few different size Quadrajets, and some many different size Holleys. The main reason I recommend the bigger Quadrajet over the smaller Holley, is that the Quadrajet will have smaller primaries. This will give better low RPM performance around town.

I'm running a 600 Holley on my 4.3L V6, but it's a spread bore. I wouldn't want to use a Holley 600 square bore on my engine. At wide open throttle the square & spread bore would seem simalure, but that part throttle the spread bore would be much more responsive.

[res0o7eb]

I like the Holley Spreadbore.
I thought Holley used to make a smaller Spreadbore

[acstestinc]

Holley did make a small 450 cfm spread bore but that was a long time ago. Set up was a little tricky because of the mechanical secondaries.

[NixVegaGT]

Here's one:

http://cgi.ebay.com/ebaymotors/NEW-8149 ... enameZWD1V

I was looking at the 650 Holley Spreadbore. There was a bunch of them for sale. I ended up with a damn near brand new 4777 (Square) 650 double pumper for $185. There's deals out there...

[spyder_xlch]

Would a stock intake with a Q-jet be a better choice than the Edelbrock intake/ Holley 600? I'm thinking the Q-jet would be more responsive and better in the low to mid range, better mileage, etc. Anybody got a stock 4 barrel intake?

[Astre-mutt]

Matt, the Q-jet fits other Elelbrocks. Why not yours?

[megavega]

I wouldnt worry too much about the 4 bl on the v6, from your post , the carbs youll be using are all vac. secondary carbs, which means the engine opens the secondarys based on load applied via the engine, so if the engine cant open the secondarys all the way up,its not going to be over carbed or flowing 600cfm. So if the engine can only open the secondarys 3/4 the way up wide open, it might only be flowing say 450cfm, even though the carb is or can be opened to 600cfm. Thats whats nice with a vac. secondary carb for the street, you dont get that option/convienance with the dbl. pumpers, they will show you too much carb as soon as you smash the gas pedal.....bog....

Now granted a q-jet will be a little more responsive in the low end due to the small primary throttle blades and smaller venturi, the smaller the venturi/throttle blades the stronger the vac.signal is recieved by the carb/engine, thus improving throttle response. The smaller the venturi/throttle blades are the better the gas mpg,throttle response will be if thats what your after. Have you ever had a 2bl older v8? they had very crisp throttle response, got decent mileage, when you went to a square bore, 4 bl carb like a holley, you loose some of that for a gain in topend hp from the added airflow, because the venturi and throttle blades are now bigger then those of the small 2 bl carb(losing velocity from the larger diameter). Just comes down to what your doing with the car and what you want from it. pick your poison.

[res0o7eb]

Good stuff in this thread - I've learned a few things. Thanks guys for imparting your wisdom.

Matt,
Isn't your Edelbrock manifold a dual plane, which is good for mid-range torque and part-throttle response - all good street characteristics?

[spyder_xlch]

Scott, the Edelbrock performer intake for ther V6 Buick is only for a square bore carb, a Q-jet will not fit.
MegaVega, I think you made up my mind for me. I never really thought about the Holley vacuum secondary only flowing what is needed from the engine. I'll leave it on for now and see how it runs.
Tom, yes it is a dual plane. The divider in the plenum comes all the way up to the carb so each cylinder will only see one primary and one secondary barrel anyway.
Thanks guys for making me actually think about this.

[Astre-mutt]

You right Matt, I had to pull my manifold off the self to look at it. The strange part is there is extra material on the manifold you can take off to mount a Q-jet.