rcdynamic88

I Ordered a 800 cfm Quadrajet from SMI to replace a Holley style carb on my 455 with an Edelbrock Performer intake. I'm wondering if there is a mounting gasket for Quadrajets that some of you think is the best one to use. I have been using Holley carbs for so long I am unfamilar with Quadrajet particulars. Don't some of the gaskets have "crush sleeves" or something like that around each mounting hole so you don't tighten them down too much? What about carb spacers for Quadrajets, any of them any good?

firefrost gold

My smi carb is a 750 only but it will or should come with a new thicker close to 1/2 gasket to a keep heat out and a good seal. He says like 12 to 18 pounds if i remember right. and Yes you have to get a new one if it didnt come with one . The big secondarys will hit on the small holes ( I did that with my edelbrock to smi ) was going back and fourth and didnt change that out and boy the q jet was slow oops .

Rickman48

I've never used more than the 1/2" gasket mentioned on a QJ, [hood clearance] but have used them on Holleys w/a open plenum manifold, which worked well!
If you've hood clearance and linkage adjustibility, let us know!

firefrost gold

why did you pick him? I see that opgi has smi carbs in the oarts book .

rcdynamic88

"SMI" came up in several forums when I used a google search for "high performance quadrajet". There were many positive comments and links to his website http://www.smicarburetor.com/ . After reading the description of what he does for one of his Stage II build-ups, it sounded like just what I needed. I called, and Sean answered the phone himself. He went over his "tech info" form to get all the details about my application. I like the fact that I didn't have to have an original equipment Quadrajet to send him, or even locate a rebuildable core. He provides the cores himself. His prices appear to be very reasonable to me (lower than some others). It is supposed to take 2 to 3 weeks to get my new carb, that doesn't seem like all that long of a wait for a custom built carb.

Do you like your SMI Quadrajet?

rcdynamic88

Are Quadrajets "taller" than Holleys? This is all in a 1965 Cutlass with a stock flat hood. I had a 1/2" 4-hole spacer under my Holley and it just fit under my hood. If I am using a mounting gasket a 1/2" thick, I don't think I will be able to use a spacer.

firefrost gold

I know it is taller than my edelbrock . I had to get a different air cleaner too because
the old one hit in two spots on the carb acc pump arm and linkage . Did it come witha olds
pontiac front style fuel inlet or was it a chevy side inlet ?

rcdynamic88

I havn't received the carb yet. It is supposed to be the Olds style front inlet with a -08 AN fitting to match up to the fuel line I have from the fuel regulator. SMI tech page says to run 4 lbs of fuel pressure, but the regulator I have will only go down to 5 lbs. Is that going to be an issue? Can a fuel pressure difference of that amount cause a problem?

dc2x4drvr

Your Q-Jet should handle up to 7# of fuel pressure, I like to run mine at 5-6 #'s..

rcdynamic88

I installed my new carb today and WOW what a difference! I had to make one adjustment to the fast idle speed. Bumped it up to 1500 rpm because the car didn't want to start and warm up. Its 52 degrees out here today, so the choke was doing what its supposed to do. Once that was taken care of the engine warmed up and the choke came off. Followed up with the idle speed and then the idle mixture screws. I get 12" of vacuum with the car in gear and the brakes on, which is higher than the 9" with the 4150 style Holley. Maybe because of the smaller primaries on the Q-Jet?
Fuel pressure is set at 5.5 lbs, and no issues with flooding or leaking. Went for a short test drive and this thing is running so much smoother. I havn't gone out for a blast down the highway yet, but part throttle response is excellent.

I too am having a problem getting my air cleaner base to fit over the accelerator pump hardware and part of the choke bracket. Just got a 1/2" air cleaner spacer from Jegs and I'm going back out to the garage to see if that will do the trick. Once I get that figured out it will be time to open up those secondaries and see what happens!

firefrost gold

mine is on a pontiac so I used the pancake set up ill post or see if the wife will post some shots

firefrost gold

Some shots of my carb and motor in my Lemans- keep in mind I only paid $1500 for the motor.