hey, im installing a single turbo on a 355 and wanna know if a 750 cfm Rochester non blow thru can handle this turbo:

stage 4
.60 ar ratio comp/housing
T5/T6 COMPRESSOR WHEEL TRIM

w/o crappin itself. it'll only be runnin about 6 pounds of boost, and i figure maybe if i turn the jets out or something it'll be able to hold, im a little broke right now and cant dish out the 500+ for a blow thru

 

honestly no one knows?!

 

I can't imagine how a QJet could be modified to work in a blow-through application.

 

im not trying to mod it im just wondering if it would hold under minimal boost with a pretty small turbo, say if i open up the jets all the way, and set the secondaries to open when the primaries do or best of all have em open when the choke opens the primaries

 

So I take it this is not possible?

 

Find yourself a cheap alternative (Holley w/mechanical secondaries), and modify yourself for blow-thru. A quadrajet won't work. I did the same thing w/mine, but w/vacuum secondaries, which is a little more involved though, but you can pick up a used carburetor from any bone yard for very very cheap (in some cases, $20.00). Could have it modified for blow-thru for less than the cost of the carb....

www.hangar18fabrication.com/blowthru.html

 

ok, WTF?
What do you mean "open up the jets", do you have any idea how a carb even works? You don't "open up the jets". Do you mean drill them open more? Never do that....


- Just build a carb enclosure, and you won't have to modify anything. (other then putting in larger jets to compensate for the extra HP you'll be making...)

- If you want to do a carb hat, you have to modify the carb for blow through. There is an article I read once upon a time ago about how to. I think it was on turbo mustangs. Do a search on "blow through quadrajet" if you're serious about this. It's virtually the same as the hanger18 link above.

 

http://www.wallaceracing.com/TFProjectUpdate1b.html

I wouldn't recommend it though, the Holley is so much easier to tune for the street, as you can manipulate the Power Valve for part throttle to allow for smaller primaries during idle....

 

Right! I never read that exact article, but it was similar. I believe they used a marine acc pump, such that it had a seal on it.
Also, they used a phenolic float, as the carb they started with was brass... Mine is phenolic stock so...

Well Street Lethal, after they are both modified for blow through operation, now we're just comparing holley carbs to Quadrajets - so it's personal opinion...

 

Everything is personal preference, yes, but Quadrajet's don't necessarily transition better from idle to part throttle under boost. The primaries are small as it is, then you need to add fuel via secondary metering rods to make up the difference. Plus, a bonnet really isn't desired w/vacuum secondaries, because it is venturi vacuum that allows for the secondaries to open, not manifold vacuum, which is why a resistor is needed to measure when to open the secondaries when using a bonnet....

A carb enclosure works, but it's dicey, and nobody has had their blow-thru totally enclosed quadrajet in excess of 10+psi to know how well it will do. A quadrajet can work, but it is so much more tunable with a Holley. This pic is a week old, but it was the preliminary stages of my Holley 600-CFM w/VS. Choke housing has been removed, w/its vac port filled w/epoxy....