Quadrajets

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Quadrajets

Postby Vanmor » Fri Nov 12, 2010 3:52 pm

OK......

I drug out the Q-jets I have. I actually had four, not three like I thought. These were given to me years ago so they are in pretty sad shape.

Looks like I have two Chevy (even though one code shows Cadillac), one Buick, and one that I can't ID. It has the number 29231-0229. This one doesn't look that bad. It still has some of the brown dye on the carb and the butterflies are not rusted. Maybe it was a replacement Q-jet. All seem to be from around 1974 or 1975.

Three of the carbs have the side connection while the Buick model has the front fuel connection like a Pontiac.

I figure that the Buick carb body could be used and the other parts mixed and matched. The top primary inlet has been damaged on the Buick carb and the other carb tops look the same. I think just switching tops would work out. I don't want to swap out anymore parts than I have to.

There's no choke housing on any of these Q-jets. I guess they used the little coil in a box on the intake manifold.

My stepdad has a rebuild kit, so I might get buy on this with zero dollars.
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Re: Quadrajets

Postby critter » Fri Nov 12, 2010 8:48 pm

Nothing wrong with the Chevy carbs. I put one on a 455 that's still running strong from what I hear.

I say pick your best body and build it.
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Re: Quadrajets

Postby Vanmor » Sun Nov 14, 2010 1:17 am

I got the book today from my stepdad. Vely Interesting, Ya ?

I decided to take the Buick Q-jet apart first. That way, if I dorked it up, I would know what NOT to do on one of the others.

As far as rusty butterflies, is it OK just to clean the rust off them and reuse them ? They're not eat up or anything, just need to be cleaned off.
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Re: Quadrajets

Postby critter » Sun Nov 14, 2010 8:27 am

I would think so. As long as they are not rusted through and function properly after being cleaned up they should be fine.
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Re: Quadrajets

Postby ArkGL01 » Tue Nov 16, 2010 10:19 am

I always herd if you had a Q-jet tuned right there is no better carb. The guy cara knows can tune them great..

www.marksbanditcar.com
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Re: Quadrajets

Postby critter » Tue Nov 16, 2010 10:30 am

I'm pretty darned happy with mine. It was built by Cliff Ruggles for Jay Delaigle's FAST race car. It's a 1974 TA as well. Prior to that I ran my stock SD Quadrajet but when those started selling for $2,500 a pop on Ebay I decided to retire it. Amazing what a few numbers stamped in a part can do for the price.

The only other carb that came close was a Speed Demon 850 (sorry Cara) that I ran when I was drag racing the car more. I bought it off another racer and he'd worked out the bugs. It idled well and I never had fuel delivery problems but, boy, that sucker was thirsty.
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Re: Quadrajets

Postby 77TA » Tue Nov 16, 2010 11:06 am

I used Cliffs book to guide me through modifying my Stock Qjet and it seemed to work pretty well.
Id done some mods using another Qjet book years back, but left the idle circuits stock and while it ran fine the mixture screws had no effect. I set idle with the curb idle screw and it really ran ok....
After the level three mods described in cliffs book the mixtures screws worked so I am eager to find time to get it back on the car again for a longer test. I rebuilt it and a week before a drag race trip last time and I decided to go with the Holley 950HP for its known performance which is a great running carb other then it also tends to be thirsty......

Qjets are neat carbs and do perform well when matched to the car and engine.
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Re: Quadrajets

Postby Vanmor » Tue Nov 16, 2010 2:06 pm

Any carb will perform well if it's set up for the engine it feeds. For the street and some racing at certain hp levels, the Q-jet is a fine carburetor.

I got mine apart but the base plate was a real you know what. The little screws broke that held on the primary butterflies.(expected that) The secondary screws came out OK but the shaft was really stuck. I mean really stuck.

I broke one of the big springs that go on the secondary shaft. I found out that pin on one side ain't coming out. It don't want to so it ain't.

One of the front mixture screws is still stuck. I'll put some heat on that and I'm sure it will come out. I hope so anyway.

I also have to drill and tap the rear orifice for my power breaks.

This Buick carb is an 800cfm Q-jet, so I hope it turns out OK. I don't think it's ever been rebuilt.
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Re: Quadrajets

Postby RamAirDave » Tue Nov 16, 2010 10:55 pm

critter wrote:Prior to that I ran my stock SD Quadrajet but when those started selling for $2,500 a pop on Ebay I decided to retire it. Amazing what a few numbers stamped in a part can do for the price.


Dude, you aren't kidding. 69 Judge 4spd Qjets (273# IIRC) are going for around $5K :shock:So we found a SR Qjet and sent it to my carb guy Eric Jackson at www.vintagemusclecarparts.com His work is absolutely beautiful, and they run as good as they look.

Image

Image

Image


The Qjet on my silver car is a late 70s, maybe 80 Chevy. Runs like a top other than it leaks down after a couple of days (wells are JB welded) and you have to crank the hell out of it to start it. NBD though.
69 GTO RAIII 4spd, 70 Z28 RS



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Re: Quadrajets

Postby critter » Wed Nov 17, 2010 6:30 am

That does look nice. Anything RAIV is in that stratosphere price range like the Judge stuff. If only I had a time machine...
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Re: Quadrajets

Postby Vanmor » Sun Nov 21, 2010 4:50 am

I have broken off several of these screws on the butterflies. I know their staked, but they get halfway out before they snap off. I can drill them out but I must be doing something wrong.
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Re: Quadrajets

Postby critter » Sun Nov 21, 2010 8:44 am

Did you grind off the tips that protrude where they were staked?
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Re: Quadrajets

Postby Vanmor » Sun Nov 21, 2010 11:04 am

Nope. They didn't look like they were staked that well. Most of them came out on their own, but there have a been few that broke.

What's the best way to smooth off the staked hardware ? Use a Dremel and just lightly flaten the part of the fastener they protudes out the back of the shaft ?

Now I have to drill out the ones that are broken off(not fun on these small screws), or just rob the shafts out of one on the others. I'm sure I already ruined the primary shaft in the base plate.

I used locktite on the ones I replaced. Not sure if I'm comfortable with this. I don't want anything going into the new engine.

I can always go back to using the Holly.
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Re: Quadrajets

Postby critter » Sun Nov 21, 2010 11:54 am

Yes, always grind them off, no matter how they look. I learned the hard way like you're learning. The dremel is a good way but a flat file can work.
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Re: Quadrajets

Postby Vanmor » Sun Nov 21, 2010 12:44 pm

Thanks Chris. I don't know why I didn't think of a file. I have a small file that's perfect for that.

Question. On the 800cfm Q-jets, is the veturi in the carb body the only difference ? In other words, do they use the same base plate and airhorn as the others ?

Two of the other carbs have the big fitting on the back of the base plate. If I can use one of the others, that would keep me from having to drill and tap the one that came off the Buick carb. The Buicks have a small tube in that location. I guess I could find another source for power brake vacuum.

All the Q-jets I have are from 1974 and don't have the APT.
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Re: Quadrajets

Postby critter » Sun Nov 21, 2010 1:15 pm

Hard to say on base plates. I know there are a bunch of minor changes but without doing a stare and compare I don't think there's going to be any way to know. If memory serves me all that discharges down there is the idle passages. But you'd also have to match up all the linkages as well.

What's the number on the Buick carb?

APT isn't a game breaker. The one I did try with APT was a set it and forget it deal. My 1974 Qjets are fine as long as the idle circuit is opened up per Cliff's book.
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Re: Quadrajets

Postby Vanmor » Sun Nov 21, 2010 3:01 pm

Number on the carb is:

7045204 1005

For some reason, the 4 and 5 are hard to see. Like it wasn't stamped very well. I'm sure about the 4. The 5 is iffy.

My research shows it was made for a 1974 350 Olds.

I'd love to know what jets these are. They don't have numbers on them. They may be too small anyway.

The secondary rods look like they have BP stamped on them.
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Re: Quadrajets

Postby critter » Sun Nov 21, 2010 5:46 pm

I checked my stash. I don't have one to match although I have a couple of Buick carbs. How bad is it? Can they be drilled and save the shaft?

I have to put a photo loupe on the jets to read the numbers. Part of that is because I'm old and blind but those numbers are pretty danged small on the jets.
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Re: Quadrajets

Postby Vanmor » Sun Nov 21, 2010 7:17 pm

There's only one that broke off on the secondaries air flap that goes in the airhorn.. It's big enough that I can drill it out. I hope anyway. C

Can't say the same for the ones on the base plate. I really screwed the pooch on those. :naughty:

Thanks for looking, but I have three more Q-jets I can rob. I'm going to have to rob them anyway to rebuild the base plate anyway. Or else I'll just switch them out.

Rest assured I learned my lesson on removing the butterflies! :rolleyes:
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