Should I rebuild my Quadrajet or get a new carburetor?

Hello,

This is my first post to the board. I have been reading different threads since I got my '67 Riviera in March of this year. Lot's of helpful information!

Here's a little background...I got the car from the 2nd owner. The engine and transmision were rebuilt approximately 30k miles ago. Unfortunately, they did not do a very good job of cleaning up the engine compartment and motor at that time. The engine had some leaking gaskets and a few parts that needed to be replaced (water, fuel and power steering pumps, power steering hoses, etc).

I recently had the engine and transmission pulled, cleaned thoroughly, primed and repainted. Any parts that looked doubtful were replaced with new ones. Some parts were media blasted (oil pan, pulleys, valve covers, water pump, alternator braket, etc.), then primed and painted also. All exterior gaskets were also changed. Everything turned out beautiful!

The engine runs really well, except at idle and low throttle speeds where it gets choppy - feels like the carburetor isn't getting a steady supply of air. We tried adjusting the carburetor to no avail (the adjustment screws have no affect at all). This leads us to beleive that it needs to be rebuilt.

I'm in the process of deciding if I should rebuilt the Rochester Quadrajet that seems like the original (number 7027248 - used on Buick 430 in the later part of '67); or if I should buy a new carburetor from a different maker. I was considering an Edelbrock. I have a friend who's been running an Edelbrock on his '63 Riviera with stock 425 and says it's a great carb.

I have been recommended by a few knowledgeable Buick guys to stay with the Quadrajet and have it rebuilt. Others I've spoken to(including my mechanic), love Edelbrock carbs. My concern is that rebuilding will cost as much, or more, as buying a new one.

Any thoughts/suggestions would be greatly appreciated.

Regards,
Dan

 

Quadrajet

Hi Danny -

I say rebuild the Q-jet. This carb was calibrated exactly to your car when it was new. A careful rebuild should make it run like new.

The Edelbrock, Holley, and other carbs are general purpose units that will never be matched as well to your engine as the stock calibrated Q-jet. Driveability may be as good, but you should get better mileage with the Q-jet.

One important item to check that is beyond the home rebuilder is the throttle shaft to carb body fit. The steel shaft turns in the aluminum carb body and eventually wears a sloppy big hole. The carb then leaks air through the shaft and does not idle repeatably. The fix is to have a carb shop bore the carb base and install bronze bushings. This is about a $50 fix and a permanent cure to the problem.

You could send the whole carb to Norm Diehle or John Osborne (search on the site for contact info) and have it professionally rebuilt for about the cost of a new Edelbrock. If you want to save money you can get the Tomco rebuild kit and do it yourself for less than $30, but you might spend more time and money if you have throttle shaft problems or warpage.

 

I HAVE NEVER HAD A PROBLEM WITH Q JETS, WHEN THEY ARE COMPLETELY REBUILT, ABOUT $300, I BOUGHT MY LAST ONE THREW POSTONS AND RUN IT NOW, ALL I DID IS ADJUST THE IDLE, I PLAN ON GETTING IN THE 11'S WITH IT, MY LAST PROFESSONLY REBUILT QJET WENT 100,000 MILES + WITH OUT TOUCHING IT. I DONT KNOW OF ENEY ONE DOING THAT WITH AN AFTER MARKET CARB , THIS IS JUST MY EXPERENCE.

 

Dan,

Edelbrock castings are identical to your Q-jet, you're really paying for the same thing. Mevchanics love `em because they are no hassle, unbolt & install new one. Most mechanics will pick out a 600 CFM edelbrock because that's what they put on a chev, but it's way too small for your Buick.

Most home Q-jet rebuilds will cost you $50, a pro can do it for about $200-$250. A rebuild is not complex if you have the time to do the research & practice. It really depends how confident you are.

I'll throw a big vote in for the Q-jet!

 

I would have the Q-jet rebuilt. There are some really good places to have it done that do a quality job. The linkage will fit and everything will work properly. If you are not able to adjust the mixture then you probably have an air leak most likely at the base of the carburetor. Try taking it off and look for carbon build up at the base. Replace the gasket and try it again. You may avoid the expense of a rebuild or a new one.

Good Luck!

 

Thanks everybody!

Lot's of good info. We did remove the carburetor a few times and tried different gaskets to no avail. It also got a thorough cleaning.

I am going to keep the original Quadrajet after all. I've found a couple of sources that do professional rebuilds. One of them is very reasonably priced and here in town (the guy's retired and still does a few rebuilds a month).

Now I just need to find a kit, choke pull-off and a float. Any suggestions on who might have these - the shop I usually order from didn't have a source for them?

Danny

 

Rebuild Kit, Float: Auto Zone

Choke pulloff: www.carbsunlimited.com

Good luck! It's easy, just remember how it goes back together:TU:

 

I RECENLY COMPLETELY REBUILT ONE ON MY OWN, AND DID THE HI PERFORMANCE MODS, IT WAS EASY, BUT I DID TAKE AN OLD JUNKER CARB AND TOOK IT COMPLETELY APART FIRST, SO I WASNT INTIMADATED, THERE ARE GOOD BOOKS ON THEM ALSO

 

Danny if you get a chance give me a call at 475-2475 during the day or 759-1796 - evening. I am in austin and may have a few good leads for you.

:TU:

 

Dan,

UAP-NAPA has the choke pulloff. They're pricey but available.

 

Thanks for the leads everybody! Much appreciated.

I just got a call from Donna at A-line Auto, here in Austin. She can get just about anything. She had everything in stock, so I'm good to go on parts.

I do have a guy to rebuild it for me here in town also. He came highly recommended and his price is very reasonable. I should be able to get it on the bench next week.

Thanks for the numbers Phil. Either way, I'll give you a shout. I'd love to see your cars!

Dan

 

Danny there is lots to talk about. Give me a call when you get a chance if I am not home leave a message with a contact number and I will call you.

 

Hey folks,

Well, I did have my Rochester Quadrajet rebuilt by a guy in town who's been rebuilding them since the 60's. It looks pretty good...I only wish the car ran as good though.

He noticed that the carb had been rebuilt in the past, most likely by some high volume factory rebuilder. He also noticed the following:

- The hot idle compensator valve has been removed.

- There is a small hole behind the fast idle cam that doesn't look like anything should be coming out of...at least not a vacuum line since the fast idle cam and other components would be in the way of any hose.

The problem now is that we can't get the engine to idle smoothly. Also, in order to get the car running, we have to set the idle very high and mixture very rich. Otherwise, the engine stalls as soon as you put it in gear. We tested at length for a vacuum leak, but didn't find any. A vacuum gage flutters a lot at any engine speed (you can also feel the engine jerk when driving).

The idle screws don't have much affect when trying to lean out the mixture. When they're completely in, it should kill the engine. We can turn them both in, but the engine keeps running.

We did locate a guy who has a Sun diagnostics machine. I'm going to have him take a look at it on Monday.

I don't know much about carburetors, but my uneducated guess is that the things mentionned above that have been done to it are causing the problem. He's convinced, however, that my problem is not due to carburation. Anyway, we'll see if the Sun machine can tell us anything.

Any thoughts on something we may have overlooked in the meantime??

If the Sun machine points to the carburetor, I'm not putting any more money into it. I'm going with a new carburetor. Any suggestions on model(s) that people have found to be a good match for the 430 engine in a Riviera would be great!

Thanks,
Dan

 

John Eberly's reply pretty much nailed it on the head. Personally, I'd still keep the Q-jet.

The engine runs worse after the carb rebuild? Nothing else was touched on the engine? I'd suspect the carb.

Just my guess....If your engine idle is as high as you say it is, then you are probably by-passing the idle port and pulling gas from the off-idle transition slots. That's probably why you can't kill the engine by turning the idle screws in all the way.

- The hot idle compensator valve has been removed.

If you remove it and don't plug the hole, then you'll always have a small air leak. On the street, there is really no reason not run a hot idle compensator. It doesn't hurt performance.

- There is a small hole behind the fast idle cam that doesn't look like anything should be coming out of...at least not a vacuum line since the fast idle cam and other components would be in the way of any hose.

Can't help you with that one right now. Sorry. Can you post a photo?

 

Just wanted to give everyone an update on the status on my carburetor

There was originally a plate between the carburetor gasket and the intake manifold, that served to block off exhaust fumes. The missing plate covered two holes in the intake manifold. The holes were plugged with silicon and a thicker Quadrajet gasket was used. Carb now works great! Idle speed was set slightly higher then recommended in the shop manual - around 600 rpm vs. 550.

Has anyone plugged these holes and ran the engine without this plate? If so, do you forsee any problems?

Thanks for all your suggestions and tips!

Dan

 

Q-jet

If you want it done right, send it to John Osborne!!
270-7374467
Sam

 

If I want what done right?

The carburetor's already been rebuilt 2 weeks ago by a 40+ year veteran of the carb business. The car's running great. What I want to know is if plugging the exhaust holes under the carburetor with silicone and running the engine without the plate is ok. I've heard from someone who ran his like this for years with no issues.


Thanks,
Dan

 

Re: Q-jet

I have to agree with BBallsam. John REALY know's his Buick Carbs! If you want it done right (a no hassel, bolt it on and go rebuild, send it to him).

 

Don't know the answer to that one, but if it runs great, why mess with it? Is the plate a problem?

 

Danny - Hello again. I talked with you a little bit on the ROA list. Glad to hear you decided to stick with the Q-jet. I am unfamiliar with the plate you are talking about. Do you know exactly what it was for? What kind of silicone did you use to block the holes with? Was it high temp? To me it sounds like a better idea to try and find a plate. I don't usually feel comfortable with plugging holes up with silicone.