I have an '81 Corvette with the original Rochester Quadrajet. I have had nothing but problems with this and want to change. I have heard that the Edelbrock was the way to go. Which model? What are the other things I need? Or does anyone have any better ideas? Thanks

 

Thats like asking what your favorite drink is.....everyone will have their own answer. Let me share my limited knowledge.

Edelbrocks are great for the average guy. They run right out of the box. Cons: They suffer a little bit off the line (nothing a daily driver will notice) and are susceptible to heat sink. Overall probably the best choice for a beginner to moderately experienced wrench.

Holley's- a little more performance oriented. They are a little more tunable but require a bit of understanding and are a little more expensive. Great selection for moderate to experienced rodders.

Q-jets- IMHO, the BEST performing carbs out there....BUT....they are made of magical dust and voodoo legends and require a degree in Carbetology to tune. Im running aq-jet that was tweaked by a professional rebuilder. Once this one gives out on me, Ill be going back to a Holley because its way over my head.

 

Thanks Scott. I appreciate your thoughts. I think I will go with the Edelbrock. Should I go 650 or 750?

 

Smarter people than myself say that 90% of carb problems are really ignition problems.

Is your ignition setup properly? Good spark? Does your timing mark bounce around? Does both the vacuum and mechanical advance work properly? How's the engine vacuum? Any vacuum leaks?

I'd check all that before I switched carbs.

 

For a stock engine, 650 should be enough carb. Also - just curious - will the Edelbrock work with the factory air cleaner? if you are running that, you should check.

You may also want to keep in mind that most Edelbrock carbs are square bore - so if you still have the factory intake, you may need a new one.

There are still Qjet options out there that can compare with the cost of a new Edelbrock. For my money, a rebuilt Qjet is worth (at least) as much as a new Edelbrock AVS. Search on Lars threads on Quadrajet rebuilds - very well liked and he is reasonable on cost.

I also have a rebuilt Qjet by Cliff Ruggles - it still cost less than a new Holley performance carb, and about the same as a new Thunder series Edelbrock.

Factor in the cost of an intake and reworking fuel lines, and you can see how a rebuild may be a better way to go as long as you go with a reputable rebuilder. Lars and Cliff are the top choices in my opinion.

Having said all of that, I'm running a holley 4150 style quickfuel (large stroker and intake is limiting my choice of carbs). If I could find a large spreadbore intake that equals or is better than the airflow of my RPM Air Gap - I would run my Quadrajet in a New York minute.

 

Edelbrocks will work on spreadbore intakes just fine. The carb base even has 2 sets of bolt holes to mount on stock or aftermarket carbs. Im sure it effects flow numbers a little bit, but most guys wont notice the difference.

Lars built my Q-jet and my only complaint about this particular carb is the accelerator pump has frozen in the bore twice during winter storage. Other than that, my q-jet runs like a raped ape. But Lars is out of the business now, and I find Holleys are much more user serviceable than the Q-jets. Its a shame really, because when my secondaries open it feels like Im downshifting! I love the carb but I just think they are too complicated for the average (or even above average) shade tree mechanic.

 

Thanks Jim. Yes I had a vacuum leak. We replaced all the tubing, timing is good, have good spark replacing all the plugs, cap etc. It is hard starting, rough idle, runs good other than at low idle but when you shut it off the smell of gas is really bad. I have had this to 3 people that were supposed to be proficient with Rochester and it still doesn't run right

 

Good point Cooper. When looking at ordering from Edelbrock, I need 2 adapters to use my original air cleaner. I wasn't aware that I had to change my manifold. I will check with Lars and Cliff. This is the third rebuilt Rochester that has been put on this car and I can't find anybody that can set them right. Thanks

 

Scottd - Do you mean a factory intake? The air cleaner may actually be a bigger deal if Mcnees wants to retain the factory one.

I totally agree with you on Holley or Holley-style carbs - easy to learn and easy to set up.

Mcnees - I had not heard that Lars was out of the business, but wouldn't hurt to ask -You can probably reach him at v8fastcars@msn.com. He may know of a good resource.

Cliff is very good, but when he rebuilt mine, he had a backlog (at that time he had one person helping him). When I took my carb to him, he had a large number of carbs lined up waiting for him to work through them. I also recall that it was a well organized set up.

Whatever his lead time is nowadays, you can be sure that he will do a great job, and if you can supply your engine specs the carb will be set up and ready to go once done. Cliff also offered a wealth of tips for some engine builds I was researching at the time.

If you go that route, you can bet your Qjet will be as close as you can get to new once he's done. Its hard to find someone who is truly good with these carbs, which as scottd stated earlier is a real shame.

Also - are you sure that your timing/ignition is set up properly? Timing has been known to act like a carburation issue. I had a bog when I first bought my corvette and was sure it was a carb problem - it turned out to be timing/tuning.

Whatever route you go, good luck.

 

Henry Olsen in San Mateo, CA is another source.

www.olesautoparts.com

 

Get the book by Cliff Juggles. Tells you everything you wanted to know about your quadrate but were afraid to ask. I also recommend get a kit from him as the accel pump is better than what you get at a parts store as his work with ethanol that is in today's gas. Bad ones will stick. He also has his own forum you might want to check out. I had talked to him when doing my '69 GTO and now car runs perfect. Only problem I have is keeping rubber on rear tires. I do not know about the computer controlled carb on the '81's. Good luck.

 

There's rebuilt and rebuilt correctly. If you have reasonable mechanical skills you can rebuild one yourself. The biggest challenge is fixing the previous rebuilders mistakes. If you put 3 other carbs on your car none of them may be properly jetted for your car etc....

Starting with an untouched carb is best....read Lars' papers and follow his instructions as gospel. Combine his papers with the Ruggles book and the appropriate Haynes/Chilton book for you car and go for it.

The Haynes/Chilton books have step by step adjustments for the carb, follow them but remember, whatever Lars says supersedes what's in the books!!

 

if the 81 corvette you have has the original computer controlled q-jet you would need to replace both the carb and distributor with aftermarket units since they both use inputs from the computer to make a/f mixture and ignition timing adjustments but keep in mind you would be violating state and federal smog laws if you did it.

I would find a local carb shop or mechanic that can diagnosis and if necessary overhaul the original carb. It is not rocket science but you will need a scan tool to read the inputs and outputs from the computer to see what is causing the problems.

A q-jet is one of the best carbs on the market but the computer controlled issue makes thing more complicated, the edelbrock Carter afb and avs clones are good carbs but I avoid the 750 and 800 cfm units because of a lean off idle problem they have. Holleys are good carbs for performance but like every carb they need to be tuned for the fuel and engine you are working with.

I hope this helps Henry @ oles carb

 

We run Holleys on all our performance off road engines, just can't beat them. But for street use the old Carter afb is the one to have, Get the carb tuned one time and it is good for life. I think Edelbrock is making them now. If that is a stock 81 motor I feel 650 cfm is too big.

 

I'm not sure I follow. In your original post, you said that the car had the original quadrajet on it, but here you seem to say that the carb is not original.

If the carb is the original one, it is going to be far better for the application than any aftermarket carb you buy off the shelf. If the carb is a commercial rebuild––well, may as well put it on a shelf in the garage and move on.

Quadrajets are really very easy to deal with when they haven't been hacked to pieces on the inside.

 

Many carbs will work good for you, including the Rochester QJ that is on your car now. Too many people just throw away perfectly good carbs. A renew kit, cleaning and proper tuning is usually all you need.

QFT is a fantastic carb if you want performance but don't want to spend big $. A 650 QFT will be perfect, especially if you ever plan to do some minor performance upgrades.

Edelbrocks are fine, they are pretty well tuned from the factory.

 

Tough to beat the old 1406 Edelbrock out of the box for a mild 350.
Read the manual! It is chock full of everything you need to know about the unit.

Edelbrocks make great street blower carbs....but naturally aspirated 1x4 application they truly are power limited......and they do not like low vacuum (Read: Big Cam). Low vacuum plays hell with the metering rods....causing drivebility issues....

A great entry level alternative is the 670 Holley Truck Avenger...yes, Truck Avenger.....it has tiny billet annular primary boosters....very crisp response....I think the part# is 0-80670.

I have used this carb a dozen times on street small blocks......much nicer than an Edelbrock...but almost twice the cash.

Jebby

 

I just want to say again.....like Ole said.....
That his car is an 81 which needs the computer controlled Rochester carb...

 

If you change out the the distributor to a non-computer style....you can run whatever carb you want.
Not sure if the OP wants to get into that....but.....it is an option.

Jebby

 

It's easy to do away with that. It's still a Chevy 350 small block.