off topic carburator question

[Russ]

I have a question about which would be a good aftermarket carburator swap. This is for a buddy of mine who recently purchased a 71 corvette with the original 350 engine. It has a remanufactured quadrajet on it. We have gone through a tuneup and the car runs OK, but is very lacking in power for a 270 horse 350.
He wants to pick up an aftermarket replacement carb, but does not know which would be the best replacement? Carter, Edelbrock, Holley? And what size? Appreciate any help with this.

Russ

 

[84_Chevy_K10]

I doubt anything would run as well as the Q-jet.

I just put one back on mine after three years of having an Edelbrock, and honestly, I don't know what I was thinking when I got rid of the Q-jet.

 

[backcountry]

So many people underestimate the Quadra jet carb. It is a great carb and when set up and tuned properly it stays that way for a long time.

One of the reasons for a “lack of popularity” if you will; is because the lack of hype/advertisement.

•I currently have a Edelbrock 650 cfm, square-flange, electric choke #1806 with Dual-Feed Fuel Line with polished aluminum filter #8128.

The Edelbrock does have a little better throttle response; however the Quadra jet will flat out perform it.

After my rebuild, I will place the Quadra jet back in service.

/forums/images/graemlins/peace.gif

 

[dyeager535]

Russ, I know you are asking about a replacement, but to let you know, there are a bunch of adjustments on the Q-jets, some of which require disassembly, and if that rebuilt unit was "generic" there very well could be performance to be had that is lacking due to the parts it was built with.

Some of the differences based on engine size, year, color of the car, etc., are: primary rods, primary jets, power piston spring, accelerator pump, secondary air valve stop, secondary rods, secondary hangers, and probably a couple of other things I've missed.

If it's a "generic" carburetor, more than likely ALL of those above are not specifically tailored to that '71 Corvette engine.

 

[Russ]

You are probably right about this carburator. I have had a few of the quadrajets over the years and some worked great and others didn't. This is the first one that I have tried adjusting where I could run the air/fuel mixture screws all the way in or out without affecting the engine. That makes me think there is something wrong with this carburator.
I need to check the operation of the secondary's also as I put the pedal to the floor yesterday and my ford escort has more acceleration than this corvette. I have a rochester book that I bought about 25 years ago to work on a GTO I had, I will try to find that book and see if there is something I am missing on this one.
Thanks,

Russ

 

[dyeager535]

I think the name of the book is "Rochester Carburetors", but I know the author is Doug Roe.

It is certainly an informative book, I got much mileage out of mine.

One other thing I forgot was the tension on the secondary air valve. Passenger side, rear, top of carb, secondary air valve shaft. There is a screw on the underside, and it holds the adjustment of how easy or hard the air valve is to open.

That's an "easy" adjustment that might be worth playing with.

 

[Russ]

Thanks for the info. That is the book I have. I will go through it and see what I can do to tweak this carburator any more.

I don't believe my buddy is going to leave the carb on their though. He is very unhappy with it and is planning to swap it anyway. So if anyone has had any good experiences with an aftermarket replacement, let me know.
Thanks,

Russ

 

[mrk5]

[ QUOTE ]
This is the first one that I have tried adjusting where I could run the air/fuel mixture screws all the way in or out without affecting the engine.

[/ QUOTE ]

I had the same problem and was told by a mechanic that it meant one or both of the idle mixture passages is plugged up with dirt. I pulled the carb off and blew some carb cleaner through everything I could, and that fixed my problem. Sounds like you need to pull the carb off and at least do a good cleaning on it.

If he is still interested in buying a new carb, I would recommend a Demon Carb on the 'vette. I've had two and they are awesome for street/strip use. /forums/images/graemlins/thumb.gif