A few years ago my original 4bbl quadrajet had to be retired because the threads on the fuel intake had become stripped out and I was told that there was not enough there to be rethreaded. The mechanic that was rebuilding my engine at the time had an Edelbrock Performer carb on the shelf and installed it as a replacement. To be honest, I miss my quadrajet (which is currently a paperweight in my garage), and other than the electric choke I've never really been happy with the Edelbrock.

I'm currently looking around for a "new" quadrajet. I'll start off by saying I'm a body guy with a general knowledge of the engine and able to do normal maintenance w/o doing any harm.
What I would like to know is what the CFM was on a stock 4bbl quadrajet for a '71 Olds with a 350? All of the ones that I'm looking at are saying 700, 750 and 800 CFM.

 

750 cfm

Carb number should be 7041250.

Year & Application......Carb #.........Main Jet...........Primary Rod..............Secondary Rod
1971 350...................7041250.....7031970......... . 7034849-"49B".......... 7038256- "AS"

 

Thanks. Would 800 cause a problem? Here's a link to one that I was looking at.

https://www.opgi.com/air-fuel-delive...1-C240465.html

 

That appears to be Chinesium copy.
Why not get a used REAL Quadrajet by placing a "Parts Wanted" ad on here and getting it rebuilt ?

 

This is a nice price for this carburetor. Accelerator pump pins are readily available, bushings & linkages are also available. Great candidate for a refresh/rebuild.

1971 OLDSMOBILE 350 QUADRAJET CARBURETOR 4 BARREL 7041250 CUTLASS

 

Consider asking a Quadrajet rebuilder if it can be rethreaded/repaired with a thread insert.. The mechanic may not be familiar with the repair process, if it can be rethreaded you're back to the original carb.

 

No, not at all.

 

The Jet Qjet is a reman, not a Chinese copy. It will be the later castings with a generic tune in it. Is your motor stock? It is modified for an aftermarket cam. That Ebay Qjet with a quality kit might be exactly what want on a stock motor.

 

Chip,
Where are you in Maryland ? There are some newer methods of thread repair that might save your carb. If you are anywhere close and you want to run it by I will gladly take a look at it for you.

 

My engine is completely stock.

 

If I'm looking at Google maps right, are you off Industrial? If so, I'm about 1/2 mile from you.

 

Thats the place

 

I had always heard that there are two flavors of Q-Jet, 715 CFM and the later 800 CFM.

 

A 7042250 core is probably less expensive than having the fuel inlet helicoil installed.

 

I might sound like a broken record, but the 800 CFM later 170-series carb would be an upgrade over your earlier, though much more correct, 70-series. You’ll pick up an additional 50 CFM and the front fuel inlet (vs. the side inlet). I believe the front inlet is safer. Also you’ll get an adjustable part throttle screw, which means you can tune your part throttle metering better. If you wind up the engine here & there for fun, the additional CFM might make you very happy.

The bigger carb will arrive with a generic tune. That may work just fine for your engine, so test it for a week or 2 and see if it needs further tuning. It just might be that the selected rods & jets it comes with will work well for your car.

If it bogs, runs rich, has a crappy idle or feel under powered, you’re into qjet tuning land. It’s a very large search space. Depending on how picky you get, the number of possible combinations of parts for a perfect tune is easily in the millions.

That means you need a strategy for finding the best tune for your car. I tune for best results at idle (looking for smooth), part throttle (looking for no ping + smooth transition), and WOT (looking for another smooth transition + max power). It may be a little extreme but I use oxygen sensors to tell me AFR/Lambda in real time to get to the best tune using this: https://www.jegs.com/i/Innovate-Moto...iABEgLPUPD_BwE But it’s pricey & you really only need the output from one bank of the V8.
For a simple, possibly all-too-crude start to tuning, calculate the 800 CFM as a % of the 750 CFM, then bump the square metering area of the primary circuit rods/jets by a similar percentage.

If I can help more from here, please ask on this thread or message me on CO.

Cheers
Chris

 

The Ebay Qjet rebuilt is all he needs in his situation. A bone stock late 70's Olds 350 or 403 carb would also work. My later 78 403 800 cfm custom tuned, modified by me and tweaked with a wideband got my AFR where I wanted them. High 13's idle, low 15's part throttle and high 12's WOT. It needed idle circuit mods, Cliff's high performance kit, slower pull off, his custom 44 primary rods, orange power piston spring with 73 jets and leaner secondary rods that the super rich I started with. My idle mixture, part throttle and WOT AFR takes two minutes to adjust. Without the wideband check, would have been mid 14's till WOT then 11.6 with the rich rods I had in it. I set the secondary air door to 1.240" but may adjust to the 1.270" spec to take advantage of better cam and much better heads going on this Winter. Your current Edelbrock carb may also be way off, having a generic tune.