Let's hear it for the Quadrajet!

[dieselgeek]

Jim, have you had a chance to observe change in AFR per elevation change? Would be neat to compare with Randal's observations. From what I am told, the carb is "a little less sensitive" in elevation change compared to the EFI - it would be neat to see how much, and how the Q-jet compares to other carbs.

This is certainly good data and information, keep it coming!

[JeffMcKC]

You guy laugh, when in that guys ford carb thread I put a Q-jet on it.

[min301]

IMO, if it's stock(or close to it...) the Q-jet is the best carb money can buy,
even if it's modified, if set up correctly, by someone who knows all the problem area's,
and has repaired them, there is no better.

[TheSilverBuick]

You guy laugh, when in that guys ford carb thread I put a Q-jet on it.

I was an inch away from putting a Q-jet on the Thunderbird before I stuck the TBI on the car.

[JeffMcKC]

The only thing I would caution is the "Magic Number" if it was not leaned out enough to surge then backed up it might be able to run leaner yet. The AFR can be fooled by reversion and countless other things not accounted for. I like to tune to a plug or just off the lean surge then use that number to tune to.

[SpiderGearsMan]

I was an inch away from putting a Q-jet on the Thunderbird before I stuck the TBI on the car.

1968 lincoln had a q jet on the 429

[TheSilverBuick]

1968 lincoln had a q jet on the 429

I have the crap Autolight 4300, which is a square bore, and the 429 got the crap Autolite 4300D, which was a spread bore. Both have a really weird way of controlling idle speed and mixture.

[ls7gto]

So who is volunteering to rebuild the q-jet on Bruabs future caprice?

[dieselgeek]

The only thing I would caution is the "Magic Number" if it was not leaned out enough to surge then backed up it might be able to run leaner yet. The AFR can be fooled by reversion and countless other things not accounted for. I like to tune to a plug or just off the lean surge then use that number to tune to.

I used to believe in plug reading, but not after I started using 8 O2 sensors.

[DanStokes]

There's a bunch of good tuning tools and I think it depends on the tuner.

Remember, the QJ was developed when GM had all the money on the planet and they decided to make a big carb that worked pretty much no matter what. It took a lot of years for anyone to come up with anything better for street use (the Holley, of course, will throw a LOT of fuel into a big motor for cheap). So it's not surprising to me that Jim's works as it should and it's cool that recent technology says it's doing what it ought to. As GM developed this they HAD AFR meters (forerunner of the O2 sensor) and you can bet the farm that they knew these values back when they produced it.

QJ's have their idiosyncrasies, for sure. Loose throttle shafts and leaking well plugs are among the more common but these things are fixable and worth it. Still, it's hard to beat EFI if you have the cash.

Dan

[min301]

So who is volunteering to rebuild the q-jet on Bruabs future caprice?

I'll do it!!!

[Barry Donovan]

The only thing I would caution is the "Magic Number" if it was not leaned out enough to surge then backed up it might be able to run leaner yet. The AFR can be fooled by reversion and countless other things not accounted for. I like to tune to a plug or just off the lean surge then use that number to tune to.

there is always room for lean. they rich to stay safe to parts during liablity of warranty.

A lesson I learned from a carbed japanese car, as they do not want fat fuel. The lean eats headgaskets, rumbles valves, makes cam knockers..even sounds like the end of the wolrd in the base sometimes....

25 years later on the same engine. well. What in hell is there to worry about.

gm stuff is robust. the same little 278cfm is giant meters, giant power valve, more fuel in the bowl..all bigger for the same job. they underestimated themselves.
I look forward to tinkering with it again.

I started driving the year injection came about as a throttle body nightmare. More carbs than anything. EFI got a hold in a weird way...

[antmnte]

I found one on the floor in my buddys garage,he didnt even know it was there. I gave it to another friend for a 78 Malibu.It works great and cost the rebuild kit and float.I really dont think there is a better carb.

[200kss]

Who wants to build a CCC Q-jet for me to put on say, a GM ZZ430HP 350 or a similar engine?

[Beagle]

A/F seems to be doing pretty dang good Jim?