Quadrajet help
 

I have an issue with my 1969 Chevrolet C20. It has the 350 V8 with the automatic transmission, the carb is the Rochester Quadrajet. The truck starts up fine, comes to a idle after a few minutes. The problem that is occurring is that after driving for 15 mins or so, you come to a stop and the truck wants to die. The truck has 88,000 miles and I'm guessing that the carb is original. Any thoughts....adjustments or rebuild ?

Thanks!

Re: Quadrajet help
 

Is it running out of fuel? I think those had a filter at the inlet, might check it. Quadrajets are good.....when they work

Re: Quadrajet help
 

Sounds similar to the problem I had
http://67-72chevytrucks.com/vboard/s...d.php?t=760430

Re: Quadrajet help
 

Yes, gas filter was replaced.

Re: Quadrajet help
 

Check for a vacuum leak.

Is this a recent occurrence or has it been ongoing?

Re: Quadrajet help
 

It just started... just had some work done to the truck - new exhaust, hoses, belts and brake lines.

Re: Quadrajet help
 

www.cliffshighperformance.com

You need a rebuild. Cliff can sell you a kit and all the parts to calibrate your carb for todays gas, and his parts are ethanol resistant. His stuff isn't cheap, but it IS the best!!!
Get his book ,also!

Re: Quadrajet help
 

Yes you might need a rebuild but find the source first. You might be chasing it after a rebuild too.

When you say it comes to an idle after a few minutes, is that from you kicking the high idle off?
And when it does that is the choke completely off?

Re: Quadrajet help
 

Yes, after a few minutes, I'll tap / kick the accelerator to bring the engine to an idle....I'll have to look later today regarding the choke...

Thanks!

Re: Quadrajet help
 

Easiest visual check is look at the tang on the secondary lockout. If it’s dropped off the pin on the end of the secondary shaft then the choke is completely off.

Here’s a pic on a link.

https://www.google.com/search?tbm=is...d5PpmhDXHRHTM:

Re: Quadrajet help
 

It does sound like something in the choke circuit (passenger side of carb) is off somehow.
When they did the work on the truck, did they touch the timing?
I'll take a page from Geezer's book and say check that first to make sure you have (at least) 8°..personally I would recommend 10-12° to start.

Regardless, make sure the choke equipment is working properly....check all carb hoses as well...or simply replace them (they are cheap).
These include the main hose up to the power brake booster, the PCV valve, the short air cleaner connection, the vacuum advance hose, and even the little short one between the choke pull off and the carb.
Also check the transmission vacuum hose which comes down from the upper manifold to the trans.

When the truck is idling...is it smooth? or does it sound a little rough?
...if it not a smooth idle, all cylinders hitting...then you probably have a vacuum leak.

Do you have any pics of your set up?


Coley:chevy:

Re: Quadrajet help
 

Nothing was touch regarding the engine... the truck runs smooth on all cylinders...here are some pic:

Re: Quadrajet help
 

1969 c20....

Re: Quadrajet help
 

Nice pics!
I can see your choke plate wide open but the lockout tang is still hooked on the secondary pin.
Could just be some crud on the tang.
I’d spray it and clean the whole choke area with some carb/choke cleaner first. Then if that doesn’t help we can help you with a couple more possible things to check.

Re: Quadrajet help
 

Thanks again.... will give it a try

Re: Quadrajet help
 

Just an update, I did clean up the carburetor and gave the truck a run later that day...... so far so good...

Will keep you all posted

Thanks !

Re: Quadrajet help
 

I thought I was all set with the idling issue, but it's back. Took it out over the weekend, about 10 mins into the drive while at a stop light, it felt like it was going to stall out, so I place it in neutral until the light change. Not sure on what to check next...

Any suggestions....Thx !

Re: Quadrajet help
 

Spray carb cleaner around the primary throttle shaft on the driver's side and see if the idle speed changes. You likely have a worn bore where the throttle shaft goes through the base plate. If there is a vacuum leak there, it will be covered up by the richer mixture when it is on the choke.

Re: Quadrajet help
 

Check your timing.
What’s your initial timing set at?

Re: Quadrajet help
 

Heading off to work now, I'll check it tomorrow and post it here.....

Re: Quadrajet help
 

Finally got to checking the timing, it's at 2* BTDC . I forgot to mention that it has a electronic ignition set up from prior owner.

Thanks

Re: Quadrajet help
 

No wonder it dies!
Bump your initial up to 12.
You’ll see a world of difference.

Re: Quadrajet help
 

Thanks for your input geezer ! I'll post results tomorrow.


Steve

Re: Quadrajet help
 

Set timing at 12.....went for a drive.... no issues !

Thanks again !

Re: Quadrajet help
 

Good deal!