Sputtering off idle under load...
 

I have a 69 Chevy with a fairly new crate 350 with the original manifold and Qjet carb. Just resently it has started to sputter off idle under load. The engine idles great and in park I can rev it slow or fast and it sounds great.

I'm not a trained mechanic but I'm able to figure things out by asking questions and reading from manuals. My first thought was this has to be a vacuum advance problem. Then some other said it sounds like a fuel starve situation. What do you guys think it is and how would I go about testing to determine exactly what is causing this?

BTW, the carb ID is 7029207 with indicates that it was for a manual transmission. I have a TT400. The original owner said the carb was stock. What's the differenc between this carb and on made for an automatic?

Thanks in advance for any help.

Ken

Re: Sputtering off idle under load...
 

it looks like you beat me to posting this same question. pm if you found your problem.

Re: Sputtering off idle under load...
 

x2, i had a very similar question as well

Re: Sputtering off idle under load...
 

Since it just started doing it, I'd check for vacuum leaks and fuel delivery first. Make sure all the filters are clean and that the pump is squirting a strong stream when you crank it. I believe it should be around 4 or 5 psi and fill a plastic pint container in 20-30 seconds.

After that, you have to dig into the ignition and make sure your wires, coil, distributor components such as rotor, condenser are good. I'd check the timing even though you said it was running fine before. This is just in case something else caused it to go off.

Check the mechanical advance to make sure they move freely.

Check the vacuum advance by putting some negative pressure (sounds better than sucking ;) ) on the hose to the carb. It should move easily and hold in place as long as you continue placing negative pressure.

Then after all this, you will probably have to do the deed and dig into the quadrajet... Not the easiest to take apart but it could have some gunk in iside.

Can't think of other things to check at this time.

Re: Sputtering off idle under load...
 

these are good ideas. thanks for the help. the original thread is alittle old. i have a edelbrock 1406 on mine.

thanks.

Re: Sputtering off idle under load...
 

its not going to be fuel delivery, it would act up at higher RPMs first. It could be a carb issue, but I would dig into the tune up first. Swap out the plugs, and then inspect the cap and rotor, with the newer craptastic made in china parts, I have noticed that the new caps and rotors just don't hold up like they used to. Also check the plug wires for burns like where they go real close to the manifolds.
If the tune up is good, then you can start looking into the carb.
I wouldn't even consider timing. if the hold down bolt is tight on the dist clamp, then there should be no reason to even consider it. (assuming it was properly set to begin with)