Help. Engine not running right

[twoskies]

Hi
Ok. My truck is a 1972 c10. With a 1979 Chevy 350/4 bolt. Hei. New plugs plug wires. Was running ok to drive. But not quite right. Switched the brake booster to manifold. Capped off the carb outlet. Had the carb rebuilt. Made an improvement but the 4 barrels were not kicking in. Had my carb guy stop by took the carb to check. Changed the jets. Here’s where it went bad. Put the carb back on. Idles great. Can throttle up in neutral. Sounds great. Put in gear. Starts stalling and almost dies. Carb guy gave me a known good carb to try. Just slightly better. Still can’t drive around block. Here’s where’s I went back to basics. Changed plugs again. Checked timing. 10 advance. Put brake booster lines back to original. Put original carb back on. Still runs good at idle but can’t drive anywhere. I do have a good hei from a corvette I might try. Next. Any help appreciated

[geezer#99]

What carb?
Are you blocking off the vac line to thevac pot while setting your timing?
If so bump your initial up to 14.

[twoskies]

rochester quadrajet, and yes im blocking off vacuum when setting timing, just weird it was running ok, just like it was on 2 barrels, i know the back 2 dont kick in right away

Thank You

[geezer#99]

Things to check!
Look for vacuum leaks.
Check the weights and springs move freely in the distributor.
Check the vac pot to see if it holds vacuum.
When the engine is fully warmed up and the choke is fully off, check the secondary lockout has dropped out of the way.
With motor off reach inside the vent on the carb and check the metering rods moves freely up/down.

[Mbeef61]

I agree to check vacuum. Also there are different circuits in the carb. Seems like it could be an issue with one.

I had the opposite issue once. The idle circuit was clogged. It would run with throttle great but wouldn’t idle. Yours will idle but won’t run

Was it cleaned when rebuilt?

[twoskies]

ok, ill check everything tomorrow, yes the carb was cleaned during rebuild, the 2nd carb was a known good running carb

Thanks

[Steeveedee]

You've pretty much eliminated the carburetor as the problem, given that the two tries made little difference. Changing the jets on the original carburetor is a mistake, IMO. It used to run OK with the originals, right!?

Pull the rotor out of the distributor and see what it looks like. If you have high resistance plug wires, the ignition can burn through the rotor to ground. It's an easy check, and is free. Back in the day when I worked on these vehicles, the rotor was the number one failure mode for an HEI. While you're in there, check the distributor cap for carbon tracking between the electrodes.

[twoskies]

Thank You for the responses

ive got the truck running again, although still not right,tried another distributor, bad choice, changed plugs r45ts ac/delco good choice, went through the timing again, top dead center good choice, put original distributor back in good, will fire up and run now,idles great, 12 degrees advance with vacuum advance plugged, try to take off, stumbles and tries to die, if i push clutch in it goes back to idle
rochester quadrajet with electric choke, i did notice the adjustment screws make no difference, but if you throw a rag on top of carb, it dies

ill try to upload pictures tomorrow

sorry everyone, im not a mechanic, just trying to get her running better
again Thank You for the Responses

[geezer#99]

The mix screws not working says you’re idling on the power circuit.
You need to get the primaries closed.
And maybe try a bit more timing.

[twoskies]

Thank You Geezer#99

ok the timing i understand

how do i do the other

[geezer#99]

Pop thecarb off and check the transfer slot.
There’s info in this link for a Holley but your qjet is the same.
http://www.crankshaftcoalition.com/w...EI_distributor

If you can’t get the transfer slot correct you’ll need to find out what’s holding the primaries open.

What’s your idle rpm?

[twoskies]

Thanks for the replies

my carb guy is going to check the carb again and switch the jets back to what they were, so for a couple days im without a carb somewhat, ive got a chance to get an edelbrock for a small block chevy tomorrow so i can try it see what it does
was on a 1975 corvette small block, stock motor

good to try or stay away from it

Thanks

[Steeveedee]

Originally Posted by twoskies

Thanks for the replies

my carb guy is going to check the carb again and switch the jets back to what they were, so for a couple days im without a carb somewhat, ive got a chance to get an edelbrock for a small block chevy tomorrow so i can try it see what it does
was on a 1975 corvette small block, stock motor

good to try or stay away from it

Thanks

Now THAT may or not be jetted right for your truck. Anyone who buys an Edelbrock and doesn't buy the tuning kit usually ends up buying it...unless it runs pig rich and they don't care, since it won't stumble off idle.

[twoskies]

Ok
The edelbrock ended up being a Rochester Quadra jet. Put it on. Got gas. Idles great runs great. It has a vacuum choke that I capped off so right now I have no choke. But it runs good. I’ll figure out the choke. Thanks for all the help

[Steeveedee]

Excellent!