Carb Issues

[jgonzo]

So I did the basic rebuild on my 2100 2 barrel for my 72 351c motor. The car has been sitting since '99 and all the gaskets leaked like a fountain. The rebuild, or should I say the parts and gasket replacement, went fine. The car runs out good, choke works good and no leaks. The issue I am having is that I can't give it any gas without a carb backfire. There isn't much adjustment with these things so I'm not really sure what to do. The mixture screws are at 1 1/2 turns out according to the factory manual. They were at 3 1/2 out and that's the way I ran it at first because I just matched what it was before the rebuild. I thought maybe that was the issue but it wasn't. Any help would be great..........jim

 

[captthundarr]

Check for vacuum leaks, check your timing.

 

[coilwire]

+1 on checking the timing. Had the same problem backfiring through the carb. It turned out to be a timimg issue.

Jim

 

[Don C]

The idle mixture screws may need adjusting. Adjust for the highest rpm or manifold vacuum. If the idle speed gets too high back it down.

Also check the accelerator pump action. Look down the carburetor and pump the throttle a couple of times to make sure they're squirting.

The most common causes are timing and lean issues (vacuum leaks or carburetor).

 

[jgonzo]

No vacuum leak that I can detect, accelerator pump squirting nicely. I will check the timing and keep messing with the mixture screws. Thanks for the responces...... I'll keep trying. Please keep the suggestions coming, I appreciate them.........

 

[MeZapU]

Take the top of the carb off and I bet your main jets are clogged with debris or corrosion. I had the same issue way back when I let the car sit for a year. Car would start and idle fine, but would not "take the gas" when you stepped on the pedal. It would cough and shudder. As soon as I would lift the throttle it would idle fine again.

I'd also clean the booster assembly and blow out any debris with compressed air.

 

[jgonzo]

Take the top of the carb off and I bet your main jets are clogged with debris or corrosion. I had the same issue way back when I let the car sit for a year. Car would start and idle fine, but would not "take the gas" when you stepped on the pedal. It would cough and shudder. As soon as I would lift the throttle it would idle fine again.

I'd also clean the booster assembly and blow out any debris with compressed air.

I'll check the mains this weekend.......Good tip, when I was in there cleaning I could not get them out on the bench. Strapped to the car now may give me more torque so I should have better luck getting them out........thanks

 

[jgonzo]

Well I pulled the top of the carb off this weekend to check the jets. Got them out no problem........I did a great job when I cleaned and rebuilt because they were spotless. Put it back together and played with the needles some.....still ran the same. Next I thought, I better check the firing order, just to be sure. The manual says firing order is (according to the cap drawing) 15426378...........................unless the motor is a 351c or 400m, then firing order is 13726548.........oops.......car runs great now. Recheck the small print, sometimes it can really help. I know, d!psh!t, but at least I did figure it out.............

Wanted to make sure motor was good before I start the removal of the radiator support and front aprons from the collision......Onward!!!!

Thanks for all the help.

 

[Mikes73]

We've all been there, glad you figured it out.