Carb disassembled, cleaned, still runs poor please help!

[Black70c10]

I have a rubber line running from the brake booster to the intake manifold. It's a very sturdy line, would be surprised if it collapses but I'll check it out this afternoon.

So I've heard one response for and one against the idea that covering the carburetor with my hands with unveil a vacuum leak.. Seems to make sense to me, and it definitely increases RPM and runs smoother when I do this. I would think if there weren't a vacuum leak, covering the air would choke out the engine and it would struggle not run better

With the truck off, when I pump and hold the brake pedal, it holds tight and I hear no hissing or any type of sound that would indicate the booster is leaking...

Man I hope I don't have to get into the intake manifold... Sounds like fun

[CC69Rat]

Reading back through the posts, and I should have read a bit better .. I agree about the vacuum leak. Have you replaced the gasket underneath the carb to the intake?

I had an Edelbrock carb issue a while back and ended up replacing the engine yes .. the entire engine for a crate swap, .. put it back together with the same intake and carb.. and the bog, hesitation, vacuum leak symtoms you described just moved over to the new engine.

The end all fix was the gasket under the carb. The edge of it had kinda burned through a little and created a huge vacuum leak.

Do you have a carb spacer under the Edelbrock (ex. Intake, gasket, spacer, gasket, then the carb) Could one of those gaskets be leaking?

[Black70c10]

Sweet relief!

Thank you all so much for the help. CCRat's last post got me to thinking. So as I was getting ready to take the intake manifold off, I looked closer at the gasket and sure enough there was a tiny hair line fracture on the corner... I cannot believe this is responsible for completely upsetting the idle..

I replaced it and she's back to running normal. Idle speed screw has a normal impact on rpm with a fraction of a turn, idle mixture screws affect idle, does not want to stumble off the line..

Learned a lot through the troubleshooting process but I still can't believe how much of an effect that tiny fracture had.. Thanks again for all your effort

[swamp rat]

Glad ya got it figured out! man its difficult to diagnose a problem when your behind a keyboard a couple thousand miles away LOL!

[DGulliver]

This board rocks!! You guys are awesome..

[70SBC10BOB]

Great job! Some times you just got to be more stubborn than the d%$#%# truck.

70SBC10BOB

[Black70c10]

That's the truth! It was driving me nuts, especially how it came out of no where...my equilibrium has been restored

[Motoxrrar]

I had a similar issue where I was rebuilding the carb every month. Turned out it didn't have an 6.0 LS in it. So I swapped that out for a gen 4 and never had any problems from there.

I live in Arizona where it was really dry kept drying up accelerator pump and getting a flat spot in the carb.

[CC69Rat]

Glad you got it worked out ! I take Visa, MasterCard and Discover. . ..kidding..

It must be something about the way those Edelbrocks are made(?). The base might be shaped a little different in that area or whatever.. that gasket just looked a little thin. We replaced it and it fixed the problem. Only cost me about $3k..

Later..

[Steeveedee]

While I realize that the original problem has been solved, I'd like to offer a suggestion that can help isolate carburetor problems. I had a problem with my 600 CFM Edelbrock carb awhile back, and rebuilt it. During the process, I noticed that the throttle valves could move quite a bit in the throttle body. I took the thing to a carb shop and had bushings put in. The throttle body wears, and you can get a vacuum leak, or it will not return to a nice idle due to the mispositioning of the throttle blades. A simple check is to spray carb cleaner on the throttle shaft on either side of the primaries. Any variation in engine speed indicates a leak, and the necessity of this repair.o the

Generally, problems with a bad running engine are related to the ignition. Electronic ignition systems have pretty much eliminated that.

[Steeveedee]

Originally Posted by Motoxrrar

I had a similar issue where I was rebuilding the carb every month. Turned out it didn't have an 6.0 LS in it. So I swapped that out for a gen 4 and never had any problems from there.

I live in Arizona where it was really dry kept drying up accelerator pump and getting a flat spot in the carb.

This was likely caused by higher levels of ethanol in the fuel. There are kits made special that have a different type of accelerator pump diaphragm that is immune to the ethanol. Search the intertubes...

[litew8]

Great job CC69Rat and Black70c10 for the follow-through. I think it was/is a carb issue and not a vacuum system issue. Granted they are intertwined, vacuum system leak and carb issues aren't the same imho Holding your hand over the carb - you were manually choking it, it ran better and from that conclusion, isolated to the carb itself.