Thread: Engine miss through out rpm range? SBC

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I installed a newly rebuilt carb on my truck, 84 c-10 Chevy, 350/350. The engine seemed to idle and run fine and since I had recently set the timing prior to the carb switch I ran it like that. It heated up while driving so I checked the timing and it was way advance not even in site. I set it to 6 degrees where it ran fine before and it stumble but idled fine. Set it all the way up to 13 degrees in increments of 2 degrees and it got better each time but is still not perfect. It idles fine now, but as soon as I start to give it gas it misses throughout the rpm range ,if I push it it will backfire. Accelerator pump is working fine and since it goes up in rpm with the same miss I dont believe that the problem. The engine is a older GM Goodwrench crate engine from the early 90's, everything is stock. Any ideas?

I may be out of the ball park here, but I would say check vacuum advance first, then fuel delivery.

thanks . I just put a new vacuum advance over the weekend , the other was bad. Also its hooked to a full vacuum port, not ported.and have a fuel regulator and gauge showing 5lbs on pressure, its a stock set up no mods. I have raised the fuel pressure and it starts to idle rough.

I don`t want to offend your work, but have you double cheched the vacuum advance to ensure its working....? I`ve bought one bad one I know of.

All you did was install another carb and the timing changed?

You could have moved your distributor when installing the carb.

Did you check all of your plug wires for a good connection and that they are not being pinched somewhere.

Did you check the distributor cap to be sure that it is setting correctly on the distributor?

Do you have all of the vacuum lines connected and none of them are cracked & sucking air.

I bought a 52 Chevy PU that had a 283 in it. The complaint from the guy that I bought it from is that it had a miss and that he could not find and it of course was sluggish. He had been fighting with this for over 3 months and was tired of messing with it.

I drove it home and when I went to get out (with it running) I touched the door and got shocked. The guy had 1 plug wire that was too long and it was routed (had moved) between the frame and the inner finder well. You know what that does.

I drove it back the next day because he did not have the pink slip with him when I bought it (he worked with my brother-in-law). I told him what it was and offered to sell it back to him for the same as I bought it for. He said "no" a deal is a deal.

The wires looked fine. Tomorrow I am going to put the old carb back on to see what it does.

You did not say what rebuilt carb you put on it. If it was a Rodchester Q-jet, I have found with those, if you get a good one hold on to it, because when they are bad, they almost can't be fixed.

Of course, that was in the old days. Things might be a bit different now.

Possible burnt valve? Do a compression test.

Originally Posted by BigTruckDriver

thanks . I just put a new vacuum advance over the weekend , the other was bad. Also its hooked to a full vacuum port, not ported.and have a fuel regulator and gauge showing 5lbs on pressure, its a stock set up no mods. I have raised the fuel pressure and it starts to idle rough.

Fuel pressure should not be more than 5psi -

Timing chain jumping? That explains the distributor timing being off, and not running well when you adjust it.

I found one problem , I replaced the fuel pressure gauge on the regulator with another. The first on that I had (new) was reading 5psi. the second on that I put on with out touching a thing but the gauge was reading 3psi. I adjusted and it seems to be doing better. It has a small miss still but does not backfire and stumble like before.