Thread: SBC 350 - Only certain cylinders are firing. HELP!

Tweet

Alright, here's my story:
I got a 75 k10 from a local widow. Said it was her husbands old truck way back when.
Motor was garbage, so i yanked it, bought a 76 k10 with a goodwrench motor with low miles that pretty much just sat for the last few years. Pulled that motor out, dropped an aluminum intake and a edelbrock 1406 on it and then dropped it in my 75. I put headers on it, then had it welded to fit the existing exhaust. It ran decent, but smoked a bit. LEft out of town for like a month, came back to a truck that wont run. I was mind boggled. Pulled and swapped distributors out, but still wont run.
Curiously unbolted my exhaust, and then it started to run kind of
Ends up theres nesting from rodents and such all in the mufflers, jamming it up. (also causing some smoke.
Now i'm here. Only a few cylinders are firing. then when you push the throttle a little bit in, it starts to fire a few more, but still not all. I'm sure i have tdc, and i have good gas. Wires are in the right firing order, and when i put my timing light on each wire they all light up, so theyre getting spark. I also have a wire with a switch going from the battery straight to the dist., as others have suggested to get that out of the picture. I JUST pulled the plugs out, (they were brand new from autozone when i dropped the motor in a few months ago) gaps look good, they're all black but should give spark. Next i'l put them in the wires to make sure i'm seeing a spark.



ANYONE have ANY idea what else could cause only a few cylinders to fire?
Thanks in advanced.

I think there's still junk in the exhaust and bottling up the engine. To test, unbolt the headers and then test run.

I once had a 76 dodge p'u and the converter plugged up and it stopped dead.. and there used to be a practical joke where you'd push a potato into the tailpipe, big enough to stop all flow.. car would start for a few seconds never to run again if the potato (and the exhaust) were sealed tight.

I had a customer from the shop who backed into a snowpile then went into a store.. when he came out his car wouldn't start.. he called me and I was lucky to hear the exhaust pipe wheezing.. I used a tire iron to poke a hole in the pipe and it started and once hot enough it blew the snow out and was fine.

So try it, it might surprise you..

Originally Posted by 34_40

I think there's still junk in the exhaust and bottling up the engine. To test, unbolt the headers and then test run.

I once had a 76 dodge p'u and the converter plugged up and it stopped dead.. and there used to be a practical joke where you'd push a potato into the tailpipe, big enough to stop all flow.. car would start for a few seconds never to run again if the potato (and the exhaust) were sealed tight.

I had a customer from the shop who backed into a snowpile then went into a store.. when he came out his car wouldn't start.. he called me and I was lucky to hear the exhaust pipe wheezing.. I used a tire iron to poke a hole in the pipe and it started and once hot enough it blew the snow out and was fine.

So try it, it might surprise you..

I'm actually still unbolted. I haven't bolted up since.

I'd invest in a new set of quality spark plugs. I'm thinking you fouled the ones you have so bad you may not be able to clean them. Plugs are not that expensive, and replacing them with a known good set eliminates them as a problem. I like NGK's.

An old trick we used to do to clear fouled plugs was to put the plug wire on them loosely so the spark had to jump a little to the plug before lighting the plug off. Theory was that it made the plug run hotter and cleaned it up, don't know, but had success with the method a couple of times way back when I was a young man, if the plug wasn't too fouled.

Doesn't cost anything to try it and only takes a two or three minutes to see wether it is going to work or not. Course back then, we used to lightly sprinkle borax down the carb to re-seat the rings on a worn motor too. I'm not recommending that though. LOL!

Originally Posted by 36 sedan

Course back then, we used to lightly sprinkle borax down the carb to re-seat the rings on a worn motor too.

Don't know about borax, but have used feldspar and limestone (Bon-Ami cleaner) to seat rings.

.

But, did you use benzene to clean plugs? LOL!