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350 c.u.i.
02-08-2017, 02:19 PM
Post: #1
350 c.u.i.
Well I have a 1974 chev.3/4 t 4x4 pick-up. I put a 1980 350 motor in. It starts and runs on six cylinders. It seems to gas foul #3, #5 cylinders. I have replaced plugs until I am blue in the face. I even double checked the valve adjustment. I have a 0 lash plus 1/4 turn setting. ( yes Hydr. Lifters). It still gases those two cyl. Does anyone have a suggestion? Everything is new dist., coil, ign.module, cap, rotor cap, wires, plugs. the only thing not new is the carb. it is rebuilt. the wiring harness is a nightmare. I am starting to think of replacing the harness, but that doesn't explain the gas fouling.
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02-08-2017, 09:18 PM
Post: #2
RE: 350 c.u.i.
Maybe the head gaskets may be blown between those two
Cylinders. Or the block might be cracked there
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02-08-2017, 10:25 PM
Post: #3
RE: 350 c.u.i.
Let's hold the head gasket possibility in reserve till we do some diagnosis, plus sort out what we have under the hood.

Let's start with who rebuilt the engine: Brand name or local shop?
I presume the original engine had a carb and the intake parts got transferred from the old engine to the new one, right?
I'll also presume your mention of fouled plugs means black with carbon deposits, and the rest are the normal tan color, right?
Does the new distributor have points or an electronic pick-up?
If it's electronic ignition, did you swap any of the old parts over?
Have you checked to see if you have spark at the end of those plug wires when it's running?

Have you done a compression test to see if all cyls are near the same?
Have you double checked the firing order to confirm that's correct?
Does it run well when the plugs are first put in?
Is the choke hanging up causing the cyls with the short runners to foul first?
Is the choke pull-off working properly?
If you look down the carb with the engine running do you see any fuel dripping, especially on that one side?

If we can get answers to these questions then we can start to narrow down the problem.
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