Think a weak cylinder will ever heal itself?

[TylerW]

Normally, I would say no.

However, my scenario is a bit different. I bought a '79 SWB Scottsdale a couple months back to use and eventually(maybe)restore).

I got this thing cheap because it barely ran. Compression sounded even when it spun over and it didn't make bad noises when it did run so I decided it had some potential.

The engine is a no-name reman 350 with an estimated 60,000 on it. I struggled to get it running right for quite a while. I checked cam lift, timing chain slop, both those passed. I finally realized that the timing pointer and balancer were a mismatch, so the timing was about 30 degrees retarded.

Now, the engine runs much better, idles on it's own, but it still has a slightly rough idle and much more pronounced when cold. I ran a compression test and got 120-125lbs across the board, except for #5 which came in at 90lbs.

I immediately did a wet test which brought that cylinder up to about 135lbs, so evidently there's a ring seal issue looks like.

Here's the backstory on that:

When I got this truck #5 plug was fouled out with gas. In fact, the oil smelled like gas also, which in retrospect was likely from the engine being so far out of tune. The other discovery was that all 4 drains in the heads were stopped up, so the valvetrain was being flooded with oil. I know because when I took off the driver side valve cover about 1/2 a quart dumped out.

So, based on the PO saying it was only used around his farm occasionally for the last several years, I'm surmising that #5 was ran dead a long time and had fuel wash.

Has experience proven that this can reverse itself with use, or has the damage been done? The engine is solid otherwise, no noises, the cam and chain looked great. No smoke at all now.

Thanks for any insight.