Did my first compression test: thoughts?

[swelltimes]

Now that it's not below freezing here in MA, I've been trying to get out to the shop to get some projects done on my truck.

I took the carb off last weekend, for a rebuild, and posted about that. In the process, I learned I need to replace the oil galley plug: thanks to @John McVicker and @unklwedy for the heads up on that.

Since I'm already into some engine / carb work, I tested the compression today.

Here's what I found, starting with cylinder 6 at the fire wall, and dry / wet testing numbers:
6: 145 / 150
5: 120 / 120
4: 120 / 125
3: 120 / 120
2: 100 / 115
1: 145 / 150

There are two symptoms that lead me to believe I need to check compression.

1; when I was parked on a relatively steep hill, with parking brake engaged (parking brake needs to be tightened), the truck rolled backwards, "pulsing" as it rolled slowly. I was in the truck, and used the foot brake to stop the rolling, but took note.

2; when in 1st gear, foot off the brake, and descending a steep driveway, I get a sound from the tailpipe like backfiring / rumbling. Same thing happens if I let off the gas when going downhill, even in 3rd gear.

So, that's the info that I have. Keep in mind I'm new to wrenching on a 2F.

I'm curious to hear MUD's collective thoughts on what my next best move is. I'm posting some pics of the process, and the 'plugs that I pulled out (clearly need to be replaced, also assuming other issues).

 

[John McVicker]

Those numbers are not really 'that' bad. And the difference between wet & dry differences with the exception of #2 is not that bad either. Plenty of f/2f's are running around with worse.

However, now would be the time to adjust your valves & then recheck your compression.

 

[thebigredrocker]

Had nearly the same exact numbers on my F. Spent some time dialing the valves in, sealed up a intake manifold leak, compression numbers went way up.

 

[brian]

no.2 symptom has nothing to do with compression or lack there of.
it does have something to do with the overly rich condition that your plugs are showing.

 

[Pete]

I agree with the other guys. Those compression numbers suggest to me a tired motor but still within factory specs and one you can probably get several thousand more miles out of. If I recall correctly and the old memory ain't what it used to be, minimum compression I think is 114 psi. I'd do the easy stuff first like adjust the valves then recheck the compression.

Pete

 

[swelltimes]

OK, great. I'll do the valve adjustment and report back, after I get the carb rebuilt and put back on. I'm assuming that dialing in the carb tune a bit better will help with the richness of the gas / fouling of plugs.

 

[LAMBCRUSHER]

yes, it will.

 

[swelltimes]

Pulled the valve cover today to deal with the oil galley plug and valve adjustment.

I was surprised to find that the 4 nuts holding the valve cover on were only on there finger tight or so...

Looks like some corrosion back by cylinders 5 / 6, so hopefully that won't impede things too much as I dig further into this project.