I actually posted the cut and paste below in the big block forum, but did not have too many replies. So, I thought I would repost here, hoping for a little sage advice. The main thing: I understand I won't know the whole story until I pull the heads, but thinking I was 100% in this thing for piston rings, a guy at the auto parts store looked at my numbers below and recommended leaving them alone, that the second number is what I needed to look at, and that those all showed fine. So, for clarification of the original:

1. The three culprits for fouled plugs are bad piston rings, bad valve guide seals, and/or a bad head gasket, right? In other words, if your plugs are being fouled it would be from one of those three things alone, or are there others?

2. Is it only the second compression number that matters, or the first? I was led to believe that the first rollover mattered, whereas I'm being told it's the number on the seventh that counts.

3. Anyone ever have a radiator that BREATHES on these trucks? What I mean, is sometimes, when the truck hasn't even been run in a day or two, the radiator will end up with pressure on it, and also, you can see the level in the puke tank rise and fall, too--again, without the truck having been cranked. Is this the sign of a head gasket starting to go?

The truck runs awesome besides, now that I did a bunch of other things to it from where it'd been sitting up for years, more than anything, it's just fouling plugs and stutters some when accelerating or backing off. Also it DOES HAVE SORT OF A SWEET SICKLY SMELL TO THE EXHAUST, though no smoke, and though, if I am indeed losing coolant, man, it's so little as to not be able to tell it visibly, at least, driving it the short distances I have in testing it out.


Anyway, I'm desperate here and don't want to do more than I need to, but don't want to tear the top off an not do the rings if I need to, too. Below is the original post and my compression numbers, though I did the wet test and am adding those numbers, as well. I'm really thinking the low first stroke between one and two may be the head gasket, but... that's what I'm posting.

ORIGINAL POST:

Problem: This 89 F250 I bought is fouling plugs 1, 5, 7, and 4, though only a tad, tad bit on no. 4, whereas the others are conspicuously being fouled. The truck, after other work I've done, actually runs great, though it is burning oil, it turns out. So, I rented a compression tester to see what I came up with and am posting the numbers below, with what I think I'm looking at.

Procedure:

Engine at operating temp
All plugs removed
Throttle held wide open
Turned each over x7, as per Haynes
Two numbers are listed below; the first number is what the pressure hit on first stroke, the last number is what it achieved after the seventh turn

I then went back and add a few squirts of 30wt oil to number 1 and 2, turned it over a couple of times to let the oil settle in the cylinder, and rechecked it.

Numbers: Dry------------------ Wet

Cylinder 1: 90 psi/175 psi-------120/175
Cylinder 2: 90/175--------------120/175
Cylinder 3: 120/175
Cylinder 4: 120/180
Cylinder 5: 115/175
Cylinder 6: 100/175
Cylinder 7: 115/180
Cylinder 8: 120/190

My thought is head gasket, not bad rings, but I'm told the wet test should not make a difference if that is the case, and adding oil did increase the initial reading on 1 and 2, too.

I actually came up with 60 psi as the first stroke on the number 1, but thought that was an anomaly and went back to it after I'd done the rest and came up with 90 psi.

DIAGNOSIS:

I'm thinking I need to go ahead and replace the piston rings when I tear it down to deal with the oil issue up top (I'm not pulling the motor, so I won't be doing the crank- or camshaft or main bearings, but will do the rest), but that the oil on five and seven is probably valve guide seals, while the issue on 1 is probably the rings themselves, or a combination??? One is being fouled the most, with five and seven coming in a close second. Does that sound close to due north, or am I off on what I'm thinking?

Mainly, I'm just thinking I need to pull the heads and make sure they're okay, and rework valve guide seals and o-rings or anything else up top (not sure about the valves themselves), but that I might as well replace the rod bearings, wrist pins, and piston rings while I'm at it (as I can do all this with the block still in the truck, which is how I'm going to have to do it--and, PLEASE, no commentary about how I should pull the motor, as I'm not setup like most of you to be able to; having removed the y-pipe and jacked the engine up off the frame to replace the oil pan gasket and check the rear main, I think I can manage it this way and not tear up all the work on the timing cover gasket, front main seal, water pump, etc., I've just recently done).



Again, I'm doing this with the block in the truck--it can be done, I know for sure--and am just not sure which way is up: one minute, I think I need to go ahead and overhaul the bottom, the next I'm being told I don't need to, and I just don't know.