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1 = 110
2 = 112
3 = 100
4 = 122
5 = 120
6 = 120

This looks good to me, can anybody offer any insight or helpful info?

Hot engine compression readings?

Best Regards - MM

Compression readings should be within 10% of the highest reading, so no. 3 is a little weak but with a 100psi reading you probably won't notice much of a miss. Try some gas treatment for a couple tankfuls, could be the valve sticking a little. Also when checking compression the highest reading should come up quickly like 4-5 revolutions, if it takes a lot of cranking to get high reading usually indicates sticky valves. Put a couple pumps of oil into the cylinder and recheck compression if reading is alot higher then it indicates worn rings.

Engine was hot, 180 degrees I think? What type of additive, Seafoam or something of the like?
Thanks J mc,Tony!

m-37Bruce wrote:1 = 110
2 = 112
3 = 100
4 = 122
5 = 120
6 = 120

This looks good to me, can anybody offer any insight or helpful info?

#3 is the bottom end of borderline, more likely than not, the miracle additives and supplements will be money spent to no avail. Adding 3 good pumps of oil through the plug hole and retesting #3 will tell the story quickly. If the 100 psi reading remains virtually unchanged after adding oil and retesting, valves are the likely issue, and this is repairable for more miles of service; however if the psi reading goes up significantly, the problem will be ring and cylinder wall wear, and I guess you know what that points to directly.

One may think that since the other cylinders offer a good showing, the issue must be something else besides wear, and sometimes it is; but if the test shows evidence of ring cylinder wall wear, bite the bullet. At best there may be a slight chance opening it up for further investigation may possibly show something that could be repaired to make it serviceable for a while longer; but I've seen precious few cases where it went that way. Most often it comes down to spending bucks in an effort to get by and issue that you see plainly on the wall. Then it is time for a decision; do you spend bucks attempting to patch or go ahead and face the inevitible music of a complete rebuild, which usually in the end cost less overall than wasting $$ on patching, then going back in to do the complete job after you are not happy with the patch.

MSeriesRebuild wrote:

m-37Bruce wrote:1 = 110
2 = 112
3 = 100
4 = 122
5 = 120
6 = 120

This looks good to me, can anybody offer any insight or helpful info?

#3 is the bottom end of borderline, more likely than not, the miracle additives and supplements will be money spent to no avail. Adding 3 good pumps of oil through the plug hole and retesting #3 will tell the story quickly. If the 100 psi reading remains virtually unchanged after adding oil and retesting, valves are the likely issue, and this is repairable for more miles of service; however if the psi reading goes up significantly, the problem will be ring and cylinder wall wear, and I guess you know what that points to directly.

One may think that since the other cylinders offer a good showing, the issue must be something else besides wear, and sometimes it is; but if the test shows evidence of ring cylinder wall wear, bite the bullet. At best there may be a slight chance opening it up for further investigation may possibly show something that could be repaired to make it serviceable for a while longer; but I've seen precious few cases where it went that way. Most often it comes down to spending bucks in an effort to get by and issue that you see plainly on the wall. Then it is time for a decision; do you spend bucks attempting to patch or go ahead and face the inevitible music of a complete rebuild, which usually in the end cost less overall than wasting $$ on patching, then going back in to do the complete job after you are not happy with the patch.

I can do this, I'll do the 3 pumps of oil & see where this takes me.
Thanks Charles, jmacc and Everyone Else,

It doesn't have to be a miracle additive to do this, just some STP gas treatment or Marvel mystery in the gas should free it up if sticking is the problem.

j mccormick wrote:It doesn't have to be a miracle additive to do this, just some STP gas treatment or Marvel mystery in the gas should free it up if sticking is the problem.

Thanks!!

Miracle additives are just a saying I use for all those types of products, not speaking of anything outside of ordinary product lines usually seen on the shelf. I'm simply saying we have seen many cases where people thought spending money on products that make the claim these do is mostly a waste. If a valve is sticky that would cause this, most likey it would free up on its own without anything being added or would stick tight in short order, one of the 2. In fact valves do not usually cause the issue as described above. If they have developed a tendancy to stick, most often they do it well causing a 0 reading. If one is burned ever so slightly, it could be just beginning to leak and produce a 100 psi reading, but that isn't likely to be the case either. With simply a low reading of 100, it is much more likely to be a broken ring or rings that are cutting a groove or simply father time and wear. Sometimes for no apparent reason it just happens prematurely in 1 hole.

Nobody can diagnose it without further investigation, I'm just telling you the normal findings we see based on the info that has been offered about the situation.