Wierd Compression.

[Zac]

Yesterday I did a compression test on my 82 360 most of the cylinders had 150psi in them but one had 165 and another had 85(untill I squirted oil in there and it went up to 105) I know the low one was because of the piston ring, but why were the others so high? Is it normal for a 360 with 157,000 miles and new cylinder heads to run with that high of a pressure. It isn't carbon build up because when I changed the heads the pistons were a little black but they did not have any build up on them.
If I am getting only 85psi in one cylinder should I run the engine.
Also I did a search on milky buildup in the breather tube. but it didnt say anything about it being caused buy a bad crankcase breather or something like that. Could it be anything like that?
Thanks,
Zac

[Serious Johnson]

Absolute guage readings are not particularly relavent, as they depend on cranking speed, cam overlap, etc. Relative values do tell a useful story.

The fact that squirting oil into the low cylinder brought it a bit closer to the others just confirms that it's probably not a leaky valve.

Milky buildup on the breather tube can result from something as benign as unusually cold winter temperatures, but in concert with a very low compression reading on one cylinder, it likely stems from a blown head gasket, or a cracked block or head.

I wouldn't hesitate to drive something like that for a while, because it probably needs a teardown anyway. Just keep close check on coolant and oil levels.

:-

[Zac]

The low pressure on the one cylinder is from blow by due to a worn out ring. The milky oil started after it got colder it also happened near the time I changed the oil I put pennzoil oil in it could this have anything to do with it. I now know from previous posts that pennzoil sucks and I wont use it again.

[Don S]

Originally posted by Zac:
The low pressure on the one cylinder is from blow by due to a worn out ring. The milky oil started after it got colder it also happened near the time I changed the oil I put pennzoil oil in it could this have anything to do with it. I now know from previous posts that pennzoil sucks and I wont use it again...
Zac:...
...I see you believe in old wives tales and the tooth fairy.
… I checked with an old time peto-cemical engineer who said..
“In the past Pennsoil has been accused of causing problems when added to high mileage engines. The Z-7 in the Pennzoil could possibly loosen various sludge and/or deposits and thus possibly clogging small oil passageways but in these cases the engine was already gone. All modern oils that meet the proper API-SAE ratings are very good”.

… I have been using Pennsoil for over 50 years in about half the cars I’ve owned. I’ve also had very good luck with Valvoline and Kendall. I didn’t like Havoline, Phillips Trop-Atric, or Quaker State.

Just for grins here is a list of the wife and my old daily drivers and still have six running. :D
………Cars & Wagons
AMC Rambler classic wag. 1966. Had it for 30 years now (not running)
Buick Century I-8 Fact. Duel carbs 1938
Cadilacs ’50, ‘51, ‘63
Chevys ‘50sed.del., ‘52ht, ‘55w, ‘61w, ‘66w
DeSoto ‘52
Ford ‘32 Highboy/59A block, ‘46cpe, ‘47
Mavrick cpe ‘70cpe
Plymouths ‘34cpe, ‘34cpe, ‘40cpe, ‘50, ‘51conv., ‘53
two Sentra ‘ 01s
Studebaker ‘51cpe
Toyoda Cressida ‘83
………..P.U.Trucks
Datsun ‘76
GMC ’52 dlx cab
IHC ‘51, ‘55
………..4x4s
AMC Jeep Wagoneers ‘76 401 QT, ‘81 360 PT
D.C. Jeep WJ 4.7 QD ‘99
Nissan KC V-6s ‘95, ‘99
………Murdercycles
BSA ‘53 40”, ‘56 30.5” Goldstar
Honda ‘ 73&1/2 350cc
Indian ‘56 30.5”Tomahawk
Matchless ‘43”
……..Sail Power
Finn US 281 Olympic Raceboat

……OHHH!!! ……I see you’ve all gone to SLEEP…….Sorry ‘bout that…..

Good Luck ;) and CUL.. Don S..

[CowKiller]

quaker state is pennzoil now. pennzoil bough them.