Engine: R2 cranking pressure

[Ron Dame]

The shop manual calls for 160 -170 PSI. This 59,000 mile engine shows 123-132 PSI, hot, all plugs out, and throttle open. Oil in two holes made no change, at that point I stopped trying. I'm at 2100 feet altitude, but I doubt it would make that much difference. What is real life cranking pressure on an R2?

[dynolou2]

Ron, Motors says 160 PSI, now if the origional steel head gaskets were replaced with composition head gasket that could explain the difference. Valves not sealing as well after how many years? Valves properly adjusted? Lou Cote

[greyben]

Considering the readings are reasonably consistent it seems unlikely that any wear would be so even across all 8 cylinders. On the other hand the readings you are getting are about what would be expected in an engine with dished pistons.

[PackardV8]

Check your valve adjustment. Note what you've got now and then set them to spec. If they're at all tight, if you've had exhaust valve seat recession, that can lower the cranking compression.

jack vines

[64studeavanti]

Stock cam?

[StudeRich]

/Cut/On the other hand the readings you are getting are about what would be expected in an engine with dished pistons.

However if still stock, an R1 and R2 Both have Flattop Pistons with stock R2 Heads about; 9 to 9.5 Compression Ratio.

[Ron Dame]

Put the borescope in and see I have flat top pistons, but lots of carbon

[64studeavanti]

Just as a double check, measure stroke to ensure you have 289 crank. You never know...

If you have a thick dark layer of 'carbon ' it is likely bad rings as you could be pumping a lot of oil.

[TWChamp]

Usually engines with bad rings will be clean around the outer part of the piston tops.

[Ron Dame]

Best as I can tell from comparing what little I can see to a feeler gauge, the gaskets are around .035". It's not at all accurate, but the best I can guess.

Ron, Motors says 160 PSI, now if the origional steel head gaskets were replaced with composition head gasket that could explain the difference. Valves not sealing as well after how many years? Valves properly adjusted? Lou Cote

- - - Updated - - -

I'm really not using any oil, and the plugs stay clean.

Usually engines with bad rings will be clean around the outer part of the piston tops.

[Ron Dame]

I adjusted the valves to .026"cold today, all were a bit tight, from .023 to .025. Yesterday, the compression was tested with the engine warm, today, cold. Not much difference, maybe 5 pounds. And though it cranked fine, I had forgotten to recharge the battery.
How much difference between hot with a fresh battery and cold with a not too bad, but not too fresh battery should I expect? I hate the idea of putting the plugs in, warmong it up, and pulling them again, but I guess I better get used to it.

[64studeavanti]

Sounds like composite head gaskets instead of shim. There is usually a small portion on the outside edge of the heads where you can inspect. If there are 2 pieces of steel with a filler, they are not the shim gaskets. Could lower compression to about 8.5.

[PackardV8]

I adjusted the valves to .026"cold today, all were a bit tight, from .023 to .025. Yesterday, the compression was tested with the engine warm, today, cold. Not much difference, maybe 5 pounds. And though it cranked fine, I had forgotten to recharge the battery.
How much difference between hot with a fresh battery and cold with a not too bad, but not too fresh battery should I expect? I hate the idea of putting the plugs in, warmong it up, and pulling them again, but I guess I better get used to it.

All the Shop Manual specs are for cold cranking compression.

And yes, having a fully charged battery cranking over fast does make a noticeable difference on some engines.

jack vines

[Chipmaker]

Any chance you have a bad gage? I have seen the ones with the rubber hose between the plug hole adopter and gage go bad, and flex out when cranking.

[Jeffry Cassel]

If you checked it cold it is probably okay. Warm it up to operating temp 160 deg and check again. It'll be higher. If there is no blow-by or excessive oil consumption, I wouldn't lose a wink of sleep over it----it wouldn't be worth dropping several grand into it just to raise compression 20 psi.