Packard Forum Index » V-8 (1955-56)

Here is just some data for your interest. I replaced plugs and then pulled them after about 1 hr of total running time over several weeks. While I was doing that I checked the compression as well, both dry and with a few squirts of oil in the cylinder.

There isn't necessarily a question here, but I thought y'all would be interested in the results. Your comments are always useful to me. Overall, compression is low and most cylinders do not see a significant increase in compression with oil. This makes me deduce that it could use a valve job more than a engine/piston ring rebuild although I don't have any short term plans for either.

In this pic, the first # is compression 'dry' and the second is compression with oil squirted in.

Note. It isn't on this pic but cyl #8 is 100/105

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IIRC, your car is a '55 Patrician 352" with 8.5 compression ratio. The Shop Manual specifies a cranking compression of 120 lbs/sq in. minimum at 150 RPMs.

Assuming you performed the test as directed; throttle full open, all plugs removed, fully charged battery, yours is definitely lacking.

The next step would be a leak-down test of each cylinder on TDC. This is more exact than a cranking compression test and listening for where the air is leaking will indicate intake, exhaust or rings.

jack vines

Here is an update. I did not perform the compression test as per the manual so I repeated it plus bought a cylinder leak tester (OTC 5609) as per Jack's suggestion:

Compression test was done with engine warmed up from driving around, all plugs removed, throttle blocked full open, and charged/strong battery. Test was done 'dry' with no additional with oil squirted in.

For the Cylinder Leak test, inlet pressure was set to 100 psi.

Cyl, Compression, Cylinder (leak test) psi, Audible location of leak

1, 120, 92, Oil vent/fill tube
2, 120, 90, Oil vent/fill tube
3, 125, 92, Oil vent/fill tube
4, 110, 94, Oil vent/fill tube
5, 120, 92, Oil vent/fill tube
6, 110, 88, Oil vent/fill tube, maybe exhaust
7, 120, 92, Oil vent/fill tube
8, ---, 91, Oil vent/fill tube

(Tried repeatedly but gave up getting compression tester hose into #8....)

Big difference in results by doing the compression test as prescribed. The leak test numbers surprise me as to how high they are. I repeated the tests and got the same values. Odd that #4 had lowest compression but also has lowest leak rate. Any comments regarding the results or test setup are appreciated.

thx
Bob

My only remark:
If the engine starts and runs good. If it will hold a good 80 mph out on the interstate hiway for 15 or 20 miles and there are no undesireable behaivour of the engine while under OPERATION then i would not go looking for problems nor make any attempt to remedy anything that is not just to perfect spec.


OR, in other words, if it ain't broke then don't fix it.

One of the problems with many of the posts about engine issues is that the posts rarely give any history about the engine. Such how many miles are on the engine, any recent major repaairs made or how long (in terms of miles) has the current owner actualy driven the car.

This has been great post. Thank u posting your findings.