Engine at normal operating temperature

Compression

#1 #2 #3 #4
110 100 100 100

Compression after 3cc's of 30 wt oil added to each cylinder

#1 #2 #3 #4
110 102 110 110

Vacuum was steady at 16 in hg.

Relatively new plugs look a little foul.

It looks like all cylinders could be higher. However, this is a brand new compression gauge so I have no readings taken previously and I have no way to know if it reads high or low. From what's been explained to me it appears that 3 & 4 have some ring problems because the addition of oil improved the compression. I also suspect some valve guide problems but it wouldn't hurt my feelings if you guys told me I was way off base. So, wade in and tell me what you think.

Dave

Those numbers are a little low, but all the numbers are within 10%, which is a good sign. Looks to me like you have a good motor with a little smoking problem...I'd say keep on driving it...but I will let the experts chime in whith what they think...



Tony

Did you have the throttle wide open as you turn the engine over atleast 5 revolutions? They seem alittle low to me for a 20k motor.


Geoff

Compression test are over rated. Do a leak down test. If you don't have the gauges to do that. Bring each piston up in the cylinder on a compression stroke and braze up an old spark plug and a chuck for you compressor's air line. Then put the car in 5th and have some one apply the brakes and put about 80 psi into the cylinder and listen for where you hear the air leaking out. Oil cap or exhaust or carb you should hear some, but if it sounds like alot ahhhhh...bad news. Then you'll know where the problem is with that cylinder.
I think you have a valve guide/seal issue. I'm not a air cooled experience person. But, that would be my guess.
Good luck

Compression tests are good as they do tell you where its leaking, valves or rings. What more do you need to know.

Geoff