I just got my engine rebuilt and did a compression check and am wondering if the numbers are to low. 1966 200 ci cyclinder, manual tranny.

#1 had 120....#2 thru 6 had 145-150.

I did the check with the engine cold,coil disconnected. I thought the numbers should be in the 180 range


Thanks for any help/info

 

That's a pretty wide range for a fresh engine. How many miles on it when this test was done? If the rings aren't seated yet, I'm not surprised. Have you done a wet compression test?

 

Aslong as they are within 10% of each other you will be fine.

 

#1 is not within 10%

 

the engine has about 325 miles on it,, drove around for awhile this am, then only checked the #3 cyclinder(didn't have time to do them all) and it was the same 150,, will check the whole thing this week after I drive around to see if ay of them change,, thanks for getting back to me

 

What is happening to make you want to do a compression check? #1 is a bit troubling but with so few miles it just might be that the rings need some more run time. So in my mind it comes back to whats happening to cause you to do the check.

 

it's hard to tell how high the numbers should be. But as mentioned above, within 10% is normal. So if you have all of them at 150 and one is 120, then there's clearly something wrong with this cylinder (hasket, valves, piston rings, valve seals)
Add a dribble of oil into the cylinder (a teaspoon full of it) and re-test. if pressure improves by a lot then your problem is piston rings (this is called a wet test).

whne testing the cylinders, make sure you have the throttle wide open and choke open at all tests. just mentioning it since you didn't

 

youve only got a few hundred miles on it. geez, check it after a few thousand miles. by the way, did you adjust the valves when you got it, or did you check them. as i remember there solid lifters. if the valves are set right and after a few thousand mies the readings are the same, although id check it warmed up, then id say the shop did something wrong, they should be even, or at least withing a couple pounds of each other. as for the compression, well 180 would be expected from a V8, a 6, depends on the compression ratio and if the rebuilt has lower compression pistons or head on it.