I have a mid 70's 250 in my 53 chevy, Ive been considering a rebuild so decided to do a quick compression test. Im at 125 in all 6 cylinders. Its been awhile, since Ive worked on a auto engine but that seems like fairly goods compression for the 250? am I wrong. did a search, but did come up with what I was looking for a range of numbers and reading. thanks
Sounds like pretty good numbers to me. The real indicator of needing work is if there is a significant variation between cylinders, usually something in excess of 15 psi or so. If you engine is not consuming oil or smoking and runs smoothly.......sounds like you're in good shape. Ray
thats kinda what I was thinking. The 125 is the same is all cylinders. No smoke, just a bit cold blooded, bit of smoke on start up but from too much fuel. thanks
If you do pull it apart, don't be surprised if cylinder #1 has a bigger ridge at the top than the other five----for some reason, the 230/250s I've torn down seem to do that.
Actually, that has been documented and proven through testing procedures. The conclusion arrived at was that on stopping/deceleration, there is little cylinder pressure since the throttle is closed, and the 5 cylinders behind #1 always lean forward due to inertia, putting pressure on the cylinder #1 causing deformation of the bore and wear. Since on acceleration, which is slow with a chevy 6, and the fact the throttle is open, hence greater internal cylinder pressure, the opposite does not occur. Ray
I have an early sixties 250 in my 58Apache. I wish I could get all of mine to read good and even like that. They're good little motors. I like mine.
thanks for all the input. I bought the car with the engine tranny combo in it. Had no idea what was what. She runs strong, just wanted to get a baseline, and know where I stood. I knew that if all the numbers were close, i was looking good. Just wasnt sure about 125 compression, I know it's a low compression engine and all. I think I'll stay with it as is, thanks brad
Please don't take any offense to my above post. I was just in a whimsical mood at the moment I wrote that. I am something of an inliner fan and have a couple of Chevy sixes in my parts room with some ideas how they might be put to use. Ray
The books used to tell compression pressure for a specific engine, ie. 125 psi, now the books say check all cylinders and if they are within 20% from low to high everything is ok. 125 psi in all cylinders is perfect.