Low Compression

[PRM Motorsport]

Looking to buy another car. It has a sealed 1250 with about 10 races on it.  A couple cylinders are reading low on compression. Owner is convinced it just needs the valves adjusted.  Could valves out of adjusment be a potential cause for the low compression?  Thanks

[knoxracing]

what do you consider low? What are the numbers cross the 4 cylinders?

[VMS Motorsports]

They checked the engines of some of the guys up here that went to the Knoxville race this week, had sealed 1250's with compression between 135 and 150. Both of those engines were new this year and are in multiple feature winning cars.

Like Dennis said, what's low, and what is the range of difference?

[Winterracing]

hot or cold? If the valves are tight (which can happen with new motors) then yes compression numbers can be low, like the others have said what are the numbers.  Also make sure the guage is correct, I have a longacre one that's 15 psi off.

Dan

[PRM Motorsport]

Checked cold with throttle full open the compression numbers were from front to back: 120,  90,  70,  120.

[Gimpster]

 Do a dry compression test (battery fully charged and carbs held wide open or removed) document the numbers. Put a squirt or two of oil in each hole,  do another compression test on each cylinder. If the compression comes up, it is a piston or ring issue. If it doesnt come up then it is valve or head gasket related. Fire the engine up after the wet test and let it warm up. Torque the head and do another dry compression test.

~G~

[PRM Motorsport]

I'll give it a shot and let you know how it goes.  Thanks G!