So I bought a used 2000 lightning motor and with the throttle wide open and oil pressure cold the test is coming back at 120-125 on all cylinders. What is stock cold and what the heck do I do to see if its just the rings?

Thanks Dave

 

I don't know what the should have when they are new, but if your within 5 lbs on all cylinders and you have a low of 120, I would think your rings are in good shape.

I remember the old smog motors from the 70's only putting out 75-80 psi when they were new, so if you got 120 on a used L motor, get it put in already and go enjoy it.

If you were to have an engine buider build you two identical motors and have one blueprinted to run N/A and the other blueprinted for forced induction, the N/A motor will pull higher numbers on a compression check then the blown motor will.

 

Thanks Red, I hope your right! I just want to make sure before I run this thing. Anyone know what these put out on a compression test?

 

I will check Ford shop manual, but I would agree that 120 and variation you are seeing is not bad. When I rebuilt my engine, the high boost (14lbs on non L block) waisted the rings and the exhaust valve guides. Valves and cyclinder walls were fine.

 

That would be great if you could check for me Cobra! Just want to put my mind at ease.

 

Those numbers sound about right to me

 

Forgot last night. Promise I will do tonight and post. Ford shop manual (actually Heim) is crap. Its hard as h... to find things.

 

Manual did not call out. Said 75 percent diffrence allowed between high and low. Add oil on low to see if it makes a diffrence. If it does rings, if not valves. Chart showed max pressure from 134 to 250 and low to 101.

 

Thanks Cobra! I dont know why I didnt think of testing my cobra but I went ahead and tested it (03 low compression motor) and it came back at 125-130 with 10k on the factory motor so i am going to run it!