Just rebuilt top end of my Big Boss 400l, what is good compression, I hit 118.

Thanks,
HoopD

 

115 is the service limit on 400's. I would expect your number to increase to around 125 after break in. Checked my 400 after the rings were seated and it was @ 123.

 

118 is good... i would say.. if it was like 80 then i would be conserned but 118 i think anyone would tell you thats ok

 

anything above 100 is considered operatable. optimum is above 115

 

Great thanks!

 

should be rebuild about 75 to up 90 comp psi top end rebuild. your is fine 118 ever good. I was on my explorer 400 had rebuild top end about 5,000-6,000 mile wrost at 38 psi comp bit knock piston on wall cycline look like "slap".

 

118 is good after brake in it will be a bit higher

 

Make sure you get plenty of oil in the Gas for break in