firetird

i was curious if anyone could help me out on this. the problem im having is that i did a compression check on my 95 t/a and i got approx 175-180 psi except for cylinders 7 and 8. i only got about 155-160 psi on those two. so i adjusted my valves to where i got 175-180 psi just like the other cylinders. well i started my car and the rockers for those two cylinders were making alot of noise so i had to tighten them up, making me loose compression. now im wondering what my problem could be, a weak spring or bad lifter? i just rebuilt the motor about 4000 miles ago and put new springs, valve job, rings, bearings, and cam. what could my problem be? btw i have a 236 duration cam, i dont know if that makes a difference.

JamesNobles

Well, they are that low...let me explain...

When doing a comp. test, you need to compare the highest reading to the lowest reading. Then if the lowest reading is less than 75% of the highest readings, then you have problems!! 75% of 175-180psi is approx 131 psi. So you are in that range.

If you are still doubting and worried, pour a tablespoon of oil into the cylinder through the spark plug hole. If the pressure rises then it means your piston rings are bad and/or your cylinder bores are damaged or worn.

If If the pressure remains low, the valves may not be seated properly (need valvejob) or the head gasket may be blown near that cylinder.

If the compression in any two adjacent cylinders is low, and if the addition of oil doesnt help raise compression, there is a leakage past the head gasket. Oil and coolant in the combustion chamber, combined with blue or constan white smoke from the tail pipe are Visible symptoms of the problems....

Hope that helps!!

James

firetird

thanks for the help. about your suggestion to pour a tablespoon of oil in the spark plug hole to see if it raises the compression, would that be something that the original compression test would not have caught? i had the blocked honed and new rings put in. the cylinder wall came out to only have two thouandths play in them. i also had a valve job done by the best in the business and he went over them twice. the same gentleman the did my motor when i rebuilt it told me that it sounds like those two lifters are not operating like they should. i also did a radiator pressure check to see if a head gasket was blown but that turned out ok. i guess that i am being paranoid about those two cylinders not being quite as strong as the rest.

JamesNobles

Well thats why I said as long as they are within 75% of the highest reading....which they are!! So you should be good...Those were just suggestions to maybe further your knowledge on where you are losing pressure.....