Originally Posted by 71fj40guy
Replaced all of the valve springs with a set of Edelbrock 5894 springs. When I lined up all 16 of the old springs it looks like 5 of them were noticeably shorter. After the new springs were installed and adjusted, I took it out for a test drive. The good news is the motor runs a lot better, power is good, and almost all of the mystery noise is gone. The bad new is I can still here it a bit while accelerating and when I hooked up the compressor to swap out the springs the number 4 cylinder was leaking bad and would only hold about 50 psi of air. The number 6 cylinder was also leaking air and would only hold 90 psi of air. All others seem to hold 120 no problem. When running theirs no smoke comming out of the exhaust and it doesn't burn oil. Any ideas why those 2 cylinders would not hold air?
Awesome progress, i can tell you with a certain degree of certainty that the 2 cylinders you are having trouble with either A) have a bent valve or B) are in need of a simple valve job, i dont recall what kind of heads are on the car are they stock? if so they probably need a freshen up, if they are out of the box heads and bolted directly on it is a COMMON problem that when new cylinder heads are built the tolerances are WAY wide, i would recommend taking the heads in to a machine shop have them cleaned inside and out get a 3 angle valve job done to guarantee a tight seal AND!!! when reassembling the engine remember to index the spark plugs, this last part is very important and will effect the overall way you're engine runs, the machinist should check valves for straightness, grind the tips if needed, test the spring pressures to ensure they are within spec, and new valve stem seals, i think if you go this route you will be VERY happy and satisfied with the result. also by removing the heads you will be able to inspect the cylinder walls
this will be good because if you have a broken ring (which i dont think you do) you will see heavy oily buildup on the piston face or even excessive wear on the cylinder wall its self, just remember what you do on one side you should do on the other otherwise you may end up chasing gremlins, and on a side note in regards to you're short springs, some engine have shorter springs on the intake side if im correct and there usually is shims underneath to set the proper height. i hope all my jawing helps out