jtranger

I just bought a new compression gauge and took readings on my '65 327/365. I obtained readings on the drivers side bank of 190 psi and 200 psi on the passenger side bank. The ST60 indicates that the compression should be 150 psi. What gives? I got the motor the way it is and it appears stock and numbers matching, although I do not know what kind of pistons it now has. Any idea's? Engine guys please chime in. Thanks Larry

L78racer

compression is dependant on cam profile, cam timing, deck height, head chamber volume, head gasket thickness etc. if anything has been done to the engine; you can expect to see some variance to "stock" numbers. are the heads the correct casting number? are they the same rt and left? if the block has been decked and/ or the heads cut to clean them up it will affect your readings. valve lash with solid lifters will also affect compression readings

jtranger

The head casting numbers are stock and match the date of the block. I do not know anymore about the internals of the engine. Cam also appears stock by a smooth idle. I do not know if it is over bored or if that would effect the compression numbers.

66BlkBB

You might want to check your compression tester on another engine to see how it reads. Try to pick a newer or rebuilt unit. Should give you some idea if it is the tester or your compression is higher than normal. Just a thought.

Steve

67L36Driver

It ain't broke so don't plan on 'fixing' it.

Check your compression tester guage against your air compressor guage.

DansYellow66

I'm a big block owner so I may not have a good frame of reference - but if your 327/365 idles smooth I would suggest you don't have the stock cam. And the cam you have probably has less duration and overlap - thus with high compression pistons you have high cranking cylinder pressure. Does it sound like a solid lifter cam?

aaronz28

It is most likely that you do not have the stock 30-30 cam in that car.

it is not uncommon during rebuilds that people switch the original L76 cam with a smaller piece (any less duration or wider LSA will increase cylinder pressure)


if it sounds like the stock cam (lopey idle) its possible and probably that someone installed the LT1 cam... which would bring your cylinder pressure up some.

If all 8 cylinders read within a few lbs of each other... don't worry. Just drive it and have fun.
Thanks

Aaron

ghoastrider1

I agree completely.I When something is amiss with a "calibration tool," alwas check the tool first.I am thinking with 200 CP,that thing would be pinging like crazy evertime you gassed her.