got a 1968 440 its D stamped that makes it 68 right?
anyways had it compression tested and this was the results i got syl-psi: 8-150, 6-140, 4-135, 2-145, 7-150, 5-150, 3-150, 1-155,
this makes it a kinda low compression engine right? anyways you can all see that there is some gap in the numbers. but is it so bad i should take it to a shop and get it fixed?
the engine got edelbrock rpm heads. and probably some sort of edelbrock cams.
thanks in advance for any tips. :cheers:
My understanding is that the compression measured with a compression tester is referred to as dynamic compression and the link to static compression (which is the ratio of the compressed volume to the swept volume in the cylinder) is complex, depending on things like the point at which the valves open and close on the compression stroke (so the cam mostly). This makes it difficult to directly relate the cylinder pressure to the compression ratio usually given. For some reason the pressure measured also does not simply scale with compression and atmospheric pressure (~14-15 psi), I had thought because of adiabatic or semiadiabatic heating but someone else said that was not the case.
I think the key then is whether the numbers are in the ballpark range where you would expect them to be (this depends on cam, but I believe 150 PSI is acceptable) and also on how much difference there is cylinder to cylinder. You numbers look within +/- 7% of each other. I do not know whether that is considered good or bad. Others on the board will be able to tell.
From a health standpoint, it is good. From a static compression standpoint, we need specs on the cam. Is there a problem that has taken you to a compression test?
no idea of what kind of cam it is, never looked, and i simply forgot to ask the last owner when i bought my car :smilielol:
but it has a edelbrock rpm dual intake and 2 edelbrock 650 carbs,
together with the edelbrock rpm heads i can guess there is some sort of package from edelbrock with a mild cam included.
i sent my car to the shop to tune the carburetors, and some other small stuff here and there, gave up trying to dial in dual carbs.
and yes the car was not running properly so wanted a check up.
and now it looks like i am going to upgrade to a electric msd ignition system with ignition control. and let the mechanic install it.
apparently i hate having money in the bank... :2thumbs:
i guess since the car is already at the shop i can ask them to check what kind of cam the engine has.. they cant charge much for that right? ;)
Before you spend the $ on MSD I would recommend checking with FireFighter3931 on the Firecore ignition solution.
D is 68.
I don't see any cause for concern unless you just want to got through it to increase output.