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Just bought a sweet 1970 Roadrunner 3 months ago. Previous owner built car and put in 440 stroked to 496CID. Car has been running great, still runs awesome but noticed different sound like air shooting out somewhere with each revolution. So leak down test fine on all cylinders except cylinder 1 with air heard and felt coming out somewhere between engine block and cylinder head under I can feel but can’t see. So not sure if gasket, cracked head or engine block. I take a picture and it almost looks like a gap in block like a chip in it? Not sure what to do at this point. Haven’t worked too much on engines before so do I start taking apart or take to mechanic? All fluids are fine compression fine on all cylinders. I have all details on build and service manual etc. Thoughts?
First off welcome to the forum.
I personally can't see anything in the photo, but it is possible to have a blown head gasket. Your going to have to tear in down and find out.
Get a spark plug to air hose fitting and pressurize each cylinder to “hear” air coming out exhaust, intake, oil breather or bubbles in radiator at fill neck.
Thanks for reply. Yes I did a cooling system pressure test to all cylinders. There is no air coming out of exhaust, carb, no bubbles in radiator, no leaks coming out of anywhere except externally I can feel air shooting out under cylinder head right by cylinder one, where the head meets the block. It seems like it is a blown gasket. I originally thought it was going to be something with the valve train or a piston ring on piston one etc but not the case. Funny thing is that there is no problems with the oil/radiator fluid mixing, and only cylinder one has a compression drop. So it doesn't seem like the gasket is blown anywhere else but that one little spot. Never seen this before
Yeah I wish the compression was fine. All cylinders were tested and within 10 psi of each other except cylinder 1- which is down by 80psi from the rest.
Down by 80 psi you need to pull the head, I'd try to do it without destroying the gasket. You could have a burnt valve or a bad gasket. With air coming forming the head I'd say you have a gasket issue.
