onefast65 said:
I assume that a crack between the intake and exhaust ports would create low compression. I have 150-160 on all cylinders, including number 4. I have new lifters on order.
I don't think a crack between the intake and exhaust ports would effect compression, unless the crack extended into the combustion chamber.
The crack theory does seem like a bit of a long shot, but you have already eliminated a lot of the likely causes, so it might be worth looking into.
There is definitely something going on in that #4 cylinder though. Is it possible your intake gasket wasn't sealing well around the #4 intake port, and you were sucking oil from the lifter valley?
You said you swapped injectors already, correct? Is it possible that your wiring for #4 injector is defective somehow? I just noticed you swapped the injector harness plugs, so maybe that's not an issue.
I would double check the plug wire and plug just to be sure.
Have you tried a different distributor cap? I just did some work on my buddy's '68, and the distributor cap looked fine, but it wasn't firing 2 cylinders.
I agree with 310 stanger that it could still be a valve issue. If your intake valve was too tight, it would let combustion gasses back into the intake, making the port black and likely causing a miss too.
You could always adjust that one cylinder with the engine running. I know it's not the preferred method, but it will work.
I know some of the things I said may be a stretch, but I'm just throwing ideas out there. Good luck and let us know how it goes.
Jeff