Slant 6 Vibration

nm9stheham said

It is just a rough check to see if anything is really grossly bad on one bore or piston. I was just thinking of how could the OP look for a really bad piston issue, since that seemed to be a concern. I do it only for that reason: just some assurance that a 1-2 reeeeally bad problems aren't there. It does not quantify regular wear in any useful way or tell you anything about rings, grooves, etc.... A broken ring would have typically shown some compression improvement with oil (since the 2nd ring is now the compression ring), and some vertical scars in the bores. It sounds like that is not the case.

The only REAL way to examine a piston is to pull it. That is why a pressure test in cylinder 2 and listening on intake and exhaust would have been good before pulling the head; that would have told the story on the valves, and if one was bad, then would have made a piston issue even less likely.

Click to expand...

I'll check all that on the pistons while the head is at the shop. We've got a place here where you can trade yours in as a core on a rebuilt one, or they will do yours MTO. As long as things check out on the lower end, does increasing the compression by milling the head doom the lower end as long as there's no major known problems? I figured that since it was all apart, might as well give it some gumption. Ideally, I'd like to keep the slant and hop it up via head work (now), a different intake/carb/exhaust combo (later), and even turbo it (MUCH LATER). Slants are an enigma engine for me, and not a belly button engine. I just wasn't willing to do a full rebuild right now if the whole thing was shot, hence if that had been the case, dropping in a v8.

When I put some oil in cylinder 2 to redo the compression test, it jumped from 35 to a whopping 40-45. I didn't figure that qualified as "improvement".