Econoline":1mow3jur said:+1, you'll know everything you need to know after you do a leak down or do what B RON CO says. It may be a valve or lifter/valvetrain issue.
The #6 cylinder seems to be the most susceptible to lean burn and detonation damage from too much timing or heat. I wouldn't be surprised if a ring land is broken or damaged.
Well, unfortunately, it's my understanding that the engine hasn't been run since the rebuild the owner before last did. Which means if it's a problem with the rings, it's probably an actual broken ring, which means hoping it didn't score the hell out of the bore, or get stuck in any of the bearings.
Econoline":1mow3jur said:Or swap to a V8, once you go down the path of the lowly straight 6 you can get hooked. Turn back while you still can!
Unfortunately, that's the likely scenario if the motor needs pulled and rebuilt. The car would have already gotten an upgraded rear end, and then new 5 lug hubs in front to match, so dropping a V8 in isn't going to be that much extra work when it comes to it. It's probably also likely to be a similar price, which really doesn't leave much downside to doing it in my mind.
I'll check out the valves and wet test it before I write off the motor, but I'm not hopeful, a mechanical timing issue with the cam should result in low readings in at least one other cylinder, and any pushrod/rocker/valve issue should result in a reading of closer to 0.
The problem here is that getting it to run if it has low compression is great for moving it around as needed, but I'll never actually be ok with it. It's just ignoring an obvious issue. I've wanted this project for a long time, and got rid of my MK3 Supra Turbo in order to make room for it, so I'm not going to cut corners and half ass the project. If I drive it around, it's going to be because it's ready to be driven around, not because I'm willing to ignore an obviously sick motor.