We've been working on a rebuild for my wife's MG Midget motor that had about 120,000 on the odometer and #2 cylinder rings finally gave it up. (She just wouldn't quit driving it) At least the rings were my diagnosis - squirted oil in #2 and it brought the compression reading back up. Only other thing on teardown I found was #3 piston had some scoring on the skirt.
Anyhow, the PO had the head rebuilt about 15-20,000 miles ago. The machinist had also told the PO the bores looked good so don't rebuild the block end. I left the head alone beside just a quick look. It's got little double valve springs I didn't want to mess with and besides, it'd been rebuilt not that long ago so I figure I'll do a good clean and check later.
We get the block back and the wife gets to work wiping it down, so I decide it's later and time to get the head cleaned up - lots of carbon from burnt oil, etc.
Found something odd. From the factory there was a brass plug in the block between #2 and #3. The brilliant part is, the plug tends to extend into the cylinder chamber!? And apparently they tend to sink a bit over time, so the best fix is to thread the hole and put a steel plug in before surfacing the head.
It seems that is what the PO's machinist did. BUT they left gaps on the sides of the plug past the crush ring of #3 so it didn't seal 100%. Obvious by the burn in the gasket. It didn't leak anywhere beyond the plug area.
So, I decided to take it apart and see if my shop can't do a better job of it. While taking the valves out, I find intake of #3 is sticking and the guide is moving too, and there is a gouge in the valve base, but it still sealed. All others seemed OK.
Unless someone says otherwise, I think I'm just gonna have the whole head redone. Disregarding the valve guide problem, IMO that head shouldn't have left shop with that gap around the threaded plug. So what else did they not do diligently?
Am I right in that thinking?
Anyhow, the PO had the head rebuilt about 15-20,000 miles ago. The machinist had also told the PO the bores looked good so don't rebuild the block end. I left the head alone beside just a quick look. It's got little double valve springs I didn't want to mess with and besides, it'd been rebuilt not that long ago so I figure I'll do a good clean and check later.
We get the block back and the wife gets to work wiping it down, so I decide it's later and time to get the head cleaned up - lots of carbon from burnt oil, etc.
Found something odd. From the factory there was a brass plug in the block between #2 and #3. The brilliant part is, the plug tends to extend into the cylinder chamber!? And apparently they tend to sink a bit over time, so the best fix is to thread the hole and put a steel plug in before surfacing the head.
It seems that is what the PO's machinist did. BUT they left gaps on the sides of the plug past the crush ring of #3 so it didn't seal 100%. Obvious by the burn in the gasket. It didn't leak anywhere beyond the plug area.
So, I decided to take it apart and see if my shop can't do a better job of it. While taking the valves out, I find intake of #3 is sticking and the guide is moving too, and there is a gouge in the valve base, but it still sealed. All others seemed OK.
Unless someone says otherwise, I think I'm just gonna have the whole head redone. Disregarding the valve guide problem, IMO that head shouldn't have left shop with that gap around the threaded plug. So what else did they not do diligently?
Am I right in that thinking?