I'm a questionable mechanic and need some advice. I've tried to list the series of events. I'm hoping it's a simple..."Hey buddy, just change the _ and it'll be fine" but I'm afraid it's much worse. Just change the rings and it will be fine.
1994 Miata
- Install “70k mile” wrecking yard engine.
- Engine consistently loses coolant.
- Can’t find any leaks
- Runs poorly
- No visible white smoke
- Pulled the head
- Cylinder #1 is steam cleaned, all others oily
- Machine shop pressure tests head, seals, guides indicate a low mile engine
- Machine shop resurfaces the head
- Install new MLS head gasket
- New timing belt, water pump, hoses, gaskets etc
- Starts up, runs a bit lumpy but not bad.
- After 10 minutes it runs poorly, 2-3 cylinders.
- Re-torque head, adjust timing.
- Starts up, runs a bit lumpy but not bad.
- After 10 minutes it runs poorly, 2-3 cylinders.
- This time blue smoke
- Compression test dry: 118/118/120/118
- Assuming the head is still flat, guides are good.
- Assuming rings are bad and bottom end needs rebuilding.
Any ideas?
If your compression tester is reading correctly (I had one that wasn't), that compression is below wear limits IIRC.
Did you try a wet test to see how much it improved the compression?
I had an NA with a seized 1.6 engine. After I freed the engine (soaking in a magical combo of diesel fuel, ATF, and PBlaster) it would white smoke a bit after start up and, well, kept smoking. I did a couple of oil changes on it after the soaking, always with the cheapest 10W-30 I could find, and then after driving for a bit began driivng it HARD- always redline shifts. Eventually the smoke cleared up and the engine started and ran perfectly afterwards. Engine had like 140k on it, IIRC. Ended up selling the car, but as far as I know the new owners never had a problem with it.
Your comp seems on the low end but at least its consistent. That's more important.
I've always wanted to put a flathead ford v8 into an NA. Roughly the same power, completely different torque curve. Probably would get about the same fuel economy, too.
In reply to volvoclearinghouse:
This is good advice. Beat on it and I wouldn't be surprised if the rings free up.
Are you still loosing coolant?
What items did you reuse from the old engine?
Not sure about the 1.8L, but I know with my 92 that coolant passes through the throttle body. Haven't looked at the design close enough to see if there's a possibility of a coolant leak into the intake.
How old are the plug wires?
Fuel pressure good?
What happened to the old motor?
So it DID have coolant leaking past the head gasket but the head wasn't warped. So I did replace the head gasket. Over the 20-30 minutes of running it hasn't lost a measurable amount of coolant. I've only reused ancillary parts, alternator, power steering pump, AC...New water pump and timing belt, plug wires. All new coolant hoses.
Burning oil/rough running is my concern at this point.
I gave the old motor back as a core.
I do have a set of pistons, rings and headgasket for sale if you want to build a 1.9-ish engine 
.
Well it would be prudent to change the pistons just in case. Fresh start and all. Right? ;-)
Tim, PM with info?
I do agree it's mostly likely the rings, but since that's kind of a worst case scenario, I just wanted to make sure you'd considered all angles.
There are any number of things that can make an engine run rough and smoke (though blue smoke is typically oil as you mentioned). Are we talking a huge continuous cloud of blue smoke, or something smaller that could be open to interpretation? (I used to be a service adviser at a Honda dealership, and I came to realize two people can describe the same problem in very different ways).
Did you reuse the injectors on the junk yard motor? Any chance one is sticking?
How do the spark plugs look?
Oh and I was asking what killed the old engine. Just to make sure there's not a chance a previous problem could have been transferred over to the new engine.
