Built miata motor issues. Any help/advice?

Sorry, this is kinda long.

I had my motor built almost 2 years ago. And I have had nothing but issues with it. Seemed fine at first, although, after start up you could see a little blue smoke coming from the exhaust for a bit. Not a lot. Very faint. Car has no cat or muffler, if that matters. Then I seemed I developed a head gasket issue. Side of motor was wet. Also, the front main seal started leaking, and car was using a quite large amount of oil. Figured oil usage was due to HG, and front main seal was just not done well. So, repaired both this winter/spring.

Started up, after all back together, massive amount of smoke. But not at first start up. Only once you give it some gas to move it. Kinda goes away after a bit. Would do this every time I started the car cold. When warm, not so bad. But still there. Car would smoke pulling away from stops decently, as well. Car was still using copious amounts of oil. We are talking 1/2 quart in a 20-30 minute drive. Did leak down, 1 was good, 2 and 3 were less then 5%, 4 was bad. Figured ring didn't seat. So, we pulled motor to take a look.

What we found is not pretty. No cylinder had ANY crosshatching left. All polished in look. Irregular wear at tops and bottom. Pistons rock back and forth in bore. Pistons (FM's Wisecos) have coating polished off sides (to be expected a bit) but also have the sides above the top ring heavily worn on #4, and slightly worn on the rest. We start thinking bore is too big. Check bore (admittedly only at top of cylinder), and they are decent. #4, once again, is the most off. We are talking .26mm. The rest were .0, .7, and .3, 1-3 respectively. Piston skirts measure as should. Are the pistons really supposed to be that loose in the block? You can actually rock them back and forth in the bore.

Next up is ring gap. Took the top ring out of piston, and put in cylinder #4. Pushed down into cylinder about in inch. Gap appears to be almost a 1/8 of an inch. Seems excessive.

So, my cylinders are polished smooth as if the pistons or rings were beating them to death, but yet the bore and piston measurements are spot on, close, and a bit too much, from front to back. Also, the gap on the rings are excessive, not too close, so not sure why rings would be damaging cylinder walls there.

If ANYONE has any light they can shed on this situation, that would be great. We will be calling Wiseco, and FM, to see if they can shed any light, but that won't be until Monday.

I wouldn't think that the pistons should be that lose and I'd expect the ring gap to be a little smaller, too...

What was the actual brief for the person building the motor and was their price in line with the specs? Oh, and how far have you driven the car with that engine in?

IMHO you'd expect cyl 4 to have the most wear on a Miata as it runs hottest unless you modded the cooling system.

Sorry to have left out that info.

Cooling re-route. Motor has 2-3K on it. Seriously.

Not sure what you mean by brief for the person building it, but they were a machine shop that I was told I could trust. They had the specs for the Wisecos in the box. I had a new sheet from one of those boxes faxed over to us already, so we could double check the specs.

Posts like this remind me of why God created crate motors.

Piston to cylinder clearance should be app .002"-.05mm.or less. Ring gap , .010"-.030" for compression and .016"-.066". Got this from my Ford workshop manual for the 2.0L Zetec.

HunterJP wrote: Sorry to have left out that info. Cooling re-route. Motor has 2-3K on it. Seriously.

Ouch. Barring issues like injectors that are leaking like there's no tomorrow and problems like that, this sounds like you didn't quite get the engine you thought you paid for.

HunterJP wrote: Not sure what you mean by brief for the person building it, but they were a machine shop that I was told I could trust. They had the specs for the Wisecos in the box. I had a new sheet from one of those boxes faxed over to us already, so we could double check the specs.

Well, I assumed that you've dropped the bits off with them and asked them to do something specific with them, right? Did they talk you through the options that you had (rebore, hone only, whatever or just throw it together and leg it?) and did you agree exactly what they were supposed to build? Also, who got the bits - did you drop off a load of performance parts like the Wisecos and ask them just to put them together, did they have input into the process and all that?

The reason I'm asking is that it might be that they thought you asked for a cheap refresh of the motor when you were actually asking for a decent build? OTOH it sounds like they didn't even do a particularly good job on the cheap refresh...

To me it sounds like your engine now needs a proper rebuild - at least to the short engine - and before you take a heavy blunt object to the machine shop it would be a good idea to reflect on what was agreed with the shop that built this engine in order to avoid another nasty surprise like this.

What I'd be tempted to do now that the engine is partially stripped down anyway is to check that the bottom end is still OK, possible refresh that if necessary, and then get a known good machine shop to measure the bores and spec new pistons, get the pistons and get the shop to bore the block to the exact pistons instead of a spec sheet. Get them to build up the short block by all means but check it over once it's built up and before sticking the head back on.

My .02....

Agreed with the above post. Sometimes a shop simply does a poor job, but often a communication error will have the same result. And sometimes life just stinks. I had a 2900 dollar short block eat a thrust bearing in 9K miles on a light duty clutch because they did not use the mains tuds I specified and also did not align-hone the mains. That was a bad feeling when I pulled the engine and could litteraly move the flywheel and crank pulley in and out with normal hand force.

On the up side, it seems like some machine work will solve the issue. Do the pistons show any signs of heat damage, like really interesting colors in and around the ring lands in certain small areas?

The reason the enigne was doing what it did is the rediculus ring gap and loose PTW, not to mention the inconsistency in the clearances. You basically had nasty oil blowby all the time, which got a bit better as the whole thing heated up and therfore tightened up.

A good machine shop sould be able to rebuid it and get it right.

Wow, sounds like world class bad rebuild. Mismatch pieces and all.

Next decision, do you want this same shop to do it a second time?

Well, we have been a couple of ways since I posted this. Still no final decision. The guy with my motor has found some cracked/broken rings, though.

(Keith, that thing we talked about... my guy, highly doubts thats it, with the things he is finding. Which makes me feel a bit better.)

And, no, do not want original builder doing the motor again. However, with me finding out this weekend that I have to replace the walls in the bathroom, and not really having much $$ to fix the motor in the first place, I am left in a bit of a jam. Suppose the car can sit some more. Not really that big of a deal. Either way, this block will not be reused, and the pistons are paper weights. I have another block, so will probably end up doing an OE piston on forged rods, in spare block, using rebuilt head. The biggest question is: when?

Thanks for the input and help. Will post up what we find.

Whew.