M20 Rebuild Progress and Questions

[Hallen]

I posted over in the projects forum and don't want to post it all twice.
Please check it out here: http://www.r3vlimited.com/board/show...09#post1156609

Basically, there are some scratches on the cylinder walls that I would like some of you experienced guys to take a look at. Any comments would be appreciated.

[h82crash]

Broken rings, for sure. Will need rebore and oversized pistons.

[kenika65]

I agree perfect time for oversized pistons!

Maybe 2.7 crank and your i rods with 10.0:1 compression!

Get that head reworked and ported.

Now your talking.

[Madhatter]

i wouldnt be surprised if its actually a cracked ring land, but then, there doesnt seem to be signs of gas escaping up over the crown, did it ping/knock before you pulled the head? They cant be wrist pins because of the location of the marks in relation to the block, too offset. Have you dropped a piston yet?

If its really bad and you cant take it out properly with a rebore, you can have the block sleeved, however for this cost, i would just get another block imho.

[Hallen]

Thanks for the comments guys. All 6 cylinders have the same general markings, but none are as deep as the one in the picture. Some of the scratches are in multiples, like 6 or 7 all in the same general area, but much lighter scratching.

I will be dropping the pistons here in a little bit. We'll see what we see then.

I hope it isn't going to lead to a new block and I would rather not have to over bore it either since that would mean new pistons. At $200 each, that gets expensive in a hurry. I would probably try to find a decent block in that case.

[Hallen]

Well, I posted up more pictures and descriptions on the projects section.

http://www.r3vlimited.com/board/showthread.php?t=105887&page=5

Lots more icky things to look at.

Any comments or ideas on what to do? I am at a bit of a loss right now.

[itsbrokeagain]

I posted up in the other section before.....wow that engine really look like it took a a hit. The crank looks like it saw quite a bit of heat too around the bearing area. I think that motor is tanked man.

Unfortunatley, given your decisions about what you want to with the engine, you will need to start of with a fresh engine. Go find another one and start from scratch. Trying to rebuild that mess without turning it into a 2.7 will only heed more problems down the line.

Also, get yourself a bigger oil cooler. Road racing puts pretty big demands on a cars oiling system, and keeping the oil temps low will keep the engine alive...the newer 335s have the same issues...just driving around we see temps of 230-250 degrees....thats hot....oil temps really shouldnt be higher than 220. Get an oil temp gauge while you are at it.

[Hallen]

Unfortunately, this car has only seen a couple track days and they weren't even full days. It was cool too. I doubt the oil cooler was the problem in this case. I suspect infrequent oil changes and somebody who rebuilt this thing without knowing what the heck they were doing.

The crank doesn't look bad to me. I don't see any discoloration that would lead me to believe that it was over heated. I do see scoring on the bearing surfaces once I got the crank out. The #6 bearing (between the 5th and 6th cylinders... the one that has the lips on it that hang over the flange) seemed to have the worst of it. This matches with the worst damage in the cylinders and pistons too.

I don't know what they did, other than having everything unbalanced because of the improper rebuild.

I can put more pictures of the crank up later. My batteries died in my camera.

The front main seal was definitely leaking too. The poor thing was bleeding out almost every orifice.

It is completely disassembled now except for the head. You are probably right, I will most likely either need to bore it and stroke it, or I will need a new block. I was kinda hoping to keep it PRO3 legal. But a stroker also has a certain appeal :D

Not one thing that was done to this car was done right. I mean everything, everything that was worked on was either over torqued, stripped, wrong hardware, or ignored. It goes way beyond the normal annoyances of working on a 20 year old car.

[itsbrokeagain]

yeah i hear that...I owned a 240 once that had its fair share of problems like yours.

Im sure the car is happy that you are breathing new life into it :)

Also what kinda black is that on the valvecover? Is it like semi-flat black or something? I see everyone is getting their covers powdercoated that color

[Hallen]

I don't know what the paint on the valve cover is... I think it is just the stock black paint. I haven't done anything with it. But the PO was more into bling than bang so he might have done something with it.

[AlarmedBread]

Ouch, that looks almost as bad as mine did!

Are your rod bearings blue by chance? I would pull the cam out of the head and check those bearings too, all of mine were badly scored. The crank main bearings were all in good shape though. Oil starvation in my case, now is a good time to fit a crank scraper and maybe even an accumulator.

I feel your pain about all the messed up bolts from other people working on the car, seems like our cars are kindred spirits with many similar issues and goals. Hoping the last bits I need for the engine will be here today.

[Hallen]

The main rod bearings where they contact the crank are not blue. They are a bit scored, but I don't think they were over heated.

I think the head is in decent shape, actually. I haven't torn it down yet though. The cam was recently ground (just to clean it up according to the PO). I will be taking a look at it though.

Yeah, I was thinking about a scraper. Most of the PRO3 guys around here use one. Where is a good place to get one? How would an accumulator come into play here? What would you use it for?

She is a little beast for sure. I suspected something was not right with the engine the first time I drove it hard after replacing the rear subframe bushings and all the rest of the bushings. There was too much vibration. The clutch and flywheel were badly out of balance and getting that fixed solved a lot of the problems. But I still felt like the engine wasn't as smooth as it should have been even with hard urethane mounts.

I think some of the problem was that the engine was not assembled properly. Some people just don't understand how important balancing things are. The rod caps were facing different directions and that goofy mismatched bolt make me suspect that things were enough out of balance that it caused some of the damage.

But, those scores on the cylinder walls are strange. They don't match up with the scores on the pistons. I am guessing that some nasty gunk got in the engine either due to some really dirty oil or because something got sucked in through the intake.

I will try to get a machine shop to look at the block to see if it can be honed out or not. Then I will have to decide which way to go with this.

If you want to read about the other crappy things done to the car, check out my blog. www.griplimit.net.

I haven't gotten this engine stuff posted up there yet though.

[Hallen]

The block and the head got dropped off at the machine shop this morning. We'll see where the measurements take us.

I did find MaxSil sells a complete piston kit at .5mm over size for $500. That would be a good option.

Are there any other piston manufacturers out there that would also provide something similar?

[AlarmedBread]

Yeah, I was thinking about a scraper. Most of the PRO3 guys around here use one. Where is a good place to get one? How would an accumulator come into play here? What would you use it for?
.

I just install an IJ one, you can see them here, they're available at racer's market and a few other places too. I chose it because it is the only one I found that is a double scraper, meaning it works on both sides of the block. Fitting was a snap, I didn't even have to grind anything, just moved it around until I found the sweet spot where it cleared everything within tolerance.

http://www.crank-scrapers.com/bmw.html

Mine - http://img.photobucket.com/albums/v3...r/P1030049.jpg

An oil accumulator/accusump will keep some oil pressure stored up for when the pump pickup is sucking air. They aren't very expensive and are easy to install, if you get a cheap moroso gravity feed it should just work fine around the area the coil is in. Between the two of them things should stay covered, my pressure drops were only fractions of a second.

I believe the rule is 1% oversize allowed, but I would check the rule book and then get near the maximum allowed, every bit counts right? :)

[Hallen]

Thanks. One thing about PIR though... it is mostly right hand turns. :D Not so hard on the old engine that way.

The scraper looks interesting and not too expensive. I don't like the idea of having to align the darned thing every time I take off the pan though. Do you have to use two gaskets with it?

I am more interested right now in finding a way to keep the oil out of the intake. I suppose it is no big deal, but man, what a mess it makes.

Yeah, as long as I don't go over size too much, the engine will still be legal. I don't know if I will ever convert the car to full race mode, but I do want to leave the option open. Even if I do that though, I suppose I will want a fresh engine at that point. If I could find a cheap 81mm crank, then I might consider stroking it. :)