89 951 engine overhaul

[four0four]

Slowly moving, but....moving

Acquired a new pump, my suspension, and rebuilt 1.5 ball joints (one has a chowdered up snap ring land, so need to clean it up properly). But that's not engine work

This is:

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Unfortunately, that piston got yanked once I measured ~1.5 thousandths clearance (edit: realizing this is specified across diameter for some reason, not radial like I thought). Waiting on delivery of a bore gauge at this point in hopes that my and my old telescoping gauges were inconsistent.

Hoping I don't need to drag this thing back down to Portland. Kicking myself for not checking this sooner.


Edit: Of course I didn't take pictures of this, but I printed a simple jig to press the rings to the same depth repeatably. Waaay easily than lining up a piston. OpenSCAD file here, but you can probably imagine what it looks like

Edit The Third: Bore gauge came in, measured clearance to bang on 2. While I asked for 2.5, I'm sure they have better tools than I do, so I think this is alright...Will just check with Mahle on Monday, they've been helpful thus far.

[four0four]

Well, I messed up a bit - caught just the oil ring set on the cylinder. Not sure how I managed that with a tapered ring compressor - guess I'm just that talented

Here's the damage - I can't feel any of it at all, so I'm (barring sudden words of caution) just gonna order some new rings and keep plugging away. Frustrating nevertheless.

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Edit: Had someone with better tools do the measuring last week, everything is as ordered.

[ealoken]

You can try to send it, just do a lot of oil change on the beginning.

[four0four]

That's the hope/plan - i suspect it's largely ring material, which ...should... wear right off?

Been waiting on a single cylinder ringset from Mahle for like a *month* now. Should've just forked out the $400 for a full set of 4. Rest of the engine is basically together, I've had the time to assemble it, helicoil the oil pickup M8, disassemble it to clean, and assemble it again. Oy...

I also threw together a little bracket to help the new driver's side oil cooler mount + clear the AC condenser lines. I've never drawn anything up for bending before, so we'll see how that shakes out when sendcutsend gets it out the door, but my hope is it's a little cleaner than the plumbing straps I've seen other folks use


In non-engine news, I've installed the KW suspension and some RE camber plates. Really looking forward to trying all that out

[four0four]

OK, well. I goofed. Or something.

Got the ringset in, and promptly repeated the same mistake (caught oil scraper ring). Disassembled and cleaned the piston and rings, fit them again, rotated the ring compressor a full rotation to check that everything was seated nicely...and did it again, but this time I left a mar I can feel :\

Adding a little more on the pile, at some point the spreader ring marred up its land. Luckily all that damage is on the portion of the piston that is a good bit narrower than the skirt, but I took down the high points anyway.

So I need to have a think on where to take this now. I can strip the block again and have them take it up just enough to clear the scratch, or I can try to take down the high parts of the damage, AN-30 it, accept the imperfection, and send it. Ugh.

Imgur album of the nasty stuff here.

On the bright side, the oil cooler bracket fit great, so I'll just include that inline

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[Tom]

Are you sure the rings are compatible and the right size? Upside down? What ring compression tool are you using?

[four0four]

Yep - though I didn't check the new oil rails in the bore first, they're the same size and gap as the others (also, the part numbers match up).

Not upside down, they're symmetric. Ring compressor is the smooth Summit one sized for ~100mm.

I'm sure it's operator error, but I can't figure out why. Probably going to get a local shop to take it out another 0.5-1.0 thou and refinish it myself.

[Tom]

You mentioned a single ring set from Mahle. Is that the only one giving you the trouble?

Seems like there is something else going on, but for what it's worth, I like the non-adjustable ring compressors like these:

https://www.summitracing.com/parts/tsr-rc3937

[Dave W.]

I've successfully used both types of ring compressors. Make sure you coat the ring compressor with a little oil, only use hand pressure to push the piston down into the cylinder. Don't overtighten the adjustable compressors, it's important to get the tension right. if it feels like the ring is getting snagged on the top of the cylinder you can move the compressor around in a circular motion while pushing down at the same time to help align the rings and ease them into the cylinder. I've also used a non-adjustable compressor that was 0.5mm too big by moving it around in a circular motion. Finesse, not force.

[four0four]

You mentioned a single ring set from Mahle. Is that the only one giving you the trouble?

Seems like there is something else going on, but for what it's worth, I like the non-adjustable ring compressors like these:

https://www.summitracing.com/parts/tsr-rc3937

I picked up the single set after bending the oil rails that came with it previously. It's exactly 1/4 of the set that comes with the pistons, though. And yeah, just that cylinder/piston

I had no idea those other compressors existed. I like being able to align the gap on mine to keep an eye on the expander ring while doing installation, but I might've picked that one up if I'd know they existed.

I've successfully used both types of ring compressors. Make sure you coat the ring compressor with a little oil, only use hand pressure to push the piston down into the cylinder. Don't overtighten the adjustable compressors, it's important to get the tension right. if it feels like the ring is getting snagged on the top of the cylinder you can move the compressor around in a circular motion while pushing down at the same time to help align the rings and ease them into the cylinder. I've also used a non-adjustable compressor that was 0.5mm too big by moving it around in a circular motion. Finesse, not force.

Definitely oiling everything. I might be running it a bit tight, so perhaps there's something. It takes a couple firm whacks with a plastic hammer, but that was no trouble at all for the others. I'll mess around with it later today...I still need to fix the bore at this point, but it can't hurt to practice.