Something Something Tony G's E30 Sedan (we're using a coupe now) - S54 Swap

[moatilliatta]

An easy route and maybe the same cost in the long run is just to find a used good 100K motor with Compression numbers for 6K and sell what you have.

Most Peformance rings are harder so you just have to make sure you go hard at break in right off the bat and have the correct hone job to break them in.

It’s fine for most, but the bore finished size is actually correlated to the pistons size, not rings.

[spike68]

Yeah thats a tough route for me to go. The only reason why I went with this motor was because I got the motor for cheap. Like way cheap.

If the machine shop said they can hone the scoring out while still being within spec is that not appropriate enough?

[Andre3127]

Yeah thats a tough route for me to go. The only reason why I went with this motor was because I got the motor for cheap. Like way cheap.

If the machine shop said they can hone the scoring out while still being within spec is that not appropriate enough?

Honing out the scoring and throwing OE pistons back in will be just fine. Whenever you change rings you need to deglaze the cylinders anyways. And to be honest, even if a score or two was left behind, it's not the end of the world.

I'm looking forward to the rest of the rebuild! Sure you could just buy another 100k motor for 6 grand, but then you'd still be left with a 100k motor. Rebuild this one and you'll have a fresh start.

[spike68]

Honing out the scoring and throwing OE pistons back in will be just fine. Whenever you change rings you need to deglaze the cylinders anyways. And to be honest, even if a score or two was left behind, it's not the end of the world.

I'm looking forward to the rest of the rebuild! Sure you could just buy another 100k motor for 6 grand, but then you'd still be left with a 100k motor. Rebuild this one and you'll have a fresh start.

Hey thanks! Appreciate that info.

I am still on the fence right now for what I should do. For a second there I thought it wouldn't be bad to re-run the old rings, but it sounds like thats not a good idea. I'm back to either shelling out the money for new rings or just getting the forged pistons for $100 more than the rings. Starting to seem like a no brainer to me. Even if the machine shop already performed the honing work I'd pay the extra to get the boring done.

[spike68]

Just thinking of something else if I go the forged piston route. moatilliatta do you know if I need to go with a standalone DME if I have to overbore the cylinders? Or is this too small of a change for this application?

Would prefer to avoid having to step up to a standalone for the time being.

[moatilliatta]

Stock DME works quite well. Epic, Kassel, Rk Tunes.

Prefer Epic Alpha-n. Good for 350whp with supporting mods, good Drivabilty.

[spike68]

Alright well I'm just gonna send it. Ordered some 87.5mm bore pistons from VAC last night. Calling the machine shop first thing tomorrow morning to have them to bore the cylinders out.

[moatilliatta]

The importance of the RA finish will be even more important with thinner cylinder walls.

Have the machine shop do the machine work with pistons in hand, the piston wall to wall clearance, the hone finish will be on the spec sheet with the pistons. Maybe Vac has a tq plate the could loan out. Speak to Hayyan, he is usually the sales guy I deal with.

The used good motor rules out any machine shop errors. That's my biggest lean on that recommendation.

[spike68]

The importance of the RA finish will be even more important with thinner cylinder walls.

Have the machine shop do the machine work with pistons in hand, the piston wall to wall clearance, the hone finish will be on the spec sheet with the pistons. Maybe Vac has a tq plate the could loan out. Speak to Hayyan, he is usually the sales guy I deal with.

The used good motor rules out any machine shop errors. That's my biggest lean on that recommendation.

I feel like I'm really putting myself through the ringer on this project. I usually one to think through things pretty thoroughly but definitely didn't think about the torque plate. I'll see if the machine shop has one, but if not I'll call VAC and see if they've got a rental and/or just purchase it. Hopefully the wait times aren't too long either.

[ForcedFirebird]

OE s54 rings are expensive, but if you shop, you can find good deals... https://www.ebay.com/itm/114339700479

We rebuilt an s54 with slight hone few years ago for a local, rings were even more scarce then. Car runs great and is now getting a turbo, we gapped the rings and installed o-rings on the deck to suit.

Nothing wrong with taking a couple tenths (.0001"), the new rings will seat fine.

[spike68]

OE s54 rings are expensive, but if you shop, you can find good deals... https://www.ebay.com/itm/114339700479

We rebuilt an s54 with slight hone few years ago for a local, rings were even more scarce then. Car runs great and is now getting a turbo, we gapped the rings and installed o-rings on the deck to suit.

Nothing wrong with taking a couple tenths (.0001"), the new rings will seat fine.

So I ran into that exact link and was about to pull the trigger on those, but after reading online most are saying that those are chinese Mahle rings. Notice how you only see a partial logo on the box and you don't see the word "Mahle" noted anywhere in the ad title or description below. Kinda shady.

[ForcedFirebird]

I just did a quick search, didn't use that exact link (would have to dig in records).

EDIT: Grant piston rings, Part # S5365

[spike68]

Called both the machine shop and VAC motorsports this morning and knocked a few things out.

1. Called Ordered a torque plate, MLS Head gasket, and arp head studs on top of the forged piston kit from VAC. Also got an idea of lead times on everything. Piston kit, head gasket, and head studs are in stock. Torque plate is waiting on material to arrive. Will probably show up after the new year.

Note that VAC no longer rents out torque plates, however I did not speak to Hayyan but someone in sales and in their service department.

2. Called the machine shop and let them know of the change. They're cool with holding onto the block in the meantime and are looking to deck the block to make a nice surface for the MLS gasket. They noted to me that they all their work is to an MLS standard since it's mostly the kind of stuff they work on.

What I don't know is if I'll need a thicker head gasket for final assembly. From what I read stock head gasket is .040" so I went with that. I'll talk to the machine shop about the values they knocked the head and deck down by (something I should have asked about when I picked the head up. If it turns out I need something thicker it should be easy to sell this gasket.

[moatilliatta]

Probably ok, the machine shop maybe able to CC the head and piston to calculate your CR. Then make a decision there for HG thickness if it’s too far out of spec.

[ForcedFirebird]

Shouldn't use HG thickness to change CR, it messes with the squish. You want to aim for ~.040" between the piston and head, irregardless of compression. Too much, and you not only leave power ont he table, it actually will cause MORE hot spots (aka pre-detonation spots).

Usually a decking of the block will only take .002" (.05mm) which really shouldn't mess with anything. I just shaved an m52 block and the stamped numbers will still present (.0015" or .038mm). You should be fine with the stock thickness gasket, but you can always clay on final assembly for piece of mind. From memory, I want to say the stock s54 pistons are ~.010" in the hole, so with a .040" gasket, you have the typical BMW ~.050". Unless they take over .010", head and block combined, then you are well within factory rebuild limits. On an 87mm bore, you lose .5cc for every .1mm shaved. The chamber is 33cc stock, so a typical .3mm shave will give you about .4:1 more. The head chamber is smaller than the piston,so it will have even less effect than block shaving (block is easy to calc).

Always have the pistons in hand when over boring, if a machinist is willing to bore without them, run away - fast.