S52 build with M52 block

[mikegar]

I have the S52 rotating assembly and a M52 block. I dropped off the block at the machine shop to get cleaned and checked if its good im going to have it bored out to s52 specs. The question I have is what rings should I be using and what should the clearance be?

[efficient]

I thought that the m52 and s52 block were the same except for the heads. Am I wrong?

[mikegar]

The block is the same but the bore is different. M52 has 84mm bore S52 has 86.5mm bore

[2mAn]

what clearance are you wondering about? Rings would be spec'd to whatever piston you are using since the M52 block will have to be bored out to fit the S52 pistons

[mikegar]

Ive never had a motor fully rebuilt so im a bit lost, please bear with me. The machinist said he needed the clearance between the piston and the block. Should he be able to determine that with just the pistons and rings?

[sweet3]

I would just bore it to the stock s52 bore size. I believe that is 86.4mm. That should allow the stock piston rings to work like normal.

efficient, the heads are actually identical. The only differences are the springs, spring washers, and cams.

[2mAn]

Thats a good way to go, but I would still buy new rings. Good peace of mind insurance!

[Sh3rpak!ng]

I suggest you do some reading through the BMW TIS for e36 M3. You can view it online, though it's in Russian. Chrome translates for me... your machinist is referring to the piston to wall clearance. That data is in the TIS, you want to look at the "repair manual" for the e36m3 for all of the measurements. It contains ALL of the data to rebuild a BMW motor to BMW spec, here is the s52 page: HERE

If you read through the documents, you will see several dimensions which should help you understand the correct bore size.

Piston size: 86.365mm
Piston to bore gap: 0.026 - 0.058mm

This would give you a tolerable bore size of 86.391mm to 86.423mm

Or you can also see that the bore size is stated to be 86.400mm (which gives you a piston to cylinder wall gap of .035mm which is on the lower side of the tolerable range, aka perfect)

I am also doing an s52 rebuild/swap and boring out an m52 block to 86.400mm

You need to read read reeaaaddddddd

EDIT: I don't know what your goals are, but I would replace everything if you are rebuilding. rod bearings, main bearings, piston rings, every gasket, every o ring, you need new main and rod bolts (they are stretch bolts - one time use). It is not a cheap nor easy endeavor, but well worth it imo when it is finished.

[mikegar]

Thank you verry much. My goals are to replace everything. Id like to have a 0 mile lower end to replace my current junkyard built 2.8 lower end.
I know what you mean with it not being a cheap endevor. Even the junkyard build was pricy

[Sh3rpak!ng]

Thank you verry much. My goals are to replace everything. Id like to have a 0 mile lower end to replace my current junkyard built 2.8 lower end.
I know what you mean with it not being a cheap endevor. Even the junkyard build was pricy

No problem. Sounds like we are both working on the same project. I have been researching this heavily for the last several months, buying parts reading etc. Finally ready to build, getting my block back from the shop in a day or so. I wanted a brand new bottom end and no leak motor for daily/autox duty. Honestly though, without going crazy, I think it can be done for around 1k.

[mpowerful]

^not possible with machine work and all new parts.

[Sh3rpak!ng]

^not possible with machine work and all new parts.

Yea, agreed. I forgot a few items while quickly adding it in my head. More like 13-1500

[justin_l_]

Every motor I've ever built, the machine shop would not bore the block without the piston/rings in hand.

[ForcedFirebird]

^not possible with machine work and all new parts.

When we do a full rebuild, the machine work for the bottom end alone will exceed $1k. This is a bore/hone, deck, aline bore mains, weight match rotating parts, polish crank, re-bush/resize rods, and balance rotating assembly.