High compression pistons, need forged rods?

[madjurgen]

I hope you aren't building that alum block for anything other than driving to work. The alum block twists when puched hard, ie club racing like you mentioned. I hope you do a LOT more research before you blow all your $$$.

Have any proof or are you just spouting internet hearsay? The M54 has been pushed hard in pro racing for nearly a decade now. If Bimmerworld and Stickley have no problems building an Al race motor, I think Im going to believe them over you. Stop spreading stupidity.

[MIKe30]

Looks like there are many 87mm s52 piston kits... anybody ever have any issues boring the s52 block out to 87mm?

[nando]

isn't the stock S52 bore 86.4mm? so that's 2nd or 3rd oversize?

[MIKe30]

isn't the stock S52 bore 86.4mm? so that's 2nd or 3rd oversize?

yes, stock is 86.4. I'd like to keep as close to stock as possible while cleaning up the cylinder. I just see 87 a lot in my searches so I thought I'd ask. Just asked Jay what the machinest thinks will clean it up, I will order pistons after I get a number.

It was honed, and you can still feel it with your fingernail. Don't know how much of an idea that gives you but just throwing that out there.

[nando]

just honing the cylinder isn't going to bump it out much, that would be a couple thousands of an inch at the most.

[MIKe30]

just honing the cylinder isn't going to bump it out much, that would be a couple thousands of an inch at the most.

In that case I'm hoping first oversize will work. There isn't much (if any) to gain from the slight bore that I'd really like the peace of mind knowing the cylinder walls are as close to stock as possible.

Guess I'll see what the machinest has to say...

[asubimmer]

Have any proof or are you just spouting internet hearsay? The M54 has been pushed hard in pro racing for nearly a decade now. If Bimmerworld and Stickley have no problems building an Al race motor, I think Im going to believe them over you. Stop spreading stupidity.

no never heard about it on the interwebz. If you don't wanna believe truth then fine. Just join the liberals and give our country the "change" we need!

[e30this]

Mike why dont you run my M54B30 rods since your getting pistons anyways?
:)

[nando]

Mike why dont you run my M54B30 rods since your getting pistons anyways?
:)

what's the advantage to this? strength maybe? the S52 rods are pretty darn light, and the same length, so the only thin I can think of are the M54 rods are heavier/thicker. Just curious if there's something else, maybe they're an H beam instead of an I beam?

[e30this]

Ahh yeah I forgot 135mm. My fault.

[MIKe30]

Got a response. Just looking for a second opinion since I'm a newb when it comes to building engines.

I talked to jim, and he says they pretty much took out .004" with the hone.. That works out to the bore being at 86.5 right now. He didn't think it would be worth going in between the 86.5 and the 87 because when they bore it, they need to take a decent cut and then will still hone the bored hole. So they would bore it to like ~86.9 and then finish hone it to size. of course all this would be done once the pistons are in hand, and we can confirm the actual size.

Sound about right or sounds half ass?

[matt]

Sounds right, but not a good idea.

If you bore out to 87mm, you can't use a stock head gasket anymore, so you're stuck buying MLSs.

[MIKe30]

Sounds right, but not a good idea.

If you bore out to 87mm, you can't use a stock head gasket anymore, so you're stuck buying MLSs.

Great. Shouldn't have any problems with 87mm pistons otherwise, right? Btw, stock head bolts with MLS gasket do just fine? Same with rod and main bolts, will they hold up just fine - or do i need arp's?

Are arp's just a good precaution, or are they a waste of money even for a high compression n/a build?

[nando]

Sounds right, but not a good idea.

If you bore out to 87mm, you can't use a stock head gasket anymore, so you're stuck buying MLSs.

do M50 pistons prodtrude out of the block at TDC?

[mazur]

do M50 pistons prodtrude out of the block at TDC?

Yes.