2.7i stroker, b25 rods?

[Jordan325iC]

My 2.7i setup for a low compression turbo motor:
2.5i head
2.5i block
2.7s-eta crank, pistons and connecting rods

My machine shop tells me my (s-eta) connecting rods are out of spec and will need to be machined. I have a set of possibly good "i" rods. I know that "i" rods are 135mm and "e" rods are 130mm.

Could I just use my 2.5i rods and still be a low-comp 2.7, or would I be looking at increased compression and lower displacement if I used 2.5 rods?

[peerless]

Think about it, if 130 rods and pistons are even with the deck, now use 135 rods, can you visualize the piston extending beyond the top of the deck by 5mm. Thats your answer.

Your eta rods just need to be reconditioned. They resize the big end and install a new wrist pin bushing and size to your piston pins. Standard procedure. I have all my rods re-conditioned on every build.

Personally I have all my rods lightened and strengthened. They are acid dipped, magnafluxed, all the casting flash is removed from the sides, deburred, shot peened. The big end is resized to factory specification. New wrist pin bushing resized to fit the pins and static balanced.

I have played with a few different BMW rods ;)

Oh ya, I offer this re-conditioning service to everyone. $225 includes new wrist pin bushing and everything described below plus return shipping. Does not include new rod bolts, As a note one of my M20 130mm rods went into a turbo M20 that pulled 350hp on the dyno. Interested parties can simply PM me.

M42 reconditioned rods (NASCAR spec tri-armor coated rod bearings)

S50 reconditioned rods (2.9L Stroker into a E21)

M42 140mm / S50 135mm / M20 135mm / M20 130mm (the two on the left are reconditioned,lightened,shot peened,balanced))


M20 130mm eta rods reconditioned as above


M20 Turbo

[Jordan325iC]

I know compression will increase and displacement will decrease, I just wasn't sure how much. I don't quite understand how those numbers are measured, nor am I really sure how s-eta pistons differ from i pistons.

By the way, cool deal on the rods. If I didn't have my machine shop doing the work already, I might have taken you up on that.

[nando]

just have your eta rods reconditioned, that's pretty normal.

seta pistons have a slightly deeper dish (.3 difference in CR), a longer skirt and the wrist pin is further down. BTW, rod length has *nothing* to do with displacement.

[SpecM]

I know compression will increase and displacement will decrease, I just wasn't sure how much.

you're a bit mixed up here, rods don't change displacement, only bore (piston diameter) and stroke (lenth of crankshaft throw).

135mm rods WILL NOT work with s-eta pistons and crank

[Jordan325iC]

Ok, ok. I see now. Thanks for the help everybody.