Quick summary

[SA E30]

The problem with using an S50B32 or S52 crank, is that u either have to shave the inside of the block to allow for clearance (which is really pricey), or shae down the crank ( really not advised, cause it causes an unbalanced crank).

Although, I've got a mate running a M54B30 crank in his M20, I'm not sure what he's done to make it work, or if there was any work required, other than modifying the nose to accept a timing belt, but I would imagine so. Cause I'm sure the crank is like an 89mm throw.

I would say the longest crank u could run is the 328i crank. U could also run the 328i rods with this setup on M3 pistons, but the rod ratio would be out.

The biggest piston u can run is 86.1mm... but that is taking ur block into ur own hands... it doesn't give a noticable gain over 86mm piston.

On another note, I'm actually selling my old motor, the one with 328i crank.

I'm busy buildin up a M20, with a 325iS Evo2 (South African car) Crank (it's the same as a 324td), the 325iS rods, and S50B30 Pistons. I'm going to run 1mm oversize intake valves, and the exhaust valves r gonna be the same size (to improve mid range torque) ... Also gonna do a few other things :D

[kylebes1]

I just want to figure out what parts I can use, I like the challenge of building it myself.

[SA E30]

I just want to figure out what parts I can use, I like the challenge of building it myself.

Well there are loads of things u can use... I mean u could even go for some SR20 Pistons, and deck the block... There are so many different choices :shock:

[ragehardintothebendies]

some good info coming out here.
Do you know if it will work using all the 328 components crank, rods and pistons in an m20?

Been told by a few people that the 328 pistons are pretty light, compared to some of the others.

[SA E30]

I actually think it might work cause a stock bore is 84mm, same as the 328i.

but... There is always a but, I think u would have to cut the tops of the pistons for clearance, cause the M50 block is a longer block than the M20, so if u use unmodified pistons, they would probably stick out the top of the block.

Another thing, if ur using S50 Pistons, the rings are really expensive, and the dealer quotes the equivelant of $170, per piston for rings (well thats over here). A solution is to run SR20 Rings, but the pistons need to be modified, for the oil ring to fit, cause the SR20 oil ring is amost double the size of S50B30 ring.

Here is a picture of an S50B30 piston that has been modified. The one on the left is modified, and the right hand on isn't. Personally they work, and they work well... but I don't like the idea of runnin Jap parts in a German car (Weird eh ? )

Also the top has been cut to fit the M20... it still needed to be cut at 45deg on the edge, so that it fits inside the 84mm Head Gasket