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      09-03-2020, 10:49 PM   #8
noogaM2
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Drives: BMW M2
Join Date: Aug 2020
Location: Chattanooga, TN

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Quote:
Originally Posted by nothingman View Post
I've had several motors built back in my SR20 days with forged rods and pistons, so I've been through the process. Although there are plenty or reputable engine builders out there, finding one that will follow the tighter clearance tolerances required of high performance engines can be tough. Looking for a builder with BMW experience would be a good start. Here are a few I've found:
ABR in Houston
Ghassan Automotive
Bavarian Rennsport

If I were rebuilding my N55, I would lower the compression from 10.2:1 down to around 9:1 to allow more boost with either Wiseco or JE Pistons, and Carillo or Crower rods. I would also take time to do a piston coating to help reduce friction and heat.

I would make sure the shop I am contracting to build my engine has an N55 torque plate. A torque plate is a sheet of metal with cylinder holes which is bolted to your block to simulate the stress of the head. When the two are torqued together, your cylinder bores distort slightly (instead of being completely round - imagine them being slightly oval) which can result in blowby. A torque plate is used to simulate the head on the block before honing the cylinder walls and fitting the pistons and piston rings. VAC Motorports makes a torque plate for our engines.

Next, I would make sure to use a new set of head studs to prevent the head from lifting from the block during high boost. ARP is a well known brand throughout automotive racing circles, but unfortunately they don't have anything for the N55. VAC Motorports has N55 head studs.

Lastly, if I already had my engine disassembled I would look into having the head ported. Porting allows better airflow trough both the intake and exhaust valves, can remove burrs and other spots from the casting process, and reduces turbulence allowing for more power. Head Works is an example of a good shop focused on improvements with BMW head porting.

Oh man thanks for the info!
Appreciate 0