So your aiming for 13:1 compressions? That's massive.
Those are massive cams your trumpets will have to be really long. Unless you raise your revs of course.
Xrallyparts do a x42(basically a m42, with s42 bits made to fit) but your right the 18 mm piston pin would force you to use there rods! They get 260 hp out of 2l at 12.5:1. At 13:1 your probably being a bit conservative with 244 hp.
What are the specs of the piston? Dia, pin, comp height, mass etc
Yep, its a pretty insane level of compression, but thats because of the compression losses as a result of the extreme cams.
The trumpets are going to be setup on the dyno, and yeah they're going to need to be massive. Revs should be higher because I'm using the 81mm stroke of the M42 rather than one of the other crank options. This gives me an over square engine that should rev nice and high, and if you check the rest of this thread everything I've done has been to reduce weight while improving strength of the parts.
You're right about Xrallyparts, I spent far too long pouring over their site, but the parts blew the budget I had to pieces. If this engine works then I might start a phase 2, but I have a Honda B16B to rebuild before all of that. As for power, I really only expect 200 - 220bhp as I've been disappointed by NA tuning in the past. A mate of mine put the S50 ITBs and a fast road cam in his M44 and got 178bhp so who knows where it will end up.
As for specs, 86.5mm diameter, 22mm pin, 31.5mm comp height, mass is as yet unknown, I am totally relying on the recommendation of the BMW guy on this whole aspect of the project...
