building a super hot street motor

[dapbmw]

i was thinking about going with a camshaft duration higher than 304, and i would not mind sacrifing low end grunt for top end power, as this will not be a daily driver but a once in a while weekend driver. dbilas has a large selction of sport/race cams up to a 342 but i was thinking of durations from 310,312, 316, 310/304 or 324.

so what would be the best cam for my mods?

the other engine mods will be 11:1 forged dome pistons, pauter or carrillo rods, knife edge crank, aluminum flywheel. 48mm intake and 40mm exhaust valves, sport valve springs, adjustable cam sprocket, 48mm weber dcoes or 48mm TB's. i was thinking about an m3 crank too

[bmw1602.com]

as far I my research has shown, anything over a 304 cam and 10:1 compression will require race gas.

even on my 304 my powerband is wayyy up there. something like a 316 or a 336 will be making power above 7000 and still going strong around 8000. Therefore requireing the billet rocker arms.

I belive such a motor on the street would be kinda unusable....imagine how much attention you would get screaming at 7000rpms? It's kinda like a modern 600cc streetbike....lots of HP but at 17,000rpms I got tired of screaming around in the canyons at such rpms so I bought a 1000c bike and I'm much happier now, I can keep the revs lower and still have power and fun

to me a street motor must have a lower powerband and more torque....

probably a stroker motor with a 292 cam.....would be good.

[Tommy]

General opinion is that Schrick 316 is best overall race cam. I think it would suit your purpose too. I run normal european pump gas with 316 and CR over 11.5:1. My race engine could be used in traffic - allthough it would require some attitude. With std type clutch it would be fine. I have used 7200 rev limit because of stock rockers. There's still plenty of power band starting from about 3000 and it's not all dead even below that.

Good luck with your project.

Tommy

[bmw1602.com]

pump gas here in cali is 91octane...... I think europe is 93.

[Tommy]

We have 95 and 98 that I'm using but the ratings are all different than over there. I recall seeing a comparison somewhere and the difference wasn't that big.

Anyway it depends on the cam too. According to simple calculation of trapped compression ratio -> If you can survive with 10:1 CR and 304 with 316 you can go to 10.3:1. Calculation assumes that the cams are timed according to specs.

[Anthony]

Your extra large valves may cause some issues particularly with a high lift, long duration cam.

Besides you make a valve too big and will become an obstruction.

[Tommy]

Yes, valves may limit the maximum cam. I just test fitted my 39/48 valves with the cam that's supposed to be exact copy of early (hmm I believe it was early type) Schrick 316. I had 1mm gap between the valves at minimum.