Roadgoing Sprint/Hillclimb Engine Choice

Fri Dec 02, 2011 5:14 pm

Hoobs - wings, doors, glass, rear seats & trim have to remain; front seats, battery, bonnet & boot lid can all be replaced/ lightened. Underseal can be removed too - lovely job! Obviously the spare wheel isn't carried, nor a full tank....

Fri Dec 02, 2011 5:19 pm

Drifty: you won't see decent power without TBs or carbs; by all means keep your inlet manifold - get a sheet of glass and use it as a coffee table!

Sat Dec 03, 2011 3:36 pm

pistonbroke wrote:Yes - the Series Production Class A3 regs. dictate any capacity 1800cc > 2600cc; same block & head as production cars, internals incl. valve sizes are free as is normally aspirated induction. So - head work, high comp. pistons, cam & carbs/ TBs are all there to be made the most of, plus remap. IMHO attend to all of these plus an exhaust & lightweight flywheel/ clutch - job done! Simplification in itself.....

This also seems to rule out any head swappery - so the 885 is what you'll have to use, no flat top pistons / 731 head.
I've got an ex Kumho M20B25 in the garage currently in bits but WILL be done this winter. The motor is a Griffin Motorsport modded (although I'm sure some of the bits have been robbed over the years). Nevertheless, it gave (from memory) 230 bhp on the Kumho brake when last tested, so it is possible.
Was running on triple Webers, now with ITB's and full management - looking for 250+ bhp @ around 7500rpm from 2.5 litres.
Got an idea in the back of my head to build the 'ultimate' M20 with 2.8 stroker crank, oversize pistons and everything else as we've already got - reckon 300bhp should be do-able from 3.0 litres - wont be cheap though!
Kim.

Sat Dec 03, 2011 6:15 pm

I see Webcon list a new inlet they're doing for ITB's @ about £600

http://www.performancebmwmag.com/newsit ... newsID=218

Mon Dec 05, 2011 12:40 am

is there a copy of the regulations online somewhere so we can paw through them first hand?

there is or course the 76.8mm stroke 323 engine with an 80mm bore and 731 head.

now by my calcs that leaves a 84.75mm bore giving a perfect 2.6 with 731 head.

i expect there are even more loop holes possible but that depends on the exact wording of the regs.