One of my cars runs a HPI .12R SS engine. Using the awesome power of elementary-school math, I calculated based on the top speed, tire size, and gear ratios that the engine is peaking at about 30,000rpm. I did a little grinding and polishing on the sleeve (and the hole in the side of the piston) to improve breathing through the transfer ports, and testing showed the car gained ~1mph, i.e. ~600rpm. Not a huge improvement.

I've been doing more reading and it looks like the next thing to try is modifying the intake port timing on the crankshaft. The general rule seems to be "opening earlier = more low-end power" and "closing later = higher max RPM". I wouldn't complain about more low-end power, but it's really the max RPM I want to raise. This engine just doesn't rev as high as I think it should, and it has the same conrod as HPI's .18 engine from the same time period, so there should be no concern about the conrod breaking from increased stress.

Having said that, I'd like someone with more experience to look at the pictures below and tell me if they think there's actually room to improve the intake port timing. If air had no inertia, then the answer would obviously be yes, because the intake port closes well before before the exhaust port and transfer ports open -- but of course air *does* have inertia, *and* it's elastic too, and I don't have enough experience to account for those effects at 30,000rpm.

Here are the crank positions when the various ports open and close:



What do you think? Is there enough room to have the intake port close later, to get more max RPM out of this engine? Or do the port timings suggest a different approach that would work better? Or am I S.O.L. and I should accept the engine as-is?

Also, I should mention that I recently got a Novarossi .12-.15 pipe tuned for higher max RPMs, but I haven't had a chance to test it compared to the stock HPI pipe, so take that into account if you think it will matter at all.