Low End Power on 103

We race a Big Wheel Supermini. I think we've got the gearing where we want it (14-52) but still looking for more low end out of the turns. Motor is 85 bored to 100, HotRods stroker crank, ported and polished and 85 head milled to fit bore & stroke, FMF exhaust.

After reading some comments on here I was thinking about the PC Power Valve and the Phathead head. Should I do both, one or the other? The thing I most confused on is the Phathead stuff. If I'm looking at it right think I want to use the 2 or 3 dome (I use and 50/50 mix of 93 and 110 fuel) and do I go with the o-ring or head gasket?

Maybe we just need to work on skills but he always complains of the bike not coming out of turns like he wants. For example there are 2 sections of a track we ran last weekend that if he takes the middle or outside line he was good but trying to take the inside he stuggled to clear the next jump. We haven't tried a 13-52 setup but that seems like it will take too much off the top end.

How old and how much does he weigh?

Sorry. 14 years old and 110. Also should have mentioned suspension has be re-valved for his weight.

Try moving the ignition timing mark a little to the advanced side. Then you may want to get some different sized base gaskets (thinner more bottom end) and more compression.

More importantly work on cornering technique, momentum momentum momentum!!! He has to do his part also and not just rely on that motor. Umm can ya tell it's "been there done that" for me? LOL

I love our 103 motor but just put in a 112, so I'm starting with a new combination just have to see how this goes.

JBFL, definately let me know how it works out for you.

OP, On the tighter tracks we ran a 13/52. mostly 14/52. there was even 1 track he ran 15/52, I think he even hit 6th on a straightaway.

That phathead is setup for the OEM gasket. You get your choice of 2 domes. get the stock and one under. You'll want to run the 1 under using race fuel mix. The PC valve and spring will make a huge difference in how fast the pipe hits but is still very smooth.

Our 103 will run circles around the 112 right now. Way too tight of squish on the 112 and pretty high compression= HEAT!! 112 pulled like crazy then shut off before it really ever wound up. Went from a 145 main to a 150 and no difference at all. Even retarded the timing and it barely got another 500 rpm by the sound of it. Going to put a thicker base gasket and may have the head cut for a better squish band.

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