Topic: Tractability vs Track-Ability

[754]

I am at a crossroads here as far as my next engine goes.

I have had simply too much fun with the torque I have been making and am wondering about headwork.

All I ever read on here (re headwork) is top end, top end , limitless high revs, top end.. so I am thinking, that kind of headwork must be wrong for what I want?

So i am thinking mild porting, not porting for max flow, if I want to keep the torquey midrange?

Any thoughts on this...?

[crazypj]

Probably leave the intakes with a really mild clean up ( mainly match to manifolds and blending) and re profile only the top part of exhaust so you have a well defined anti-reversion step (not a lip) at bottom of port.
 I tend to take them out to gasket size at top edge and blend to about half way down port, leaving the bottom completely stock
PJ

[eurban]

Have you increased displacement and compression yet?  Good place to start.

[754]

I was 836 with 10.5s, RC 315 cam and Webers..stock head with triplecut & stiffer springs.

I will end up either 970 or 1000 cc..probably 10.5 or 11 CR , 315 cam, Webers. I have a head (not tried by me) with Stainless valves, bigger intakes, and has port work done ( dont know how well).

My biggest worry is that if I use a head ported for maximum flow, I think it may suffer where it gets used the most.

I have had an engine that felt overcammed.. yet it was probably milder than what I run above. but it was probably just the wrong combination of parts, that really ended up not too much fun to ride. What I mean is it was fine at 6K or higher wanted to run like crazy but really sucked around town.. literally no fun..unless you were doing something illegal!

[pampadori]

your are right that it will remove some torque.  i don't know that it will be enough to not make it fun though.  with the extra displacment i would think you would be fine.  that sounds like a monster motor you got there. If it were me, i'd port it and just keep the engine buzzing at 10k all the time.  Then i would race every 600cc sportbike i came across.  I don't think you are going to upset any liter bikes, but give them a try to.

[kayaker43]

Clean up and match the ports, but don't enlarge them much or you will lose velocity. Its not the porting that changes your power curve, its really the cam timing and exhaust that determines where it makes the power. If you make power on top, you want big ports, otherwise stock size but cleaned and matched is fine.

I like a street motor to have the same or more low end as stock but a healthier surge from 6-8K. Big bore and compression help across the board. A mild street cam and street 4 into 1 will give the upper midrange rush without killing the low end. A hot cam with race header (short primaries) pushes power farther up the rev scale and loses tractability.