will AV(aviation) fuel work?

 

I'll second the good fuel discussion! These motors are prone to detonation even in stock form.. don't run the cheap junk... AV gas is better, but still not as good as race fuel (110+octane).

I will disagree about boring/porting changes... depending on how the porting is set up, (Roof angles, etc,etc) A bore job can alter the characteristics of your port work.. usually not significant... but to those of us who are **** beyond belief... I end up correcting things after it comes back from the machinist.
It also depends on how much material is removed... boring from stock (86mm) to 88mm changes things quite drastically...

Just my $.02

 

I will be having it bored next week, when I get some money... How much does race fuel cost?

 

Depends on your distributors local to you.... the ones here screw me pretty good... around $4.50/gal

 

AV fuel here I come! [img]i/expressions/face-icon-small-happy.gif[/img]

I am gonna order a piston set and wristpin bearing when I get paid next week. Do ya'll think I should run the 55cc dome or the 59cc dome?

 

It's a matter of choice really... I personally would not use the 'canned' design that pro-design offers, but that's just my opinion.
Merely dome size (cc's) is not the only variable in question.... relating to octane and detonation.
I also feel the stock head is not optimal either... but some simple machining can make it work well.

Just my $.02

 

Duneaddict, regarding your opinions on porting, I'm not sure I completely understand. I realize that largely the cylinder volume determines the window area but is a bore job really going to make a noticeable difference. As far as roof angles, don't most good porters make the cylinder sleeve part of the port windows straight? This wouldn't be important with nicasil cylinders but having the roof of the exhaust port angled (for example) seems like a very bad idea with an old iron sleeve that will inevitably get bored. With my ported cylinder, most of the ports in the sleeve go straight back (no angle) and THEN match the contour. That way, every time my cylinder gets bored, my exhaust height does not change. Also, the windows become a little bigger as the cylinder gets bigger (although not at the same rate).

Is your exhaust port window angled? If so, is it really worth it? Do you see enough additional hp's (with your sleeve at the same angle as the rest of the exhaust) to make it worthwhile?

I had a new sleeve installed before the porting. Now I just had it bored for the first time. If I dyno'd this machine before and after, do you think I have now lost power? Or do you think that there are new, unwanted dips to the curve?

I really don't know these answers so I'm just trying to learn. I never would have guessed that a good port job could become bad simply because the bore became larger.

Thanks

 

Duneaddict, it is a powerhead made by duncan racing. Not sure if that is any different....

 

The Powerhead and the Coolhead are the same. However, Duncan claims that they checkout/set-up the domes themselves. Thus, I would feel more confident ordering a dome from Duncan racing than from a Coolhead distributor.

 

I figured they were the same. Mine is probably just old(porting was done in '97)