hey guys, i have a rev MXZx 440 and the guy i bought it from gave me both sets of heads with it. i'm sure i'll do some tweaking one i get her out on the trail, but what is the best setup i can start with for trail riding?

high compression or low compression?
what jets should i run with these?
at what outside temperature should you start changing the jetting?
how will i know if the jetting is wrong for the conditions?

any and all info will be greatly appreciated. thanks for your time.

James

Start with low compression for trail so you can use pump gas. As far as jetting, read your plugs.

no one else has any input?

I run a #3 bg w/LC inserts and use 87 octane. I have no choice in the fuel as where we go ride that is all there is.
Never a problem with 320-330 and #40 pilot.

I have spoke to several 440 owners via email or phone who have told me of burndowns. Most times the burndown is in the midrange near 3/4 throttle for distances of less than a mile...OR...at w.o.t for less than a mile using 300-310.

I burned an 03 this winter past at nearly full throttle...no warning, just "BAAAaaaaaawww...."

My opinion for trail riding the slides are too lean at 4.5 cutaway using Hi-Comp heads.
Most I have seen is burndown in slightly less than full throttle.
Oh and always...ALWAYS run Iso Propylene.....Not gasline antifreeze...
Iso Prop keeps the water from freezing and not to be mistaken with making water evaporate.
Iso lets the water stay in liquid form to run thru your mainjet instead of blocking the jet just long enough to burn the engine down.
Alcohol promotes separation of the oil from gas so in your floatbowls the two mediums will be separated. Not good for rings and in theory it promotes washing down the cylinders.

I do have a few clutch kit owners with 03's who are running a #8 gasket with high comp heads and 330-340 jets 40 pilots, air screw on 1/2, needle on #3. They tell me their sled runs great.

I still have fear of the high comp heads in an 03 because of the cdi timing.

could someone post or send me a pic of a 440 combustion chamber? if it had a metric ruler layed centered across it that would be even cooler thanks

If Rad Chad looks in my Red box at his place, he could find my 14:1 domes.
I have some Low comp domes also...and some 15:+ domes.

I will get Chad on it.

Laterz
Joeyz

thanks Joe, my interest is in the squish band area to bore ratio (just need the width i can do the math), that's why the ruler. Also what's the aprox hp and torque peak #s on those motors?