I was talking to a friend who said that he has 14:1 compression in his 350X. How did he do this? Did he change the Piston(thats what i think he told me he did)? If he really did this would he be able to kick it over to start it? Would you have to do anything else to it to make it run properlylike: rejet the carb, or have a aftermarket exhaust, or run trick fuel. Does it make a big diference in preformance? R.R.

 

Well you'd have to run pure race fuel. Probably need to run a aftermarket cam to get the full effect outta that beast. But I don't know much about that stuff.

 

LOL, the old 350 chev diesel was only 15:1..... I wouldnt kick start it

 

There is a guy in town here that built a Laeger 350X motored 250R. He had the motor bored and sleeved to a 476, it is running on 15:1 compression and 114 race fuel. Its had every motor mod possibe (cam, porting, valve job, everything) I think the piston can get up to 13:1 comp. Then by milling the head, you can raise the compression a little more. It is possible to kickstart his quad, but he always pull starts it. I can stand on the kick starter and bounce up and down (im around 200) and i barely move it. Its fast though, scary fast.

 

I rember the days, back in 90' I had a 83' XR500R that I ported and polished with a 5 angle valve grind while also putting in a high comp pistion with a super thin head gasket..... It would throw me off the bike when it kicked back on hot starts! (after about 1,000 miles of hard use the high comp did its toll on the pistion pin and it developed a nasty rod knock. Sold it to another power hungry nut that wanted to build it again

 

If you didn't run at least 110 octane gas in that beast you better wear a cup for when the head blows off the motor and comes up through the gas tank.

I have heard of people running around that compression, but it takes a great toll on the motor if it isn't built right. I would shot-peen the stock rod, or replace it with something much stronger and lighter, replace the head bolts, and make absolutely sure your valve train and piston are compatiable so you aren't smaking valves with that high of a dome piston. Crhye is right, you would probably be able to find a 13.1 piston and then calculate how much milling would be needed on the head to reduce the chamber to the desired area.

 

Yeah i would probably run 120 Octane. Either buy it in a 55 gallon Drum for $200 or just buy the octane booster and mix it in the gas. Right now with the stock piston (10.5:1 I think) will the octane booster hurt it?