Top end?

[biggun6ss]

My buddy has a 2004 Shee LE. It has been ported ( by some guy in Arkansas), a hemi head, fatties, and clamp on k&n's. He keeps burning up the top end and having to bore the cylinders, replace pistons, rings etc... Is it because he runs 91 octane? Should he use a higher octane fuel or does it not have anything to do with the fuel?

[wayfst]

change cdi boxes, reset his timing back to zero, richen up his jetting by one or two. i had this problem last year the cdi wigged out a took 4, count them, four motors and since you can't test cdi's its best just to change them and be sure. hope this helps.

[joker149999]

it has nothing too do with the fuel, i would say one possibilty is that guy may have done a ratical port job and opened it up way too much

[biggun6ss]

His timing never was advanced so it should still be at zero. He is running 300 main and 30 pilots. We are at 3300 ft. Should the timing be advanced?

[fastbanshee4u]

It could be several things.

detenation- eating away piston ,not enough octane if compression is over160

lean condition- melting top piston getting to hot

If your port job is good 300 mains will not do the job.learn about jetting or pay someone to do it for you,rebuilds will cost you more.I say you will need closer to 400 mains .More fuel is better than not enough fuel.Good luck Oh yea 91 octane for 20 ,21,22, domes only.

[biggun6ss]

I don't know how much porting was done and either does he. Sent it to Arkansas and then it was sent back. Before the port job a yfz 450 with revbox,pipes, and jetting was beating him by about two. After porting, banshee was screeming past him by about 5 quads. Dont know how far they were racing ( I was laughing too hard). Then he lost his top end. Bored it .030 and lost it. Now its bored .050 and he is going to try race gas.