compression

[33dauer]

Well had mine and my buddys predators out today, mine is a 04 his a 03 and his is a horse compared to mine, both stock jetting and intake, his has a fmf slip on,mine stock with rear baffel removed, so took his fmf and put it on mine and helpd a lil but not much. Going to build a tool that i can hook my compresion tester on and pump them both and see what i get, mine has had some alluminum and metal in the oil due to the bolts on the backside of fywheel coming out, also going to try and pu a timming light on them to c what i get. Does anybody know what the compresion and timing specs are supost to be? Its obvious that mine has been rode had and not taken care of, so thinking maybee it needs freshend and if so will probly put a nice higher compresion piston in it!!

[33dauer]

well went out and made a adapter to check compression and came up with about a 100psi, checkd my buddys and his is easy 130psi, sprayed some penetrating oil in mine and got 140psi, thinking my rings are needing attention, checked valve clearence and came up with intake 1 .005-.006and other under.005, exhaust are both .005-.006. if i tear this down i am going to get a 12.5 wiseco piston and maybe do a valve job if we have the right tooling at the machine shop i work for part time!! any help or ideas are great and i appreciate them good or bad!!!

[joshr08]

you wont really gain much from the std bore hi comp piston 558 big bore is only gaining 3-5 hp

[33dauer]

dont realy want to do a big bore to it as dont have the funds or needs to, and for the price of the 12.5 piston and being a better piston than stock i hate to buy rings for the stock piston and just put it back together when i could have just spent another 100 and gained a lil and know it is better than what i had!! heck my lil 4.3 in my boat has nice light weight forged icon pistons in it being i had them left over from racing, its a full roller motor that gets the job done prety dam good lol

[joshr08]

heres what im saying. your not going to notice the 12.5 piston std bore because they arent really 12.5 to 1 they are closer to 11.5 and stock is already over 10 to 1. if it was me i would just re ring the stock piston unless it is junk

[Nate782005]

Build it the right way. Put the 12.5 piston and fresh rings in it. Having metal shavings in the motor is a sure sign that there's excessive wear and tear, regardless of how it runs. You may need to have it bored, fresh bearings, etc.