I ordered without thinking, can someone please help me figure out what ones i need im gonna call intense int he morning to fix it if i need the other set

 

10.5:1 will make more power but require higher octane

 

enough said i was 10:5:1 i only use premium

 

power > octane

 

Why are you gonna up the compression if you just cracked a piston. I am no expert but shouldn't you be lowering it?

 

he cracked a piston because of a bade tune would be my guess. probably ran it lean. if you get a good set of forged pistons, rods and crank the posabilities are endless

 

Like a cracked forged piston, they are stronger but they aren't invincable.

 

I would think that theyd be alot more resistant to wear and tear than stock pistons though

 

yeah i think it was too much boost, right? blew the headgasket and ran coolant on the piston causing it to crack. I wouldn't go any higher than stock in compression. It should allow for more boost with less detonation. I think Rice_Eater had a heck of a time tuning his 10:1 diamonds he put in.

 

I am sure they are. But why did they fail in the first place, they are supposed to hold to around 300 HP and they failed for some reason.

Any signs of detonation ?

 

yea but 10.5:1 certainly isn't enough to crance a piston. if you crack a piston or a ring land or anything like that there are other factors. like i said it sounds like he was running lean and burned the pistons up. just my opinion.

 

If he blew a headgasket and coolant leaked on the piston, that could have caused it, in which case he now has an aftermarket headgasket which is much stronger

 

If it was me, I would go with 10.1 and go to a 2.8 pulley and some 42 lbs's.

I can't imagine going lean with 60 lbs injectors. That would be a horrible calibration.

 

10.5:1 seems kind of high for a forced induction application. You'll require a good high octane gasoline to prevent detonation. (Id imagine even higher than 93 to run optimually. (sp) I'd go for the 10.1:1 Stock is 9.5:1. Most turbo applications run 9.0:1 or lower....

 

I didnt blow the headgasket it was 100% fine when i pulled the head off

 

ponts bace to running lean. it was custom tuned right?

 

yeppo rob tuned it

used same tune he used

i had same mods as he did so hmmmmmmm 05's suck ballz

 

Most large boost apps run 9:5 or lower yes. Are you poosting past 25PSI? Nope? Then dont' worry about it. And with teh higher compression you get more power out of every added lb of boost. Take a Whippled LS-1 and stock it runs 300WHP on a good motor, run 6 lbs on stock internals 10.1:1 and you get 500hp. Now if you were to run 9.5:1 you would need aorund 10 lbs of boost to get the same power. Boost isn't the end all for power, it's the explosive force inside the piston that makes power, not your boost gaudge.

Go for the 10.1 s though. Much more than that and you'll have a real tempermental engine even with the stock pulley.

 

I don't claim to be an expert with the 2.0 but if you have 10.5:1 compression and a blower will 93 octane fuel be enough?
My 2 cents: On big block engines I ran in the past with blueprinted 10.6:1 compression I had to run 100 LL aviation fuel to keep them from pinging. Every article I've read on boosted engines (turbo and SC) always stated the compression had to be lowered to keep from blowing headgaskets. Sounds like you'll end up with the knock sensor always retarding the timing and wind up with less power. ?

 

yes but the big blocks you are used to playing with at the very least probably have cast iron blocks and aluminum heads but more than likely have cast iron blocks and heads which don't dicipate the heat as well which is another reason your motor will knock and ping. you can run higher compression on a motor with aluminum heads on a cast iron block than one with cast iron heads and block and you can run more compression yet on a motor with aluminum heads and block and still run the same octane on all three motors all other things equal (timing, tune, pistons, etc.) so to answer your question you should be able to run higher compression with the lsj and still be able to run pump gas than you can on the big blocks you are used to as long as you have the proper tune.

 

hmmm ive never heard of that fuel for air crafts but i havnt heard of em all im sure. but most the time aircraft fuel is garbage. most of the stuff we use is just crappy deisel mixed with kerosene. i dont know like i said ive never heard of that 100 ll aviation fuel. but i guess if it worked it probably wasnt anywhere similar to a lot of fuels like that.

 

It's 100 Octane Low Lead (by AC standards not car). Used to get it by driving out on the flight line at the downtown airport in Shreveport LA when I was at Barksdale AFB in the '80s. Fuel Truck driver would park behind my car and fill 'er up.

 

Question along the same lines... aren't the rods and crank forged on the lsj, and the 300hp mark you speak of as the breaking point for stock pistons is that to the wheels or motor hp. Thanks

 

yes under optimal conditions. but as i said i think he was running lean with will damage any motor

 

10.5:1 compression is going to be pretty high. I would say that if you keep the pulley to 2.8 w/ 42# you can probably get away with running 93 octane gas. If you want to go smaller on the pulley you will need to start thinking about ways to lower compression or you will start losing HP instead of gaining, i.e. bigger exhaust, better headers, ringed head gasket, changing the cams.