00_buck

I understand but if the OP is gonna buy a 2.6L blowzilla which the minimum boost is 15 psi, why would you forge your motor with a higher CR when its not wise to run higher boost than 15 psi unless you have a CR of 8-8.5. Sure at 15 psi (which is max for a high CR motor is fine) it will make good power but we all know that 15 psi will not be enough after long and now you have to go back and rebuild your motor again because you bought high compression pistons that won't handle 20-24 psi. You're gonna buy a very powerful SC and use it at its least powerful setting and even pay for a short block that can barely handle it? My goal is about 600 rwhp on my automatic, that is why i'm running low compression pistons.

smashten

some good info. like to thank grogan for the mmr sale info, just bought the 600.

My question is what size dish my pistons should have. My long term goal is a KB 2.1 at 9psi with a 14 psi swap at the track every now and then. I have a 02 gt and i read the stock pistons are -15cc. They wrote my order up at -18cc which is what some of the earlier gt's had. I want as much power in the year or so it will take for me to save for the kb 2.1 but dont want detonation issues after FI. I have 93 octane available for now and read where the kb 2.1 was setup for stock engines. Will the forged rods/pistons and balanced/bprint engine make up for the high compression so I can go with the -15cc?

00_buck

I recommend going to KB's website, they tell you everything you need to know. A KB 2.1 is only efficient up to 9 psi (KB claims) and makes about 431 rwhp at 9 psi. It can be used on the stock motor. If you want more psi than that then you want the 2.6L, a forged motor, and a fuel system upgrade. KB claims the stock motor isn't good past 450 rwhp (judging from a manual). but for your piston question: if you plan on making power past the 450 rwhp mark, you should go with the 18cc pistons. By the by, if your making below 450 rwhp (as stated earlier by another poster) you will loose power with low compression pistons. They're only made to withstand higher boost levels that higher compression pistons can't handle.

smashten

thanks buck. iknow the kb guys start pushing the 2.6 for low compression or strokers. also read about them pushing 14 psi on a stock 4.6 although article read like they didn't know how long the setup would last. i guess the 3 cc difference between the 15 and 18 couldn't make too much diff. and i wont have a forged crank, but the forged pistons and rods should be solid.

b96gtman

dude , 00 buck, the dish of a forged piston does NOT i repeat DOES NOT determine the strength of the piston. the type of material and the design of the piston is wht determines that. if yur theory is right how come the fastest modular 4.6l motor.(john mihovetz) from Acufab runs high compression and high boost with it? 4v twin 76mm turbos makin 1600-1700rwhp! 52PDS of BOOST MAN! 11.1 compression. his car was the first 4.6l to hit 8sec and 7sec and now 6sec 1/4 times! compression and boost is a neverending argument. to each his own i say. My theory is tht if u run a positive displacement blower like a kenne bell than u shud run a lil lower compression. easier on the motor with the heat thy make,and easier to tune. with a centri blower like a pro charger id say run higher boost than u wud the kenne bell. like my motor is at 9.5 to1 and will have a Novi 2000 on it and will probly see about 15 to 17 psi. centri blowers need compression to operate more efficiently whn in the lower rpm's.

00_buck

thats awesome but i'm talking about a 2v motor. I'm not gonna compare apples to oranges. The 4v breathes totally different and has a different combustion chamber. How many 2v's are running 11.1 CR with say... 650+ rwhp? just call the experts at KB which make the SC that the OP wants to run (not a turbo) and tell them they're dumb assess. I can take it but i'm sure they'll just hang up the phone and continue to sell to sensible people. I'm gonna quote what they say about the "2V":
"The 4.6 2V with a Kenne Bell Twin Screw is a real performer. Ask anyone who owns one. However, if your plans are to make over 450HP by adding heads, cams and/or increasing boost, forget it. Upgrade to forged rods and 8-8.5 pistons."

and from their rods and pistons section: "When exceeding 450RWHP, we recommend replacing the stock cast pistons and powdered metal rods with forged H beam rods and forged 8.0-8.5 pistons which should allow the engine to run another 3-5 psi (12-15 psi) depending on pump fuel octane. Remember this. Power is all about cylinder pressure and it is easier and far less expensive to change supercharger boost than pistons and compression ratio. Reducing the compression ratio from the stock 9.5 to 8.5 or 8.0 will lower power by approx. 3%-4% respectively (see "HP vs. Compression Ratio"), but the
lower compression will permit the engine to run 3-5 psi (40-65HP) of additional boost which will more than offset the relatively small power loss from CR."

Now I'm not talking about what a Corvette Z06 does at whatever CR I'm talking about a 2v with a 2.6L KB which is what the OP wanted to use. I don't care about any other app or turbo, or Hemi, or LS engine, or SVT, I'm talking about a KB 2.6L for a 2v. I'm done here so call KB with any other theories or accusations; and above all else, have fun!