1slowfbody

i'm buying the forged 346 rotating assembly from Scoggin Dickey and was wondering which pistons to have them switch out for a lower compression on the engine? from what i've been reading the dish top are the ones i'll need but which brand makes a better piston or are they all as good as eachother? i'd like 9.0-9.5:1 and I plan on running 10 lbs of boost through 317 heads. the cam will either be the TR Blower Cam 214/230 .601/.579 117 LSA or maybe the Speed Inc 226/234 .598/.599 117 LSA. Thanks guys for the help!

candlelit

iTrader: (21)

Diamond, Mahle, JE, Lunati, Wiseco etc will all handle 10psi no problem. Just make sure to get good rings. I'm going with Texas Speed's deal on a set of Wisecos.

old motorhead

iTrader: (10)

Any particular reason you're going so low on the C/R? Is the engine going in a dedicated track car? Truck in my signature is running 9psi and C/R is a little over 10:1. Vette is at 8.5psi and running stock LS3 compression which I believe is 10.7:1. Both are running stock GM pistons. Truck probably has 30K on the LQ4. Vette has about 6K on it. When and if I have to build a replacement, I'll shoot for around 10.5:1. Your motor will run better when not in boost if you can keep the c/r up a little.

1slowfbody

car will see more cruises/street/twisties than the track, i will take it to the track several times throughout the year but it will not be a dedicated track car. i was reading about SCR last night and i think what i'm thinking what i learned about was what compression someone should run with a centrifugal style blower and not a maggie . . . or is it all the same? in the thread i was reading the main point was less compression more boost and more compression is less boost, but also what i understood from it was run lower compression if you want to run pump gas and be safe, did i read it wrong? if so please help me out with it. my original plans before i read last night are forged 346 with 243 heads and a nice size blower cam, after the read i was thinking lower the compression with 317 heads and dish top pistons. so higher compression with a maggie is a god thing or it's just a good thing in general for boosted applications?

1slowfbody

also which rings to run? standard or nitrous?

dschmittie1

iTrader: (64)

Get some 243 heads and come Diamond -8.6cc dish pistons will get you right around 10.0:1 And will be good for 10psi.

I was running stock heads and -8.6 cc pistons at about 9.6:1 now going to 243 heads that have been work over. also the car will be seeing 14-15 psi. Hope this helps

dschmittie1

iTrader: (64)

Also I am running Boost rings

1slowfbody

when i call on monday and talk to Tim i'll talk to him about switching out the pistons and adding in the rings. the 243's heads i have, i think i might be sending those out to a shop i know of. thanks for the reply and help!!

1slowfbody

btw do you have a part number on those pistons?

dschmittie1

iTrader: (64)

I think it is 11503 3.905 bore 3.622" Stoke and -8.6cc dish

XtremeDime

iTrader: (16)

for a street car. anything less than 9.3ish:1CR will lose some low end on the street. Of course it depends on your turbo, cam choice and the stall you go with, assuming youre an auto. You are right, the lower the compression the more boost you can run on pump gas but you can run 10 psi on 93 at 9.5. We dont have 93 in Alaska so Ill be trying to run 10psi on 91 @ 9.7 lol. Too be honest, meth is always nice even at lower CR.

1slowfbody

i'm going with the MP112 magnacharger, cam will be 22X/23X and yeah i'm an auto; i'll be running a 3000 stall with 3.23's for now until i get a new rear end that will have 3.42's. i bought some 243's so should i leave them untouched or send em in the help out with the compression? i'm a noob at this right here

XtremeDime

iTrader: (16)

Lol, missed the part about the maggie! I dont know much about blowers or what ranges each of them work in, sorry. I would go with 317s and some mild dished pistons to achieve 9.5ish CR. Realistically, anything over 9 is pretty bearable.

1slowfbody

i'll be going with dished pistons but i might just stick with the 243's and send them out for a stage 1 job. reason being is the magnacharger set-up's i've seen are being run with either 241 heads, stock 243's or stage X 243 heads. with centrifugal blowers i see people run the 317's and dropping SCR but not one 317 pair have i seen on a maggie set-up, not sure why this is but if it's proven to work good with the 243's i'm goin to use them since i bought them lol maybe the maggie like more compression

old motorhead

iTrader: (10)

If you have LT's, dual free flowing muffs, good heads, and either of the cams you referenced, I don't think you'll see 10psi with the mp112. That's not all bad either. You'll still make good power and less heat. Keep the compression up and you'll have a very responsive street machine. I'm assuming you have access to 93 octane. As one of the other guys mentioned, some type of boost cooler or meth injection would be good too.

There's not much difference between the 243's and 317's besides combustion chamber volume. Either will do fine. Just let the folks you're buying your pistons from know which heads you are going to use and they can spec the pistons to the c/r you want.

1slowfbody

yep LT's with true duals will be the exhaust. thanks motorhead, when i call Tim on monday i'll let him know the heads so i get the right pistons and i'll ask for the rings for boost. we have 91 here in california my options are run 91 alone, run 91 with 5 gallons of 10X ocatane or run only the high octane. we don't have 92 or 93. this is why i was reading up on lowering the compression, because we don't have have 92 or 93