lttransam

iTrader: (12)

i recently just built a 355 forged ltx and the compression ratio is about 11:1. i think i want to throw a supercharger on it, what is the maximum compression ratio i can have? not sure exactly how much boost i want to push.. i just know that 400 hp wasn't enough. i figure i will have to change my pistons but dont know if i would need to change anything more.. my heads have already been on a boosted car that ran 10.50s so im good there.. just dont know much about superchargers but looking to learn. thanks guys.

xdanny510x

That's to high of a comp. To run a blower.. The perffect ratio is around 8:9:1 I think... But someone can chime in...and correct me.

93v8clone

you can run higher comp motors on boost but timing is gonna be pulled and race fuel will be a must . ideally a lower comp motor is hat ya want , butt there is ways around it with meth injection and so on as long as the motor is forged

96capricemgr

iTrader: (1)

Most people want to apply gen 1 compression rules to the LT1 for boost. The single most impressive pump gas blower LTx build I know of is 9.7:1. So up in the 9s can be fine for a boosted LT1 where for a gen 1 you probably do want to be down in the 8s.

Depending what the current chamber volume is you could look at TrickFlows ported. Since they are available with a 62cc chamber they can usually lower compression unless the current head already has a big chamber.

lifeisgood

iTrader: (4)

most boosted engines ive seen are in the 9.5-1 range.
11 would be pretty high. its doable, with good tuning and fuel.
meth wouldnt be a bad option either.
why not go nitrous?

lttransam

iTrader: (12)

yeah i figured 11 would be.. now i just need to figure out what pistons i could use to bump my compression down a little, and it has nitrous but i would just like to have the power all the time.. its a street car and i just hate messing with the nitrous all the time.. and i see a lot of guys with the meth..ill have to look into that.

96capricemgr

iTrader: (1)

If the rings are set for nitrous that should work for a blower too. Making larger chamber heads still a good alternative. I know pistons looks cheaper at first but consider new rings, balancing etc and having to completely pull the engine and it may not be as cheap and easy as you thought at first, and by the time you sell off the current heads I bet a set of large chamber Trickflows is cheaper..

lifeisgood

iTrader: (4)

yup would better choice. you could talk with the head manufacture, and get your compression down a lil and you should be fine. if you could get around the 10s, and run meth itd be great.
by the time you spent the money in all the new gaskets and pistons, machining, you could fet some heads and a meth kit.

lttransam

iTrader: (12)

well i have had some issues with my new set up and might have washed or glazed the cylinders so the motor will most likey have to come back out, and ill have to see what the damage is but either way ill need rings so i could just throw new pistons and call it good. im pretty sure my bottom end should hold up, 4 bolt splayed, stock crack, 4340 scat Ibeam rods forged pistons.
well they were locally CNC'd they are 200cc heads.. like i said the person i bought these from had the heads on a boosted car that ran 10.50s, so the heads should be fine.. might have to change the cam also..

Z28Roxy

iTrader: (4)

Wiseco -20cc pistons or JE -31cc pistons.

Trickflow 62cc heads or AFR has options too.

BLK,97,T/A,M-6

For the first time, I completely agree with capricemgr. Most good engine builders will agree that it is actualy better to drop the CR by using a larger combustion chamber than -cc pistons. supposedly flat top pistons atomize the fuel better.

gregrob

iTrader: (8)

Theres a set of those trick flows for sale cheap on Racingjunk

Bob@BruteSpeed

iTrader: (16)

http://www.exoticperformanceplus.com...tCar.php?car=7
http://www.exoticperformanceplus.com...Car.php?car=61

Here are two LT1 ProCharger equipped f body's from the old website. The first one is my brother's '95 Formula that we will be taking back out to the track in a week or so. We're going to experiment between M/T ET streets and M/T drag radials. I was seeing 1.29 60 ft times with the M/T drag radials on my '99 Z28 so we're trying them on the Formula. Bob

LTXBOI

iTrader: (2)

your compression seems kinda high for a F.I build unless you wanna run 3-5 psi of boost.courious to why your compression is high? for a good F.I build you would want to be @ between 8.5 to 1 or 9.5 to 1... blower cam,valve springs and low compression pistons and rings, heads for a good lt F.I motor

lttransam

iTrader: (12)

both of those cars are awesome!! i would love to see it run! looks like alittle bit of work installing one, but not too hard.. my goal is somewhere in the 500 rwhp range.. the motor i have now is about 400 whp, but i just want a blower!! thank you for the good info!
yeah i know its high, i didnt build this motor for FI but after installing the motor i just want more, and dont want to use n20, so figured i need to add some boost, so now i just need to figure out what pistons i need and so forth.

Z28Roxy

iTrader: (4)

Yeah but those might not drop his CR enough. He'll definitely at least need some thick head gaskets to do go with those trick flows.

I'm running -20cc pistons and trick flows but "only" will have my CR down to about 9.3ish to 1. Granted I'm building a 383, but still....

lttransam

iTrader: (12)

i dont plan on getting rid of my heads.. they will work on a boosted application, are they the best no.. but i already have them lol i am hoping to just change pistons.. but not sure.

1redta

you could run E-85 to help

lttransam

iTrader: (12)

that looks like a really interesting setup.. some of my buddies have it on there carb applications.. but what would you have to change for a efi? how big of injectors?

OneBadTA

Set the compression up to how much boost you want to run. My old turbo engine was under 8.5:1 and was doing 24psi with 93 octane. Im contemplating a turbo 355 right now and will have compression around 8.5:1 so i can be safe close to 20psi. My other turbo engines had 9.5:1 and werent recommended taking over 14psi on 93 octane. The higher compression made better tq off boost but the boost is what really makes the car fun so why not run lower compression and more boost.