Wicked94z28

Procharged 408 corvette advice needed!

Hey, finally to the stage of building a motor for the c5 and figured I'd ask some advice from the people who have been there and done it. I already have a 6.0 cast lq4 block, Callie's 4.0 crank, compstar 6.125 rods, now it's piston time and that's where I need your help.. This is my first FI build and first LS build so here goes. I'm shooting for around 1k whp and plan on going with a f1a or f1c and keeping the a.c., car has twin pumps and a boost a pump set up for e85 but I'm still up in the air about keeping it e85 due to the lack of supply locally where I live ( have about a 40min drive to the nearest station with e85, so if it's possible with pump gas id rather go that route but if not then e85 it is) the car will be on meth, so my question to you all is what would be a good compression to shoot for? I was gonna go low 9s but after reading around I've been seeing a lot of high compression boosted cars making crazy power, my car won't be a daily but a weekend warrior/ cruiser car. I know I have to factor in heads and all that good stuff but as of now I'm just kinda looking for a # compression wise that will put me at my goal. Thanks and I look forward to hearing your info.

quickvert1

I hope its auto

Wicked94z28

Tr6060 with a rxt and fingers crossed lol

Detoxx03

iTrader: (14)

F1C is probably the better option to hit and top 1K at the wheels. Hit up Dsteck for a flex fuel kit that way you can run e85 and any other type of gas you want. I'd do compression in the 10:2 range or higher.

Bob@BruteSpeed

iTrader: (16)

I agree on the compression ratio if E85 is used. To the op, I'd go with the F-1A-94 and it will make more power than a standard F-1C. Bob

MIAmotorsports

9.0 for pump gas if you can choose. You need to decide on it before you get going though because e85 won't need an intercooler and like some higher intake temps.

oscs

iTrader: (19)

My vote is a lower CR.. However if you plan on going high CR buy some good thick deck heads and do your self a favor and don't buy a cheap crank. I've read a lot of threads in this section about 408 S/C cars tearing **** up.

Detoxx03

iTrader: (14)

I was thinking of the F1C-94.

OP no need to go to 9.0 on pump. That's way too low and people have been doing the 9.8-10.2 range on pump for a while now. I'd say go a little lower if you don't plan to run meth and higher for e85. Higher compression, lower boost and timing needed.

oscs

iTrader: (19)

I agree that 9.0 is to low. A healthy upper 9 range would be ok for me. Im curious though why is it that all S/C guys try to run a alot of compression and timing vs more boost and lower CR/Timing? it just seems like the most risky way to make power.

Detoxx03

iTrader: (14)

Boost and timing are killers. Better to make the same power using less boost and timing by having a little more compression. It's been working for a while now. Days of the high 8's and low 9's have passed us by.

oscs

iTrader: (19)

The days of making power using boost safely are behind us? I couldn't disagree anymore. Also boost is only a "killer" when it's used irresponsibly. Shoving a bunch of compressed air into a high combustion high timing motor is just asking for trouble. I agree it works but it's a much finer line to be walking. IMO it is by far a more risky way of making power.

There is absolutely no reason to be scared of boost.. You need to fear aggressive timing and unnecessarily high Compression ratios much more.

Detoxx03

iTrader: (14)

Just as dangerous cramming a bunch of boost in a setup because of its compression short comings. I never said higher timing was better at all. I said higher compression is better cause you can run lower boost and timing to make the same power as a low compression setup utilizing more timing and boost.

Technology has advanced and people are still running to low of a compression on boosted setups when you can bump it some. I'm not saying run mid 10's or 11's on pump but you don't have to be in the 8's or low 9's like back in the day.

oscs

iTrader: (19)

Why do you think cramming a bunch boost into a motor is unsafe? And a better question is why do you think mechanically creating X cylinder pressure with less boost is safer?

I'm genuinely curious why you think that and not trying to argue with you. I'm a turbo guy and do things differently than you SC guys.

Detoxx03

iTrader: (14)

It's not that I think it but the results people have been having with lower boost/timing and a little higher compression setups have proven to be working well. Friend of mine with almost identical setup to mine has his comp at 10.0 on a pump/meth setup. Only needs 13psi and low timing to make over 900rwhp. I know turbo's are different. Another friend with twins on his 5th gen has his comp at 9.6 but the mid range hits so hard with the turbo's it seems safer on that setup. Proper octane is the key. For a strictly pump gas car that won't see meth or race gas yeah lower is safer.

When I do my build it will be a 10.2 comp setup. Hell right now in stock bottom end the comp is 10.7:1 and my timing is set at 18* on my face tune and 14* on my pump tune but I only need 11psi to achieve 780rwhp. Completely safe with no detonation or anything.

Realcanuk

I would keep the compression somewhere around 10 on pump gas. Running 9.9 myself and as Detoxx says, don't need a ton of timing or boost to make power. Conservative tune and still make enough power this way.

oscs

iTrader: (19)

I agreed with mid to high 9 CR however i don't agree with any thing over 10:1.1 on pump gas. Personally though I would run a 9:5.1 9:6.1 and throw a bunch of boost at it. There is nothing wrong with a lot of boost.. The Cylinder pressures are what you are trying to minimize. IMO It is easier to control what is going on inside your CC with a lower CR and more boost.

In the next few weeks i will have my hands on a 9.8:1 Novi 2000 LS6 to play around with. Im excited about that as i will get to learn a lot about how a S/C effects CP/TC/ etc.

Wicked94z28

ok so it looks like 10.2 is the way to go, by chance does anyone have or know a site for a good compression estimator so I can figure out what -cc piston I should pick up... also another note, is the F1R streetable? theres a awesome deal on one over on the vette foum that has me tempted but im not sure if that would be a little to much.. thanks for all the tips and advice!

Bob@BruteSpeed

iTrader: (16)

The F-1R is very streetable, it takes more power to drive it than say an F-1A-94 but if you can get a killer deal on one, then I'd say to go with it. Below is a Z06 where we used an F-1R at the old shop. Bob

Detoxx03

iTrader: (14)

I would just run the F1A-94 or F1C-94 over the F1R.

ajrothm

10.0-1 Compression, Callies DRAGONSLAYER crank and Ultra H Beam rods, (no compstar junk on a big blower build). F1A-94 or F1X....Or better yet a YSi. E85/meth or 93/meth.

F1c and F1R won't get you 1000rwhp..atleast not without a VERY aggressive tune... An R is done at 950 rwhp on average..and larger the cubes, sooner it will peak and nose over.

I'm of the camp of medium compression, more boost and less timing. In my experience, timing will yack head gaskets(detonation) faster then boost.

Thick deck heads and atleast ARP 2000 head studs are a good idea.

Good luck on your build.


Me and Detoxx are on the same page on this stuff....I guess because we've done it.