vernw

iTrader: (2)

OK, getting ready to make the plunge, got some serious questions about suitability for an SC on my current set up. Currently I'm running:

4-bolt 70's era 60-over block
AFR 195 Eliminator heads w/035-quence (.028 Cometic gaskets)
10.5 compression
Comp hyd roller cam: 236/242 @.050, .581"/.579" lift w/1.6 ProMag RR's
MiniRam 1205 intake
BBK 58mm throttle body
Walbro 255 in tank
Dual wideband O2's
"Built" T56
Ford 9" w/4.11 and Auburn posi
DIY prom

Current setup according to DD2K is 529HP, 514TQ --- dyno confirmed/matched very closely by GMHTP mag with slightly weaker cam

The SC I'm looking to add is a Vortech V1 S-Trim, according to Vortech it will fit fine under the 91 Formula "Power Bulge" hood (looks awfully close though).

OK - here's the questions:

1. Am I stoopit to even consider this?
2. What issues will I run into with my 10.4 compression?
3. What level boost would be reasonable?
4. Cam specs - is this cam even useable with this SC?
5. Is this entirely the wrong motor to even be considering using for a blower?

I'll be honest here. I've read the forum, and am having my doubts. I'm an old phat phart gearhead and have worked on this Formula for years, but I've never done anything with superchargers or turbos. I'm real ignorant on this topic and need some good solid advice.

Shinobi'sZ

I tried running 10#s of boost with my ATI SC on my (then) 01 stock Z06 (LS6 10.5:1 CR). The LSx have hyperuetetic pistons and are very brittle...so the first time I had a fueling issue...4 pistons popped. This was back in 2002. However I know a lot of people who have ran SC on LS6s using meth/alky injection and have been ok. It's all about managing detonation and your tune.

A better option might be to have the chambers opened up on the heads or to increase the head gasket thickness to drop the CR. I used a combination by having the chambers on my LS6 head opened up from 62cc to 77cc and used a thicker cometic MLS gasket (-2cc valve relief pistons) to drop my CR from 10.5:1 to 8.9:1..then with another head gasket change to make it 9.2:1. While this isn't the best way (like using a dish to drop CR) it is effective and I have been pushing 650-1K hp with this setup (flat top -2cc valve relief pistons) and have been running 3 different power adders for the past 7 years. The reason I like the way I did it is because if I ditched the TT on my car, I could do a head swap and be back at 10.5:1 CR and run NA...it just gives me options with out having to touch the rotating assembly.

Most of the best LS powered SC are running a CR between 9.7-10:1 CR. As long as you use 91 octane and have a good tune it should last at the CR. I don't run meth but my car is tuned around 18#s using 100 octane (Sunoco) that I can buy at the pump. But I only really run the car at 9# boost using 91 octane.

You can leave your setup at 10.5:1 if you use meth/alky injection, higher octane mix, or additive like Torco also. You just want and afr of about 11.7 on the dyno, max timing with no knock. Remember that boost changes with temperature so you will want to tune your car during the coldest time of the year and make sure that you always run with the same fuel or alky. This should help avoid any piston popping issues.

BTW you have an impressive NA setup. That is the type of power I expect from a stroker H&C NA motor. I have only seen a couple of people with impressive SBC built motor numbers on this board and it has made me wonder a bunch what the issues are....probably just people not spending or having the money to prioritize for a correct performance build...but you certainly have what I would expect out of a 383 SBC performance setup.

vernw

iTrader: (2)

Thanks for the reply. I'm beginning to have 2nd thoughts on the idea as I really didn't want to have to mod the heads or cam, or pistons since mine are hypereutic as well.

May need to look at a built for boost motor to start with.

Any other suggestions?

Shinobi'sZ

LOL....I cracked 4 stock hyperuetetic pistons on my stock LS6 motors the first time I hooked a Centri SC up to it. No room for error using those brittle pistons. I have been forged ever since.

vernw

iTrader: (2)

Anybody else want to chime in?

junkcltr

iTrader: (1)

It's all in the tune. Been running hypereutectics and cast for years and it has been fine.

I would not put forced induction on a 10.5:1 street engine. My opinion is the only way to do it with forced induction is to run it on E85 or methanol.

Shinobi'sZ

Venture to say that there are upwards of 100 guys (on the CF) running FI on 10:1 CR motors, built with forged internals (at least pistons and rods) making over 600 rwhp, there are probably another 50-60 on the LS1tech forum. Most the time people will only discuss whp not fwhp because it is based on their actual results, rarely do people try their systems out on a engine dyno. The stock hyper pistons were never intended to be run under boost.

I agree that it is not a good idea to run boost on a 10.5:1 CR engine. I run my car at 9#s boost using 91 octane...when I crank up the boost I mix in 100 octane. My current CR is 9.2:1, it was 8.94:1 but I changed the HG.

vernw

iTrader: (2)

Thanks again for the replies. Since I don't have forged pistols or bottom end on this 383, sounds like a head change for lower compression is probably the best move. Unfortunately, I don't want to modify my existing $1500 heads, so I'm kind of at a stand still until I can get the right heads and cam to be able to proceed.