vrybad

I've made a few calls about FI for an ls6 setup in a z06(should be buying the car this summer)
I was told that with a 402-427ci displacement and afr225 heads, I could get away with 10:1 to 10.25:1 compression for a procharger setup, with about 10psi boost.
I am still undecided wether it will be turbo or sc, but the sc looks better the more I look into it, especially in the $$ department.
I would like to acheive a minimum 650rwhp on pump gas.

I have always thought lower compression, about 9:1, would be a better choice, but I was told that it would reduce low speed torque, which makes sense, and that to acheive those hp #'s, I'd have to run more boost, in the neighborhood of 15+ psi.

Personally, the slightly higher compression/lower boost route sounds like a better idea when it comes to low speed torque.

Just curious what you guys think about this in regards to streetability and my hp goals.
I know I can acheive those hp #'s, just curious as to the "best" way to get there with a stroker setup.

Thanks in advance.

ddnspider

iTrader: (26)

for starters your not going to lack in the torque department with a 402-427....9:1 is nice and what i went with so you can run a good amount of boost.Another thing is that if you go S/C'd you can still have a lower CR seeing as how the boost kicks in straight from idle....MORE LOW RPM torque.Id drop the CR to 9:1 like you were thinking.Shoot either PSJ or Brian Wilkinson a pm seeing as Brian had a C5R motor s/c's making over 800rwhp and now going to an iron block....and PSJ is S/C with a 346 make 750rwhp.Both of them dropped the CR.

ddnspider

iTrader: (26)

just another thought...not for nothing but for the small price to get dished pistons instead and drop the CR....you could run more boost,and if you got say and F1 s/c er setup you could make quite a bit more than 650rwhp....and on race gas alot more.just my $.02 good luck

vrybad

Thanks for the reply.
I'll look into the dished pistons as an option.
I saw that ATI has the f1 s/c listed as an option for the z06 setup, but I am wondering about fitment, considering the volute diameter is almost an inch bigger.
I understand there may be some custom fitting I need to do for that head unit.
Based on their site, I think the d1sc may be a decent choice, but you are correct, the f1 will give me a whole lot more room to expand.
Hope to get some more feedback from other members, but for now I'll search this site for more info.

Thanks again.
Brian

Pro Stock John

iTrader: (34)

Most folks who diss lower compression because they say you will lose bottom end torque are generalizing waaaaaaaay too much.

A one point drop in compression, ie. from 10:1 to 9:1 is said to cause a drop of 3% of total HP. So what is 3% of 400?

The real challenge for a big inch motor is getting a piston with a custom dish that will work with a 4.000 stroke and still maintain good piston specifications in terms oil ring and pin height.

vrybad

Thanks, I'll keep that in mind as I move forward.
I realize there is much for me to learn.
Thank goodness I've got time to do some research.
I hark back to the old school sbc days when 400 flywheel hp was alot!
I'm going to look deeper into the stroker setup.
I'll probably buy a shortblock ready to drop in from one of the suppliers, like MTI, Scoggin-Dickey, etc.

ddnspider

iTrader: (26)

12HP!

ddnspider

iTrader: (26)

i might suggest talking to HPE,they been awesome working with me...im a very picky person and need to know everything and they've come though big time.They're building my motor. send a pm to racer 7088 his name is Eric,hes the head builder over there.A great guy to work with.

racer7088

You are right about making more low end and running less boost with a higher static compression ratio but like has been said already if you are running that much more compression you will NOT be able to run as much boost on pump gas because of possible detonation. It's all a tradeoff of some kind unfortunately.

Bryan Wilkinson

iTrader: (1)

Here are some helpful suggestions.

With 10:1 CR. I ran 14 PSI consistently on 93Oct with 22Degrees of timing.
With that said, it was a 427, C5-R block, and the best parts money could buy and it was not a AFR but a LS6 head opened to 72cc.

If you dont change anything in the bottom end, in my opinion 550RWHP is reliably doable on pump gas all day with no more than 8psi. with 10:1 CR.

Dont believe everything you read about CR. In my expensive endeavors, (no Theory here) my best friend did his car the exact same time I did mine, but we took completely different paths.
Mine a 2002 Trans Am, his a 2000 Corvette
Mine a C5-R 427
His a 383
Mine build Moldex crank, carrillo rods, LS6 heads, LSX intake CR 10:1
His, Lunati, Lunati, LS1 heads, LSX intake his 8.5:1 Little more agressive cam
Mine Result on the dyno Mine 822RWHP on 93 OCT Stock Computer
His Result on the dyno 700RWHP on 93 OCT stock computer
Mine on the Road, I am not as agressive a drive as most on the forum, but car launches extremely hard
His on the road, Sideways.
So much for low compression ratios not making power.

I got stupid with mine. at 14PSI, I wanted more, so I pulled the filter off the front of the blower, it jumped to 18psi. The C5-R block said I dont think so.
The jist of the story is, that story was an expensive lesson, but it proved two things, at 14psi, that motor was safe all day, at 16psi, lost 1 set of head gaskets, and proved that the ls6 heads are good to 14psi, after that they have a hard time staying put, at 18psi, with a dynamic compression ratio of somthing like 25:1. that is way too much for anything that GM makes.

Hope this helps. Be careful what people tell you about what you can and cannot do with pump gas. Had I stayed at 14psi, It would have lived a very long life.

You can PM me and we can talk specifics you would like.

Bryan Wilkinson

iTrader: (1)

Another thing to be very careful of is piston configuration.
The C5-R block remember is built for a 4.00 inch stroke, meaning that the length of the sleeve is 6.00 inches.
The 6.0 IRON block is only 5.5 inches long so with a 4.00 inch stroke, mind what John is saying, piston design is important because the skirt will come really far down out of the hole and will cause wobbling and rocking and skirt scrape.
The LS2 is a little better with a length of 5.75", but again piston design is very important here as well.
The better solution may be to go with a 6.200 inch rod, and a custom designed piston. Wiseco or JE in either of their FSR type designs is the smart move.

vrybad

Well, I must say you guys sure know quite a bit about this subject.
I really appreciate the help and information.

I'm going to digest everything you've said, and yea, I'll probably be PM'ng to discuss this further.

I think I have to set down some clear goals for the car, and go from there.

Looks like there might be a couple of new TT kits for the c5/z06, so I have time to decide turbo or s/c.

I may even source the parts and have a guy local to me, do the shortblock build.
Alot of decisions to make.

Thanks again.

Bryan Wilkinson

iTrader: (1)

If you decide to S/C, Andy at A&A corvette has done and does on a regular basis the F1-R, he has a custom bracket setup just for the corvette.
www.aandacorvette.com
The tt setup for the corvette, stuffs everything under the front of the nose section. That is a lot of weight added to the car.

Good luck with what ever direction you go in.

Got Me SOM

iTrader: (2)

I dont know what kind of budget you have but stock displacement forged bottom end blocks with stock heads and cam are making crazy power now. 600 rear wheel.

The Vette guys with ATI's and a forged bottom end are making power in the low 600's/high 500's easy. With heads and cam 700's. And that is on pump gas!

I'd save the money on teh extra displacement and use it toward a good clutch, hardened axles and output shaft and get that girdle.

I wish I had the funds for a Vette.

ddnspider

iTrader: (26)

is a girdle really necessary at 600rwhp?

vrybad

The problem is that you guys are all getting great results, some with tt and some with sc.
I like the sc route, but wonder about belt reliability.
I like tt, but that's a whole lot of plumbing.
I'm blessed with a tough decision.

Regards the stock displacement, my thinking is that I could go forged at 346, but for the additional cost of the block, I'd have the potential of the stroker.
Might be the first thing I do, build the stroker engine, 9:1 comp, and run na for a short time. Should make good torque and power, break it in a bit, and then throw the fi setup on.

Anyway, this forum is a wealth of info.
Appreciate the suggestions.

First I have to go buy the car!!! roflmao

ddnspider

iTrader: (26)

if youre that blessed...then im curious how a C5R with a thumper turbo attached to it would fare....

Pro Stock John

iTrader: (34)

You can make 650rwhp with a forged 346ci and 93 pump gas.

I consider 700rwhp+ to be over the edge for safe pump gas performance.

I've made between 680-754rwhp and have gone 144mph @ 3450 raceweight so I am up there on power. I race with 116 leaded and make 18-21psi. But keep in mind I have a T400, and if I had a M6 trans I would be easily be hitting 800-825rwhp.

If I built another engine it would be an 8:1 LS2 with a stock stroke crank but I'd access that nice 4.000 bore of the LS2. I guess that would be about a 366ci or so. I'd run about 15ps for the street and hit around 650-700rwhp.

If you really think you want to hit 700-800rwhp you should go 9:1 or lower. Do some research on octane vs. compression and see where you would be in terms of gas.

Got Me SOM

iTrader: (2)

absolutely. call it cheap insurance.

ddnspider

iTrader: (26)

how come i hear so few people have them?