bluecamaroz28

Which would yield better power off and on boost. Thinking to put 6.0L 317 heads on a 346 LS1 engine to be able to lower CR and run 10# of boost intercooled and maybe with water injection.

Will this be a good choice or better get it to 8.5CR and up the boost to 16-18#. It will run on 93 octane if it is 10# boost. Will the stock pistons and rods handle the 10# boost safely with 6.0L heads on a 346 LS1 engine. What will be CR with 6.0L heads on stock 346 LS1 engine.

It will get a custom cam and valvetrain to handle 6500RPM.

Slowhawk

iTrader: (12)

Supercharger or Turbo?

bluecamaroz28

Turbo, if that matters.

bluecamaroz28

Anyone.

jyeager

Well, first the valvetrain only knows RPMs, not boost. All you need is enough valvetrain to handle 6500 rpms.
Also, a stock cam does very well with boost. Not quite as well as a purpose-designed cam, but still very well. If you stick with a stock cam and go with better springs then 6500 rpm is fine without loads of $.

As for the CR. Well, You need more than heads to get to 8.5:1 You need dished pistons too right? So then you are getting in to having to rebalance the whole rotating assembly.
My guess is that cost and logistics make it a whole lot easier for you to go with the relatively higher CR and less boost. I'm not sure that 10lbs of boost with 6.0L heads and pump gas is safely doable (well you could always tune out some timing), although it might not be too unrealistic with good intercooling. Yes, water injection might make that fine.

The good news is that the higher CR will have better response when your boost isn't there yet.

M6HuggerSS

i think wit h16-18psi your motor will grenade, no matter what heads you put on....
you should build up that bottom end!

and even at 10psi you are pushing the it.....

7-8psi should give you 500rwhp depending on other mods.....
and 500-550rwhp is danger zone (so ive been told)

good luck.

bluecamaroz28

I am trying to find out if 10# of boost on a 9.0CR motor is close in HP to an 8.5CR motor with say 16# of boost, without going into an expensive rebuild for higher boost.

I know that a higher CR motor doesn't need same boost as a lower CR motor to produce nearly the same level of power. But, if can be done safely on 93 pump gas with an intercooler and water injection, that's my question.

bluecamaroz28

I think I've read 650RWHP is the limit on stock bottom end, pistons/rods.

jyeager

Without running it through an engine simulator I'll guess that 8.5 and 16# would produce more power. But at this power level your rings will probably close up and break piston lands.

I think you'll be plenty happy with the 9:1 motor and the 10# boost target. Even at that level I'd get an experienced engine builder to make the pronouncement about whether your rings are safe (I'm assuming stock bottom end).

bluecamaroz28

I am sure that with 16# of boost, 8.5CR is a must and that won't be had without a rebuild, forged pistons/rods.

kp

iTrader: (34)

The 8.5:1 motor with 16psi is going to make a lot more power then then 10psi on a 9:1 motor if everything else is the same. Typically you will see nearly 20-25rwhp per pound of boost on one of these, half a point of compression alone isnt going to affect the output much at all.

kp

iTrader: (34)

FWIW here is 10psi with 9:1 and 16psi with 8.5:1 compression. The sim is for a procharged 346 with a 01 Z06 cam, close enough, I'm too lazy to swap back to a stock cam and figure out the right turbo combo Sorry for the fuzzy pics but they should be readable..

bluecamaroz28

Thanks for posting. I looked at peak numbers and there was like 97RWHP difference. The 6# boost will net around 120RWHP, assuming 20RWHP/1# of boost.

Now, if the the 592RWHP at 10# of boost can be had on stock bottom end, it would be more cost effective for me to go with. I can live without the 97RWHP if it will save me the cost of rebuild with forged pistons/rods.

Still unanswered question, will the 6.0L 317 heads lower CR to 9.0 on stock 346 LS1 engine.

Inspector12

iTrader: (29)

Yes that is what I did although the stock bottom end will not live for ever. Mine lasted 18 miles @575 rwhp. Just a little heads up from my experience.

mdhmi

iTrader: (1)

I think 16 pounds of boost on a 346 with pump gas is nuts, buy hey - it's your motor.

Mark

bluecamaroz28

What was your CR, boost and octane #'s? Was it intrcooled and with water/meth injection?

bluecamaroz28

With built 8.5CR motor, water/meth injection and good tune, I think it's not.

kp

iTrader: (34)

Thats SAE flywheel HP, not rwhp BTW, its just a quick dyno sim.

9psi at stock compression will get ~500-525rwhp on a stock motor (M6) with headers. I ran my old SS for a year like that and even ran a 50 shot on top of it and never hurt the stock short block. Took out the ole #7 piston when I switched to heads/cam and a 150 shot though

With 8.5:1 and 16psi it may live for a bit but the stock pistons just wont take it. I ran ~15psi on a forged piston/stock connecting rodded 346 last year at nearly stock compression and the only problem I had was the head gaskets were pretty gone @ 150 passes or so.

72CC (6.0L) head will drop you down to ~9.5:1

mahhddgtp

18 miles or 18k miles?

kp: How come the boost levels stay the same during the last 1000rpm of the pull? I thought S/Cs kept putting out boost almost linearly until you stop reving. There must be more physics behind them than I've picked up on.

Pro Stock John

iTrader: (34)

6.0 heads will drop the engine from 10.1:1 to maybe 9.5:1.

I might have mine for sale in a month, they are ported 6.0's and have seen 21 psi.