RMK

I'm getting my engine rebuilt with forged parts (while I'm at it I figure I may as well stroke it to 335) and was told by the guy at speed-o-motive that I should use bowl pistons to lower the compression ratio as I plan to use a supercharger next year. I have the stock heads by the way.

What is the best compression ratio for supercharging? Also, what will the car be like to drive with the low compression without the blower?


Thanks for the time


Robert

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1987 IROC-Z Auto (LB9)
Black/grey interior with the stance of a streetfighter
I like to think of her as Arnold Schwartzeneger in a dinner suit

Mods
Custom exhaust. 4 Inch pipe from the headders all the way back to a single muffler at the rear. No Cat. K&Ns, AFPR and Air foil.

Future mods:
Cam change
New torque converter
New heads (maybe corvette L98)
Strut brace
Sub frame connectors
Ram Air

Current G-Tech times
0-60mph 6.26 seconds
1/4 14.74@100.2mph

Guido

That kind of depends on what kind of boost you are going to be running.
Stock TPI cars are around 9.5:1 and they will take 6psi but that is with the stock hypereu-crap-tic pistons.

Im running 10-15psi and I have 9.2:1 compression. Its decent compression for driving on the street. If you have too low of compression, its going to feel sluggish on the low end of the RPM band. I have an MSD BTM at the moment which I can retard timing. That isnt the BEST way but when you are running enough boost on something that will pre-ignite under boost, you need to do something wether it be water injection or timing retard.

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-86 IROC
Jacked up like a mother!
this years goal: 10.50 @ 130+ mph
-=ICON Motorsports=-

RMK

So I should go for a compression of about 9.2?

Guido

I say you will be safe anywhere between 9.0:1 and 9.5:1. As long as you are using a spark retard or water injection to avoid pre-detonation.

Good luck!

afgun

Looks like I'm getting a Vortech S-trim to run on my L98... forged bottom end, super ram intake and getting AFR heads. I can choose my chamber size at this point, so I'd be interested in a recommended compression ratio also.

No inter/aftercooler at this point... spending enough on everything else *G* After I blow it up or don't think it's fast enough I'll upgrade the forced induction system.

So, recommendations for my combo?

Thanks!

--andrew

Guido

You want a smaller combustion chamber size in the head. The smaller area provides less dwell time for the combustion to heat up and pre-ignite. The best way to achieve lower compression is through a dished piston.

I know it sounds strange and it does to me too but I think a smaller head chamber and a dished piston is the better way of going about lowering compression.

Anyone else want to chime in here on this one?

Bob Wooten

I think that you hit that nail right on the head.

BW

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Bob Wooten
71 Camaro, 91 EFI
r71chevy@earthlink.net
www.r71camaro.homestead.com
<><

afgun

I agree with the smaller chamber and dished pistons, but I've already got the bottom end and I'm not made of money, so I'm going with the SpeedPro forged slugs I already have. Maybe once I blow it up... *G*

So, I'm thinking somewhere in the range of 9:1 with a mild Vortech... Keeping the boost around 6psi. Opinions?

--andrew