LT1-LT4 Modifications 1993-97 Gen II Small Block V8

9:7.1 compression How many pounds of boost?

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Old 04-22-2010 | 11:54 PM
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Default 9:7.1 compression How many pounds of boost?

Im runnin a 355 LT1, 9:7.1 compression, stock cam, coated skirt spreed pro pistons, Hell Fire rings, Eagle I-beam rods, stock polished crank and H-series bearings, ARP head and main studs, Cometic head gaskets, aluminum camaro heads, gasket matched, bowl blended and back cut valve seats, stock diameter Manley tool steel springs and hardened pushrods.

How many pounds of boost am I gonna be able to run.

I was thinkin 10 lbs max. Not sure tho.
Old 04-22-2010 | 11:56 PM
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what gas ya wanna run?
Old 04-22-2010 | 11:57 PM
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Intercooled?
Old 04-23-2010 | 12:02 AM
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going to run meth?
Old 04-23-2010 | 12:04 AM
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93 octane. Not sure about meth tho. Should I need meth with 10lbs on that compression?
Old 04-23-2010 | 12:34 AM
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mm I would think 14 would be fine, depends how much power you want to gamble for
Old 04-23-2010 | 12:37 AM
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That compression with 12-14lbs and good gas shouldn't give you any trouble. W/O meth injection.
Old 04-23-2010 | 12:40 AM
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Well I was hopin for about 450-460 hp.
It's gonna be a single 60mm from HP Performance. They claim the turbo can make somehtin like 600 horse.
Old 04-23-2010 | 12:47 AM
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Thanks for the reply's.
The wastegate has a 8.7 lb spring in it. I also have a 10 lb spring. Now I guess that I have alittle more room for a few more pounds.
Old 04-23-2010 | 02:41 AM
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Is it ok to run that high of boost on a stock steel crank, even if the compression is lower?
(not that i know and am trying to make a cocky remark, im just interested!)
Old 04-23-2010 | 02:52 AM
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Stock crank has been ran at 600hp and beyond. Is run e85 if its accessible for you.
Old 04-23-2010 | 04:26 AM
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the rods are junk imo
Old 04-23-2010 | 04:56 AM
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I think that the 8.7 lb wastegate spring should get you to the 450-460hp that you want. you shouldn't need the meth injection but it would be safer and a lil more hp. what size injectors are you running?
Old 04-23-2010 | 08:38 AM
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Originally Posted by GM PHASST
Well I was hopin for about 450-460 hp.
It's gonna be a single 60mm from HP Performance. They claim the turbo can make somehtin like 600 horse.
I assume you mean to the ground...that turbo is too small. Even if it is on a T4 you will be choking the engine, the IATs will go sky high and with that CR expect crappy performance and excessive knock.

If you haven't bought the turbo yet get a T70. Master Power has em for ~$600 delivered Rob @ Modular Turbo is a sponsor here. For comparison I have a rearmount with a T70, stock iron heads, stock 191/196 .45/.46 and it would suck a 60mm turbo dry. The RR makes ~400 RWHP. Also the cam is a big part of the CR and boost equation especially look at LS. Most say 112 -114 should be your goal.

Good luck

Also most believe meth injection is best >~12 psi but it also provides increased octane and allows more timing and boost. My inlet air temps go down as I accelerate last time at track I launched at ~83 degrees F and finished <80 F.
Old 04-23-2010 | 08:41 AM
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As for stock cranks they take a ton!

A friend is making ~675 RWHP with stock rods and crank, the engine has three years at the track on it. The important part is to use good rod bolts and we also use main girdles. The stock blocks and internals are alot stronger than most give them credit for.
Old 04-23-2010 | 08:46 AM
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And for how many psi, I ran the RR with stock pistons and with 93 I ran 9 psi without a problem. I switched because I broke a valve spring and just built it correctly.

PSI is just a number. A motor with larger cam, valves, head etc may have 9 psi but make twice the HP of a smaller headed setup with 15 psi.

You want to avoid detonation! Meth is an excellent aid, but it should not be used to fix a system that was poorly planned.

Good luck
Old 04-23-2010 | 01:59 PM
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Just for future reference its 9.7:1 not 9:7.1.
Old 04-23-2010 | 05:37 PM
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The stock rods will fail before the crank. Some people have good luck with them but I would just spend the extra 250 for cheap i beams.

I would try to run meth and aim for 12 psi. you should be happy with that and it should be trouble free.



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