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Boost with 11:1 compression ratio

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Old May 4, 2010 | 10:31 PM
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Default Boost with 11:1 compression ratio

So im kind of geting the itch for fi either a maggie or procharger. Well i had my motor rebuilt it has stock crank, rods, forged pistens, arp main studs, and arp rod bolts. With my heads and gaskets its right at 11:1 compression so if i were to run a blower should i change the head gaskets? The heads werent milled or anything i went with thinner gaskets to bump the compression. I wouldnt be runing much boost maybe like 6-10lbs unless i get a meth kit.
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Old May 4, 2010 | 10:40 PM
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Lot's o' meth, 317's, and the 3.5 lbs tial spring. This seems to be a popular subject...
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Old May 4, 2010 | 10:54 PM
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I didnt want to change heads cause i spent $1600 on them plus $450 for rockers so is there any safe way to stay with my heads/shortblock and run fi like changing head gaskets to stock ones or if there is any thicker gaskets?
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Old May 4, 2010 | 10:56 PM
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If you're running cometic 0.40's yeah, but if you're 0.45+ don't worry about it. GM MLS are awesome with boost.
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Old May 4, 2010 | 11:26 PM
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Thats what i was thinking put stock gm mls gaskets back in. The heads have 64cc chambers im not sure what the compression would be with stock gaskets im guessing around the same as a stock motor right?
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Old May 5, 2010 | 12:21 AM
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head gasket is not going to lower compression by much.

i would at least switch to 317's to lower the CR

also there is not going to be much room for error with 11:1 CR and boost, so make sure you get a VERY good tuner
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Old May 5, 2010 | 01:37 AM
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Yea i didnt think 11:1 and boost would be very good but with stock gaskets wouldnt i be at the stock compression level? So then it would be like runing boost on a stock ls1 except i have forged pistens. Cause i really dont want to get rid of my tfs heads or buy a new motor.
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Old May 5, 2010 | 06:39 AM
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I'd add methanol to it and I don't see you having any problems with it. Back at the old shop we built an engine for max N/A torque, and we settled on a compression ratio of 11.0/0. The next year the customer wanted to add an APS turbo system to the car. We added methanol injection to it, and the engine did just fine at 7 psi of boost with the turbo. Centrifical superchargers generally can handle high compression ratios than positive displacement superchargers, I think you'd be much happier with an ATI ProCharger over a Maggie. Bob
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Old May 5, 2010 | 09:12 AM
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I ran 12lbs of boost and pump gas on mine without any issues, it can be done, its all about the tune.
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Old May 5, 2010 | 10:22 AM
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You probably won't be too happy with it unless you lower the compression or run really high octane fuel all the time. If e85 is available in your area you can use that and keep high comp.

Running low boost gets old quick. Sell the heads.
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Old May 5, 2010 | 12:27 PM
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You can sell those heads for more than what you can get a set of 317s for and you will be able to make way more power safely with the lower compression.
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Old May 5, 2010 | 01:15 PM
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the ls7 has 11cr and the procharger kit boosts it to 10psi on 91 octane me im gonna run 12.5cr on c16 with 10psi.
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Old May 5, 2010 | 07:11 PM
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There is lots of LS2 GTO's running around with Maggie's and about 11:1 compression, . Just run a little less timing and makes for a fine DD on pump gas.
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Old May 5, 2010 | 07:35 PM
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It would best to swap to a head that would give lower compression. 11:1 is to much for pump gas and especial for the street,
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Old May 5, 2010 | 08:03 PM
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Originally Posted by 383lt1impala
the ls7 has 11cr and the procharger kit boosts it to 10psi on 91 octane me im gonna run 12.5cr on c16 with 10psi.
10.7:1 actually
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Old May 5, 2010 | 08:54 PM
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I've done this on a car we built for the Pinks all out in Seattle. The most boost I could run with C16 and 11 to 1 compression was 8 psi. Anything more and it would pressurized the cooling system and push water out. At first we thought it may be the gaskets because they had felpro mls and arp bolts so I changed it to GM with arp studs and same thing at just 8 psi. I had the timing at 24 degrees. The car ran well, 10.40 @ 138 but we wanted more. I'm in the process of changing the heads to a cnc ported 73cc chamber and we'll see what happens, should have it back on the dyno next week. G
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Old May 6, 2010 | 10:36 PM
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11:0 compression here on 10psi boost on E85 with 20 degrees total timing...no problem.
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Old May 6, 2010 | 11:39 PM
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Originally Posted by maxgee
11:0 compression here on 10psi boost on E85 with 20 degrees total timing...no problem.
DAMN! E85 is god like fuel. I know some EVO guys in town running 28-35psi for daily driving.
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Old May 7, 2010 | 12:42 AM
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I've got 11:1 with 13-14psi on 93pump and meth injection. But it can't be done...
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Old May 7, 2010 | 12:48 AM
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Ok so im starting to get pretty serious about doing this lol. This is what i have in mind. Sell my tfs and either get a set of stock 317 with springs or tea stage 1.5 317 heads (not sure if the ported heads will benifit me much) stock gm mls head gaskets, and epp blower cam. I was looking at this procharger kit
http://www.exoticperformanceplus.com....html?item=798
Would i need anything else like meth or addtional fuel upgrades. Also should i keep my yella terra rockers or use stock ones with the 317 heads?
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