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Low compression forged ls2

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Old Mar 2, 2011 | 04:20 PM
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Default Low compression forged ls2

I'm getting ready to forge my ls2 I want it to have low compression thinking 8:5:1 so I can run the most boost and make the most power I can using pump gas and a alky kit.What are your thoughts?I don't think because of the low c r it will be a dog out of boost if I want more power then ill get her into boost but I don't think it will be bad anyways I've owned two grand nationals which were low c r v6's and out of boost they were not bad to me so your thoughts
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Old Mar 2, 2011 | 04:47 PM
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Any more details about the setup? Supercharger or turbo? What size? Goals?
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Old Mar 2, 2011 | 05:12 PM
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O sorry about that its a 98 ta al ls2 with Turbo cam and springs 4l60 kytp truck manifold kit tc78 my goals are about 900 rwhp when I change the Turbo to a gt91 and the transfer will be a powerglide.I want to run 880's or so street stop car if there's any other info u need just ask me
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Old Mar 2, 2011 | 05:27 PM
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8.5:1 is too low in my opinion. You need at least 9.3:1 - 9.5:1 compression.
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Old Mar 2, 2011 | 05:30 PM
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Why is it too low?and too low to do what I'm trying?
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Old Mar 2, 2011 | 05:32 PM
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What can 9:3:1 or 9:5:1 do that 8:5:1 can't?
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Old Mar 2, 2011 | 05:47 PM
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Originally Posted by Frametwista
Why is it too low?and too low to do what I'm trying?
Track or street build?
If both ide go 9.5 to 1 like i did with my LS2 364 turbo set up!I put down 650 rwhp on a small 10psi setting for the street and can go to 20to 25 for the track with meth if i ever felt the need,which i dont lol . 8.5 to 1 is just way to low IMO. Turbos will be a dog to spool up with that low of a CR unless your planning on a VERY high stall convertor which ='s more heat to the tranny IMO
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Old Mar 2, 2011 | 06:35 PM
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I disagree grand national v6's are very low c r and I was spoiling a 70mm Turbo with only a 3800 stall I'm just trying to find a basis on why people think it will be such a dog speed Inc sells a boost block that's 8:5:1 comp and the made 995rwhp with it I think they know there stuff if its only making 350hp it will still spool the hell out of any Turbo smaller than a 98mm
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Old Mar 2, 2011 | 06:40 PM
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It will be a street strip car with a lot of strip time I'm really not concerned with instant boost if I was I would have a roots blower around town just driving a 8:5 comp ls2 off boost should still have enough grunt to pass people
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Old Mar 3, 2011 | 03:22 AM
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Too lazy and tired to get into it right now but I was also going to say the same thing, that CR is too low IMO. I would run it about a point higher to hit the sweet spot.
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Old Mar 3, 2011 | 03:33 AM
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too low better to stay between 9:2:1 to 9:5:1
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Old Mar 3, 2011 | 05:13 AM
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way to low if your doing meth. I did 16 psi on 11.1 with cheap pump gas and meth
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Old Mar 3, 2011 | 06:38 AM
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8.5 means you have the potential for big boost on pump gas without having the complication of meth etc. Which to me is a big bonus.
Personally I like much lower so can see 30psi on pump fuel with no AI. Boost = Torque. Not like thats ever lacking on a LS2...!

Ive ran as low as 7.2:1 before on engines as small as 1.4 litres, and in my eyes it doesnt make much difference to off-boost low rpm performance, not as much as a long duration cam or huge head ports does anyhow.
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Old Mar 3, 2011 | 06:53 AM
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I would rater run 8.5 comp and avoid meth all together. relying on meth to keep your engine alive is just stupid
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Old Mar 3, 2011 | 07:53 AM
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Originally Posted by tittan1500
I would rater run 8.5 comp and avoid meth all together. relying on meth to keep your engine alive is just stupid
My last engine expired due to the AI failing halfway down the strip. 23psi on 9:1 and pump fuel. Wasnt happy with much more than 15 without it.
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Old Mar 3, 2011 | 09:00 AM
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I run 8.7 comp. on my setup.... Off of boost, i think it has enough torque on the street. if i had to do it over, i would run another point of compression but that is only because i am greedy. Best of luck
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Old Mar 3, 2011 | 09:30 AM
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How much power and how fast are you looking to go. Setup with the procharger was 10.0/1 Ran well on pump and Meth. 13psi and went 9.8@141mph.

My new setup for the Turbo build I am doing will be more like 9.8/1 and plan on seeing 15 psi regularly. a properly setup meth system with the a car that is properly tuned so that IF you loose the Meth it pulls timing and saves the motor. I know MrBig or whatever his name is had a Meth failure doing a Mile pull and having it tuned properly pulling timing when it saw the IATs go up saved his motor


These cars like CR even on boost. And with a forged motor there is no reason to go as low as 8.5/1 If you want to stay lower on the CR the lowest I would go it 9.0/1 but 9.2-9.6 is what I would shoot for
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Old Mar 3, 2011 | 05:45 PM
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Nobody is giving me any basis on why its too low and wont work well like stated earlier in the post with low c r u have the potential to run night boost numbers on pump gas what do you mean it will be lazy when boost comes on it will hit like a freight train and the ally is just for a safeguard nobody is relying on it my low c r motor will do just as good as a higher c r motor until I hear a good reason y ill stick with it
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Old Mar 3, 2011 | 05:49 PM
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Sorry bout the spelling I'm on my Droid
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Old Mar 3, 2011 | 05:55 PM
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I stated earlier in the thread that it is street strip a lot of strip I don't care about street manners I want to run 8.80s
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