Generation III Internal Engine 1997-2006 LS1 | LS6
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View Poll Results: 10.75:1 or 11.5:1
10.75:1 CR with big cam (MS3 or 233/239)
22.73%
11.5:1 CR with small cam (224R or 228R)
77.27%
Voters: 88. You may not vote on this poll

11.5:1 Cr?

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Old 04-29-2009 | 07:35 PM
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Originally Posted by 67rsss
Youre claiming a 234/242 cam will not need flycutting on milled heads? I would definately measure, but I would be prepared to cut.
G5X3 and patriot LS6 59cc heads no need to flycut
Old 04-29-2009 | 11:00 PM
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Where were you when I couldn't even get anyone to commit to a 228R with 59cc heads and 2.055 intake valves! We did have a ton of clearance with the VRX3, but a lot of people start looking at cutting in the low 23x range. Milled heads make it worse. I would measure before flipping the key over...
Old 04-30-2009 | 06:00 AM
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My new cam choice 224/230 .581/.588 114LSA. I'm thinking about milling my 5.3L head to 60cc. Bcuz of the shitty gas in CA can't run too high CR without KR issue.
Old 04-30-2009 | 01:29 PM
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My friend wanna ask if his cam will clear the PTV with 60cc 5.3L head. His spec is 231/237 .589/.595 on a 112 + 4
Old 04-30-2009 | 04:36 PM
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Maybe.
Old 05-01-2009 | 03:14 AM
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always always measure. i have 2nd hand experciance. my buddy decided to take texas speeds advice when they told him his PRC heads would clear no problem with his cam, well. they were wrong. i'll see if i can find the pictures, but it was a mistake that cost him 4000 bucks or so. honestly, just fly cut. just plan on it. plus you can get more compression that way anyways. big cam + big compression =
Old 05-02-2009 | 03:38 AM
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Originally Posted by kmracer
always always measure. i have 2nd hand experciance. my buddy decided to take texas speeds advice when they told him his PRC heads would clear no problem with his cam, well. they were wrong. i'll see if i can find the pictures, but it was a mistake that cost him 4000 bucks or so. honestly, just fly cut. just plan on it. plus you can get more compression that way anyways. big cam + big compression =
I was told that the MS4 cam would clear. It left eyebrows on my piston. I will now always and forever check my PTVC.
Old 05-02-2009 | 04:26 AM
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Ok, guys new project for my friend.

I'm doing a cam swap for him. It's a custom Comp cam 228/232 .588/.591 112LSA. Original plan is cam swap only, now he wanna port his 241 head (Stock valve) too. He'll be using stock NON-MLS head gasket. According to previous post, 241 is 67cc. If I ask the machine shop to mill the head .020, will this cam still clear PTV? If I do the math right, after the mill it should be 64cc just like the 243. It should clear no problem.

Also from another previous post that use modeling clay to measure PTV clearance, is there other way to measure it? I've the 241 out of the engine already.
Old 05-02-2009 | 04:57 AM
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it SHOULD be ok, but honestly just check it. it takes an extra 10 minutes when you're doing the heads anyways... all of us on here could sit here and say YA YA! ITS GONNA WORK GREAT! but your buddy isn't gonna be happy with you if something DOESN'T work out. i know how it goes, I've built cars with/for numerous good friends of mine. i always treat them as if they were a customer, and would feel horrible if something went catastrophic because i told them how awesome this new cam would be.
Old 05-02-2009 | 05:53 AM
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So except the modeling clay menthol, anyother way to measure PTV?
Old 05-29-2023 | 03:23 PM
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Im looking into building my first engine. LQ9 flat top pistons zero deck, TEA 243 heads milled, 228r 112lsa or BTR stage 2 cam, Johnson lifters to rev out to 7k-8k. looking to get a .041 gasket quench to get me around 11.3 cr. How much cr is to much for 91 pump? Build would be on C5 mild street with occasional track
Old 05-29-2023 | 06:51 PM
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Start a new thread please
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Old 06-08-2023 | 01:49 AM
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Originally Posted by SIRBOOM
Im looking into building my first engine. LQ9 flat top pistons zero deck, TEA 243 heads milled, 228r 112lsa or BTR stage 2 cam, Johnson lifters to rev out to 7k-8k. looking to get a .041 gasket quench to get me around 11.3 cr. How much cr is to much for 91 pump? Build would be on C5 mild street with occasional track
11.5 is about it for max timing on 91 octane. I would do a solid tune on 91 and then run some boostane or torco just to be on the safe side if you’re going to run her ragged.

If you’re going to throw nitrous on top run a stand alone and either run VP Racing 109 or C16.




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