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Generation III Internal Engine
1997-2006 LS1 | LS6
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Old 04-09-2010, 04:03 PM   #1
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Default Lm7 5.3 to 5.7 questions

I have an iron block LM7 from a 1999 truck. It is a 5.3, and I will be boring it out to 5.7, keeping stock stroke. My questions are:

1)I have read that with forged pistons I need a slightly longer rod

2)It is safe as long as I have a gen 3 iron block

3) I should use a MLS head gasket to the largest bore diameter

4)where is the best place to find some good forged boost pistons/rod combos for turning my 5.3 into a 5.7 (3.898 bore) Should I just look to get a LS1 rebuild set at stock bore?

-Garrett
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Old 04-09-2010, 06:10 PM   #2
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Rod length for the 5.3 and the LS1 (5.7) are the same which is 6.098". Rod length changes on many forged and stroker kits.

"Is it safe" I'm assuming means is it safe to bore to 3.898. Yes, it is.

You are essentially building an LS1 so use the recommended head gasket for an LS1.

Here where it's going to get tricky. The stock LS1 bore of 3.898 is very difficult to find forged pistons for. Mahle is the only one I know who makes one for your application. The part number from Texas Speed is 168-340898F04. They are pricey at $652 a set. Sucks doesn't it. Seems like all the manufacturers would have them but they all assume you'll be rebuilding a LS1 and would be boring your motor. So you can take it to the maximum bore of 3.905" and your piston selection gets greater but then you essentially are done as far as rebuilding in the future.
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Old 04-09-2010, 06:39 PM   #3
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oh ok, makes sense. If I going to use 3.905" how much would a set of wiseco pistons cost, or what brand is common with the LSx style engine? also what brand for rods?

I have used wiseco and eagle rods, and I liked them
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Old 04-11-2010, 09:56 PM   #4
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I just emailed texas-speed about the pistons. $650 is still much cheaper than a set of wiseco's, just curious if they are any good for boost.

-Garrett
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Old 04-14-2010, 04:24 PM   #5
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Quote:
Originally Posted by Bilster View Post
Rod length for the 5.3 and the LS1 (5.7) are the same which is 6.098". Rod length changes on many forged and stroker kits.

"Is it safe" I'm assuming means is it safe to bore to 3.898. Yes, it is.

You are essentially building an LS1 so use the recommended head gasket for an LS1.

Here where it's going to get tricky. The stock LS1 bore of 3.898 is very difficult to find forged pistons for. Mahle is the only one I know who makes one for your application. The part number from Texas Speed is 168-340898F04. They are pricey at $652 a set. Sucks doesn't it. Seems like all the manufacturers would have them but they all assume you'll be rebuilding a LS1 and would be boring your motor. So you can take it to the maximum bore of 3.905" and your piston selection gets greater but then you essentially are done as far as rebuilding in the future.

Just got off the phone with Wiseco and these are the pistons the had.

Wiseco - k392x3905 $752.52 -25cc dish
k444x3903 $752.52 -11cc dish

You were saying that I can go to a 3.903 bore, how about to a 3.905? I am not looking to reuse this block in the future.

-Garrett
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Old 04-14-2010, 04:24 PM
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