LM7 rebuild YouTube video

MARSHJOHN10

MEMBER
2008 CHEVROLET SILVERADO
V8
4WD
AUTOMATIC
253,000 MILES

Hey, I watched your full rebuild video of the LM7 on YouTube and had a couple questions relating to my rebuild of the LH6 I am about to dive into. For background I am taking my LH6 and going to replace nearly everything on it other than the block, crankshaft and heads themselves and adding a turbo.

1) For piston rods both of our motors had the I beam style connecting rod with a 6.098” length but in your build, you went with an H style rod with a length of 6.125” I am looking at doing the same but am curious if you had to get a specific piston head that would have been shorter than stock to account for the extra length in the rod?
Essentially, I am looking at getting these eagle rods CRS6125O3DL19 from summit. With these Wiseco pistons also from summit WIS-K0041X1 let me know your thoughts.

2) Shouldn’t taking the motor to the machine shop really be a two-step process? First step being have them clean it and hone it and once you know what the cylinder cleaned up at for an overbore you would then order the correct pistons diameter and step two would be to bring the rotating assembly back for balancing once the pistons arrive? My concern is that my motor is not apart yet, so I don’t know the condition of the cylinder walls. I don’t want to order pistons for.010 over and it ends up being.030 over, unless of course that isn’t a massive deal, but I feel like it would be.

Thank you for taking the time to review this and I appreciate the in-depth content.

Marshall Johnson

2 Replies

JACOBANDNICKOLAS

MECHANIC
108,269 POSTS

Hi Marshall, and welcome.

I came across your questions. I am going to forward them to the person in the video for him to help you directly. Let me know if you don't hear from him within a day or two at most.

Take care and thanks for watching the video.

Take care,

Joe

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Thursday, February 10th, 2022 AT 7:02 PM

RYAN L

ADMIN
242 POSTS

Hello Marshall,

Thank you so much for watching the series! Your build sounds like it is going to be an absolute monster. I hope you come back and post a video; I really want to hear it.

So, on your combination it is basically the same set up where the piston wants a stock length, but you have the longer rod. But here is the thing, your dome is 4cc greater than ours was. If I were you, I would call Wiseco's technical support line and ask them what they recommend for a connecting rod for whatever compression ratio you are aiming for. It should work because you are basically copying what we did but I would sure feel terrible if it was just slightly off because of something Wiseco knows that I do not.

Yeah, technically it really depends on what your engine cleans up at. Typically, it is 0.030 but it might be 0.060 or something else. But as long as you are in contact with your machine shop, they will call and tell you what your block is bored to and you can order pistons then. After they machine up your block it will probably be ready to be picked up and you can drop off the pistons and rods to be balanced. It is never a one and done shot. It always takes two to four trips back and forth to get everything just right. Yeah, it is a massive deal your pistons have to be ordered to exactly the bore that your engine is. It cannot be off even a little bit.

Hope this helps! Thank you for using 2CarPros!

Best,
Ryan

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Friday, February 11th, 2022 AT 8:44 PM