Saw these LS videos from Paragon Engines with high quality machine work and wanted to share for discussion.

This LQ9 ran like 300,000 miles but neither both block or heads were flat. Per comments in the videos, the LQ9 spun a bearing, it didn't have head gasket issues.

When rebuilding an LS do you think this machine work is critical to do?

 

Maybe the head was warped the same as the block?

I don't know what everyone else gets quoted at their machine shop, but the last time I went looking for a complete engine machining it was as near as makes no difference $1000 to have everything machine, honed, decked, ground, and new cam bearings installed. If I was putting money into the engine beyond a cam swap I would probably have it machined, that way you know what you have.

 

Depends on how far out either one is, but the flatter both are, the easier the head gasket can do its job.

as seen, it can be not 100% and still seal, but for a shop specializing in rebuilds(and putting a warranty on it) why risk it?

 

Offsetting errors? Maybe the head bolts pulled down enough to help flatten head? Indeed, $1,000 for block machine work sounds about right price wise.

The one head was off like .008 in a small area and the block was off ~.006 or so. GM factory head gaskets must do an excellent job of sealing.

 

Or, they warped TOGETHER over all those years they were bolted together.

Kinda not worth taking a chance on. I'd start em out STRAIGHT if I were building it. One of the most basic "blueprinting" operations.

 

For me, just about everything get's machined.

Even when you bore a block over sized, the new replacement pistons will be lower down in the hole.
One reason is to compensate for the difference in compression for the larger diameter. Another is is because they assume you may need to surface the block to get a good seal on the head gasket whether it be from corrosion on the deck in the cool area or if it was damaged by a blown head gasket. Even if you need to sleeve a cylinder you will still end up decking the block to get it cleaned up.

I have an iron 5.3L block that my machine shop kicked back on me because the decks were so far off side to side. The 1 side took a standard few thousands to clean up. When they flipped the block They had to drop the Z height more just to get the tool to make contact. He initially thought he made a mistake so he flipped back over to take a measurement and realised the other side was in fact lower. He called me and I told him to proceed I can get different gaskets. A little while later he called back and said something is not right. We are going to have take about .010 off just to clean this up and then flip the block to get the other side to match up. We have never seen this before on any manufactures block. Maybe there is an issue with the machine It's xx years old and never been rebuilt, I am going to replace the bearings just to make sure and I will call you back. A few days later I get another call... Come pick up this pile of ***** I don't know how it ever ran right from the factory like this. I have never seen a block need this much machining to correct the decks and I don't want to waist any more time on it for any amount of money....

If I remember correctly, the one side was lower by around .010 before he even started. With the amount of machining it needed it was going to be about .010 to get a clean surface all the way across the deck. Then he would need to take that same .020 amount back off the other side so that they were both even. He was afraid they would have to mill the pistons and that it could also possibly end up with other fitment issues and just didn't want to go down that road.