Block Correction Machining - Belt Surfaced Block
 

Block Correction Machining


This block was machined at another shop, then ended up at my shop.

https://www.miataturbo.net/attachmen...ine=1341544714

To start with the block gasket surface was belt surfaced.
I have heard of this being done, but this was the first time I have seen it in person.
https://www.miataturbo.net/attachmen...ine=1341544714

A longer view
https://www.miataturbo.net/attachmen...ine=1341544714

The hone job was sub par also. But I did not get a pic of that.

When setting the block up to be milled, I did the “quick set up”
This method indexes the gasket surface to the oil pain rails, and not the main journals.

The oil pan rails had some light surface rust on them

https://www.miataturbo.net/attachmen...ine=1341544714

I long boarded the oil pain rails, to make sure they were clean and no burs that would hinder the accuracy of the set up.

https://www.miataturbo.net/attachmen...ine=1341544714

After they were cleaned.
https://www.miataturbo.net/attachmen...ine=1341544714

I do not much care for this set up, for the simple reason that most block oil rails have a wide range in tolerance.

https://www.miataturbo.net/attachmen...ine=1341544714

Some shops will set up like this and then use shims to level the block deck.

I found .002 tilt from front to back on this set up. That dose not seem too bad.
https://www.miataturbo.net/attachmen...ine=1341544714

But Blocks are NOT machined to the oil pan rails, they are machined indexed to the main journals.

So I took this set up down and set up to deck the block to the mains.

This is the bar the main journals of the block will rest on.
https://www.miataturbo.net/attachmen...ine=1341544714

I checked the bar and it had less than .0005 from end to end distortion.

Setting the block on the bar
https://www.miataturbo.net/attachmen...ine=1341544714
Notice the hold down on the left side.


Now that the block is set up on the mains, checking the tilt showed .0045
This lets me know the oil pain rails are .002 off from the main journals.
https://www.miataturbo.net/attachmen...ine=1341544714

Now to mill the block, I will start with a .0005 “getting to know you pass”
https://www.miataturbo.net/attachmen...ine=1341544714

Now that I am sure of the set up, I cut another .002
https://www.miataturbo.net/attachmen...ine=1341544714

The block still has a low corner.
https://www.miataturbo.net/attachmen...ine=1341544714

After another .002 pass for a total of .0045 removed, I was left with this.
https://www.miataturbo.net/attachmen...ine=1341544714

I made a final pass of .001 for a total mill of .0055 removed.
https://www.miataturbo.net/attachmen...ine=1341544714

Now that the block was milled, it removed some of the top champher from the cylinder bore, this aids in the installation of the piston and rings into the block.

The “hi-tech” tool used to champher the block.
https://www.miataturbo.net/attachmen...ine=1341544714

The cylinder on the left has had the champher cut, the right has not been.
https://www.miataturbo.net/attachmen...ine=1341544714

The crosshatch I honed in the block.
https://www.miataturbo.net/attachmen...ine=1341544714

After the block has been washed to remove metal flake and grit from machining.
This block still will need a final wash before assembly.
https://www.miataturbo.net/attachmen...ine=1341544714

Very nice. I think the pictures in this one are great.

Nice pics and writeup. Is it safe to say that belt surfaced isn't tied to any surface, just flattening to whatever deck surface there was to start with? They don't tie to the journals at all do they?

Stein.... you know the little belt sander you have in your shop? Make it huge.. grab the part to be surfaced, hold it as steady as you can and step on the pedle.

Hold on like a man.

You now have been trained on a belt surfacer...

Attachment 48424

Thanks for the thread. I always enjoy your writeups and pics.

Got a new camera???

Great writeup and pics!

I'm sure at least a few of your 100+ props have come from me, but here's another. Mods should make a set of stickies out of your machine shop and build threads. Thank you for your contributions! :party: