BackYard Straight Edge
 

I know not everyone has a machinist straight edge in with the tools they own.

:idea:

This is not the most accuate check But it should be close enough to help you decide if a MLS will seal or the block needs to come out and me milled flat.


Tools needed
20" or longer extention, 1/2 perfered.
Decent set of feeler gauges
.0015, .002, .0025, .003

Sharpie marker

A good know flat item, a piece of glass or mom's glass top table work best.
https://www.miataturbo.net/attachmen...ine=1357314205

Pull out the .0015 feeler gauge.
https://www.miataturbo.net/attachmen...ine=1357314205

Lay the extention on the glass, make sure the square drive end hangs off the edge.
https://www.miataturbo.net/attachmen...ine=1357314205

Take the feeler gauge, and check the extention for bow.
Spin the extention untill you can not get the .0015 feeler gauge under it.
https://www.miataturbo.net/attachmen...ine=1357314205

Once the feeler gauge will not go under the extention, take the sharpie marker and mark the top.
https://www.miataturbo.net/attachmen...ine=1357314205

You are now read to check your block, head, intake mani or anything else you need for warp.:bigtu:

https://www.miataturbo.net/attachmen...ine=1357314205

For Head gaskets
MLS if the .0015/.002 slides under, get the part milled, or go to a composite
Composite, if a .003 or more slides under, get part milled.

About any flange with a warp of .005 or more, needs closer inspection, and a good chance of being milled

Thanks for the tips, all of them, and the rest to come.

Bogus... I don't know you, and I'm new here, but I want to say thanks for sharing your knowledge and tips/tricks with us. Not only are you sharing, but you're taking quite a bit of time to take pictures and write explanations... For free! I'd go out of my way to support your business just because of this, and I'm sure others feel the same!

Maiter, Frumby Thanks!

I been wrenching on cars for 25 years or so, and doing machine shop work for 20.

I have seen some horrid things, and many WTF was that shop doing.

This write up is so a guy can decide if he can bolt a head back down on a weekend, or hold off and get it machined.

Can I ask a stupid question? You'll have to forgive me since I'm a degree'd engineer, ie dumber than a bag of rocks...

I've read this a few times and it didn't make any sense to me until just now.

The point of marking the extension is to show the areas that are flat enough to use to judge a head? Is that correct. ie only use the areas "marked" to measure against your head (or whatever other surface)?

Sorry, i dumb

The mark is to show 180* from the area that will be used for the straight edge.

After it is checked and you find the least distorted part of the extention, the marks will be up, so the down surface is used for checking.

I don't particularly like this concept, as it assumes that you're marking the point under an arch that is .001" above the surface. However that arch, and therefore the gap, changes depending on how much or how little of the arch is hanging off each edge.

Am I completely off base? I know this is a "backyard machinist" method, but still.

Curly, that is correct, if there is an arch to the extention, the top of the arch can be less if the contact points are close, or more the further they are apart.

This method, is crude at best.

It is ment to let you know something more than a guess.

If you check the extention on glass, and can not get a .0015 feeler under it along the length of it.

Then go check a head, and can slip a .006 under it. That lets you know to shop and get it surfaced.

But if you go to the head, and a .0015 will not slip under, then AT your own risk can choose to bolt it down.