Help me figure out what to do (bad headgasket for sure)
 

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OEM head gasket > Fail-Pro head gasket.

If your looking to just hurry and be done, a stock rebuild for the head should be in order.

Just my .02

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Looks to me like you have an excessive amount of carbon buildup.

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I've used the fel-pro hg kit twice without any issues on my nb.

Looks like you been running pig rich, or you have an oil consumption issue, or just not been getting to op temp so you are not burning off the crud.

20k miles and that much build up is not good.

With that much build up in the combustion chamber, and the top of the pistons, how much is built up on the back of the valves????

Also the build up is a result of the bad drivablity, not being able to get over 65 with foot down.

First thing to do is rotate the engine so all 4 pistons are at mid stroke.

next pour about 1 inch of oil on top of the pistons, this will be a back yard way to check ring seal, let set for several hours to over night.
When you come back, you should have about the same amout of oil on top of all 4 pistons, if one or more has lost way more than the rest of them, you have a ring issue.

now lets check the head out a bit....

pull the cams from the head....

Now ...
How to Fluid test a Cylinder head
https://www.miataturbo.net/engine-performance-56/how-fluid-test-cylinder-head-65558/

How to Clean a Head Gasket Surface
https://www.miataturbo.net/showthrea...665#post862665

How to check a head for warp
https://www.miataturbo.net/showthrea...636#post855636

Use a LONG 3/8 or 1/2 extention to check for warp, not the most accurate, but will get you close and have an idea of how bad it is.

Now lets move to the block....

I forgot to mention use blue paper towels wads to plug the oil return, and oil feed to the head.

Head Gasket Repair-How to Clean the block surface w/ pistons installed
https://www.miataturbo.net/engine-performance-56/head-gasket-repair-how-clean-block-surface-w-pistons-installed-65074/


Also 224*F coolant temps you should not be over heating...

Water boils at 212*

For every pound of pressure the rad cap holds on the coolant system you can go 3* over boiling point.

You should have a 13psi cap.... so....

13psi X 3* = 39*

so 212* + 39* = 241*

241* is boiling....

BUT if your cap is weak say holding 7psi and not 13psi.. you will boil over sooner..
same goes for any sort of leak allowing pressure to bleed off.

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No problem!!

Yes an extention you would use on a ratchet... a long one like 18-20 inches... so the center part will span the length of the head.

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You could block the coolant flow thu the intake mani... But I am unsure what effects it would hold for you.

It is common to do down here in the south where it will not be as cold as you get in the winter months.

The reason the OE flow the intake is to heat the maini so it will heat the air as it passes so the fuel and keep it vaporized into the combustion chamber.

Also I do not know if it would cause "hot spots" in the block due to the coolant not flowing as it was designed to do by the facory engineers.

Unless someone who has studied the coolant system in depth speaks up and can give a reason one way or another, I would say do so at your own risk.

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I'm not seeing any evidence of a blown gasket, either. Possibly a cracked block?

Warped ---- from running too rich.

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What was the measurement at 9pm?

Looks like you have about a half inch worth of diffrance.

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Now me and the mad scientist are going to replace the piston rings you fried.

You should be fine.

Rock on with the head gasket

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