How to Fluid test a Cylinder head
 

How to fluid test a 4G63 Head


This is a simple and quick way to check for seat and valve seal.

First clean the head by the method of your choosing.

Once the head is cleaned, blow the runners out with compressed air to remove any carbon, oil or crud that can give a “false” seal.
https://www.miataturbo.net/attachmen...ine=1335888480

Next lay the head with the runners up, and the valves facing you. I am starting on the intake side.
https://www.miataturbo.net/attachmen...ine=1335888480
Now get a jug of fluid, I am using water.
https://www.miataturbo.net/attachmen...ine=1335888480

Now here is the hard part….. Pour the fluid in the runners, one at a time.
https://www.miataturbo.net/attachmen...ine=1335888480
Now that all four runners are filled with fluid.
https://www.miataturbo.net/attachmen...ine=1335888480
Now look at the valves in the combustion chamber, no fluid. All is dry. This side is good and the intakes are sealed well.
https://www.miataturbo.net/attachmen...ine=1335888480
Now flip the head over, and fill the exhaust runners.
https://www.miataturbo.net/attachmen...ine=1335888480
Take note that you will have to plug the EGR passage so the fluid will stay in the runner.
https://www.miataturbo.net/attachmen...ine=1335888480
Look at the fluid pour out past the valve, there is an issue that needs to be looked into. It is a bent valve.
https://www.miataturbo.net/attachmen...ine=1335888480
Notice how the runner on the left of the divider still holds fluid, but the one on the right is empty. This is cylinder #4. If the left side will not hold fluid, check to make sure you have blocked off the EGR passage. https://www.miataturbo.net/attachmen...ine=1335888480

If you used water, blow the excessive water out with compressed air.
https://www.miataturbo.net/attachmen...ine=1335888480
Then with WD-40
https://www.miataturbo.net/attachmen...ine=1335888480
Spray WD-40 in the runners to inhibit rust formation on the valve stems.
https://www.miataturbo.net/attachmen...ine=1335888480

Now at this point any valve sealing issues can be addressed and fixed.

Thanks, simple but very effective, this is something I may try with my built head before fitting to the block...... :)

Nice! I'll probably try this with the VVT head that's on my workbench.

Correct me if I'm wrong, but on all the BP series 1.8 Miata heads, the EGR is external to the head (intake and exhaust manifolds) correct?

Correct.

The top of your can of wd-40 could use some... wd-40 :)

Hi Dale,
These are great. Do you have anything in the works for CC ing the head? How about building your own flow bench? Thanks

2manyhobz...

Here you go.. How to CC a head

https://www.miataturbo.net/engine-performance-56/how-cc-combustion-chamber-64407/

As far as a "build a flow beanch" thread, I doubt I will be the one to do that.

I am a bit spoiled with my Superflow 600 :D

Using WD-40 for its original intended purpose! Water Displacement ;)

Maybe someone can do this on a '99 head and a '94 head so that we may calculate the compression ration of a '99 head on a '94 bottom end.

Thanks again, those write up are just awesome!!