How To measure a 4G63 for Cylinder Head for Thickness

[BogusSVO]

How a 4G63 cylinder head is measured for thickness.


This is a fairly simple thing to do.
This will also help in setting the timing belt and calculate combustion chamber size.

New head thickness is 5.200
The Mitsubishi factory manual says a combined total of .008 may be removed from the block and head.

AERA (Automotive Engine Rebuilders Association) says .015 can be milled from the head.

So by AERA specs the Min thickness will be 5.185


The tools needed will be few.

Something to use to clean the head gasket surface
And a set of venier calipers,
Paper and pen.

The first thing to do is remove the head from the engine.
Remove both the exhaust and intake manifolds.

Now on the work bench, remove the cam caps

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The cams and followers.

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Next roll the head over so the head gasket surface is up.

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Now the head gasket surface needs to be cleaned of any old gasket material.

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I use a stiff backed long body board.


Now roll the head so one port side is up,
I will start on the exhaust side.

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Measure from the valve cover rail to the head gasket surface.
I will also use the cam cap mating surface on the top, it will help keep the calipers square.
Make a note of the measurement.
This is Exhaust Front
On this head it was 5.193
Next I will move to the rear of the head.

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Make note of this measurement.
This is Exhaust Rear
Here I measured 5.190

Next roll the head over to the Intake side.

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This is the Intake Front
The measurement is 5.191

Now to take the forth and final measurement.
This is the Intake Rear

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This measured 5.188

So now with the 4 measurements.

EF=5.193 IF=5.191

ER=5.190 IR=5.188


We see the head is not parallel to the valve cover rail.

We can see that from side to side there is .003 difference
And the same .003 from front to back.

Note also this head was belt surfaced before.
This is not a badly surfaced head for being belt surfaced.
The combustion camber volumes will still not be equal.


This procedure will hold true for any "box style" cylinder head.

Other related links

http://www.dsmtuners.com/forums/articles-engine-fuel/341627-how-check-head-warp.html

http://www.dsmtuners.com/forums/cyl...0613-why-not-let-your-head-belt-surfaced.html

http://www.dsmtuners.com/forums/newbie-forum/341209-4g63t-valve-spring-info.html

http://www.dsmtuners.com/forums/cyl...how-aluminum-head-pressure-tested-cracks.html

http://www.dsmtuners.com/forums/newbie-forum/341218-how-change-valve-guides-4g63t-head.html

http://www.dsmtuners.com/forums/articles-engine-fuel/341636-how-lap-valve.html

 

[ckrell]

What would the side affects be if you were under 5.185"?

 

[BogusSVO]

ckrell.... the 2 main ones will be the cam to crank time will be off, the other is increased compression

 

[blink2401]

If you are under 5.185" Is there a potential issue of the valve and piston hitting?

 

[BogusSVO]

Blink, that is always a concern, it will depend how far under the 5.185 you are, and what cams you have.

 

[ckrell]

I'm at 5.180" & block is milled .003" I'm using felpro composite (with Oringed deck) it looks like it's the same thickness at OEM. I do have adj. cam pulleys and I'm using delta 272H & Ross+.020"

 

[BogusSVO]

At .005 under min spec, I doubt you will have issues.

I have seen heads as thin as 5.160 installed and run, with stock cams and gears.

If you have worries, then clay the tops of the pistons and check the valve to pison clearance.

 

[ckrell]

I planned on checking piston to valve, thanks. Wow 5.160" that's getting down there at that thickness do you have to compensate with extra head gasket thickness and or do the adj. timming pulleys have adequate adjustment?

 

[BogusSVO]

A thicker headgasket would help restore the headthickness and therefor help restore the time marks.

I would like to say I was that smart when I first strted in with the DSM heads, but i wasnt.

It was a friend of mines head, wanted to get the car up and running quick, So all I did was a quick seal change and surface.
That head was installed with a used Mitsu MLS HG and stock time gears. It ran, and ran well had alot of compression tho. He was able to tue tho with a Moates set up.

That "thin" head is back now, and is getting reworked again, check my build journal and you will see the info on it.

 

[G-UNIT]

Good info! Imo I wouldn't go past what Mitsubishi recommends @ 5.192.

 

[BogusSVO]

G-unit, With the age of these heads, you will be hard pressed to find one in spec, If I had to guess, out of 15 may be in Mitsu spec