How to Surface a Cylinder head for a MLS head gasket

[BogusSVO]

How to resurface a 4G63T Head For a MLS head gasket.



I use a Comec Auto I 1000 High Speed Milling Machine with CBN insert for Cast Iron OR a PCD Insert for Aluminum Heads
This machine is double adjustable, I can adjust the spindle speed and the table travel speed to achieve the surface finish that is required.
http://www.joebakerequipsales.com/AutoI1000.htm


The first thing to do is check the valve cover surface for any burrs and remove them.

Next is to mount the head in the machine and check the level of the head in both directions.

Then the other way, this head was not out that bad from the last time it was milled.

I did a “getting to know you” pass of .002 to see how square the head was. This was done on a faster setting.
Notice the upper and left side of the head is dull, this is a low spot. The head was not index properly and did not maintain a proper “square” to the valve cover surface.

I made another cut of .003, I sped up the cutter, and slowed the table speed.

This is the end result.

Another different view.

Now with a proper surface, and the head re-squared, The customer will have no issues with a MLS gasket sealing, and also having a closer to equal combustion chamber size.

 

[slowmkviii]

good post
what do you use to get a reference to get the original squareness
of the head to make sure that each chamber is same size

 

[BogusSVO]

on "block" style of heads, you level to the valve cover mounting surface.
most production heads are "sloppy" when you CC the combustion chamber, I have seen as much as 4cc diffrence in a head, most common is 2cc.
with out some slight porting and cc'ing the head a few times the chambers are very rarely the same.

with wedge heads the set up is a bit more of a deal to set up.

 

[kustomizingkid]

What is an MLS gasket, forgive my ignorance and laziness to google...

 

[BogusSVO]

MLS is Muli Layer Steel head gasket,( Cometic is a brand name) alot of late modle engines use them, the surface finish has to be very smooth, like glass, to get the gasket to seal properly.

The common ways to surface a head, have changed with how and what engines are built out of
In the day of Cast Iron Heads and cast iron blocks, table stone surfacers were used, think of something about the size of a large end table, with a 14 inch stone spinning in the center of it, the machinist would grab the head and hold it, working the head in a circular motion agaist rotation of the stone. till it was flat? not a very good way of surfacing a head. I have still seen this style of surfacer in use in shops to this day.

Next is the "master head surfacer" some are wet, others are Dry, very common in shops, they are cheap to buy and quick to use. Its nothing more than a big belt sander. Thease machines are not at all accurate, the head is flat, but not square or level, they tend to grind more off the leading edge of the head. On this machine the machinist holds the head and works it across the belt, assuming he has a clue of how that machine cuts. Most do not.

Rotory Broach is another common machine, found as single speed or dual speed, the head is held ridged in a hold down fixture, then a wheel with 10 carbide inserts pass under the head. its a decent machine, but the finish depends alot in how well indexed the carbide inserts are to one another, .001 makes a big diffrence, it can take hours to set the blades up. Works great on cast iron heads, and some alum, BUT it depends on what kind of Alum the head is made of.

Another machine is the surface grinder, not a bad machine, it keeps the head leveled and indexed, it uses segmented stones. The surface finish is not smooth enough most of the time for MLS gaskets, The finish is dependent on what stones, how well dressed they are, spindle speed and table speed. Still very common in shops

The new boy on the block is a High speed Milling machine, these use a .500 (1/2) inch insert, CBN for cast Iron and CBN for alum. for the most part, as far I as know, have been around about 10 years. smaller shops are slow on getting them due to there cost, But without a doubt give the best surface finish. Some machines, Like the comec I use, have variable rate spindle speed and variable rate table feed rates. This will alow for diffrent surface finishes for diffrent gaskets