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3 different head gasket types: Why?
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=83126		 Page 1 of 3
Author:  Rixram [ Fri Sep 25, 2015 12:12 am ]
Post subject:  3 different head gasket types: Why?
Okay, no hole, 1-hole or 2-hole?

Aside from making this sound like some reference to porn, why on h3ll's earth do we have 3 different head gasket types? They all are for the same engine, but give different thicknesses.

What is the advantage/disadvantage that led to this need? And what happens if we move up or down? Aside from a mild change in the compression ratio...what am I missing here?
Author:  bugnout [ Fri Sep 25, 2015 12:33 am ]
Post subject:  Re: 3 different head gasket types: Why?
I believe the head gasket thickness is based on the cylinder liner protrusion from the block deck. if you haven't done any work on the lower end, you need to replace with same thickness hg. If you've serviced one or more liners, the you have to remeasure to determine which HG to use.
Author:  Mike92104 [ Fri Sep 25, 2015 12:38 am ]
Post subject:  Re: 3 different head gasket types: Why?
bugnout wrote:
I believe the head gasket thickness is based on the cylinder liner protrusion from the block deck. if you haven't done any work on the lower end, you need to replace with same thickness hg. If you've serviced one or more liners, the you have to remeasure to determine which HG to use.


It's determined by piston protrusion, not the cylinder liners.
Author:  turblediesel [ Fri Sep 25, 2015 1:02 am ]
Post subject:  Re: 3 different head gasket types: Why?
Maybe to compensate for skim cuts taken on the head and maintain valve to piston clearances.
Author:  flash7210 [ Fri Sep 25, 2015 8:07 am ]
Post subject:  Re: 3 different head gasket types: Why?
Its liner protrusion.

The liners are pressed in to a specific depth and the head gasket thickness matches how much of the liner above the deck.
When the head is torqued down, the top edge of the liner very slightly presses against the head.
Too thin of a gasket and the head can warp slightly when torqued, never making a good seal.
Too thick of a gasket and the liner will never come into contact with the head, not making a good seal.

The head gasket is a multi-layer-steel (MLS) gasket. When torqued it compresses very slightly, allowing for the head to gently press against the top of the liner.

Both the installed liner depth and head gasket thickness have to be "just right."
This is why there are special tools required for setting liner depth.

If you never pull the liners, you will never have to worry about this. Just replace the head gasket with exactly the same type as before.
Author:  Mike92104 [ Fri Sep 25, 2015 2:33 pm ]
Post subject:  Re: 3 different head gasket types: Why?
flash7210 wrote:
Its liner protrusion.

The liners are pressed in to a specific depth and the head gasket thickness matches how much of the liner above the deck.
When the head is torqued down, the top edge of the liner very slightly presses against the head.
Too thin of a gasket and the head can warp slightly when torqued, never making a good seal.
Too thick of a gasket and the liner will never come into contact with the head, not making a good seal.

The head gasket is a multi-layer-steel (MLS) gasket. When torqued it compresses very slightly, allowing for the head to gently press against the top of the liner.

Both the installed liner depth and head gasket thickness have to be "just right."
This is why there are special tools required for setting liner depth.

If you never pull the liners, you will never have to worry about this. Just replace the head gasket with exactly the same type as before.


This is not correct. The liner protrusion does not determine head gasket thickness. Piston protrusion is measured to determine head gasket thickness. The liners are set anywhere from 0 to .05mm above the deck height. Then piston protrusion is measured and averaged together to determine the head gasket thickness. The head does NOT contact the piston liners as long as they are within the specified range. I suspect the different thicknesses are to keep the compression ratio within a certain range.
Author:  Mountainman [ Fri Sep 25, 2015 4:56 pm ]
Post subject:  Re: 3 different head gasket types: Why?
I agree with Flash that they do contact the head most of the time, and with Mike that it's piston protrusion, as I've measured it on a few engines.

Most of the heads have an imprint of the liners in the head, but I think I have one or two that didn't. Not exactly precise work in the factory I'm afraid....
Author:  flash7210 [ Fri Sep 25, 2015 5:35 pm ]
Post subject:  Re: 3 different head gasket types: Why?
1. The liners have a lip that is higher than the surface of the block.

2. The head gasket does not seal over the top of that lip, just the rim outside the lip.

3. The piston does not travel any higher than the height of the liner. If the piston head protrudes higher than that lip of the liner, the liners are pressed in too deep.
Author:  lars0247 [ Fri Sep 25, 2015 6:44 pm ]
Post subject:  Re: 3 different head gasket types: Why?
Per the "KJ VM Diesel Engine Repair" Student Workbook that Daimler Chrysler published;

The 2.8L VM Diesel Engine uses a selectable Multi-Layered Steel (MLS) gasket and is available in three thicknesses. The gasket thickness is based on the piston protrusion measurement...
Author:  Mike92104 [ Sat Sep 26, 2015 12:30 am ]
Post subject:  Re: 3 different head gasket types: Why?
Mountainman wrote:
I agree with Flash that they do contact the head most of the time, and with Mike that it's piston protrusion, as I've measured it on a few engines.

Most of the heads have an imprint of the liners in the head, but I think I have one or two that didn't. Not exactly precise work in the factory I'm afraid....


I've only done one, so I can't compare. Was the imprint from the lip of the liner, or the crush ring of the head gasket?
Author:  Mountainman [ Sat Sep 26, 2015 9:28 am ]
Post subject:  Re: 3 different head gasket types: Why?
It was the liner stamp, and if you don't have a machine shop remove the scuffs it makes, there's a higher probability that it will leak afterwards. My machinist said the scuff is caused by the movement of the aluminum head, but you probably knew that. I knew aluminum heads like to eat head gaskets, but wasn't sure why. Hopefully the ARP's will keep them still permanently. I wonder how many VW engines with ARP's have made 2 or 300,000 miles worry free? hmm, are they using ARP's on the Subaru engines that fail as well?
Author:  Mike92104 [ Sun Sep 27, 2015 7:18 pm ]
Post subject:  Re: 3 different head gasket types: Why?
flash7210 wrote:
1. The liners have a lip that is higher than the surface of the block.

2. The head gasket does not seal over the top of that lip, just the rim outside the lip.

3. The piston does not travel any higher than the height of the liner. If the piston head protrudes higher than that lip of the liner, the liners are pressed in too deep.


The piston protrusion measurement is taken from the block surface, and doesn't involve the liners at all.

Measuring Cylinder Liner Protrusion:

Image


Measuring Piston Protrusion. The dial gauge is set to zero at the deck height.

Image

You're correct that the piston doesn't protrude past the lip of the liners, but they do protrude past the block.
Author:  flash7210 [ Sun Sep 27, 2015 9:44 pm ]
Post subject:  Re: 3 different head gasket types: Why?
Ok. You win.
You have proven that it's piston height that determines head gasket thickness.

So maybe you can help me understand...

Given that the piston never comes above that top lip of the liner.
Given that the three head gaskets are only different by fractions of a millimeter.
Given that the three head gasket thicknesses make no appreciable difference in compression ratio.
Why have the three different gasket thicknesses?
If there is enough variation in piston and rod castings to where fractions of a millimeter are what determine adequate piston to valve clearance, why not just use the thickest gasket?
If you use the thickest gasket all the time everytime you can't go wrong, correct?
Author:  Mike92104 [ Sun Sep 27, 2015 10:09 pm ]
Post subject:  Re: 3 different head gasket types: Why?
I'm not sure. I had assumed it had something to do with compression.
Author:  Mountainman [ Sun Sep 27, 2015 11:10 pm ]
Post subject:  Re: 3 different head gasket types: Why?
Someone reported having a poor starting CRD after upsizing the gasket, but tough to tell with only one report. I might be start one tonight that I upsized, I'll report back. I figured if it is valve clearance, then I'll go up since my machinist shaved it down smooth for me.
There was a discussion on this while back, and I think everyone agreed it was compression related.
All I know is that the CRD doesn't have very high compression compared to some other diesels, so maybe it is dancing around the point of (ignition or spontaneous combustion or whatever) that it makes a difference??
Author:  turblediesel [ Mon Sep 28, 2015 1:10 pm ]
Post subject:  Re: 3 different head gasket types: Why?
So, what are the thicknesses of the three different head gaskets available?

I worked on a bunch of Fiats with cast blocks and aluminum heads years ago. It was common practice to take the head to a machine shop and have the head resurfaced. They all seemed to overheat and blow head gaskets and warp the head. The 850 coupes and sedans were the worst with the engine and radiator in the back. Lose a fanbelt or hose... lose an engine. Some heads were too warped or cracked to fix. The heads that had been resurfaced needed thicker head gaskets. Fun cars to drive... 60 felt like 100. Put a lot of seat belts in so the Americanos could drive them on base.
Author:  jws84_02 [ Mon Sep 28, 2015 1:34 pm ]
Post subject:  Re: 3 different head gasket types: Why?
1 hole=1.42mm
2hole=1.52mm

I'm not certain on the no hole. But if I had to guess it would be 1.32??? Don't quote me on that one though
Author:  Phatjimmy [ Sun Nov 25, 2018 8:11 pm ]
Post subject:  Re: 3 different head gasket types: Why?
I wanted to bump this thread since I'm facing head gasket issues at 205683.0 miles. Time for a tear down of the head plus I am due a timing belt and water pump. I have been talking to some engine builders in Europe where this engine is still commonly used in the KJ Jeep Cherokees. They ALL have told me they use the thickest gasket all the time without issue and head studs. They also have several sources for head gaskets without head bolts. So has anyone figured out the question posted by Rixram in this thread? If a 2 hole gasket is used when a 1 hole was removed, is there any adverse affect for increasing 0.10 mm? Mine is a 1 hole. I am going to buy ARP studs and hate having to spring for OEM junk stretchy head bolts. As I think Geordi said in another thread, expensive paper weights!

They also said that Victor Reinz makes head gaskets for the US market.
P/N:
61-10037-00 (no hole, 1.32 mm)
61-10037-10 (1 hole, 1.42 mm)
61-10037-20 (2 hole, 1.52 mm)

Anyone know a good supplier for these?? (*wink* ID Parts guys)

Here is the link to one site they gave me.
https://www.autodoc.co.uk/car-parts/gas ... -8-crd-4x4
Author:  WWDiesel [ Sun Nov 25, 2018 11:02 pm ]
Post subject:  Re: 3 different head gasket types: Why?
Probably one of the best writeups on the head gasket thickness subject on LOST.
viewtopic.php?p=928130#p928130
Of course the Factory Service Manual covers it in great detail as well.

There are varying opinions on the subject and some simply promote the use of a single thickness gasket regardless of what is removed or specified in the manual.
The head is not recommended to be milled due to a very thin nickel coating on the surface.
Head gasket thickness is based on piston protrusion which affects valve to piston clearance, cylinder volume, and possibly EG temperatures.
Author:  Phatjimmy [ Mon Nov 26, 2018 12:44 am ]
Post subject:  Re: 3 different head gasket types: Why?
Thank you! I didn't find that thread in my search. I have some reading to do.
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