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Author Topic: Composite head gaskets  (Read 316 times)

motorman2whel

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Composite head gaskets
« on: August 17, 2014, 01:23:02 PM »
Has anyone here actually used the composite head gaskets RE & HC sells? . RE says "no more oil leaks" & HC says "American made product with flame ring which we have developed and tested in both competition and road models, we have used these without sealant and they have proved excellent". The only down side I can think of is less heat transfer vs a copper gasket. What are your experience's ? .

High On Octane

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Re: Composite head gaskets
« Reply #1 on: August 17, 2014, 01:45:43 PM »
DO NOT USE THE COMPOSITE GASKETS!!!!!

They are junk!  I replaced my head gaskets with the composite ones last year.  They blew completely out within 1 month of installing them.  I was pissed.  Replaced them with the single layer copper gaskets and they are still holding strong without issues.
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ace.cafe

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Re: Composite head gaskets
« Reply #2 on: August 17, 2014, 02:22:34 PM »
They have their place. They are thicker and squishier than the regular head gaskets, and they have a metal fire ring.

Here's the analysis:
The usual thing is that the engine has an oil leak at the head joint that the owner wants to cure. This leak either was present from new because of poor assembly, or the barrel was replaced at some time(possibly with an alloy one).

Barrels don't always fit properly. In fact they hardly ever fit properly. They require some fitting work. This fitting work includes adjusting the height of the spigot to go all the way into the head recess around the chamber, while ALSO leaving the right distance of the head from the flat mating surface of the barrel to crush the head gasket enough to seal the oil around the pushrod tunnels.

This creates a complete compression seal with the barrel spigot in the head recess. That is what seals the compression. The head gasket does NOT seal the compression. At least, it is not intended for the head gasket to seal compression. The compression is to be sealed by the fit of the spigot into the head, so that the spigot goes fuuly home into the head recess, and is evenly flat all the way around so that it seals tight when you torque the head down.

The head gasket, on the other hand, is for sealing the oil at the pushrod tunnels, and for sharing some of the heat with the barrel. So, this gasket needs to be crushed enough to seal the oil when you torque the head down. Different head gasket types have different crush characteristics, so you need to crush it enough to seal, but it must allow the head to come down enough to seal the compression at the spigot too.

So, we have a "dual plane" relationship that needs to be satisfied simultaneously, with our fit of the head on the barrel(with the head gasket involved). If the gasket is too thick, it will hold the head off the spigot, and the compression won't seal properly. If the head gasket is too thin, the spigot height will hold the head off the head gasket, and you will have an oil leak there. Both things need to happen together. The compression needs to seal at the top of the spigot at the same time as the gasket gets crushed the right amount to seal rhe oil.

So, what do we do?
We cut the spigot on a lathe, so that the spigot reaches fuuly into the head recess, while leaving a gap of .025" at the head gasket mating surfaces. The OEM head gasket is typically about .035" thick, and it can crush down .010" to seal the oil.
When we set the spigot height this way, we seal the compression with the spigot, and we seal the oil at the head gasket. No leaks of any kind, and it is done once and never needs it again unless you get a different barrel or head. No fire rings needed, no extra thick squishy material to seal an incorrectly set head joint.

The main purposes of the composite gasket are to try to overcome in incorrect assembly problem by "filling the gap". However, in some cases this will set the head too high off the spigot, and lose the compression seal, and the hot combustion gases leak over the top and flame-cut the crevices. Hence, the need for the fire ring to seal that at the head gasket.
It's a "band aid".

So, you can do it right, or use a band-aid.

When we are doing head and barrel work for a customer, we always give the option for fitting the head and barrel relationship for use with the OEM copper sandwich head gasket, so he can have a leak-free fit when he assembles his engine. We have also cured these leak problems for people who were unsuccessful in their own attempts to seal leaks by lesser methods.
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motorman2whel

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Re: Composite head gaskets
« Reply #3 on: August 18, 2014, 04:51:11 AM »
Thanks Ace, good explanation of how a Bullet head to cyl relationship is different than most modern bikes. So the composite gasket is basically a "patch" to make up for improper fitting clearance during assembly or minor damage.  High on octane's composite gasket was probably too thick and didn't let the spigot seal to the head and burnt thru the fire ring & failed. I get it now, Thanks.

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Re: Composite head gaskets
« Reply #4 on: August 18, 2014, 12:17:03 PM »
I know I didn't adjust my spigot heights, because at the time I knew nothing about it.  But I don't believe that was the issue.  If copper gaskets 1/3 the thickness of the composite gaskets are sealing fine (except for an oil leak on the left cylinder) then I can't imagine the spigots being too far off from where they need to be.  The gasket itself just completely failed.  It pretty much disintegrated.










Scottie J
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Re: Composite head gaskets
« Reply #5 on: August 18, 2014, 12:44:07 PM »
Unlike the Bullet singles, the 700 twins are a flat face to face joint right across, without spigots. I don't rate composite gaskets because they can tend to fail without warning, even the copper 'sandwhich' type, but even a new solid copper head gasket is not at its' best unless annealed first, this will make it more likely to seal the oil passageways as well as the compression  ;)
 B.W.

High On Octane

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Re: Composite head gaskets
« Reply #6 on: August 18, 2014, 01:00:05 PM »
BW - Perhaps the older twins don't have spigots, but mine does.  You can see them clear as day in the 2nd pic.  That is a cool tip on annealing the copper before install.  I just did a Hot Torque on mine.  I bolted it up (leaving the head stays off) and then rode for about 20 minutes came back home and immediately retorqued them.
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Re: Composite head gaskets
« Reply #7 on: August 18, 2014, 01:23:51 PM »
You are quite right, Scottie and here is one of my own photos to prove it  - I got it the wrong way round   ::) I remember ordering some solid copper gaskets with the intention of fitting them to a 700 twin and having to open them out to clear the spigots - they were for a Meteor minor 500 and THAT was the one with no spigots at the top of the liners.
 B.W.

Vince

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Re: Composite head gaskets
« Reply #8 on: August 21, 2014, 06:18:27 PM »
     I've had the best success with the standard factory composite sandwich gasket. Here is what we do: measure the new gasket thickness. Slip the head on the cylinder spigot with no gasket. Measure the gap where the gasket would be. If the gap is larger than 1/2 the gasket thickness the spigot height must be adjusted. Use a good quality large mill file. Draw it across the spigot. Clean the file with a file card after every pass. Change the direction with each pass but do not go back and forth. One direction with each pass. Install the head every few passes and check clearance. When the clearance is less than 1/2 the gasket thickness you are good to go.
     You can even do it without removing the cylinder. Just stuff an oil soaked rag on top of the piston to catch metal filings. Remove the rag prior to re-assembly.
     Upon re-assembly use the upgraded cylinder washers. Torque to spec. Let sit at least one hour, then re-torque.

Arizoni

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Re: Composite head gaskets
« Reply #9 on: August 21, 2014, 11:29:08 PM »
Vince mentioned drawing the file across the spigot.
In the world of building Kentucky Rifles, this is called draw filing.  It is a more precision method of filing that leaves the surface flat and very smooth.
Draw filing does require a good quality, new flat file.  The "single cut" kind with the teeth all running parallel.  Not the "double cut" file with crossing teeth that form little diamonds.

The most noticeable thing about this is the file is never pushed forward with the file pointed in the direction of the stroke like you were filing something.

Rather, the file is usually held cross-ways to the direction of the stroke.
For instance, sitting with the part to be filed in front of you, turn the file so it is pointed from your right to your left.  Place it onto the flat surface you want to file.  If you want to file while pulling the file towards you, position the files handle (tang) so its pointed towards your right side.  If you want to file while pushing the file away from you, position the files handle (tang) towards your left side.

This process is done dry.  Never apply any kind of oil to the file or to the parts surface.

Now, applying a moderate amount of downward pressure, push or pull the file towards or away from you.  Yes, the file is pointed at 90 degrees to the direction of the stroke.

If you are applying the right amount of pressure you will feel a definite resistance and very small chips will be formed.  Because these tiny chips are trapped between the file teeth they will tend to stay trapped there.  If they are left there and another stroke of the file is made, the tiny chips will "gall" or weld themselves to the surface.  That's why Vince said to use a file card to clean the files teeth after each stroke.
Applying a light coating of chalk to the file will reduce this tendency for the chips to become trapped but cleaning the file teeth with a file card is still needed.

This method of filing is very slow.  It won't get you into trouble by gouging out some area and creating a low spot.  That's what makes it very accurate.

When you are doing this draw filing, don't forget to turn the cylinder (or the direction of the filing stroke) a bit with every stroke or every other stroke.  That will keep the surface nice and flat like it should be.

Have fun.  :D
« Last Edit: August 21, 2014, 11:32:09 PM by Arizoni »
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rep_movsd

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Re: Composite head gaskets
« Reply #10 on: August 22, 2014, 07:07:34 PM »
I did this spigot fitting manually recently -

The way I did it was (you have to take the barrel off obviously):

Use a marker to paint a line of ink on the top of the spigot. Put the head on it and swivel it left and right with some pressure. Now you can see the high spots where the ink has got worn off.
File with a smoothcut Nicholson with the "draw filing" technique described above.
Wipe the dust off, repeat until the ink is getting smudged all around.
It took me about 1 hour doing it carefully

Finally do a check with a feeler gauge with mild pressure on the head and gauge the thickness of gasket you need. I've always needed thin gaskets on this bike, so I use 2 layers of copper delaminated from one of the stock gaskets. This has less "crush", because there's no paper sandwich.

I also learned to use minimal amounts of silicone sealant while fitting, because they induce more "give" and this leads to seeping oil.

This is the first time I did a perfect head job and after 3000 KM the whole engine is perfectly dry of any seeping oil (albeit dirty ).

Now if I can somehow fix the oil that gets thrown out of the primary case from the hole for the alternator wire - I should have a truly leak proof Enfield!

ERC

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Re: Composite head gaskets
« Reply #11 on: August 22, 2014, 10:57:21 PM »
Use a vent on the primary. Drill a hole in the fill.  ERC
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ace.cafe

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Re: Composite head gaskets
« Reply #12 on: August 23, 2014, 01:02:28 PM »
Use a vent on the primary. Drill a hole in the fill.  ERC

Worth a try, especially in hot climates.
A very small vent hole.
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High On Octane

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Re: Composite head gaskets
« Reply #13 on: August 23, 2014, 01:28:00 PM »
I too get lots of oil spillage out of the holes where the clutch cable and alternator wire go in and out of the primary.  I blobbed a bunch of Ultra Black RTV on it last summer and it worked well.  I've just been into the primary cover so many times this year I never sealed it back up.  In fact I'm just getting used to the fact that my bike leaks more oil than a fat girl eats chocolate cake.
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rep_movsd

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Re: Composite head gaskets
« Reply #14 on: August 27, 2014, 10:49:26 AM »
I think I'll try that vent hole - perhaps a 2 mm hole in the primary side oil filler cap.

Whats the rationale behind it? Does the ATF foam up ? or is it merely flung out due to centrifugal force?