Preferred Head Gasket

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Lineslinger

Lineslinger

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I have performed a reasonably thorough search throughout the forum.

With some information being ten years old or older and with the the advent of new 2020 materials and composites I would like your opinion and or experience on the preferred head gasket you have used or are running presently.

I am researching for 74' 850.


Not trying to start another "best oil" thread, thanks in advance for sharing.
 
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Composite has the potential to be the best for oil tightness, but when they fail they fail catastrophically and its most likely a roadside recovery.

Copper is most likely to weep a bit of oil but failure will be less traumatic and you will most likely be able to drive home.

You can get the copper gasket oil tight with some extra work, eg by using copper wire around the push-rod apertures and using a good sealant.

So your choice but I prefer copper with extra effort over composite.
 
Tried many versions of copper, alu, and composite... but have settled on this version and have had good luck so far, composite with copper rings

Preferred Head Gasket
 
Jim Comstock did once mention he might get multi layered steel types made. These work really well on Triumph/BSA triples & seem to be fitted to most modern engines.
 
I've burned out 2 flame ring gaskets over the years and managed to get home both times. Have never been able to keep the copper gaskets oil tight, despite annealing, sealing etc, so I'm back to composite.
 
Got a Cometic multi layer type on my Trident. Seems to be working well. Have they developed one for the Commando yet?
 
I went with solid copper. Probably should have used coppercoat as well. It does weep a bit.
 
The 750 commando ones I likes best were in the late 80's early 90's. black fiber steel flamering. These were WITHOUT todays thermosert glue. I could and did reuse them several times with no drama.
Todays one use only thermoset ones always tear the glue layer and make a big project out of surface prep. I think I even tried methylene cloride paint stripper to get rid of the glue layer to make them reuseable...no luck.
Never found a source of the early style again.:(
 
I have never had any issue with the stock composite gaskets from AN. They do however crush down a LOT after the initial instal. I always followed the re-torquing practice that’s been mentioned on here. No weeps and no failures.

On my current 920 motor I’m using copper as there’s no other choice. So far that’s been ok too, but I followed the JS contact cement and copper wire process with this, which is a very fiddly and unpleasant bloody job!

Personally, on a 750 or 850 I’d stick with composite.
 
By the time a flame-ring gasket goes to hell, it's time to de-coke anyway. That being said, I've used copper also. With the composite, you need to re-check head torque soon after the first run through the gears to get the oil hot. A high-comp motor may require the wire trick.
 
The only time I had a failure with my 850 head gasket was from the failure of the stud on the left cylinder. It had the composite flame ring in it when I purchased the bike. I rebuilt it and fixed all studs with helicoils and used a flame ring from an Andover gasket kit. Still tight after +40k plus miles and counting. I do at least three heat cycles
re-torque after a complete cold engine. 1 start up of rebuild.
2 Then after 50 miles.
3Final after 1000 miles on the clock
so far no problems
 
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+1 with Fast Eddie
I use a standard composite gasket in my race bike, light spray of copper kote glue both sides then do the re torques as well.
Surface prep on both barrels and head is important as well.
Regards Mike
 
CanukNortonNut said:
The only time I had a failure with my 850 head gasket was from the failure of the stud on the left cylinder. It had the composite flame ring in it when I purchased the bike. I rebuilt it and fixed all studs with helicoils and used a flame ring from an Andover gasket kit. Still tight after +40k plus miles and counting. I do at least three heat cycles
re-torque after a complete cold engine start up of rebuild.
Then after 50 miles.
Final after 1000 miles on the clock
so far no problems
Click to expand...

My sequence is more OCD than that.

I re-tourque after:
1. Initial start up after rebuild, zero miles.
2. 50 miles
3. 100 miles
4. 500 miles
5. 1000 miles.

The amount the fasteners loosen in cycles 2,3,4 amazed me the first time I did it. I thought the fasteners were stretching, or the threads stripping. But no, it was just the gasket compressing. I’m absolutely certain there’s no way the gasket would have survived to the 500 mile mark without this, or a similar sequence.
 
When you all say "re-torque" do you loosen the bolts every time and then tighten to the correct torque? If so, loosen all at once or one at the time?
 
I used the same procedure that Fast Eddie posted and after 7000 miles no leaks.
Mike
 
fiatfan said:
When you all say "re-torque" do you loosen the bolts every time and then tighten to the correct torque? If so, loosen all at once or one at the time?
Click to expand...
This is a very good question...
1. Should you be forward torqueing
2. Slackening the fixings by some degrees & the re-Torqueing

if the relative tightened positions for each are marked, the positions will be different....
 
Composite gasket is my choice
I re torque or just check the torque but I don't back the fastener off first
Never had a problem on a Norton
Once had the middle section blow out of a 10 stud triumph engine composite head gasket
 
During the '60s a friend of my dad's ran the race program for a very large California car dealership. Porsche, MG, and Triumph. His trick on head gaskets was a couple of coats of high temp aluminum spray paint. I've used this method since my head gasket blew on my brand new Combat. I also hand paint a couple of extra coats around the push rod tubes. No leaks at all. I usually use a composite gasket but I did use copper on my Drouin equipped 850. The crank broke clean in half due to my ham fisted driving, but the head gasket was still intact. I'm also religious about retorquing the head two or three times during the first 1,000 miles
 
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