Well, I punched out the holes to align with the passages and proceeded. I’m on a test stand so if this whole thing is a mess and needs to come apart, it’s no big deal.
Rick
Allen, do you remember if the XJ6 gaskets had the same reduced passage size as these current ones?
Thanks
Rick
Just fyi……I had some oil leakage work done in the engine a couple of years ago. I wanted the best gaskets be used and it’s my understanding that the cylinder head got the Cometic gasket.
Since then the car has been used quite a lot without any overheating problems. It didn’t overheat before the work was done BTW.
So, my conclusion is that the Cometic head gasket works fine, however, I have no idea if the gasket used then is the same as has been supplied to the OP.
Use a Payen gasket.
My only experience with Cometic gaskets has been their MLS ones, which are really nice.
I’ve not seen an example of a Cometic composite, but if that is one it’s crap.
I plan to call Bill Terry Monday to discuss. I know his association with the company is loose now but he might be familiar with the current Cometic choices both MLS and Composite and the passage size. I just can’t reconcile that the Payen with full size passages and the Cometic with 80% smaller passages are somehow both right.
Rick
Unfortunately, in my experience (cam cover gaskets) it does.
I had the exact same experience.
Were they Cometic? I bought Cometics to fit my S1 XJ (same as E) and got the S3 version with no rear gap. Was easy to trim, and they fit perfectly FWIW. I know that Cometic recently returned to sourcing them specifically for engines with gaps. But don’t know if it’s still the case, based on what’s reported in this thread.
Yes, Cometic. This happened 5-6 years ago ( roughly). Trimming was not the problem , the ones I received had one side longer than the other
There was an article in the Jaguar Journal about 4 years ago by an Australian engineer who reduced the exit holes from the head intake manifold interface to make the total volume that could exit equal to the area of an open thermostat. It’s a bit more complicated than this but you get the idea. He claimed an increase in cooling from this mod. This would result in the coolant remaining in the head and gathering more heat in theory.
Had the same gasket viewed in your pictures. Leaked immediately. Threw it out and went with the Payen Why oh why did I think there’s something better than OEM.
The cooling may or may not have been improved, but not due to this theory. But if the Australian did believe this theory, I wonder if the air flow through the radiator was also decreased so the air had more time to gather heat. Maybe a good reason to keep the Boeing Blade two bladed fan!
Tom
Rick, yes they have the reduced passages. The Jaguar parts man told me that decreasing the size increases the velocity of water to match the output of the water pump. Never had overheating issues with either of my cars. Also they have not leaked!
Allen
Indeed, the faster the coolant flow (and air flow) the better the cooling, just as you say, and counterintuitive to many. But in this case the phrase “coolant remaining in the head and gathering more heat” can have two meanings. Yours is one–the coolant fills the head, but exchanges more slowly. IIRC, the argument for the smaller holes (with one side even smaller than the other) is that the coolant doesn’t fill the head–leaving areas of the head passages not in contact with coolant period–no matter how fast it’s flowing. The smaller holes somehow raise the ambient pressure inside the head, and therefore the boiling point of the coolant. So more liquid coolant “remains” in the head (and less vapour) compared to a head sporting large slots. I have no idea if this is true–just trying to remember what I read some time ago.
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Robert, I do not believe I heard that theory before. I can see why you placed the word “remains” in quotes. Not sure I buy it yet, but not knowing enough details I really do not know.
Tom
Vaguely related ( somehow) we have a solar panel water system on our house. Initially it didn’t work too well using a constant flow, but rearranging the flow so the water went through the system in “slugs” allowing the water to spend more time in the heat exchangers allowed it to absorb more heat and therefore be more efficient. Same theory?
I would agree with that, too fast a flow and the coolant doesn’t stay in the head long enough to collect heat.
Your solar panels are trying to gather heat and gather it at a high temperature. The engine’s cooling system is trying to get rid of heat and to keep a lower temperature. Yes, if you want your car’s cooling system to run at 300F rather than 180F, then there may be an advantage to keeping coolant in the engine longer.
To simply move as much heat as possible, move the coolant faster.
Unless you are talking about Robert’s second scenario above, you would be incorrect.
There was a discussion on this some time ago
Fact/Fiction- cooling - E-Type - Jag-lovers Forums
Tom
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Faster flow prevents hot spots.
No matter the flow rate, the coolant is in the engine and radiator equal amounts of time.