How do I identify the correct V-12 head
#1
How do I identify the correct V-12 head
Hi.
I recently purchased an '85 XJS HE. It had a head problem that the previous owner had quoted to repair. The mechanic said the head would have to come off to be fixed. The owner said it was a broken valve spring/dropped valve....but I suspect (after reading through several forum posts) that it is a valve seat that has dropped.
I located another set of v-12 heads but the gentleman that has them isn't sure of the year/model of jag they came off of.
How do I identify if these are the correct heads
Are there casting numbers that I can go by or some obvious feature that I can inspect
As I understand it the HE engine ran over 12:1 compression and the earlier engines were about 10.5:1
If there is some visible feature that differentiates these heads pictures would be greatly appreciated.
Thanks
David
I recently purchased an '85 XJS HE. It had a head problem that the previous owner had quoted to repair. The mechanic said the head would have to come off to be fixed. The owner said it was a broken valve spring/dropped valve....but I suspect (after reading through several forum posts) that it is a valve seat that has dropped.
I located another set of v-12 heads but the gentleman that has them isn't sure of the year/model of jag they came off of.
How do I identify if these are the correct heads
Are there casting numbers that I can go by or some obvious feature that I can inspect
As I understand it the HE engine ran over 12:1 compression and the earlier engines were about 10.5:1
If there is some visible feature that differentiates these heads pictures would be greatly appreciated.
Thanks
David
#2
The earlier, non-HE engines had the combustion chamber in the pistons, The head face was flat with the valve seats and valves on this flat surface. The HE engine, (from around 1984 was it ?), has the combustion chamber partly in the pistons and partly in the head. One of the valves is recessed into the head with a small "ramp" up to it to allow the "Fireball" to form.
#4
The earlier, non-HE engines had the combustion chamber in the pistons, The head face was flat with the valve seats and valves on this flat surface. The HE engine, (from around 1984 was it ?), has the combustion chamber partly in the pistons and partly in the head. One of the valves is recessed into the head with a small "ramp" up to it to allow the "Fireball" to form.
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#8
I wonder if David got a email saying he got a response from his question?
There was one thread that I replied to because it was on top of the list - just trying to be helpful. But it turned out to be a very old post - not sure how it got to the top.
So sometimes interesting things happen
Cheers
Steve
There was one thread that I replied to because it was on top of the list - just trying to be helpful. But it turned out to be a very old post - not sure how it got to the top.
So sometimes interesting things happen
Cheers
Steve
#9
I wonder if David got a email saying he got a response from his question?
There was one thread that I replied to because it was on top of the list - just trying to be helpful. But it turned out to be a very old post - not sure how it got to the top.
So sometimes interesting things happen
Cheers
Steve
There was one thread that I replied to because it was on top of the list - just trying to be helpful. But it turned out to be a very old post - not sure how it got to the top.
So sometimes interesting things happen
Cheers
Steve
Yes. I did get an email even after 10 years. I got a complete engine and also a complete 2nd car a little after that. I think I will need to retire just to get working on all these back burner projects that have collected at my shop.
david
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