[modern] Cylinder Head Gasket Replacement

Dear Prestons,
When I changed out my head-gasket on my 94, I noticed similar corosion
arround the water pasages to the block. I was suprized by this because I too
had changed out the coolent every two years. On my old gasket, the steel
insert seems to have caused the corosion or acted as a sacrifical anaode. On
the aftermarket gasket that I installed, the water pasage holes were quite
abit bigger. My parts guy (an independant Jag shop) told me that they have
always had to replace the gaskets at between 90k and 110k miles and they
have never had a problem with the replacements. I changed mine at 95K and
now have 114K on it and its doing fine.

Regards,

Bruce Williams

'94 XJ6 (40) 114k_________________________________________________________________
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While we’re discussing headless XJ40’s & such…
I have a question that may have been touched on before, but
I don’t recall seeing it addressed.
Since headgasket issues seem to be inevitable with the AJ6,
I was wondering if anyone’s done a little massaging to the
head while it’s off (oh dear…one of those ‘while you’re
in there’ things - the kiss of death!)
Porting/polishing? Maybe shave the head a bit? What’s
the compression ratio on the 3.6? Am I just asking for trouble?

cds

While we’re discussing headless XJ40’s & such…
I have a question that may have been touched on before, but
I don’t recall seeing it addressed.
Since headgasket issues seem to be inevitable with the AJ6,
I was wondering if anyone’s done a little massaging to the
head while it’s off (oh dear…one of those ‘while you’re
in there’ things - the kiss of death!)
Porting/polishing? Maybe shave the head a bit? What’s
the compression ratio on the 3.6? Am I just asking for trouble?

cds

CDS,
You are just asking for trouble.

You can do various things with little or no improvement
in performance, because that is not where the restrictions
are.

For high rpm end performance, you need to open the exhaust
and the entire intake tract.
I think the exhaust is the big concern.

For lots of low and mid range improvement, the tuned intake
manifold makes a dramatic difference.
AJ6 engineering cuts them open and does things with the
layout of the manifold, then welds them back together.
This likely reduces the high rpm power, so they
also sell the exhaust and intake bits to more them make
up for any power loss.

I did eliminate any casting problems and gasket misfits
on the head and intake manifold when I had them off.

There is no noticeable difference…

Brett
1990 XJ6>

While we’re discussing headless XJ40’s & such…
I have a question that may have been touched on before, but
I don’t recall seeing it addressed.
Since headgasket issues seem to be inevitable with the AJ6,
I was wondering if anyone’s done a little massaging to the
head while it’s off (oh dear…one of those ‘while you’re
in there’ things - the kiss of death!)
Porting/polishing? Maybe shave the head a bit? What’s
the compression ratio on the 3.6? Am I just asking for trouble?

cds

I have removed the cylinder head and find that I have some corrosion around
the coolant passageways on both the cylinder head and the engine block.

The cylinder head will probably need resurfacing to remove the extent of
corrosion, which I don’t think will be too difficult because I have a very
good local machine shop.

The engine block is a little more problematic. It’s not as bad as the head
but there are several coolant passageways where there are 1/8" to 3/16"
diameter corroded areas next to the triangular shaped passageway, maybe 3
thou deep. Although none of them are into the sealing ring around the bore,
but pretty close, say 1/8" away in some cases.

I find this unusual because I have been fanatical about changing the coolant
every year and the car has never overheated.

Any ideas?

Andy
Sonoma CA
90 XJ6 Sov
74 MGB GT