Too much boost, too weak head gaskets
 

Pictures taken two hours ago. I am drinking some beers now.

From the pictures it looks like a stock setup, was the boost from a smaller pully? Or did you have something else going on like the twin screw setup? Still if it was only the head gaskets, it's not the worst thing.

If 11sec Jag is stock then it's stock.

11 seconds in a 1/4 mile is not stock. But does Europe use a shorter track?

Mine does 13.9, internet says 13.5 or 13.6 when new. At any rate, head gaskets are common on the XJR, I did mine.

It must be more stock than my XJR. Mine is a bit slower. LOL.

My condolences for your hardship...


How much boost? Were they stock 4.0 head gaskets?

Is there anything better than the 4.2 gaskets and some arp head studs?

I've put my +4 lower back on which ran 18-19 psi. I'm a little worried about the head gaskets, but who was I kidding at keeping my car at "only" 13 psi?

I figure if it does blow a head gasket, I'll just upgrade to the 4.2 gaskets and that should end that worry.

They were two years old stock 4.0 composite gaskets, which are easy to burn. Boost was just too high for them. I was testing AFR sensor/gauge when big BUM happened. There was grazy high pressure in the coolant system and upper radiator hose gave up. Funny that system was pressure tested and coolant analysed for possible gasket damage just day before and they did not tell anything about possible problems . At least right side gasket is badly damaged. Next gaskets will be MLS ones and maybe go for waterless coolant at the same time.

I thought that waterless coolant raised the running temps by up to 7 degrees. Would that make a difference in power if the charge coolers were running that much warmer ? I get the concept of lower coolant system pressure because of the lack of water vapour (steam ) , but I thought it was boost pressure that cooked the head gasket and popped the hose , not the other way round.

I read AJ-V8 prepair course handbook and found some confirmations for 4.0 V8 engines. Here a few of them.

" Multi-layer steel head gasket (MY2001) "
" The connecting rods are manufactured of sinter forged steel "
" Crankshaft: Manufactured in nodular cast iron "

Please tell me more about which head gaskets you are planning.

Did you know that the Evans water less coolant is FLAMMABLE

This is good info :) This helps me start planning for if/when I blow a head gasket too. I won't claim to have been the first...

Godspeed 2 rebound.

Heads are off. Never again this kind of gasket.... Good luck - no other visible damages.

Good news :)

Now it will be stronger with the 4.2 gaskets.

4.2 gasket is better, but is it best of all available gaskets - I don't know. I had no time to order special gasket from Cometic. Next time it will be strongest possible.

My gaskets blew too and the photo of your jag on the flatbed is unfortunately familiar.

That being said, what's the best/strongest head gaskets I should replace mine with? I have a 98 XJR so it's whatever was the crappiest OEM one.

I see the 4.2 ones being touted... are these the gaskets for the 4.2L engine? Do they fit well?

Thanks.

Part#: AJ88987 LHB Head Gasket
Part#: AJ88988 RHB Head Gasket

These are genuine Jaguar MLS gaskets for 4.2 but suite also for 4.0.
They are thinner than 4.0 ones: 0.030" vs 0.050", so the compression ratio goes up by 0.1-0.2.

I take it there are no noticeable effects from the slight increase in compression ratio, but what would they be in theory? The fuel burning process is slightly more efficient or something?

Thanks! Have you fixed yours yet? You recommend going the route of those 4.2 gaskets? They should fit my '98 xjr right?

It's combination of compression ratio, boost, ignition timing and used fuel.
Detonation is the enemy.

Everything should be ready tomorrow. You have same AJ26S engine.