I have a 1999 xk8 4.0 that the timing chain tensioner went south on. All has been torn down, heads milled and valve job done by machinist. The information I find on the final torque settings after the 27 ft lbs is 90 degrees then another 90 degrees in the proper sequence. Using this kind of "general" torque settings is not how I've done many heads.

Is there a final torque setting instead of this subjective approach? 45, 50, etc...

Thank you all in advance for your expertise.
Craig

 

The bolts are 'stretch-bolts' or 'torque to yield.
You torque the bolts to some nominal amount, then each is turned 90 degrees in the torque pattern, then turned an additional 90 degrees in the sequence.

Jaguar has been using this since the introduction of the AJ6 engine.

bob gauff

 

torque to angle is not subjective at all. it is the preferred
method of fastener vendor engineers second only to
direct measurement of fastener stretch.

it is far more accurate as compared to torque to number
since it is independent of friction loss.

the reason for this is that the angles are calculated as if
the thread was laid out as a straight ramp. the angle is
a translation of the distance along the ramp given the
circumference of the fastener thread. the number is
calculated to obtain a specified amount of fastener
stretch when considering the fastener thread pitch
as a height above baseline.

 

This is what I get from my XK8 2003 Workshop Manual PDF file I have...

27. NOTE: Tighten the bolts 1 to 10 in the sequence shown.
Install the left-hand cylinder head.
1. Tighten bolts 1 to 10 to 20 Nm.
2. Tighten bolts 1 to 10 to 35 Nm.
3. Tighten bolts 1 to 10 to 90°.
4. Tighten bolts 1 to 10 to 90°.
5. Tighten bolts 11 to 12 to 25 Nm.



28. Install a new right-hand cylinder head gasket.
Make sure the cylinder head dowels are correctly located.
29. NOTE: Tighten the bolts 1 to 10 in the sequence shown.
Install the right-hand cylinder head.
1. Tighten bolts 1 to 10 to 20 Nm.
2. Tighten bolts 1 to 10 to 35 Nm.
3. Tighten bolts 1 to 10 to 90°.
4. Tighten bolts 1 to 10 to 90°.
5. Tighten bolts 11 to 12 to 25 Nm.

 

From pages 675/676 of the manual

 

Would the 2003 be a 4.2L?

That would be handy information for those use the 4.2L gasket on a 4.0L

 

03 is the 4.2

 

Thanks.

Just checked the course manual, and it is the same for 4.0L

 

Thanks for your feedback. I just don't want to break a bolt off in the process.

 

I never want to break a bolt off in the process BUT it does happen occasionally.
I remember installing a head bolt in a 1992 XJ40 AJ6 engine and snapped one on the second 90 degree turn. I REALLY did not want to remove the head, remove the broken bolt and replace the gasket and bolts AGAIN.

I panicked a little but it broke on an angle so I put a dab of JB Weld on the broken angled section and dropped it into the hole to set-up overnight.

Next morning I twisted the entire broken bolt out and installed a NEW one. (WHEW!!!!!)

$h!t happens.

bob gauff

 

I just broke one of the M8 bolts i will try that JB weld

 

Bob, am I correct in thinking that the “torque to yield” bolts should not be re-used ? ie, one needs all new bolts when reassembling after any head removal ?

Z

 

first attempt with JB weld did not work. I will try again.

I did not buy new M8 bolts as I thought since they were just torqued, they would not fail on second attempt. I will get 4 new ones. If I cannot get the broken one out, I will need to remove the head to remove the broken thread bolt, then I have same question. Can I reuse the new bolts I Just put in? Can I reuse the new head gasket I just put on?

 

I would not use torque to yield bolts a second time. Even if the motor never fired up.

Others may have a different strategy, but I was taught that once they are torqued for the first time, they should never be torqued for the 2nd time.


Z

 

Jaguar issued a TSB for re-use of the head bolts for the AJ6/AJ16 engines.
I have never heard of that recommendation for the AJV8 engines.
The M8 bolts at the front of the head are not TTY bolts and I re-use those.

 

PS:

I’m shocked that JB weld worked even once. Call that a miracle.


Z

 

Call me Mr. Cautious, but neither would I.

From JTIS, though:
"Clean and inspect the cylinder head bolts. They may be re-used on two occasions. When re- used, each bolt head should be marked with one dot from an automatic centre punch."

What if someone forgot to centre punch...

 

One only needs to read the horror stories on this forum about brand new head bolts breaking to have a legitimate concern about the bolt integrity, new or used. I say my prayers and incantations every day that I never have to change the X-100 head gasket and find out exactly how lucky, or not, that I am that day.

Z

PS funny, how over a 50 year career in vintage motorcycle and automotive restoration I’ve never had a single head bolt snap. Of course all of those 1,000’s of head bolts were the old fashioned reusable type, not the “torque to yield” (superior ?) kind.

 

so i decided to buy new parts for the left side and proceed to right side
I pulled these head gaskets out of wrapper several days ago, and the surface coating is peeling off just by rubbing on it. what is the coating for and do I care?

 

I could not get bolt to come out so I removed all bolts and pulled the head. I was able to move the bolt end out a few threads by using a dremel ball cutter in left hand turn and then cut a slice in it to use a screwdriver to remove it. It was not easy coming out. I then used a tap to clean the threads.