head gaskets and bolts

[joey zingale]

i have my 97 discovery torn down to replace the head gaskets.
my question is, I have heard that you can not re-use the head bolts. Is this true?
Are there any other tips or tricks I should know about before putting it all back together?
thanks for any and all help!!!

 

[joey]

Not a good idea to reuse the head bolts.... Give Nathan a call (in my signature) he just did a head job and ordered some head bolts for Summit Racing, I just don't remember the type of head bolts they were...

 

[Chongo]

Engine

The engine in the disco 2 is the old buick 215 v-8, with no roller cam, and no rotators on the exhaust valves like US engines. The dry cylinder sleeves, “ these are not wet sleeved engines”, are straight, un - flanged and made of steel, while your block is made of aluminum. This creates a thermal condition of dissimilar materials. Many mechanics blame a blown head gasket on this thermal condition as a, “dropped liner”, but in reality at about 210 degrees operating temperature the cylinder liner actually moves around .004” of an inch away from the head gasket ring , this releases the tension on the head gasket between the liner and the head. This releases the tension between the head and the head gasket between the liner and the head, and reduces the heat sink value on the head gasket steel ring, {this is why when you remove the old head gaskets on a land rover the steel ring on the head gasket is usually yellowish or has a burnished color}, causing premature head gasket failure. Now note what I said, the head to liner distance is getting larger by .004” not the head separating from the block, but the liner actually grows 50% shorter than the aluminum block walls. And since the stock land rover liners seat at the bottom of the bore, and on the main bearing saddles the expansion ratio starts at where it seats, at the bottom of the bore, not the top.
Expansion ratio of steel is 6 parts per million per degree
Expansion ratio of aluminum is 12 parts per million per degree.
No real such thing as a dropped liner according to popular belief, it is a thermal problem with dissimilar materials. And there is only one bullet proof cure, Top flanged liners, sometimes called top hat liners in the British market.

Head bolts must be replaced every time you remove the head, they are not regular bolts, but a special designed stretch bolt. Their is a tightening sequence principle that must be followed although contrary to popular belief, and the service manual, as long as the principle is adhered to the sequence can be changed. The principle is uniformly and incrementally tightening the head down. The actual order doesn’t matter. In testing the book vs. torque standards I found the service manual, “again” in error as it says to tighten all bolts to 15 ft. lbs. then 90 degrees more in sequence, then a additional 90 degrees for final torque. This is bogus, and utter nonsense. My findings after doing this left the 3 long head bolts at 50 - 58 foot pounds of torque, while the short head bolts read 68 - 72 foot pounds of torque. I found that almost an additional 90 degrees was required on the long bolts for a total of 245 - 270 degrees before the long bolts achieved the 68 - 72 foot pound equivalent to the short bolts. This makes the tension and torque on all bolts even. Due to the dissimilar materials of the steel bolts and aluminum heads it needs a stretch bolt design. Don’t go buying studs for this engine, you won’t be happy with the long term effects.

I recommend using Amsoil in the Transmission, transfer case and differentials. Engine I use Delo 400 10-30 valvoline 10-30 or any group 3 oil will be more than required, synthetics are not required as group three oils hold up to almost 500 degrees or better, your engine is dead at around 250 degrees. Against popular belief Mobil 1 is not a true synthetic, but a high level group 3 oil, good oil, but not a true synthetic. Remember Synthetics where developed for jet aircraft engines that turn around 60,000 rpm and dealing with temperatures well over the 500 degree range, a far cry from what our automotive engines are asked to do. You’ll know you are getting a true synthetic oil when you are coughing up around $12.00 or better per quart.


Chongo


Vendors for bolts are


http://www.britishpacific.com/


http://www.roverparts.com/?source=rangerovers.net

 

[joey zingale]

head bold torque

so should i set me torque wrench to 70 pound feet?

 

[Chongo]

What I do is Torque every head bolt the way the book says, then I use a torque wrench and run them all up to the highest torque setting. If that's 65 ft, lbs on your torque wrench then put them all at 65. But since these are stretch bolts, Please do the two 90 degree increments first, then check a couple of the short bolts to see what torque is on them, then tighten the long ones to the same setting. what this does is even the pressure among all bolts, and places even torque on all portions of the head gasket.



My oldest Rover engine I've built that I did this way is now over 9 years old, on a 98 disco 4.0L And we did redo the liners as well.

Best wishes for you and your project

Chongo

 

[joey zingale]

thanks so much for the info.

 

[Disco Mike]

Do not set your torques wrench at 70, go on the rave cd and follow the directions exactly as they are spelled out as to the bolt sequence as well as the torquing procedure.

 

[chastings]

Bolt tightening

Chong and Disco Mike,
You both have good points about how to tighten the cylinder head bolts.
But whos right?
Ching, I tend to agree with Disco Mike on this. Your point is valid, but Disco Mike and a bunch of Rover engineers say otherwise.
What do I do!!!!
C

 

[Mr jinnah]

Have the head skimmed and pressure tested if it's a water loss and/or pressurising of the cooling system problem that your having.

I would advise getting a gasket from the main dealer; it will cost a small fortune but will ensure you get a part that is to the latest manufactures specification.



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