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Hi everyone

this is the first time I've done a head gasket on my 4G32 . Should I put oil on the head bolt threads? I've been reading about it and there seems to be a bit of disagreement.

Thanks for any advice.

mick

I've never bothered personally.......U can use a small amount of assembly fluid to start the bolts I guess

But I've always found that sending a tap and die to clean up the threads has always been more than sufficient

Its personal preference. In a standard 4g32 it would probably help them thread in a little easier if nothing else, but not necessary, but wont hurt.
When you start getting into high performance engines and head studs etc its best not to use motor oil and use a proper assembly fluid as i understand the temperatures/stress on the bolts isnt good for them.
TLDR; normal applications, go for it - wont hurt it. High performance applications its a no-no

Actually it can hurt
If you use to much it will create hydraulic pressure and can crack the block
You suppose to use "international compound" or assembly grease and a very small quantity
Cheers stealth

Well there you go.
Id trust Stealth over me

You need to use some type lubrication on the bolts/studs because the metal on metal will "stick" and give you a higher torque reading than it really is.
This is one of the worst conditions for any bolt or stud. Apart from a possibly blowing a head gasket due to too lower a torque, you cycle stretch the bolt/stud, which will make them fail quickly.

To explain, there are a few concepts you need to understand.

1. Bolts/studs have an elastic and plastic range.
a. The elastic range is where the bolt/stud will recover it's original dimensions.
b. The plastic range is where the bolt/stud is deformed and won't return to its' original dimensions or strength.

2. If a bolt/stud remains in its' elastic range, but it is being repetitively stretched within the elastic range, it will fatigue and fail.

3. If a bolt/stud is stretched outside its' elastic range, its' maximum strength is compromised.

With this information, you need to torque up a bolt/stud until the total of the initial torque, and expected load, don't exceed the elastic range.
Also, you want the bolt/stud to be within the elastic range, but not being further stretched by the external loading.




To try and simplify what I just wrote...

a. Bolt can will remain in its' elastic range up to 200 foot pounds.
b. Expected external repetitive load is 80 foot pounds.
c. At 100 foot pounds, the bolt will not stretch with an 80 foot pound load.

<<<<<< THEREFORE >>>>>>>

If you try to torque the bolt down to 210 foot pounds, it will get to the 200 foot pounds and then stretch into the plastic range, lose strength and break.

If you torque the bolt down over 121 foot pounds, but less than 200 foot pounds, the external load of 80 foot pounds will stretch the bolt into its' plastic range and it will lose strength and break.

If you torque the bolt down to less than 100 foot pounds, the external load of 80 foot pounds will cause the bolt to stretch within the plastic range, causing the bolt to fatigue and fail.

If you torque the bolt down between 101 and 119 foot pounds,
1) The bolt will not stretch.
2) The bolt won't lose its' strength.

Hope this helps.


Cheers.

U know what......get some appropriate assembly fluid....and torque the bolts as per the bloody manual lol

Scorpma82 wrote:U know what......get some appropriate assembly fluid....and torque the bolts as per the bloody manual lol

Normally the manual have the values in dry condition, if it should be lubricated it's mentioned.

Otherwise here is an interesting read. Just scroll down to the "LUBRICATE OR NOT" section:

http://www.popularmechanics.com/cars/ho ... -of-force/

Cheerz
Sven