Head bolt torque

[glenn]

What happens to the torque numbers when the head bolts are screwed into a bolt hole full of oil?  Does the ft-lb(lb-ft) go up or down with block temp change?

[al_lieffring]

On a cylinder head retorque the engine is supposed to be hot. I don't think that oil in the bolt holes is an issue that needs to be worried about. Removing every bolt and blowing the oil out with compressed air could possibly do more harm than good.  You just need to losten each bolt 1/4 turn and retorque it to spec, one at a time starting at the center and working out to the ends in a spiral pattern.

[RickM]

I have to agree with Al. I can see your concern as liquids will not compress but more than likely the oil will be routed up between the threads.

[ja17]

Hello,

Yes I am in agreement with Al and Richard. In fact it is common practice to coat the bolt threads with oil during  original engine assembly. However during re-torque, as Al suggests, a quarter turn is fine.

[glenn]

A little more detail-- say the bolt hole was full to the top with wheel grease, crud, etc.  I'm going to try putting a bolt in a full hole and see the resulting lb-ft and/vs threads(1,2,3 ?).

[tel76]

As stated you cannot compress oil ,grease and water,if you try it, it could end in tears as you could strip the threads in the block or even worse crack the block.
Do not try it.

[glenn]

tel76, Ah yes.  That is the question.  Situation:  The head is NOT on. The bolt hole full. Just a bolt being screwed into a threaded hole. The bolt catches the first thread and starts in.  One thread, two threads, etc.  Do I get 65FT-lb on 3 threads, 4 threads  where?   Does the torque go up as fluid is compressed?  I don't think the fluid is going to leak thru the threads. ..

[ja17]

Hello Glenn,

Ok, yes if the head is off, clean all the holes out.  compressed air works fine. You can also fish a lot of crud out with a flat screwdriver or such. I always run the correct metric tap in and out of the headbolt holes before assembly to clean any thing out and then used compressed air again. If you do not have a tap you can cut a few vertical slots in the threads an old head bolt and use it to clean the threads up.This will also allow and grease or oil to escape past the bolt. The modified head bolt is only a tool and should not be used during final assembly. Never allow the bolt to bottom out at the bottom of the hole under a lot of pressure or you could damage something. My experience is that any light oil left at the bottom of the hole does have enough room to escape past the threads. Heavier grease, grime or crud could cause issues. Nice clean threads will make toque readings more accurate. During final assembly on a newly rebuilt engine, I coat the threads and rubbing surfaces at the bolt shoulder with a little graphite oil (as per early MB factory shop manuals). Even just plain oil is better than nothing at all.

[Naj ✝︎]

Does anybody here use engine engine assembly lube when rebuilding heads/engines?
Examples:

http://www.lubriplate.com/products/greases/no-105-motor-assembly-grease.html

http://www.hrpworld.com/index.cfm?form_prod_id=890,378,363_4362&action=product

naj

[ja17]

Hello Naj,
Yes, I always use it. It looks like a light grease with graphite. I use graphite oil on my headbolts.
I like to use the assembly lube on the bearings since it  is thicker and will not drain off if the engine is stored for a while before installation.

[tel76]

Hello Naj,
If you require a product that you can use to assemble your engine parts,i use a product that i obtain from www.frost.co.uk it is called Assembly Lube costs £14 (see page 95 in there brochure) it works for me.

[Naj ✝︎]

Thanks for the thumbs up!!

naj

[JimVillers]

Naj ... I also always use assembly lube.  My brand is CRC.

[glenn]

Just happened to be looking at the Nov/Dec 2003 Star magazine. -- Page 84 says 'As the bolt is reinstalled and tightened, this oil or coolant is highly compressed by the threaded end, and the resulting pressure in the hole could crack the engine block.'  sounds like 65 lb-ft is reached in the wrong direction, bottom of bolt, before holding the head down, at the bolt head. .. 
   This error could result in leaking head gaskets and warped heads - there is not 65 ft-lb on each bolt on the gasket.  Clean out the bolt holes. ..

[mbzse]

Does anybody here use engine engine assembly lube when rebuilding heads/engines?

Yes, certainly! This is my choice, Redline product. It actually is red, too  :-)
http://www.redlineoil.com/content/files/tech/Assembly%20Lube%20Product%20Data.pdf
/Hans in Sweden

[RickM]

Some may notice most better quality assembly lubes contain molybdenum