Pearl 8

Greetings all: As some of you know I been doing the head gaskets, Belts, water pump ect ect. Conventional wisdom tells me to lube the threads on the headbolts prior to installing , I spoken to some people that apply 30 wt oil and some that use anti-sease with a copper base. Some people recomend installing dry. Looked up info on the Bentley but no mention about thread lube. Damn few people have removed heads outside this forum, so I need your advise once again. AOA says replace entire motor. LOL. Thanks JMN

Audiheavy

When rebuilding my son's A4 I used Raceware hardware and they recommend a moly-based lubricant... this to get a more accurate torque reading.

ryoung

If you use 30w oil, anti-sieze, moly, or whatever, you need to reduce the torque spec by some unknown amount (different for each lube) to avoid over-stretching and weakening the fastener.

Note that ARP specifies using a lubricant, but to avoid the uncertainties, they specify both the torque spec to use with their fasteners AND the assembly lube to use.<ul><li><a href="http://www.arp-bolts.com/Catalog/Catalog.PP/2005Catalog086.html">ARP Assembly Lube</a></li></ul>

hranaRS9oolalathumpr

no I would not do that

OOOOya

Torque the bolts in stages too - all to 20, then 40, etc...or whatever increments make sense based on the final torque value. I usually divide it into 3 stages. There's no way you are going to overtorque the fastener by using some lube.

gondar

First thing is to have clean threads, use a fine wire brush and run a tap down the holes.

There is an amazing difference among various types of lube. The torque is simply a proxy value for clamping force and it varies, I would say 50% from old dirty threads to slick lubes like moly, lanolin (don't laugh) or graphite. Some con-rod specs are now end to end bolt stretch using a micrometer. That moots the lube issue.

I twisted a head bolt off once (on a Dodge)after slathering it with antisieze. If a bolt feels funny as it makes up DO NOT continue. Get another bolt.

There is an issue (cannot be dealt with outside the factory level) about cyl wall distortion and head bolt torque. That's why some blocks are honed with torque plates bolted down to simulate heads in place, and some engines run studs down to the crank area instead of threading the deck.

If I couldn't get clear lube info on a particular application I would go dry or maybe one drop of light oil, but at the high end.

skiracer

gondar is correct- the type of lubrication used on a threaded interface can have SIGNIFICANT impact on the final preload in the fastener. A new bolt dry vs. a new bolt well lubricated can result in preload variations of at least 25% depending on the materials involved. I agree with gondar's recommendation- if lube isn't called out for these fasteners, then thoroughly clean both sides of the interface (threads) and install dry. But beware- quite often there are instruction at the beginning of a manual that states to use (fill in the blank) lube on all fasteners unless otherwise specified. Be sure to read ALL of the instructions.