Head bolts, anti-seizing compound, and torque values

[creia]

I did a search of this topic on this forum , however, it did not provide much information...
For an aluminum block/head , 4 stroke, older "L" head like a Briggs and Tecumseh, are you using antiseize paste on the steel head bolts threads when you install them? If so, does this effect torque values? That is to say, do the torque values need to be adjusted (reduced) due to the lubricating effect, to avoid over-torquing the bolt? (And if so, by how much?) As I believe that some of you know, my son and I restore these old engines, most of which are 40-60+ years old. We have had some REAL challenges removing the head bolts on these engines, presumably due to the electrolysis reaction between the steel bolt and the aluminum head. We have never used antiseize before, however, I wonder if we should be so they will be easier to remove the next time We have only been cleaning up the bolt threads and threaded bosses, and installing and torquing the bolts "dry" . Our repair manuals make no mention of "dry", "oiled", or "antiseize" when reinstalling the bolts. What are you pros doing?
Thank you in advance for any help.
Michael

[bgsengine]

I did a search of this topic on this forum , however, it did not provide much information...
For an aluminum block/head , 4 stroke, older "L" head like a Briggs and Tecumseh, are you using antiseize paste on the steel head bolts threads when you install them? If so, does this effect torque values? That is to say, do the torque values need to be adjusted (reduced) due to the lubricating effect, to avoid over-torquing the bolt? (And if so, by how much?) As I believe that some of you know, my son and I restore these old engines, most of which are 40-60+ years old. We have had some REAL challenges removing the head bolts on these engines, presumably due to the electrolysis reaction between the steel bolt and the aluminum head. We have never used antiseize before, however, I wonder if we should be so they will be easier to remove the next time We have only been cleaning up the bolt threads and threaded bosses, and installing and torquing the bolts "dry" . Our repair manuals make no mention of "dry", "oiled", or "antiseize" when reinstalling the bolts. What are you pros doing?
Thank you in advance for any help.
Michael

Dunno about anyone else but way I learned it was torque values take into account a few drops of oil (lightly lubricated) on the *threads* of the bolt - I would not recommend anti-sieze compound unless the engine is going to be exposed to a lot of excess moisture (outdoors storage, "mudding", water pumps, etc) in which case I would only apply a very sparing (treat it like Brylcreem - a dab'll do ya) dab of anti sieze and only to the threads and be VERY careful to not get any on the bolt head mating surfaces - and use bottom end of the range of normal torque values - getting any (even a tiny bit) on the bolt head surfaces (the area that actually does the clamping) will result in excessive torque.

Most "Special Case" bolts (Torque to yield, and torque to angle to name a couple) may often call for the equivalent of an oil bath (dip the whole bolt in oil and drip off all excess before install) or completely dry (some have a special coating on the bolt heads) so if a OEM service manual is available always best to check that..

[wristpin]

A few disconnected thoughts.
I read somewhere that using Loctite can lubricate threads to the extent that a 30% reduction in torque setting is required to avoid stretching and failure. Presumably the same may apply for an anti-seize compound.
Also read theby using a metal based anti seize such as " copperslip" , introduces a third element into the electrolysis equation and may be detrimental to the objective.
A UK manufactured car, the Hillman Imp, used a Coventry Climax derived aluminium block engine and there has been a lot of discussion on that forum regarding corrosion and seizure of the steel cylinder head bolts and one contributor suggested that a dab of an EP transmission oil was the way to go.
Some manuals, (may be BS , I can't remember!) use the term " lightly oiled" when specifying some bolt torques. This, of course, raises the question of just what constitutes " lightly". My own interpretation is a squirt of oil wiped all round the thread followed by rolling on a paper wipe to remove most of it leaving a bit in the bottom of the thread V. Not very scientific but has not given rise to any disasters - yet !

[KE4AVB]

Note: Seized bolts are a fact of life. You don't want use anti-seize on head bolts. They will simply work loose from the heating cooling. It bad enough the they get welded in place from the melted aluminum from over heated engines.

[Arkie]

The Small engine head bolts that I most generally have problem with finding seized are the two at the exhaust port area. (on each side) If you look inside the exhaust port you can see the block bosses casting for these two bolt holes in the block which get very hot as compared to the others.

After I get all the head bolts out I take all of them to a wire wheel brush in a bench grinder and clean the threads real good and I usually re-install the two gaulded bolts that were by the exhaust port into other places and I very lightly apply some anti-sieze to the leading threads of two of the other cleaner looking head bolts to install close to the exhaust port bolt holes.
This has worked good for me for several years. I always keep a heads up on the two head bolts that are by the exhaust port on small engines briggs because they are they two mostly likely to sieze/twist off or bring out the threads when removing. I sometimes run a bottom tap into these two holes and then use air pressure to clean out the debris. (especially on my own eq so as to make go backs more user friendly.
I've never had these two bolts get looser due to anti-sieze heat/cool or cause head gasket failures doing such.

Sadness when you twist one off.

[KE4AVB]

Must have not the 090000 L head loosen heads that were tighten to 200 in-lbs like I did last year. Finally had to install lock washers to stop it. These are spec'd at 140 ib-lbs

[wristpin]

Have to say that I've never experienced Briggs L head bolts coming loose but there's always a first time I suppose!

[38racing]

A mechanic told me copper based anti seize was good into aluminum but I found an article somewhere that said copper was really bad for steel to aluminum.

[KE4AVB]

Have to say that I've never experienced Briggs L head bolts coming loose but there's always a first time I suppose!

I have a nursery customer that would bring in the mowers in the bolts even missing; of course, they were using these in 100+ F temps too. That when I started using lock washers.

[Fulltilt]

Have to say that I've never experienced Briggs L head bolts coming loose but there's always a first time I suppose!

If you check the headbolts on just about any L head briggs , you will generally find the two or three bolts around the exhaust valve area are noticeably less tight than the others. ( as was mentioned) I wouldn't call them "loose" per se, but they usually need to be snugged up. Every one I've ever fingerprinted needed tightening.

I have a nursery customer that would bring in the mowers in the bolts even missing; of course, they were using these in 100+ F temps too. That when I started using lock washers.

Lock washers on head bolts??? Nope. Not today. Never heard of anyone using lock washers on a head bolt, never.
Most head bolts have a slight "washer/flange" type head on them, not being an engineer, I would assume to spread the clamping load a bit. So, if you use a lockwasher, it seems it would defeat the purpose of the head bolt design. I've never seen a lock washer that is as wide as a head bolt flange.