Head Bolt Tension

[Brian Davis]

Broke 1 x 3/8” head bolt when tightened .
Have a new set of head bolts for my 54 G 80S want to know what tension should I set
Also got set os 8 Viton rubber O rings replacement kit part number 010672RK
Do they replace the large rubber on the top of the push rod tube eg 4 on each tube..
Just trying to get the correct information for the motor rebuild

Thanks Brian Davis

[Reynard24]

The torque setting “according to the book” for the head bolts is 35ft/lb for longstroke motors and I’ve never encountered any problems with this figure but others have suggested that it is too high and prefer a lower figure - there was a discussion on here sometime earlier in the year.
Make sure the bolts do not bottom out on old crud at the bottom of the threads and don’t lubricate the bolts as either will give you a false torque setting. You might also run a tap down the barrel threads to make sure all is clear.
The four viton rings do indeed take the place of the large rubber seal at the top of the pushrod tube. I usually fit these dry but others have mentioned either a smear of Wellseal or even silicon rubber, don’t forget the flat and dished washers that sandwich the seals.

[SPRIDDLER]

Welcome to the club and Forums, Brian.

As above post.
I'd just add that it's important to anneal the head gasket even if it's a new one.
You'll probably find this article useful........

https://www.jampot.com/article_read.asp?id=161

If you aren't aware of it the factory manuals are available under 'Books' in the following link....

http://archives.jampot.dk/

[Joker_Bones]

I don't know if this is the thread Reynard was referring to, but it discusses the the subject:

viewtopic.php?t=30192

No problems with 30 lbs.ft on the G80 engine I mentioned, and I have to admit that I have not gone back and re-torqued the bolts.

[Joker_Bones]

I imagine this is a result of over tightening.

IMG_20231209_144333.jpg

I took these out of a 16. The top half of the thread is stretched to the point where a 20 tpi guage will not sit in the thread.
I don't know if the original head bolts are high tensile or what grade of steel is used to make replacements but I am curious if anyone knows.?

[Brian Davis]

Thanks for clearing up the tension. Have annexed the copper head gasket also use copper coat spray in gasket on the head gasket when installing.

What are the extra washers that go with the new viton rubber “O” rings I thought they just replaced the larg rubber seal ? Have new large “O” for the base of the push rod tube. And 4 Viton “O” rings for each push rod tube all new from the spares they advertise them as a replacement kit

Any help or clarification appreciated

[SPRIDDLER]

What are the extra washers that go with the new viton rubber “O” rings I thought they just replaced the larg rubber seal ? Have new large “O” for the base of the push rod tube. And 4 Viton “O” rings for each push rod tube all new from the spares they advertise them as a replacement kit

If your enquiry refers to a 1954 engine (it doesn't say what bike you have in your Profile) then this is the arrangement. Use the 'O' rings instead of the rubber sleeve.

Pushrod tube washers and seals annotated pic c.jpg

[jackstringer]

I imagine this is a result of over tightening.
IMG_20231209_144333.jpg
I took these out of a 16. The top half of the thread is stretched to the point where a 20 tpi guage will not sit in the thread.
I don't know if the original head bolts are high tensile or what grade of steel is used to make replacements but I am curious if anyone knows.?

I suspect partly the thermal expansion when the engine warms up won't help. After a few heat cycles some people re-torque the head. Do that every year for a few years and you will eventually stretch the bolt. There is also an argument for not re-using head bolts as over time they will stretch.

I also have bought head bolts off the bay and received bolts that didn't want to go in, it turns out they were metric, it's just they were kinda the right size and kinda the same thread pitch, that stuff drives me bonkers.

[Brian Davis]

Thanks for the correct details of the seals and washers on the pushrod tubes
Have always had trouble with oil leaking on the pushrod
Thanks Again for the help

[56G80S]

After T&L rebuilt the head and repaired the squished tops where the head bolts sit I took advice from an article, I think by Ken de Groome or possible Ken Bryan. I used the widest and best thickness washers under the bolt heads that were consistent with fitting the rocker box and maintaining depth of engagement in the barrel.

I torqued to 25 ft lbs and this has worked fine. As others have mentioned, when younger I stripped threads and snapped bolts. Learned to use the appropriate length spanner and sometimes not all the length. However my personal belief is that, particularly for the cylinder heads, the key element is to ensure that the bolts are evenly torqued and I have insufficient "feel" to do that. The torque wrench, even if not perfectly calibrated, should provide for the same figure for each bolt.

Johnny B