E: Engine Straight Torque

[vibrac]

I don't use torque figures on the Vincent, the old adage 'tight is tight, too tight is busted' has stood me well, there is one exception and that's the head bolts where because of the possible distortion of the head barrel components means I stick to 32ft lbs lubricated and that has stood me in good stead.
However recently I was asked about early two part studs I can see the cross section of the hollow tubes is much less that the later solid ones but my guess is that the barrel head distortion is still the limiting factor and my figure of 32ft lbs is OK, can anyone confirm?

 

[Simon Dinsdale]

Richardsons "Vincent Motorcycles" (pg 47 in my copy) says bikes with the early hollow cylinder head studs should be tightened to 30 lb. ft. Later solid head studs can go slightly higher.

 

[BigEd]

I don't use torque figures on the Vincent, the old adage 'tight is tight, too tight is busted' has stood me well, there is one exception and that's the head bolts where because of the possible distortion of the head barrel components means I stick to 32ft lbs lubricated and that has stood me in good stead.
However recently I was asked about early two part studs I can see the cross section of the hollow tubes is much less that the later solid ones but my guess is that the barrel head distortion is still the limiting factor and my figure of 32ft lbs is OK, can anyone confirm?

I've tightened my "B" head bolts to 30ft lbs and had no problems.

 

[greg brillus]

2 points of interest........ The hollow studs only pick up on the upper half of the 9/16" thread in the crankcase, this explains why on some older engines you find that section of thread is quite sloppy whereas the lower half is still a good diameter where the brass inserts are seldom removed/disturbed. The second point is that the early heads that do not have the vertical rib up the center of each side, are quite weak in their alloy towers where the hold down studs pass through. Plenty of these early heads end up badly cracked from the nuts being over tightened in an effort to seal the head to barrel joint. Torque figures would never have been quoted on account of that owners would never have had a torque wrench in those days, just like they didn't own a lathe or mill.......We are lucky these days that we can own all these tools and carry out a good job. Volkswagen engines used the same head to barrel seal form, and they are only torqued to 19 Ft lb's, but they are very small diameter studs as well. I think one issue of over tightening the head nuts arises from the visual size of the hold down studs suggests that they can be pulled down to a much higher figure. The waisted studs are quite massive, but as we all know, this all adds to the massive strength of the engine to replace the conventional frame section.