Over tightened end caps

[jansens]

Use of a stretch gauge is more accurate which is why ARP bolts should be done with a stretch gauge if
possible

My new Riley 9 crank and rods came with ARP bolts and they do say they have to be done up using a stretch gauge. I had to look up what that was and needless to say I don't have one (yet)!

I am assuming you only use that once on the final tightening?

Simon

[Dave Mann]

The bolts are measured in the free state and sizes noted, then in our case the 4 bolts were progressively tightened to the specified stretch, (not fully tighten 1 bolt then the others) a somewhat tedious operation particularly if you have 18 rods to tighten. Best with 3 men, one with the stretch gauge, note pad and pencil while the other 2 provided the grunt.

[Colin Reed]

HI Simon,
you will need to have the stretch length for your application 
and only works if you can access both ends of the bolt when installed  (ie) Bolt And Nut
you also need to measure length of bolt before you start as stretch is usually on average  5 to 8 th 
the length before you start is critical because if on a subsequent Build the length has permanently increased by .001 the bolt is scrap

Colin
NZ

[jansens]

Thanks Colin. Am a way off from needing to work it out yet. Better make sure the pistons actually go up and down in the bores first! The new crank/rods came with the measurements I need.

Simon

[Dave Wortley]

Dave M I think we used hydraulic nuts such as Pilgrim nuts to provide the stretch and sometimes hollow bolts with steam heating through the bore in order to expand the bolt. This was in the steel rolling mill industry where some bolts were 6" diameter and occasionally larger. Sounds more sophisticated than strong men on the end of a pole. This was a long time ago and memory unreliable (according to my missis!)

[Dave Mann]

Yes we did try Pilgrim Nuts in the late 1960s Dave, they were a disaster, after 12000 hours in a hot crankcase they wouldn't release and had to be gas axed out so we reverted to 2 grunts on a bar. More recently we adapted hydraulic tightening.