Originally Posted by
chaffe
All the cars mentioned have stretch bolts, and recomend new bolts, having re-used the bolts on all of them and had no problems i dont see what the problem is. Most of the above is iron blocks/alloy heads.
And as for "going plastic" if you say they do this when torqued down originally the surley they are "next to usless" after the first torquing?
All i base my info on is the 20 or so engines ive built using the same bolts that were on it when i took the head off, some even used three times to change pistons/valves. And ive never had a HG failure yet on one of these. Another point is that on a ZVH (no different to a cvh) i used 12.9 n/mm2 allen bolts, and the general concensis is that these can be re-used indefinatly.
Have you ever re-used head bolts?
No i don't re use my head bolts, all i can say is im glad nothings ever failed with you
But i did re use my arp rod bolts (non stretch).
Yes in theory they are useless after they have gone plastic, however this is what the original torque stage is for, then the angle stages. The bolts in theory sit there stretched slightly past their plastic point a bit like a rubber band (but not lol).
The bolt designer will include a safety margin, all your re-used bolts haven't failed because of this safety margin, the more you tighten/reuse/stretch a bolt the closer you get to its yield point, the point at which tightening the bolt more has little effect on clamping force... before it breaks.
Its all good tho buddy, if you've had a lot of experience doing it then fair play, but manufacturers don't use and advice their dealerships to change them to be difficult.
Rob,