Originally Posted by
Turbosystems
stop using them chip ffs
surely the fact that the top yb builders don't use them says it all
only people like yourself seem to think they are ok based on very little experience
the stretch bolt was a revolutionary design for alloy heads
studs were used in prehistoric times like the moris minor era
why people get so excited that they are throwing away a cosworth designed part specifically designed for the yb and replacing it with a morris minor head stud is beyond me
I'll start your debate and leave your brain to start up in analytical mode
The cosworth yb head has a thermal expansion rate of 17 thou form 20C to 90C
Lol, I dont really get involved in anything YB related anymore TBH mate so its all a bit acedemic other than just being interested in the reason that the YB seems to suffer when other engines dont.
What sort of failures have you actually seen though, is it just the issues with the block cracking or have you found that the studs get taken past their point of elasticity and hence stretch and dont recover like you have hinted in this thread?
I dont really see how that would happen with less than half a mm of expansion on a stud of 150mm or so, they can withstand that sort of expansion without going past their elastic limit after all, and once again, other iron block and alloy head engines work well on them.
Dont think im implying you are incorrect, I dont think that at all mate, in fact Im sure you know exactly what you are doing with the YB engine.
Im just interested in the details of the issues you've seen and why they have happened, as its counter intuitive to me that an 8740 steel alloy head stud could be forced to stretch for example when the thing doing so is an ally head, Ive seen the opposite happen in fact, ie the head being crushed.