[GTOGEORGE]

ARP


GTO George

[Murf]

This may sound dumb but,

If they are made to stretch, is there any concern about using 40 years old bolts that have been stretched lord knows how many times?

Thanks
Murf


Sent from my iPhone using Tapatalk Pro

[mgarblik]

This may help clarify The key terms are "elastic zone, yield point, yield zone". Old engines like our Pontiacs had factory critical fasteners, rod bolts, head bolts, main bolts, stretched into the elastic zone at the factory. This is a fairly broad range of stretch that if not over-tightened, the fastener will return to it's same length and can be re-used many times. Rust can greatly effect this however. The resulting clamp force, which is what really matters, however, also varies greatly by what lube is used, torque wrench accuracy, rough threads and so forth. But with the big bolts used and cast iron parts and the great safety factors engineered in, you could do a really bad job of putting an old engine together and it would still live. Enter, modern technology and flimsy, aluminum parts. Now fasteners and clamp load become much more critical. Bolts used in modern engines are stretched beyond the elastic and into the yield zone, approaching the yield point, where they break. Putting a fastener into the yield zone gives you a more consistent clamp load in that narrow zone before the bolt breaks. It is much less dependent on torque wrench accuracy, condition of threads and lubricant used. You tighten the fastener to an initial low preload, say 20 ft. lbs. Then you continue to tighten the fastener an additional number of rotational degrees to final clamp load. The torque wrench reading doesn't matter. So the clamp load is much more even. These type fasteners are permanently deformed and need to be replaced every time used. ARP doesn't typically produce or sell these type fasteners because of their one time use which doesn't work well in racing. Also race engines have different parts being fastened together than a stock engine and the yield zone is calculated based on the material density being clamped which is part of the OE engineering formulas. Fasteners and fastening technique is a complicated science when you dig into it . I used to think it's all just a bunch of nuts and bolts, not so.

[KEN CROCIE]

The main and head bolts we sold had "LE" plus the grade 8 identifier forged into the head. LE stands for Lake Erie Bolt Co. based in Ohio. Google the co. 100 year history. Look for them at the store.

[AG]

I bought a set of those from you back in the day.

[Elarson]

A bolt is only as strong as the cross section area in the threads. A full size shank does nothing for tensile strength. It actually reduces the fatigue strength where the husky shank meets the stress concentration of the first thread. Cutting the shank down to match the thread stress area doesn't lose any ultimate strength but it improves the fatigue strength and the impact absorbing ability. A full size shank is cheaper to make and helps only if you're shearing the shank instead of pulling on it.

As has been stated, if the cap is located by dowels or registers, you don't want the bolt shank binding on the sides of the hole and fighting for position.

Eric