Merle Coggins Posted September 26, 2015 Report Posted September 26, 2015 (edited) I have those same head bolts on my engine. I believe they were from Bernbaum. Edited September 26, 2015 by Merle Coggins Quote
Ulu Posted September 26, 2015 Report Posted September 26, 2015 (edited) . . . they don't work where the shank must be larger than the threads . . . Oh Lord that is pure BS. Mea culpa! I was looking at a modern .30-30 cartridge with wonder at the special forming technology to make the high tech dum-dums out of what is really a primitive 100 year old cowboy bullet. That's when reality hit me. I'm looking at various bolts in my shop right now & they do have very nice fat shanks, and shoulders, and knurls, and allen heads, and other stuff, and clearly it can all be done. They can form bolts to a broad variety of shank/shoulder/washerhead/locking wave/etc. configurations by rolling and upset-forming techniques, and it's a technology I've benefited from but never had to spec. I suppose I was only thinking about the type we see in building construction, which are designed case-by-case by formula and code, and are not tested on the same basis. in fact, not at all, which is why the requirement for a known (if weaker) quantity. Upset-forming is allowed on mass-production bolts, when the manufacturer pays for and passes certain tests. In the auto industry, everything gets tested before mass production. We're making one-offs, so all testing must be avoided. Sometimes you shoot weaker loads, for the sake of more consistent shots. The building code is often geared like that. Edited September 26, 2015 by Ulu Quote
Reg Evans Posted October 7, 2015 Author Report Posted October 7, 2015 Well, I went ahead and re-used those smaller head bolts and installed a Spitfire head I've had around here for years. It was milled .050 and after doing a compression test the new cylinder readings average 13% more than the old head. Original head averaged 92psi and new head averaged 104. I think I'll have the original head milled too but .070 instead of .050. Here's an after photo of the Spitfire head. Next .....dual exhaust. 1 Quote
Barabbas Posted October 7, 2015 Report Posted October 7, 2015 I have the smaller (1/2" head) flange bolts on my engine--I got them at Vintage Power wagon several years ago Quote
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