Quote:
Originally Posted by J-Mech
Thanks 
*No debate here, just conversation*
I researched, actually for hours, tensile strength of threads in different materials. I admit it's pretty amazing how much stress in pounds it actually takes to rip threads out, even in aluminum. I agree, that by the "book" or numbers, it takes huge amounts of stress to pull the threads out of aluminum threads roughly .5" thick. Much more than the weight of the particular engine in question. But, here's the simple fact. No amount of math (none that anyone here want's to do, even for fun) can tell you how much degradation the aluminum has gone through over the course of a million heat up and cool down cycles. You don't know how many times the spark plug has been unscrewed and threaded back in, or how much it has been over-torqued in the process. You really don't know how good of alloy the aluminum was made from, or the standard by which it was made. Point is, the threads in that head may be just at the point of failing, and you may never know just by looking in the hole. I wholeheartedly agree that the same rationale goes for the threads in the block, but my simple mind would like to think that the cast iron block is far stronger than the aluminum head. Plus, the threads in the block are about 100X less likely to have been compromised from constant threading in and out. All and all, at the end of the day, I'll take my chances with the 3/8" bolts in the cast block, over the 14MM spark plug hole. I bow to the engineering side of this debate, as I appreciate you guys ability and what you know. I really enjoy math and the formula's I searched through and played with while researching this. But, in the end, common sense and my years tug'n wrenches says "don't do it". |
Jonathan, I really respect that you took some time to dig a little and read about some of this, verses simply bashing all engineers (its pretty easy to bash whatever groups you want to, whether it be engineers, mechanics, or sales people). You could have simply taken the stance that 'I know the 'right' way to do it and my way is the only way'. In the end your recommendation didnt sway, but you were at least open to learning about a differing view.
Your experience is tremendous and I appreciate your contributions and having you on this site. I know I have learned a lot by reading your posts.
