was talking with the metallurgist at work about how much the bolt had to be heated up to remove. he was questioning how brittle the bolt may become and what grade it was. anyone know?

 

I have never had to heat up the main pulley bolt to remove it, and it is 1/4 the torque spec of the flywheel nut, which most have gotten off with a large cheater bar and no heat....

As for the grade... who knows. There is no stamp on it (?)

 

I'd say grade 8 if I had to guess. Or in metric, that's what... 10.9?

I didn't have to heat it up to remove it, but I did hit it with a 3/4" impact wrench. While in progress of removing it, I destroyed a 19mm snap-on impact socket. Ever seen one of those turn into a flower?

And even though the socket blew up, the bolt was undamaged.

 

The torque spec is something like 80 or 90 ft. lbs, but there's loctite on it too. A 3ft. piece of pipe on a breaker bar did the trick for me. There's also the trick where you lay a breaker bar on the frame & crank the engine for a second. And don't forget this: http://www.mazdatrix.com/faq/pulley.htm.

 

zipping it off with an impact gun wasnt the case for a friend of mine. after a breaker bar and an industrial impact wrench it still wouldnt budge. thus the reason he heated it... then it came.

not that this same thing will happen when it comes time to pull my engine apart, was just curious.

 

I doubt heating that bolt with a torch will harm it.

 

A little heat won't hurt the bolt. It only takes 325 deg F to do the trick to get it to let go for medium and 500 deg for red. However, lower temps sometimes soften things up just enough for that breaker bar or impact wrench to do its thing.

 

If it's glowing red, it's 1200 degrees F or hotter. I was always told any glow, no matter how slight, puts you at 1000 F degrees. This can change the temper/hardness/strength of a bolt.