"help" rocker cover broken bolts

[toby400ex]

well this is not a big problem now but when i need to do some engine work in the future it may be, but a few weeks ago when i took off the rocker arm cover to seal the cam bearing seal, a bolt snapped when i put the cover back on. And it just happened to be the second longest bolt on the cover, it was about 5 inches long and it broke off about 4 and a half inches in the cylinder head. Luckily the bottom of the bolt goes out of a hole in the bottom of the head and we just turned it out through the bottom. Well after waiting about 3 weeks to get the bolt from honda we put it all back together and another bolt snapped it was a small one though. This time i used a torque wrench. The bolts are supposed to be torqued to like 130 or 150 inch pounds and i had it set at 110 just to be safe and the damn bolt snapped anyway. well we still put it together and luckily it doesnt leak any oil. the guy i was workin on it with has been working on dirtbikes cars and motorcycles all his life, so he knew what he was doing, and he said something about the threads being weak and that in the future if i have to take it apart again to heli-coil some new thread thingys in the cylinder head. Im not exactly sure what it is but what do you guys think.

[VegasEx'r]

I had the same problem w/ 2 of the long bolts & I used heli-coils. They worked great. Use a 1/4" drill bit, then tap it w/ a m8x1.0 tap, then put in the m6x1.0 heli-coil. To be safe, I used a lot of assembly lube on those bolts, and they should be torqued to 10 ft-lbs (that's 120 in-lbs, right?), not 17 like it says in the Honda manual.

[toby400ex]

thanks for the info the next time i take the cover off, maybe when i get a cam i will heli-coil them, is it the threads inside that get weak then the bolt just spins until it snaps for some reason.

[VegasEx'r]

I think it is a little of both. The threads are aluminum, so they can stip pretty easily since they are so soft. I don't care much for the bolts that came on it stock, they just seem flimsy. I have replaced all of them (except for the 3 long ones you are talking about) with standard grade 8 fasteners, which are good for high heat situations. I don't know if the stock bolts are grade 8 or not, but like I said, they just don't seem strong enough.