the cam bolt is a 10.9 from the factory and I replaced it with a 12.9
lubed a 12.9 is supposed to ba able to take 100 ft-lbs, so dry I torqued it down more to apply the same clamping force.
the cam is made of very high quality material, I am not too worried about it, when cranking the bolt down it felt very solid.
as far as I was concerned the cam and pulley should be as close to one piece of metal as possible.
when I took the motor apart I found no foreign material in the piston that would have stopped a valve, and the only valve that was stuck in the guide was the one made 1/2" shorter by the piston.
as the cam gear damage was clearly an effect of the belt stopping because the cam stopped(and not the other way around) I settled on the cam gear slipping as it seems to be the only other explanation.
Think about this another way... If either the cam or the crank sprocket changes position while the engine is turning, things will break.
The keyway on the crank is not designed to withstand the crank sprocket forces all by it self. If the crank sprocket bolt is not securely holding the sprocket in place, you key will start to fail. This will allow the pistons to contact the valves and all the other damage you described will happen. Going to a gasser cam will not give you the timing latitude you need and the taper has worked for 30 years :-)
except that it will, with a modified adjustable cam gear(which will adjust a full tooth in either direction) I will be able to time the cam just as accurately, and with the early crank and sprocket(real woodruff key on sleeved shaft/pulley) I should be good to go.
like I said before it was clearly the cam that slipped first, causing the crank sprocket failure, not the other way around
I am done arguing.
-Owen
like I said before it was clearly the cam that slipped first, causing the crank sprocket failure, not the other way around
I am done arguing.
-Owen
Not arguing, but learning... I didn't catch how it was clear which happened first - please educate me. :-D
I suppose that the valve could have seized, it is hard to tell.
I am fairly confident that it did not, head was rebuilt by a very good machinist with all new valves/guides.
but the crank sprocket failure was clearly secondary, there was no back and forth wear, just a clean break in one direction, as if the belt stopped moving suddenly.
I spoke with my grandfather(longtime engineer/machinist with a background in metallurgy) about it, and he was sure that the metal taper was a poor design, which would only work properly if the taper on the gear was slightly tighter than the camshaft, which would only work once.
I am not sure what happened, but I am hedging my bets to try and keep whatever it was from happening again
as the cam gear damage was clearly an effect of the belt stopping because the cam stopped(and not the other way around) I settled on the cam gear slipping as it seems to be the only other explanation.
But if the cam sprocket was slipping, would the belt not keep going when the cam stopped spinning?
If it slipped a little bit to get out of time enough to do a valve-piston contact solid enough to bring the camshaft to a halt, wouldn't it simply have continued to slip from the greater force differential?
I dont have a particularly good answer for that other than if the camshaft was stationary and the pulley was spinning with the crank it would tend to tighten the bolt back down.
maybe?
hard to say.