Ok I have a 1980 4x4 ford bronco with a 351m.I put in a new camshaft and timing setI bolted everything up The cam rolled nice.After my motor wouldn't start I noticed my rocker arms weren't movin so I took everything off the front of the motor and the timing chain snapped and one of the teeth on the lower sprocket broke off the one right were the key for the crank goes.Why did my chain break was it a flaw or something.I put everything on the cam and with all the valve train hooked up I can still turn it with some resistinse.I really am stumped now.Please any help,thanks Josh

 

Was this the original timing gear? Is the teeth made of plastic? If so, you need new gears and chain. That is not an uncommon problem with these and the 302 engines. The chain probably broke when the gear tooth broke and it jumped timing.

 

I bought the timing chain and gears at the same place I bought the cam I went with the standard chain and sprockets The old chain was really really loose could that have broke my cam to begin with.The rear part of the cam broke So number 4 cylinder would work.

 

[updated:LAST EDITED ON 24-Mar-02 AT 09:25 PM (EST)]What made the first cam break? This could be part of the problem! If the cam bearings were bad and you didn't replace them, the cam may be binding under load. Try replacing the timing chain and gears again and turn the engine over before you replace the cover to see what's going on.

 

Okay thanks for the info here's another question.The lower crank gear,Which way does it go on a 351m Flat end towards engine.Or does the side that has a .25 spacer that moves the gears out away from the block go towards the engine???? Thanks Josh

 

Did you use a stock type cam shaft or high-perf one? If you used the high-perf cam, did you also swap out the springs?

 

Well It's alive and runnin pretty well now Above 70 it's a dog but up till that it's pretty damn good.