What would be the reason(s) for an engine to jump time? With #1 slug at TDC, on compresion stroke, my timing has to be advanced so far that the vaccum advance can hits my water hose. Engine won't even run with less timing. What do you all think?
Timeing chain jumped.Not uncommon on high mileage SBF engines.Or the dist gear on the dizzy is working the roll pin loose and altering the timeing(rather un-common) OR the dist gear is getting chewed up.Most likely... T-chain.
Sure it's jumped time and not the distributor off a tooth when it was stabbed? One way to check timing chain stretch is remove the distributor cap and rotate the crank back and forth with a breaker bar and socket on the crank bolt.If there's slack in the chain, there'll be lag time between the movement of the breaker bar on the crank and movement at the rotor. The Original timing sets of the 70's had a nylon coated aluminum cam gear that tended to loose the nylon coating as time went by. Once the nylon teeth were in the oil pan, the chain would jump teeth on the cam gear.
A stretched chain will also jump when loose enough. I was told by a wise oldtimer that this most often happens when the engine is shut off. The next start if you can start the car it won't hardly run like you experienced. One word of caution; Jump one tooth probably no residual damage, jump two teeth, probably frag some valves. I went through this last summer with my 1968 Cougar with 302. I replaced with a steel true roller chain set.
Do you hear a noticeable difference in the sound of the starter when you try cranking the engine??...does it sound like it's spinning faster?? If you say yes then the timing chain has jumped
Thanks everyone. I didnt know that about the nylon teeth. Sounds right. Looks like ill be pulling the engine sooner than i thought. Needs a rebuild anyway. That'll give me something to do over winter. Cya's
