pretty sure its a haunted 68 GMC with a 307
 

Hey everyone, can't tell you how much you have all actually helped me with my build before I joined(gotta love Google) anyways my trucks a 68 GMC fleet side with the original 307 which I rebuilt its bored .30 over comp cam new lifters new pistons all that fun stuff aluminium intake 600 Holley and a points dizzzy that was converted to elec with the petronix kit as it wouldn't slide down past the intake. (That's one thing this board helped me with) anyways after tweeking and tweeking it seemed all good I had been driving her daily for about a week then at a stop light idling she just quit. Pushed her off wife towed me home rotor button ain't spinning and she winds over real fast like no comp my guts are inknots. I'm gonna pull off a valve cover today and wind her over and see what I got. I'll pulled the dizzy last night and it looks fine. I don't get it though all the parts are new and I broke it in gently and I used that can grease that comp gives you and it had about 1000 kms since the build. Oh the timing gear was all new too. I'm at a loss and really irritated lol any thoughts

Re: pretty sure its a haunted 68 GMC with a 307
 

Timing chain or gear on cam that drives distributor is broken or distributor gear broke either or I'd wager

Re: pretty sure its a haunted 68 GMC with a 307
 

I'm kinda thinking the same thing, I'll tear I to it today, I mostly just don't get what would cause such a failure with no warning and no load noises......

Re: pretty sure its a haunted 68 GMC with a 307
 

Take a valve cover off and crank it to see if the valve train is working.

Re: pretty sure its a haunted 68 GMC with a 307
 

K so no valves move at all. Nada zilch. So what could cause a timing chain to snap like that and what are the chances everything else is ok

Re: pretty sure its a haunted 68 GMC with a 307
 

Is the 307 an interference motor? If so you could have more problems. :banghead:

Re: pretty sure its a haunted 68 GMC with a 307
 

,that's what I'm scared of

Re: pretty sure its a haunted 68 GMC with a 307
 

You have plenty of room in there don't sweat it. I was at the races one day years ago and my old Chevelle race car was giving me fits and sometimes when that happens to us we show our knowledge and are confident and know exactly what to do and other times it freaks some of us out and rips the confidence right away from us. Anyway my car was acting up [I think it was a needle and seat thing this old man walks up looks over the hood and then turns to me and says" boy if you never remember but one thing from fooling with this old racecar let it be this, if it has tires on it or boobies [he used a less family friendly site type word]on it it will cause trouble" then he turned and walked away. I never saw him at that track again and I looked for him for several months, although I don't know why maybe seeking more nuggets of wisdom. With the dist not moving and the valves not actuating I would dare a guess that it is in the chain area. It sounds to me as though you have indeed found the weakest link. Was it a double roller? Jim

Re: pretty sure its a haunted 68 GMC with a 307
 

Thanks guys, hopefully it all works out, ivrbnever seen an SBC this contanerous haha, no Jim it was a single roller. I just hope what caused it to snap or jump wasn't to serious. What's really mind boggling is how quietly it happened no bangs or clashes just idle smooth the blegh and stalled.

Re: pretty sure its a haunted 68 GMC with a 307
 

ttttt

Re: pretty sure its a haunted 68 GMC with a 307
 

Seems kind of basic.

If the cam isn't moving, whatever drives the cam isn't moving, or the cam broke at the front (seems unlikely). If the pistons are moving, there are 3 parts between the crank and cam.

Re: pretty sure its a haunted 68 GMC with a 307
 

Sure nuff got her apart and broken timing chain. Everything else seems fine though, so here's hoping