Timing chain/gear problem on '76 Sub

76BBSub · January 10, 2002

Driving to work yesterday morning, when "poof"...dead. Sounded funny when I cranked it, and I immediately suspected the timing chain. Took off the air cleaner and cranked it, sure enough gas and air were backfiring out the carb. Knowing I couldn't fix it on the side of the road, I called a tow truck and hauled it home. After work, I started cranking it over by hand with a wrench on the crank pulley, and noticed the rotor wasn't turning along with it. It would turn a little if I used the key to crank it, although there was a delay. I think at this point it's the timing gear(s). GM has used nylon teeth on timing gears in the past to make them run more quietly. I think I sheared some or all of them off. Crap.

So last night I pulled off all the accessorier, and yanked the radiator, shroud, fan, carb, intake manifold, and valve covers. Tonight I'll pull the harmonic balancer and timing cover and see what I've got.

The good news, if there is any, is that I orderd a new cam and lifters to go with the timing set. Remember that I just had the heads done 10K miles ago, so they're fresh, and the bottom end appears to be in great shape, so this should be the icing on the cake. It's a Comp Cams Extreme Energy 256H, supposed to have a smooth idle with tons of low-end grunt, and better top end the older cam designs. Hope to have it all in by the end of the weekend since this is my daily driver...

Later

Jeff

Torque Junkie · January 11, 2002

That sucks about the timing chain but that cam sounds like it's going to be KILLER!

Good luck with everything! Let us know the outcome of that new cam, too. I'm curious!

-Mike

76BBSub · January 14, 2002

Spent the whole weekend (until 11 last night) working on the thing. First, Summit sent me the wrong timing set, so I had to go buy another one locally. Next, the threads were crap on my harmonic balancer bolt, causing me untold hassles throughout the weekend (tough to turn the engine by hand without the balancer bolt). Probably the worst part was that my garage was a mess and I couldn't find anything when I needed it, spent half the weekend hunting tools and parts. This is my own fault, since I have been bad about straightening up after little projects over the last month or two. I've been so busy that when I can fit in a few minutes for some wrenching there never seems to be time to really clean up properly when I'm finished. So that's next on the agenda, clean the garage spic and span.

The other thing that was killing me was little trips to the auto parts store. I only made about 3, and I live in the suburbs, so it's not that far, but freakin traffic lights and parts stores not having what I need was killing me. It would eat up at least an hour per trip, usually more.

BUT, the engine is assembled, and I broke in the cam last night. It sounds pretty good, but I need to tweak the timing and carburetion. The last thing I did last night was reset the valves while the engine was warm, and change the oil to get rid of any particles from the cam break-in. I would have test driven it, but I have the hood latch and front supports off still, and just ran out of time. Maybe tonight.

I'll let you guys know how it runs!

Jeff

Jack Boelte · January 14, 2002

That really sucks. This must be the season or something. My truck broke too (Friday morning). I'll post the mini story on the board.

76BBSub · January 15, 2002

OK, finished the reassembly last night and drove the Sub to work this morning. I was pretty wasy on her (have broken too much stuff this week!!), but there is a very noticeable difference. The truck idles a little more smoothly, most likely due to the accuracy of the timing being better with a new, tight chain. The throttle response seems better, especially in the mid-range and up, and the top end is incredible. This thing howls right up the redline in a hurry...it always made good power but used to take a little time to get to the top...not anymore. I can't wait to put a few miles on it and start experimenting with tuning on the carb and ignition curve. I expect some great results, from power and mileage!!

Jeff

Torque Junkie · January 15, 2002

Great to hear man! Glad you got good results with it. I can tell you, my Performer cam really howls in the top end with that new Carb. It sounds like someone unleashed a p'd off bear under my hood! Too bad my tranny's robbing all that power.

-Mike