What the....? (can't set timing)

[MN-Engineer]

I've never set timing before, but, on my '84 Burban, I gave it a shot. It 'chuggles' a bit at low RPM and light load. It's most noticable in traffic where the tranny has just upshifted, and lugs on the engine. It will shudder at the slightest bit of acceleration just after it upshifts. Eventually it will downshift and bring up the R's where it seems to run fine. Anyway, I thought I would check timing. I pulled the vacuum line off the distributor and pluged it, and then checked with the light attached to the #1 cylinder, but the timing mark was way off. Not even close to the timing scale. I retarded the timing considerably in order to get to 8° BTDC. Once I did, it ran horrible. I eventually reset it by feel, but continue to have the hesitation problem. Anyone know why the timing indicators could be so far off? The balancer has a keyway right? How could this be?

[carpy]

My balancer is shot and I'm trying to replace it. No way I could set the timing till I do. Yes, the balancer has a keyway holding the metal center in place on the crankshaft. Over this center is a layer of rubber and the final outside is a ring of metal. I'm just understanding that this arrangement helps dampen rotational crankshaft vibrations. On my 94 Lumina APV 3.8 liter, the middle layer of rubber has broken down and so the outer metal ring is somewhat free to move independent of the crankshaft. A rattling/banging sound alerted me to the problem. MY PROBLEM is the large bolt that secures the balancer is not breaking loose, and I keep getting different answers on wether or not this bolt is reverse threaded or not. I'd hate to wring it off in the end of the crankshaft. That's why I'm searching the web and how I came to see your posting. Good luck!

[GMMerlin]

Carpy hit the nail on the head...first thing is to look and see if the balancer has slipped...this will affect timing adjustments.

Carpy, Lefty loosy, righty tighty......Use a prybar on the flywheel to hold the crankshaft in place, then use a large cheater bar on your breaker bar to break loose the bolt...its loctited in there and its a 2 person job.

[carpy]

GMMerlin,

Thanks a bunch for your reply. I've held my 500 ft-lb impact wrench on it in banging away in reverse sevaral times, and twice tried wedging the pull handle (on the socket on the bolt) against the frame and cranked the motor. These things haven't worked, of course.

In regards your suggestion, where do I put the prybar to hold the flywheel? The transaxle is on the car. I like the idea of using the pull handle by hand, because then I can gauge the pressure I'm applying, and so be sure not to wring off the bolt.

[MN-Engineer]

Thanks you very much. I had a friend at work tell me the same thing today. Seems like a poor design.

Still working on the hesitation problem though. I think I'll try the EGR valve. I can blow through the vacuum hole continuously and not build pressure. I'm suspecting that the bladder is shot.

[dirty dan]

On some of the burb's, the timing tab is mounted to the oil pan. On these models you time to the #8 or #5 plug. Just a thought.