Distributor, how long last? Timing marks

[LVJJJ]

Got a 94 GMC k1500 Suburban, now with a 383 with about 18,000 miles on it. There is 180,000 miles on the truck and on the distributor. Been having a bit of a problem with an occassional miss and backfire. Found some corrosion in coil wire from distributor, replaced dist. cap, rotor and coil. Seemed to stop the missing but did have a backfire once when accellerating up a hill on I-90. Has always stumbled a lot when cold, that's the one thing Old School EFI and I could't solve when he programed my chip to match the 383. So, we don't worry about it. The miss felt like a stumble but at cruising speed. I'm wondering if I should replace the distributor that is 28 years old and 180,000 miles worn?

I thought it might be timing, but I can't find the timing marks. Borrowed a timing light but couldn't find the marks. Seems like something is missing?????

 

[LVJJJ]

Got a 94 GMC k1500 Suburban, now with a 383 with about 18,000 miles on it. There is 180,000 miles on the truck and on the distributor. Been having a bit of a problem with an occassional miss and backfire. Found some corrosion in coil wire from distributor, replaced dist. cap, rotor and coil. Seemed to stop the missing but did have a backfire once when accellerating up a hill on I-90. Has always stumbled a lot when cold, that's the one thing Old School EFI and I could't solve when he programed my chip to match the 383. So, we don't worry about it. The miss felt like a stumble but at cruising speed. I'm wondering if I should replace the distributor that is 28 years old and 180,000 miles worn?

I thought it might be timing, but I can't find the timing marks. Borrowed a timing light but couldn't find the marks. Seems like something is missing?????

Dagnabit, just found the timing marks, was looking in the wrong place, down low instead of up higher. Now just need some opinions regarding distributor. Have heard its better to just get a new GM dist., instead of and MSD or something.?

 

[PlayingWithTBI]

I thought it might be timing, but I can't find the timing marks

You can pull #1 spark plug and turn the engine over until you feel the compression stroke. Take the piston to TDC and look at the harmonic balancer, you should see the timing mark aligned with the biggest notch in the indicator on the timing cover. Then you can take a paint stick and mark its position even if the mark isn't there (that could mean the rubber ring came loose and the outer part of the balancer slipped). Then disconnect the EST bypass wire to set your timing at zero or maybe even a couple degrees advanced. I would guess that Dave w has your calibration pretty well dialed in for zero though.

On the backfire, you may be getting lean pops. What's your fuel pressure and which injectors are you using. I'm guessing you still have TBI.

A DUI (Davis Unified Inc) is the best going FWIU.

Note: just saw your post while writing this one...

 

[Jeepwalker]

Well, you might want to pull the distributor and take a look at it. You can't really get to the 'guts' w/o partially disassembling it.

Mine for my '89 was rusted inside about 5 years back. The pickup assembly was damaged it was corroded so bad, and the distributor rotator was broken too. No wonder mine ran so rough. I probably could have repaired it with new parts, but mine's got high miles too ...and considering the parts prices. I found a brand new NOS distributor on ebay for $25 (the correct GM one) and that solved my problem. Mine's all stock with a stock tune too. With the miles you have on your truck I'd replace it ....if you find there's a problem with it. The jacket on the wires also cracks too.

And if after checking things out on the bench, it looks good and bearing is tight, then put er back in ...and look for another problem.

 

[Schurkey]

The "big" problem with TBI distributors is that the magnet breaks. Difficult to see.

I'm no fan of Chi-Com auto parts. But y' gotta do what y' gotta do. I bought a few TBI distributor shafts off of eBay; I figure I've got a lifetime supply for my one TBI vehicle.

Note broken magnet just below "Copyright" symbol, probably caused by rivet/rivet hole, and visible again on the outside of the metal piece.

You must be registered for see images attach

You must be registered for see images attach

 

[Jeepwalker]

The "big" problem with TBI distributors is that the magnet breaks. Difficult to see.

That's EXACTLY what happened to mine. Only mine was broken in a couple spots and way rustier. The magnet literally fell into pieces when I pulled out the shaft. The shaft itself didn't have noticable freeplay surprisingly (260k mi). I had exhausted about everything else in my troubleshooting process. Like I say, surprising that the motor ran at all.

OP, if you found yours to be like that and the shaft is still tight, you could always buy new parts and re-build yours.

 

[LVJJJ]

Thanks for the responses. As for the backfire problem I figured it was timing or not enough fuel. I think Desert Old Guy maybe solved the backfire problem, low fuel pressure. I just realized I haven't replaced the fuel filter in about 30,000 miles, will do so now. When Old School EFI created my chip I sent the injectors to a guy in Idaho to have them cleaned, so they are ok. My problem with finding the timing marks had to do with real brite sunlight. Was trying to find the marks in Royal City Washington on a 100 degree, brite sunshiny day, couldn't see a thing in the engine compartment. Could hardly see the timing lite flash. Located them in the evening.