Distributor. Replace or recondition?

[Lomotil]

Took the distributor apart on my '85 Suburban this evening, noticed the corrosion on the points, scraped them clean and did the same to the rotor.

Haven't had a backfire since, but also haven't gotten the engine up to proper temperature before it got late this evening (carburetor butterfly valve doesn't seem to close on it's own, but that's another issue altogether...)

Main question here, this seems to be a relatively simple setup, and cleaning off any corrosion would seem to be a relatively straightforward approach to prolong the life of the unit itself... Is a swap-out really necessary? (just replaced the plug wires, btw...)

One friend suggested that my diminished performance might be from a fouled plug or two - but, these are new plugs, but it sat for nearly a year without use (after new plugs) - guy said I should replace the plugs (take one out and see if it smells of gas, or is fouled - my first thought was "Why can't a soak/cleaning with acetone fix the plugs if they're fouled, as they were new..." He said to not believe the 'old wive's tales' about cleaning plugs - but I have my doubts...

Thoughts?

[ddawg16]

Points? You don't have points in that dist....I believe your talking about the 'posts' that the plug wires attach to....part of the dist cap.

No need to replace the dist....maybe the cap.....

I don't think you fixed your problem....backfire issues are not caused by corrosion in the cap...misfires...yes...but not backfires.....unless you have a lot of moisture in there...

[Lomotil]

Originally Posted by ddawg16

Points? You don't have points in that dist....I believe your talking about the 'posts' that the plug wires attach to....part of the dist cap.

No need to replace the dist....maybe the cap.....

I don't think you fixed your problem....backfire issues are not caused by corrosion in the cap...misfires...yes...but not backfires.....unless you have a lot of moisture in there...

I might have used the wrong term by saying 'points' in this scenario. By 'point' I meant the point at which the rotor makes contact and sends the electricity through the corresponding "contact point" and through the wire to the spark plug. Sorry if my description caused any confusion.

Adjusting the carb has been suggested by one shadetree mechanic, as has replacing the plugs (which were replaced shortly after I acquired it, within two years - he said they were fouled and unfixable - is this possible - after only 2-3K put on it, and 8 months of sitting?)

[retDAC]

I had a backfiring problem in my '79 C10 350. It was the module. When it got hot enough, it would cause erratic firing which resulted in unburned gas going into the exhaust. When that got somehow ignited - BANG!

There are some other problems causing misfires because the engine needs rebuilding, but replacing the module stopped the backfiring.

[Brad54]

Depending on how many miles you have on the distributor, it might be time to replace it.
I've put 50,000 on mine since dropping in the crate engine, and before that I put at least 10K on it while it was in the 283... and before that, the guy I bought it from had who-knows how many miles on it.

In mine, I'm sure the bushings are worn, and I KNOW the springs in the advance weights are rusted and gnarly because I've seen them.

Even so, I just recently replaced the cap, rotor and coil (basically the top half of the distributor).

Give replacing those things a try and see how it works.

Remember: 90-percent of fuel problems are actually electrical.

-Brad

[Lomotil]

Thanks for the replies...

Extra info (as it is noticed - carbs and the like aren't my specialty... )

Butterfly doesn't seem to partially close when it should... automatic choke may not be working... This may explain why the truck runs much better in the summer...

[Bruce Lancaster]

HEI's...I think you have the old huge cap one...last forever, but certain parts need checking every 10 years or so: Remove upper cap and coil and look for burning where coil goes through main cap. Replace cap if bad there. Keep going down and remove rotor...look for signs of burn through on underside of rotor. Again, replace that if fried.
85 truck has mechanical advance still, I think? If so, inspect/move weights as the pivots there somehow get fried into brown powder if run for a long time with burned through rotor.
Rotor is likeliest piece to actually need replacing.
Again, I am assuming '85 truck has the huge HEI with coil built into lid.

[Lomotil]

Originally Posted by Bruce Lancaster

Keep going down and remove rotor...look for signs of burn through on underside of rotor. Again, replace that if fried.
85 truck has mechanical advance still, I think? If so, inspect/move weights as the pivots there somehow get fried into brown powder if run for a long time with burned through rotor.
Rotor is likeliest piece to actually need replacing.
Again, I am assuming '85 truck has the huge HEI with coil built into lid.

I am not sure about the advance, this is actually the first time I've stuck my nose in a distributor, to be honest - do the pictures help to answer this? I plan on taking more pictures as I go.

Between working on this truck and the folks on this forum, I'm learning a lot - thanks again, everyone.

[Bill Crowell]

Rebuilt distributors are available for under $50 exchange at most of the major auto parts chains. I put a rebuilt one in my old truck and it ran a lot better. At the very least it will rule out distributor problems.

[jayoldschool]

Do a cap, rotor and module. Dirt cheap for GM HEI systems.

[35mastr]

Also do the pick up coil that is under the rotor. Those when the wires get frail will cause backfires. That ruin mufflers. knock the pin out of the gear assy and slide the shaft out to get to it.

[Lomotil]

Thanks for all the replies so far... I took some pictures last night of the "before" part, it was getting too late to take it apart any further, didn't remove the rotor itself, but here's as far as I got:



Another thing with the above picture, the plastic cap (not pictured) that covers the ignition coil has grooves on opposing sides near the top that say "Latch" - It looks as if there is supposed to be yet another cover that might cover the entire top of the unit (would also explain why the plug wires have a flat surface on the distributor side, and not on the plug end.)







Some have mentioned how cheap it is to replace the worn parts, but by looking at these pictures, is there an even cheaper way to breathe new life into this unit? Every penny counts, these days...

Thanks again for all the great replies!

[Kirbot]

A new cap and rotor shouldn't cost you more than about $20 (or less) at napa.
Leave the coil and the distributor itself alone, but the cap and rotor are cheap and easy to replace. (and meant to be replaced every so often)

Nothing wrong with cleaning old plugs
I wire brushed them off many time back when the Jeep was fouling them every month or so...

[Bruce Lancaster]

Advance lives beneath/within rotor...2 curved weights restrained by tiny springs. If you can pullem outward and they snap back, no worries.
OEM module and pickup seem eternal in my experience...concentrate on center of rotor (both sides) and floor of coil cavity where the little contact (which is a replaceable part) goes through. If there is no burning or only light blackening you can wipe away, no worries. Bad ones will be scorched, sometimes missing plastic.
I worried about reliability of the "black box" stuff like module and pickup when I switched my older Chevs to HEI, and simply harvested several of each in the junkyard. Since then...I have not heard of this generation of HEI ever failing to function, even on ones with rotors that looked like the aftermath of a forest fire, and I have not encountered any failure of the electronic parts.
The experience that caused me to stop doubting and scrap the points: A friend bought a '79 car with the then newish HEI. At 140,000 he began to worry about the mileage on the parts (though there was no trouble apparent) and he replaced all the plastic. The new parts caused a bit of radio noise, the old parts went back, and he went to 240,000, at which point he replaced parts again just because.

[Lomotil]

Originally Posted by Kirbot

A new cap and rotor shouldn't cost you more than about $20 (or less) at napa.
Leave the coil and the distributor itself alone, but the cap and rotor are cheap and easy to replace. (and meant to be replaced every so often)

Nothing wrong with cleaning old plugs
I wire brushed them off many time back when the Jeep was fouling them every month or so...

Hate to throw money at something when it may not need to be replaced, even if it's only $20...

Next step is to take a couple plugs out and check 'em. It always has seemed to run rich, haven't made any adjustments on the carburetor yet - still reading up on that bit. This is actually the first vehicle I've had (and worked on) that wasn't EFI.

Originally Posted by Bruce Lancaster

Advance lives beneath/within rotor...2 curved weights restrained by tiny springs. If you can pullem outward and they snap back, no worries.
OEM module and pickup seem eternal in my experience...concentrate on center of rotor (both sides) and floor of coil cavity where the little contact (which is a replaceable part) goes through. If there is no burning or only light blackening you can wipe away, no worries. Bad ones will be scorched, sometimes missing plastic.
I worried about reliability of the "black box" stuff like module and pickup when I switched my older Chevs to HEI, and simply harvested several of each in the junkyard. Since then...I have not heard of this generation of HEI ever failing to function, even on ones with rotors that looked like the aftermath of a forest fire, and I have not encountered any failure of the electronic parts.
The experience that caused me to stop doubting and scrap the points: A friend bought a '79 car with the then newish HEI. At 140,000 he began to worry about the mileage on the parts (though there was no trouble apparent) and he replaced all the plastic. The new parts caused a bit of radio noise, the old parts went back, and he went to 240,000, at which point he replaced parts again just because.

Thanks for the detail, will look into it (no pun intended.)

Good to know these things are built to last... Thanks!

(am I missing an additional top cover, though?)

[Brad54]

There is a top cover that can go on them, but it's not critical. Don't worry about it.

I'd replace that cap, and the rotor. The contacts look worn and corroded.

-Brad

[tcsalvage]

85 suburban's have EST modules that frequently take a dump and very hard to diagnose. they don't tell on themselves but easy enough to tell if you have one. on the distributor do you have a four wire plug NOT going into the cap, if you do you have EST. (electronic spark timing). the easy way to fix it is take the distributor and find a big rock, big hammer or train track with train. if you do not have the four wire plug; smile and tune it. as for the quad it sounds like its sticking so spray down with carb cleaner and lube litely.

[Charles (in GA)]

Caps do vary in quality. I hate caps with aluminum terminals. I used to get NAPA Echlin caps for my Mustang and Falcon, they have brass terminals and thicker heavier Bakelite. Much better caps. Rotors from NAPA are (or at least were) better than everyone elses.

If you have bad wires, you could have cross firing from one wire to another, causing backfiring. Also make sure all cylinders are firing, as noted by others, loading the exhaust system with raw gas will do this too.

Charles

[gezn2]

As others have said, that version of HEI is damn-near bulletproof. It's a popular conversion for other makes
It originally came with a plastic 'keeper' that snapped down on top of the coil cover, most of those disappear after a few years...
IMO as long as the advance weights and the vacuum advance are free to move you're good to go although I would invest in a new cap and rotor, preferably the 'better' grade with brass contacts, what you have will work for some time but they do have noticeable wear.
Looking over the plugs sounds like a good plan, when they're that fresh you shouldn't have to worry much about cleaning them up and moving on.
Since you don't know the history on this truck it wouldn't hurt to check the timing, BTW an '85 ought to have an electronic-advance distributor and a solenoid controlled carb, so it's probably been modified. This might also explain why your choke doesn't work quite right, I've got a '76 with an '87 intake manifold and haven't managed to make mine work right yet either
Edit: Just checked RockAuto, you could have either the nasty ESC travesty or the Good HEI, so it won't hurt to do some research...

[SpiderGearsMan]

those have ESC modules