Need a read on my spark plugs
 

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1973 L82 4sp original engine, 66,100 miles, set up to run per Lars papers. Runs strong and fast but needs a tune up as the last one was 10 years and 9000 miles ago. I drive it about 1100 miles per year and it burns about 1.5 quarts of oil during that time. Attached is a picture of the plugs I pulled today.
What are they saying?
Thanks.
Fran

Plugs, cylinders, distributor cap and/or plug wires for #4 & #8 have some problems. The others look to be relatively clean and burning well with no oil or contaminant build-up on them. What you have on #4 & #8 COULD be due to faulty (or not completely seated) plug wires, damage on dist cap contacts for #4 & #8, of plug damage (internally).

Just my .02....

:iagree:

#5 is a little odd looking. Color looks good but the electrode looks to be eroded.

I wonder if your valve seals are off on #4 and #8? Your oil consumption isn’t too bad but not negligible either.

If the engine is original and never disassembled, the valve stem seals need replacing and may be the problem with 4 & 6 as well as the excessive oil consumption. The others appear to show soot on the plug bases, too.

It's kind of hard to tell with a straight on top shot like that instead of one from the side but I agree with the others. 4 and 8 look like oil so maybe valve seals. If it was even on all it would indicate wear but it isn't so I would start with a compression check and if all are up then look at valve seals. Cheap and easy to do.

Thanks for the suggestion. Added side shots of 4 & 8 to the original post.
Fran

I agree w/ the others on valve stem seals ... some 46 years & 66K ... they should be split crumbly and perhaps a few're gone.

May also be more than a little wear on guides/stems themselves.

VS Seals fairly easy to R&R on motor in-car ... check guide/stem wear at same time.

-edit-
in addition to seals, may also be intake gasket leakage ... sucking oil into some runners.

My first thoughts were oil too. Too clumpy and thick to be just soot.

Couldn't really see the detail on 4 & 8 until you re-posted the close-ups. Looks like oil build-up. But they are so junked-up, spark is limited [or non-existent], so oil residue would continue to build-up. Valve stem seals is a good possibility, although I would expect several of the others to be worse than they presently show, if that were the ONLY problem. I think you have some weak spark issues as well on 4 & 8.

TEST: Clean up plugs 4 & 8 and move them and their respective wires to 2 & 6 (and vice versa). Run it a while, then look at all the right-side plugs. If 4 & 8 still look bad, the problem is isolated to the cylinders; if 2 & 6 look bad, the problem is with the electrical components. If you get "something else" results, you likely have problems in both areas.