Here is my #1 plug I pulled out not sure how long these have been in,but guessing it’s been a while,they are AC Delco,but hearing bad reviews on these,should I go with Autolite,or something else,I do have headers.



Not to bad,I was thinking maybe the distributor was off,because when I let off gas,it pops back.

 

Your pics' resolution is bad. The pebbles in your driveway's tarmac are in far better focus than plug's electrodes; same for your license tag's frame.
All that and plug electrodes are fuzzy wuzzy

 

Golferdad,

I would not worry about a plug at this time. A bad plug would miss at idle, at part throttle, at full throttle.
You have a misfire at deceleration when there is no load.

A backfire during deceleration 90% of the time is a Vacuum Leak. Goodluck.
With 18 miles of vacuum hoses, it's just a matter of finding the cause. Again, good luck.

The leak could be under the dash (over-ride headlight ****) to way out front with headlight fittings.
HVAC, auto-Trans, PCV, Dist, Evap, wiper door? heater hose, PB, emissions, and the list goes on.

I think I would start with a Mighty Vac tool. Disconnect the "main" line at the back of the carb.
Apply vacuum there and note the tools gauge. Keep back-tracking each line and listening for a leak.

And for what it's worth:
AC plugs went out of popularity along with Champions, Fram and Mr. Gasket.
Today its NGK, K&N, and Fel-Pro.

 

HeadsU.P. is Correct about the vacuum leak causing your engine to pop under deceleration. Not likely to be distributor related...

With the color of your Spark Plugs being all we could clearly see in the pictures I would say you have an oil consumption issue from the rough looks and color of the spark plugs.

Change your plus and go with the standard AC Delco spark Plugs and you will be fine. The basic plugs work better than many of us believe even in the worst conditions. If you pull a spark plug at 500 miles and it still looks like that then you might change the heat range a bit.

What weight oil are you using right now? Brand?

If you have smoke after startup then it sounds like the valve seals might be needing attention. If you have smoke upon deceleration then the rings are likely worn. It would then be time to do a Leak Down test to see where the oil is coming from. Compression testing is useful but the Leak Down test tells you so much more if the test is done properly.

If your engine is burning the oil then I might suggest some LUCAS Oil Stabilizer and add it to your oil. I use a quart of the Lucas Oil Stabilizer whenever I change the oil in my vehicles.

Having a small 2 stage Vacuum pump is handy when tracking down vacuum leaks. You can attach the pump and let it constantly pull a vacuum on the system while you track down the leak. Another option would to be get a small smoke system and put smoke inside the vacuum system and see where it leaks out.

 

They look bad because the engine is out of tune......99% of bad reviews on older style spark plugs are from guys with a bad tune.......
That said......UR4 NGK is a premium plug......
I just put a set of AC Delco R44T's in a fresh L-82 350 and it ran perfectly......
Have the car tuned properly.....plugs are not a magic bullet.

Jebby

 

(It's nice to see Mr. Jebby!)

Being so black, I'm thinking you're running rich. Does the blackness have a wet, oily look (worn engine) or does it look dry & sooty (too rich)? Hard to see in the pics, but if the center electrodes still have their square shoulders I think you're fine reusing these. I'd brush them with a brass brush and check the end gaps (HEI = 0.045").

Denso plugs also have a good reputation for quality, though I use NGK in both of my Corvettes.

Next time lay the plug on a neutral color background and the camera's focus won't be fooled.

 

I apologize, this is on my 1972 GTO,thought I was on My GTO forum,but hopefully better picture will help,from what I see,a little black,not oily,a little smutty but considering how long they have been in here,this is a 455,with Holley double pumper,lol..headers,also could it be a fuel issue as I have put fuel with 10% ethanol,although I do sometimes put all regular fuel in it,if they’re not out that is,we have one location that sales straight fuel,this car cranks and idles good,just popping back,and maybe a little tuning on carburetor.

Not sure if this is a better picture,the blue paint was me touching up on engine months ago,

 

And all I did was just pull number 1 plug,hadn’t cleaned or anything.

 

Dry and sooty.

 

Oh also,it still has coil and points if that makes a difference.and still has OEM wires.hell,could be original wires as far as I know.

 

I think it looks good to reuse – check gap and reinstall. Ethanol fuel is supposed to create a hotter combustion temperature and leaner conditions. Spark plugs will have tan coloration to the porcelain. It doesn't seem this plug shows these effects. I'd turn the Holley's idle mix screws in a quarter turn and see how it looks after 50 miles. I'm also thinking this engine isn't operated at highway speeds much: the higher temps will keep the deposits to a minimum.

 

seems we've switched to a '72 Pontiac

 

Yep,mostly around town,so,definitely need to get her on the hyway. Thanks

 

Sure it makes a difference.
The old points / condenser system output was less than 20,000V.
Along came HEI so one could widen the plug gap, get less fouling, better burn, with 50,000V.

That GM concept sold like crazy. Never had to change points, set dwell, and more voltage.
Unfortunately, the new HEI system left people stranded. There was never a warning sputter.
They just flat quit one day. Usually around 60,000 miles.
New Modge, Cap & Rotor. Good for another 60K

 

Use an ohmmeter on the plug wire. Should be no more than 1k per foot of wire.