My drivers side rear plugs (closest to the firewall and the one before it) Anyways, I put new plugs in it, and it ran very nicely. Then after about 20 miles or so it would crap the bed and run sluggish with backfiring. Whats up??
(1972 Chevy Blazer w/ HEI, new plugs, wires, timing at 8 BTDC, new edelbrock 600cfm, K&N, fuel filter, NEW EVERYTHING. Is it the guides letting to much oil through and candy coating the plug causing it to foul and backfire??!?!?!

What color are the plugs? Any way to post a picture? Does it smoke at all? On startup?

No pics sorry, black tarry looking shit on the butt of the plug.....mild smoke on the startup

Check to see if your pcv valve is plumbed in the right location. I had it plumbed to the vaccum port at the back of my intake manifold and it was sucking oil out of the valve cover and into the intake runners and fouling my numer eight plug every 100 miles or so. Your pcv should run to one of the vaccum ports on your carb. Btw i found that autolight spark plugs resist fouling the best of any that i tried and i tried them all before i learned what was causing my fouling problem.

Originally posted by bigfoot
Btw i found that autolight spark plugs resist fouling the best of any that i tried and i tried them all before i learned what was causing my fouling problem.

YOU HAVE GOT TO BE KIDDING... Autolites are the worst plug their is.. I went thru 3 sets in two weeks and they wouldn't honor their warranty.. I would be going down the road and the truck would shut off just like someone turned the key off..the plugs still looked new but would not fire.. I put in champions and never had another problem so I say stay away from autolites even if your only choice is them dam splitfires.. You are right they resist fouling because they dont run long enough to foul..

Bosch Platnums gapped to .060. Never had luck with autolites or champions....You get what you pay for 99c spark plugs...
Sounds like your plugs are getting saturated by oil.
How many miles is on the motor? Could be valve stems seals or worn guides. Hard to say without looking at it.
Did you try a leakdown test?:skull:

Could also be sucking oil into the intake runners from the valley. Have you had the intake off?

Well i dont know what kind of truck you were putting autolites in, but on all my older chevys(and iv'e had a lot) the autolites have always worked the best plus they dont cost 5 bucks a piece. Sometimes you dont get what you pay for.

~PCV valve is routed to the right location
~No I haven't done a leakdown test
~Autolite plugs (the last 2 on the drivers side) are covered in
gritty black oily shit
~Haven't had the intake manifold off, had the carb off and
everything looks clean as a whistle
I am thinking about replacing the guides on those 2 cylinders, because they are the only ones affected. I run the plugs (autolite) for about 15 miles and the enigine already starts to sputter and pop a little (backfiring, but it sounds closer to the engine)
:confused: :confused:

Originally posted by bigfoot
Well i dont know what kind of truck you were putting autolites in, but on all my older chevys(and iv'e had a lot) the autolites have always worked the best plus they dont cost 5 bucks a piece. Sometimes you dont get what you pay for.

I dont buy those junkie splitfires either but I would get them before autolites..one of the trucks that had problems with the autolites was a Dodge the other was an 81 Chevy with a new engine.. The Chevy never even made it out of the parking lot before THREE of the plugs QUIT firing so I still say stay away from Autolites and the two year warranty they say they have Dont believe it.. All of these plugs were returned within A week of purchase still looking new and they would not honor their warranty..I run champions now unless I cant get them in which case I get AC's..Currently both my Dodges have champions and My Suburban has AC's and my race car has AC's(it is a Camaro with a 350) because i would hate to be stuck in the middle of the track with a dead engine because of bad plugs(read AUTOLITES)..

Its still going through spark plugs like its cool! Fouls them out with black gritty tarry shit and about 2 qts of oil in about 90 miles!
Compression test (dry) came back alright however there was a couple of cylinders that were low, but weren't the crappy cylinders. I don't know if I should replace the whole frickin motor (I am about to say fawk it) or just do the heads?!?!? This sucks....it runs really good after 2 new plugs, and shits smoke like its cool, then fouls the plugs, and the power drops about 40%. WTF.....

I would still suggest that you pull the intake and put in new gaskets to make sure that it is not sucking oil from the galley. Doesn't take much time or money to try.

I'll try it, see what happens......:D

if you're puffin a little smoke at start up and (like you said) are using oil, then it may be valve seals.

When I start the truck up after the new plugs (2 on the drivers side) the truck SHITS smoke, then after about 25 miles, the plugs are fouled, and no smoke!! A few more miles and 2 quarts or more are gone!! So everyone that reads this post, take into consideration that this is DRASTIC..........not just a little coming from a bad seal.......:D Thanks

if your valve guide seals are bad than the guides them selves are too. chevy's have craping valve guides.
never the less i would quit messing around and pull the heads. you will know if it is a guide or if it is something drastic like you say, it maybe a cracked ring or broken skirt.
if it is guides e-mail me i have a line on some rebuilt heads.
:D :D :D :D :D

as for spark plugs.
i think people spend entirely too much money for gimickey crap. i've ran auto lites , ac, champion, and nippondenso. it doesn't make a difference. if you want to tune with spark plugs then experiment and find the perfect heat range or index the gap to the combuston chamber, or gap them. oh exept the platnums don't gap those cause the electrode is so small that it will break when you push your gapping tool in it.
a spark is a spark is a spark is a spark is a spark is a spark
:flipoff2: :flipoff2: :flipoff2: :flipoff2: :flipoff2: :flipoff2: :flipoff2::flipoff2:

Here's the deal, I did the intake manifold gasket, and all surrounding gaskets in the area. It definately sealed up the leak from the backside of the intake manifold, but it is still running like shit. It backfires on occasion, and hesitates throughout the RPM range. Everything is hooked up, timed, sealed, etc. I haven't pulled the plugs yet to see if they have gone bad, but it is not shitting any more smoke. We'll see, and I will post up what happens later. I wish that I could just figure it out and be done with it. Also the driveline, when I decelerate, lets out a whizzing noise that makes my toenails float.....then when I accelerate, it goes away. It is consistent, and is loud with tons of vibration that goes with the whizzing. hummmmm.........

Hmmm, now it sounds like it is not timed right, or two plug wires are swapped.

Timing is dead on, and I just replaced the cap, rotor, plugs, wires.
It seemed to run a lot cleaner and smoother, but it still misfires (was doing it on the way to work this a.m.) Tonight I am going to plug the last 2 plugs again and check em for oil and see if they are fouled out. I was thinking about checking out a hotter plug, maybe a Bosch Platinum, and seeing what that does?!?!?