Burning tips off plugs

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dusterdragracer

dusterdragracer

Drag Racer
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Has anyone had an issue with burning the electrode off their plugs. I am running a 440 w/aluminum heads, about 440 Hp at the rear wheels. It's been on the dyno, and isn't lean.Autolite 3926
It only did this to a few plugs. They are not hitting anything either.I ran the plugs all year.Last time I pulled the engine down for rebuild, everything was OK, but the same thing, a few electrodes were burnt off.
Any idea's?
Thanks Guys
 
The electrodes being the ground strap? Is the ceramin cracked? Do you have a lit magnifying glass that you can look at the ceramic with?
 
Thanks for all the info.
Headers where not glowing red (LOL)
It is the ground strap yes.
Timming is at 36, we had it at different places on the dyno, this was the max HP spot.
By the way, it' s a MSD 6 AL with Mallorey coil,stock dist.locked out, same thing I have ran on the motor for years.
I will look at the plugs closer. I have a lighted mag.
I am changing all the plugs tommorow, so I can see them all.
Darn TTI headers make it hard, but worth it. I made holes in the P/S splash pan, so that helps.
5 up numbers on the jets would be too much. We set it up slightly to the rich side (not rich) so I wouldn't have to mess with it in the summer nights, or when I ran at Seattle which is sea level, which is not 3000' like here.
We did play with larger jets, but lost 10-15 HP.
I'll post a pic then too.
I'd be talking to my Dyno guy (Dr. Phil) but his mother died yeasterday, and I am getting the car serviced to race.
By the way, it runs fine with the burnt off electrode.I made Queen of the track (runner up to King!) at our track last time it ran in the fall, and it ran the fastests it's ever ran (I broke out more on a double break out) Maybe we are on to something. You think?
Thanks Guys
 
what plug are you running ? Maybe too hot of plug....?

sorry .. missed the Auto lite part.. try next cooler plug.

could also be air leaks at manifold gasket or header gasket ?
 
I would certainly run a colder plug, at least 2 numbers colder. Then maybe consider taking a couple degrees of timing out, even tho it seems to be running good. Weather change could spell the difference between running good and running a new engine. You are on the edge, if you're melting things. Seems to me that, whoever put the heads together did a decent job of centralizing the flame travel.
 
Look at the ceramics in the plug. If they have a spotted, metallic appearance, it's detonating. Ask anybody that runs nitrous what causes disappearing plug straps. Too much timing. I'd back it down 2 degrees and try it. Just because it made the most dyno power at a certain timing setting, doesn't mean that's the best when in your car.

Like mentioned, some engines can be sensitive to weather conditions, especially ones tuned on the edge of detonation.

Step up 5 jets... yikes... If it was that lean, it would be surging badly in high gear.
 
crackedback said:
Just because it made the most dyno power at a certain timing setting, doesn't mean that's the best when in your car.

Like mentioned, some engines can be sensitive to weather conditions, especially ones tuned on the edge of detonation.
Click to expand...

This. Max performance under ideal condition wot pulls does not mean it is set best for daily driving.
 
Awesome responses,I like the idea of taking 2 degrees out.
Yes, I went to a colder plug the autolight 3924, great minds think a like.
When rebuilding the engine, I did look to make sure it wasn't burning itself up, nothing else was getting burnt up (melted).
The heads were done by a guy that does most the Nascar heads. They all get shipped to him in Idaho.
Another Mopar race friend mentioned the Vac. leak. I will check, but think it is tight. It's an M1
Headers are not leaking.
The color of the plugs right now are all black from pulling it in and out of the shop. It's so loaded up!It needs a good woopin'!I will check the new ones after a run at our TT in 2 weeks.
It's a drag car, not a street car.
Nothing like experience, and getting help here has that, experience.
Thanks for all the positive info.
More info tommorow
 
I'd suggest putting an A/F meter in the car, preferably one with data-logging. Not so much for tuning to a specific number, more about where the A/F's go and how the car responds.

Distributor locked out or does it have some curve in it.
 
If you are running unleaded , you will not get that nice tan to brown discoloration. Usually much darker , like gray to black.
Timing is the usual culprit here , but burning ground straps off indicates a situation that could get very expensive if not kept in check.
 
crackedback said:
Look at the ceramics in the plug. If they have a spotted, metallic appearance, it's detonating. Ask anybody that runs nitrous what causes disappearing plug straps. Too much timing. I'd back it down 2 degrees and try it. Just because it made the most dyno power at a certain timing setting, doesn't mean that's the best when in your car.

Like mentioned, some engines can be sensitive to weather conditions, especially ones tuned on the edge of detonation.

Step up 5 jets... yikes... If it was that lean, it would be surging badly in high gear.
Click to expand...


That's where I was going - so "x2". Especially given it's only a couple holes. Some cylinders will run differently because of the intake design (which can't be dramatically altered) and the change may give them a lean situation that can;t be tuned out. Just like Cracked says - the plugs in the bad holes will show "the balls" of material on the insulators.
You might also look into indexing the plugs or look into a turtle for the intake.
 
Hey guys Thanks
I changed the plugs today, glad I have a rack! The only 2 burnt off were in the 2 front ones 1&2 cyl.. When I had the engine in my Daytona S/G car, several were burnt off, but that was a different tune up..
They are all black, like I said, I have been driving it in and out of trailer/shop.I did wire bru=sh, and no sign of balls/metal etc.
Normally they DON'T have any balls on them or metal, and they are nice and tan/beige.
I run Sunoco 110
I already went to the Autolite 3924 which is colder.
With everyones great input, I am going to also go up 1 number in the front jets only.
Read the plugs after the TT and if its looking good, I will leave it alone and watch them through the season.Atleast the 2 front are super easy to get at.
If they look unhappy,I will go back 1 degree on the timming, which at 36 isn't that advanced.
Like many said, I think I am just on the edge, and as I said, it ran the fastests it ever ran with the 2 bad plugs, so it's not serious.
Chris
 
O.K. here is a plug after 3 passes, they look awesome.No little balls or metallic on them, but then again, it is only 3 passes.The exhaust looks perfect, biege.
I went to a colder plug. We will watch them this year.
Answer to fuel.....Sunoco 110
I am 12.5 compression.
P.S. That is greese on the porcelain
 

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Thanks Dave, that is what I am going to do.I jet size.
Do you know Ray Wooldrige, he is one of my best friends from Loganlea? He has been here 4 times also.
He has the black 73 Cuda.I have been to Brisbane 4 times, and Willowbank 5-6. I raced his Cuda there.
Also Andy Fox, with the white super charged, injected nitrous Chev. BB.Who just passed away.
Chris
 
zanderzone said:
I have the same problem 1 and 2 are always leaner than the rest.
I jet it up so 1 and 2 are ok, the rest look a little fat.

I also use an M1 manifold

Dave
Click to expand...

first i will suggest using two steps hotter plugs in the front holes. these holes run cooler because they are out in the air and pull too much heat out too fast. second with the six now rich you might consider epoxing to the floor right at the entrance to the other six intake ports a 1/2" square piece of tight grain wood or plastic. this will slow the fuel up a bit to lean these ports out a little.
 
3923 autolite racing plug should be used with that compression.
I have been using 3924's in my 9 1/2 to 1 small blocks forever.
3923 is one colder.
looks like you got it figured out.
 
I agree with T67POWER. should run the 3. 5 is considered a good street plug.
 
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