Champ Spark Plug "un-gapping" itself

[SuperHawk Jr]

Hello,

We have a 1964 3/4 ton 289 R1 Champ pick up that we drive everywhere. The engine has been detuned a bit so that we get better gas mileage and do not have to run premium. The pistons are dished and not flat topped. Engine was rebuilt about 12 years ago, and has about 50K on it by now.

It runs great, however recently my dad and I discovered that it was running a bit sluggish, so we checked the spark plugs thinking that might be the culprit, and sure enough, the #7 spark plug was a bit dirty and the gap on it was about .020. So, we re-gaped it to about .032.

Then, a few more weeks go by and it starts running bad again, we checked #7 spark plug and the gap had closed again! We took it out, re-gaped it and it ran great again.

In a few more weeks the same thing happened!

It is running fine now, but we are just waiting until the Champ starts running bad again before we inspect spark plug #7.

Does anyone out there in Studebaker land have any idea on what could be causing this to occur?
Why would the gap on #7 be changing?

We are using Autolite 85 spark plugs.

Any help/ideas would be greatly appreciated.

Thank you,

-Super Hawk Jr.

[Gunslinger]

Deposit buildup on the top of the piston striking the ground electrode?

[wolfie]

Entirely possible Gunslinger is correct but if it was mine I would replace that plug first. While you have it out bring that piston to TDC and look as well as you can into the spark plug hole for any buildup. If it looks carboned up try running a bottle of Techron in it before you tear it down. Steve

[StudeRich]

Autolite 52/Champion H-14Y is the correct plug for a NOW Std. 289, are you sure it is a 7/16 in. reach plug?

[Laemmle]

If R1 it should be J12Y Champs.

[StudeRich]

It no longer is an R1 now, with dished std. 289 Pistons. But if the reach is too long you will have problems and since I have no clue what the specs are on these incorrect plugs I question those, they may not be the problem, there could even be one loose rod bearing causing this, who knows.

[studerodder]

put that plug in a different hole and see if the same thing happens to it. if so, you have a defective plug. if the problem stays in #7, something's wrong in there.