Ignition: Best Spark Plug To Use

[3x2stude]

I am getting ready to do a tune up and intake change. I will be installing a new Petronix electronic distributor and a tri-power I built almost a decade ago and put on the shelf. It is all going on a 1961 Hawk, 289 two barrel with dual exhaust. What spark plug would be best to use?

JK

[Mike Van Veghten]

I'm moving over to GM tapered seat plugs in my Stude engines.
The 90 degree seat to thread area machined in the stock Stude heads, digs into about the center of the tapered area of the plug seat. With just a little torque, it seals all the way around and tightly.
And the best part of the whole deal...is that the ground ring ends up in about as perfect location as you can expect, with the odd surface of the chamber roof.

And if you like to locate the ground strap in a particular location in the chamber, with the tapered seat, shim gaskets, that's possible too.

Kinda surprised you guys haven't been doing this ! Especially in the "Engine Masters" engine.

Now there's almost a countless number of picks for not only heat ranges, but also for both non-extended tip, and for extended tip spark plugs, as you see fit to use.

Mike

[Bud]

The spark plug of choice for most Studebaker V8 engines is the Autolite 437 or Champion RH18Y and if you haven't raised the compression should work quite well with your set up. I don't know about using a taper seat plug in a cylinder head with a flat seat spark plug hole meant for a gasket as that could cause a problem with seating if an original style plug were to be used. Also using a taper seat plug in a plug hole meant for use with a gasket could also cause problems with heat transfer from the spark plug to the cylinder head as there is not enough metal contact between the plug and the head You could use a Champion RJ12 YC or AC R44S if you want a slightly colder plug which are the same plugs recommended for the R series engines. The only thing about using the RJ12YC plug is it has a slightly shorter thread than the Autolite 437 that could cause a problem with carbon build up in the now uncovered threads in the head. Bud

[64studeavanti]

The thread on the plugs is 18tpi. The difference between the 7/16" (RH18Y) reach and the 3/8" (RJ12Y) reach is 1/16". Doing the math, it comes out to a little over a single thread!

[gordr]

I can envision some pretty simple tooling that would enable one to run a piloted countersink in the spark plug holes in order to have them properly accept tapered-seat plugs. Metal plate bolted to bottom of head, located by dowels in valve guides, that contains 4 sleeves welded at the correct angle in holes, the sleeves being concentric to the spark plug threads. Extended pilot on countersink cutter runs in those sleeves. This ought to enable one to do an acceptable job with a hand-held power drill.

[64studeavanti]

The change to tapered plugs seems like a lot of work for little gain since plugs that fit/work are readily available.

[StudeRich]

Your Tri-Power 3, 2's and Pertronixs Ignition should not require any change to the Heat Range of the Stock Plugs: H14Y.
A Good crossover to a higher quality Plug than Champion, like the very good Autolite 437, or NGK Plugs is a good idea.

The change that IS recommended is, only to open the Plug Gap a bit from .032 to .035 to .040

[StudeRich]

Note that the Sun Corp. Tune Up Data is for the '62-'64 Std. V8 Prestolite Dist. so not pertinent to your Early Delco without a Window Dist. but other data IS.

[3x2stude]

Thanks for all the info. I'm going to go with the Autolite #437s, my engine guy is happy with them.

JK

[Mike Van Veghten]

I can envision some pretty simple tooling that would enable one to run a piloted countersink in the spark plug holes in order to have them properly accept tapered-seat plugs. Metal plate bolted to bottom of head, located by dowels in valve guides, that contains 4 sleeves welded at the correct angle in holes, the sleeves being concentric to the spark plug threads. Extended pilot on countersink cutter runs in those sleeves. This ought to enable one to do an acceptable job with a hand-held power drill.

Nope...doesn't work.
Doing this ("proper" machining) pushes the plug too far into the chamber. Read that threads causing possible hot areas to preignite.

The sharp seal works fine. Or...I haven't seen any sort of problem ! I know others that have done the same, also without problem.

AND,,,additional heat ranges to choose from are more that JUST compression ratio. Chamber pressure from a blower / supercharger of some sort, higher ignition timing, higher rpm than normal, are a few of the reasons for more (normally colder) plugs to choose from.

Mike