Spark plugs for Offy 1069-400 heads ?

[jmtaylor11]

What spark plug do I use with Offenhauser 1069-400 aluminum finned heads for my 1951 Ford? It appears that I need a plug with about 5/8 inch reach.

[ArcLighter]

Offy recommends CHAMPION SPK PLUG:39-53FHF
http://www.speedwaymotors.com/Offenh...ads,33369.html

Oops! Champion says ain't no such plug.....

[4dFord/SC]

Autolite 437.

[BUBBAS IGNITION]

We use champion H10s in ours

[RalphM]

X2 H10's

[Vic Piano]

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I use Autolite 437's with Offy aluminum heads and Autolite 216's with stock heads.

[Bored&Stroked]

I'm not a Champion fan - have had too many issues with fouling them over the years. I tend to run NGK in most everything.

A NGK replacement for the good ole' Champion H10 is the NGK B6L . . . great spark plug!

[Ronnieroadster]

Chanpion H-10 plugs are made in mexico not the best of quality any more. Like Bored and Stroked said NGK is the best choice another NGK choice is their B-4L thats a bit hotter than the B-6L. Been using them for a long time now their even better than the Autolite 216 in my opinion.

[russcc]

Is there a cross from the Autolite 437 to NGK ?

[tubman]

I am totally amazed at those who are espousing the use of Champion H10 plugs (or their equivalents) in Offenhauser aluminum aftermarket heads. Granted, I do not know exactly which heads the OP is referring to, but I have a brand new set of Offenhauser's in a their original box that I have not yet got around to using, and mine, at least, are made for a plug with a significantly longer reach plug than stock. It was always obvious to me that, since aluminum is a bit weaker than cast iron, the original designers did this on purpose so the threads would have strength equai to the original heads, therefore requiring the use of longer reach plugs. The last set of aftermarket heads I installed were Edelbrocks, but they were also designed to use a longer reach plugs as were Offenhausers. On those, we ended up using Champion "L" series plugs (3/4" reach) plugs that fit perfectly and worked well. I used a set of new Offenhausers on an 8BA in a '36 3-window I built about 20 years ago, and for that build, I used a set of "L" series Champion surface gap marine plugs with and MSD box that also worked very well.

Using stock reach plugs on aftermarket aluminum heads will leave about 1/8" of threads exposed. Not only is the plug shrouded, but the sharp edges on the exposed threads could heat up and lead to pre-ignition. I have even seen recommendation on threads on this subject where some folks recommend chamfering the threads out of the bottom of the plug hole to eliminate this. Give me a break! Are they saying that the guys who designed these heads screwed up the design badly enough to require that the purchaser modify the heads before using them?

My advice to the OP? Screw an H10 into a stock cast iron head and carefully note the relation of the bottom of the plug and the electrode to the inside surface of the head. Then go to your FLAPS and try various length plugs in your aluminum heads until you find one that puts the bottom of the plug in the same relation to the inside surface of the aftermarket heads. You now have the proper reach plug (I'll bet you will end up with "L" series or their equivalent). Then select a plug with a heat range close to an H10 and adjust from there, depending on the characteristics of your engine. The brand is up to you; as an old Irish buddy used to say, "some are better than others, but none of them are bad".

[Ronnieroadster]

Originally Posted by russcc

Is there a cross from the Autolite 437 to NGK ?

The NGK 1-800 tech line is excellent in helping with a cross reference as well as help if you give them the needed plug length and application. They have helped me with a perfect selection from stock flatheads to mildly modified flatheads as well as to my many record setting all out race flatheads adding to the list the many ARDUNs I have built also run NGK plugs.