Hot Rods Spark-plugs for Offy heads on 8BA Flathead

I have an aluminum Offenhauser head on the bench from my 8BA Flatty for unrelated issue but noticed S-plugs protrusion into head chambers looked short by a few threads. Started a thread on Fordbarn to get advise. Evidently Offy designed their aluminum Head for 14mm w 5/8” reach but seems impossible to find any in a medium heat range. Only thing I found is too cold in a Champion & same for NGK, both Racing plugs. Anyone know of a Mfgr w a mid heat range in a 14mm 5/8” reach S-plug?

 

Found one’s that work, no reply required.

 

You want to tell the rest of us?

 

Me too would like to know

 

https://www.fordbarn.com/forum/showthread.php?t=272052 I think this is the original thread about the plugs...
Champion N5C

 

I was involved in that thread. It seems that nobody knows what kind of plugs are proper for use in Offenhauser heads. I had the same problem in the early '60's when I was drag racing and after a bunch of trial and error, came upon the Champion "N" series as the right plug. Because of the thread on "The Ford Barn", I bought a new Champion N5C and screwed it into an unmolested Offenhauser head I have. Here are the pictures I posted. The first is a stock iron head with a standard plug and the second is an "N5C" in the Offenhauser head. I think they speak for themselves. I used Champion plugs as an example because I understand their numbering scheme. Also, I do not know if the "5" heat range is correct. I just used it because it's right in the middle.

 

Thanks for the pics and the information. Got any pics from your time racing in the '60s or your current racing endeavors?

 

I have posted this before. There are some pictures of my first car on page 2. https://www.jalopyjournal.com/forum...innesota-dragways-from-the-early-60s.1153582/.

Up to a couple of years ago, I vintage raced this :

 

tubman a Fordbarner remembered this issue from many years ago. did some research on old records and found he'd used a Champion N5C that fit well. He got one on Amazon tried it and the thread face of that plug was flush w head surface of the recessed area for the spark plug. Looked good so I ordered 8 & waiting for them.

 

Guilty as charged.

 

There have been some new developments on this resulting in the determination that the Champion "N" series spark plugs are NOT the proper choice for Offenhauser heads. The bottom line is that the plug holes in the head are not tapped all the way through on Offenhauser heads (at least not on the unused pair I have), and the plug bottoms out in the threads resulting in it being in the proper position. While they will probably work fine this way, it is not the proper way to do it. For more detailed information, see the original thread on "The Ford Barn" : https://www.fordbarn.com/forum/showthread.php?p=1822130#post1822130.

 

The Champion N5C requires an approx .21" spacer. Again see the Fordbarn thread.