Offy. head spark plugs

blk tudor

blk tudor

Junior Member
I know NGK BL-6 or B4-L plugs are what are used with aluminum heads, but there both 7/16 reach. Has anyone tried NGK B6HS their the same heat range as BL-6 and are 1/2 reach. I'm useing new Offy. 400 heads that I really don't want to fire spot. I saw just one ref. to this plug for this application. Thanks for any help! I don't have a high lift cam.
 
I made several measurements of my Offy heads and various plugs. The attachment shows the details. Its important to measure carefully as the exhaust valve is right under the plug; and there are different thicknesses in Offy heads.
 

Attachments

Thanks for the info BillM. If I have these heads opened around the plugs does anyone know a machine shop in the s.e. Mich. area that knows flatheads? I know of several good auto engine machine shops that say they can do flatheads but they all specialize in other types of engines, GM LS etc,.
 
Check out motorcityspeedequipment.com I know they aren't in Dundee anymore but may be able to refer you to who is doing their flatheads now. Mark kirby did my heads when he was still working and did what he called pocketing the spark plug holes. Maybe you can get some info there.
 
Any decent machine shop with a Bridgeport and a "ball" mill should be able to handle that chore with ease!

We've been doing that procedure for decades now, really, it's simple!

You need to supply the plug you intend to use and nothing more.

Thanks Gary in N.Y.

P.S. Here's a shot of one setup in the mill being done by my son!

 
flathead4rd said:
Check out motorcityspeedequipment.com I know they aren't in Dundee anymore but may be able to refer you to who is doing their flatheads now. Mark kirby did my heads when he was still working and did what he called pocketing the spark plug holes. Maybe you can get some info there.
Click to expand...

Update: Check out gollershotrods.com Evidently they have taken over the Motorcity Flathead business. They are in Defiance, Ohio
 
I countersink the threads with a 45 degree tool I do this from the combustion chamber side. I leave enough threads to use a 1/2 reach power tip plug. Have several of these running in customer engines.
 
Hi

Suggest taking the heads to a machine shop and tell them what you want, show them the photo, and give them the plugs. It a real simple operation, once it is setup.
You may have to call around to find a shop with a Bridgeport, instead of all the new CNC machines. There is plenty of those vertical milling machines around. Actually call WT Tool in Warren Michigan. They are a machine shop supplier, and can tell you who has what, and who to call.
 
To unsroud the plugs it needs to be done with a mill,if you want to do it right. Find a shop with one and take them the plugs.
 
Aw bull----. Buy yourself a countersink cutter, turn the heads upside down, turn on your hand-held 1/2" drill and start cutting from the combustion chamber side. Frequently screw a plug in to the hole, you are working on, to gauge your cutting depth. You do not want any threads on the plug body exposed, in the chamber, nor do you want excess threads showing in the head. Keep playing with your depths until you get them perfect.
 
I knocked the porcelain from a spark plug of the brand I was going to use, drilled out the hole to fit a cutter I had and used to center the cutter while removing the threads in Off 400 heads. Screwed the modified plug into the head and used cutter to cut the exposed threads down to the spark plug, then rounded of the sharp edges. Other ways to do it but used what I had.

Vergil

tool-1.JPG




tool-2.JPG



threads-2.JPG



threads-1.JPG



threads-3.JPG
 
If you use a chamfering cutter there is no need for a pilot. It will be self-centering and make the job doable by the least experienced enthusiast.
 
You must log in or register to reply here.
Back
Top