Need some help. I got 2 ignitions with 2 different boot sizes. One is a 5/8" and the other is 3/4"! Can someone tell me what the plug number is for each of these that uses the squish washer?

thanks

Ok found out the 3/4" is a BPMR6A plug. Also found a BPMR6F that is a 5/8" hex but it has a tapered seat. Does anyone know what plug would be the 5/8" plug with a gasket seat instead of the tapered seat?


thanks

Maybe this will help some.

http://www.ngksparkplugs.com/techinf...tnumberkey.pdf

I think I researched this very question a good while back and never could find a 5/8" hex plug with a gasket seat. However, on many engines they are exchangeable. The threads are the same, it is only the seat you are concerned with. Look closely at the cylinder head and see if there is a chamfer on the plug seat. If so, the 5/8" plug will work. I have been known to machine the chamfer myself to make the 5/8" plug work, but I can't recommend that; don't want someone ruining an expensive cylinder for the price of a new plug cap.

AV8TOR

Good points ..... some years ago, Ralph Cunningham recommended using the smaller BPMR6F tapered seat plug in place of the larger washered plug. I have done that ever since in engines using this size, 14mm plug. My engines (Zenoah and engines with Sachs cylinders) have enough taper above the plug threads in the cylinder and seal very well without the washer. The smaller 5/8" plugs really doesn't have enough diameter to properly allow for a large enough sealing flange for a washer to work properly.

Thanks guys for all the info. I think truck racer hit the nail on the head though. Called both NGK and Champion, they both said don't make it.

These two plugs are interchangeable in the engine but the shielded spark plug caps are different.

Even though one has a gasket and one is tapered seat, they both fit the engine cylinder the same.

Is the 5/8 hex plug 10 MM or 14MM thread size? If it is a short 10MM thread,it is a CNR6A,if long reach 10 MM it is a CMR7H.
BCCHI

14mm