Spark plug part number for Winfield head.

Whats the difference in the 6 and 7. Also I see several different ones, it appears to just be difference lengths. Is the shorter one the one to go with?
 
BP6ES or BP6HS
6 is hot than 7 road test for which 1 works best
B - 14mm thread dia
P - Insulator
6 - heat range
E - 3/4" thread reach H -1/2" reach measure the threads in your head
S - standard electrode
 
Most aluminum Winfields had 14mm thread and need a 1/2" reach plug. Before installing the head put a plug in, you want to utilize all the threads in the head but do not want the plug to extend into the chamber. I use Champion H-8 or H-10's. A 3/4" plug will likely extend into the chamber, build up carbon and ruin the threads when the plug is removed.
 
Jim Brierley said:
Most aluminum Winfields had 14mm thread and need a 1/2" reach plug. Before installing the head put a plug in, you want to utilize all the threads in the head but do not want the plug to extend into the chamber. I use Champion H-8 or H-10's. A 3/4" plug will likely extend into the chamber, build up carbon and ruin the threads when the plug is removed.
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Or will get hit by valves and make more of a mess.

If you have the luxury of having the head off the motor, you can use the longer plugs with copper "indexing" washers and optimize the installed height.

I had one where I had to weld up the existing holes, re-drill and tap on an angle and use 10mm plugs to clear. Problems solved on a not so normal motor.

J
 
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