flathead sparkplug depth

Hey!! Have Weiand F-R heads on a ford flathead, bought autolite 437 plugs,end of tip is
flush with bottom of head,(plug thread up 1/4 inch in head) should plug threads be even with head threads? If so tip would be about 3/16 past bottom of head and about 1/8 from valve. threads in head are 9/16 deep,plugs for eldelbrock heads are 3/4 long,1/16 from valve. have not run motor yet. Pete

 

I ground out around the spark plug on the head to open it up some. I think most of the heads are like that. I used a die grinder. My heads that I did this to are Edmunds.

Neal

 

Hey! Thanks! Do you index the plugs? open end toward piston? Is that correct? Pete

 

on a street engine you do not need to index the plugs, the plug should be at bottom of head so no threads are showing which can cause detonation, you can unshroud the plug by taking metal off of the heads ...... just make sure if you use longer plugs they do not hit the valves........

 

This is not the first time i have seen this "solution" advanced. It baffles me how people can think that the engineers who designed these heads could make them good enough to increase the performance of these engines, but so dumb that they blew it on the spark plug holes. Pure and simple; these heads are designed for longer reach plugs because aluminum is not as strong as cast iron.

The major manufacturers (Edelbrock and Offenhauser) spec longer plugs in their instructions. For other brands or used heads, take a look at how the stock plug sits in the stock head and try to duplicate that with various reach plugs from the FLAPS. Grinding on the plugs holes is a dumb idea and will decrease he thread-holding strength of the heads.

No modified flathead should be assmbled with out checking valve to head and piston to head clearances anyway. This practice probably got started by some misguided sole who bought a set of aftermarket heads, didn't read the instructions, tried to use the stock Champion H-10's and saw the result.

Don't modify the heads; get the proper plugs!

 

Thanks!! and thanks for the link!! Pete

 

Tubman is correct but I did it several years back and have had no problems. I did not dream up the solution all by myself but was told by others that it can be done. But as some would say, "do not try this at home".

Neal