The Ford Barn

Cartravel · 03-26-2015, 10:42 AM

Finally fired up our flathead and ran it for the 20 minute cam break in. I was doing some checks before firing it up again and noticed about half of the spark plugs are being kissed by the valves. I had checked this with clay before installation, but obviously did not do a very good job. I have Offy 450 heads and cam with about .350 net lift. I installed BP6HS plugs (1/2" reach). I machined the head around the plug holes so the thread lengths would match. The thread length is only 1/16" longer than the the H10s, but to the tip of the electrode they are 3/16" longer. I have read BP6LS plugs recommended, but they are only 1/16" shorter than the BP6HS. The P means projected insulator type. The local auto parts store has B6L plugs. Would that be a better choice? I have a preference for NGK plugs.
Larry Young

Pete · 03-26-2015, 12:01 PM

You don't need projected nose plugs. Try the B6L's.
Another alternative is to use 1/8" solid copper plug washers. This will probably move the nose back far enough to clear.
The solid washers transfer heat better also.

BillM · 03-26-2015, 07:22 PM

I f you want a projected tip plug there is a 7/16" reach for 1954 Fords that are about .605" from the washer to the end of the tip: Champion RH18Y or Autolite 437. Also there is a 3/8" reach projected tip for 1970 Chev 5.0L V8 that is about .530" long: Autolite 85. The NGK plugs listed for these applications weren't projected tip plugs though. I have about the same head and cam lift situation as you and am using the Autolite 85's presently.

Kahuna · 03-26-2015, 09:47 PM

Or, just double gasket/washer the plugs

JWL · 03-27-2015, 03:02 AM

In come cases I have used 3/8" reach plugs. However I like to chamfer out the inside, exposed, threads before I install the heads.

There are plug indexing kits with a variety of plug washer thicknesses from which to add to your existing washers. I do not like to use multiple washers because it makes the plug much easier to foul but it can be an acceptable "get by" solution.

KGS · 03-27-2015, 11:07 AM

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Quote:

Originally Posted by Kahuna

Or, just double gasket/washer the plugs

Who sells spark plug washers separately?

03-26-2015, 10:42 AM	#1
Cartravel Senior Member Join Date: May 2010 Location: Larry Young, Tulsa, OK Posts: 202	Spark plug clearance Finally fired up our flathead and ran it for the 20 minute cam break in. I was doing some checks before firing it up again and noticed about half of the spark plugs are being kissed by the valves. I had checked this with clay before installation, but obviously did not do a very good job. I have Offy 450 heads and cam with about .350 net lift. I installed BP6HS plugs (1/2" reach). I machined the head around the plug holes so the thread lengths would match. The thread length is only 1/16" longer than the the H10s, but to the tip of the electrode they are 3/16" longer. I have read BP6LS plugs recommended, but they are only 1/16" shorter than the BP6HS. The P means projected insulator type. The local auto parts store has B6L plugs. Would that be a better choice? I have a preference for NGK plugs. Larry Young

03-26-2015, 12:01 PM	#2
Pete Senior Member Join Date: May 2010 Location: Wa. Posts: 5,405	Re: Spark plug clearance You don't need projected nose plugs. Try the B6L's. Another alternative is to use 1/8" solid copper plug washers. This will probably move the nose back far enough to clear. The solid washers transfer heat better also.

03-26-2015, 07:22 PM	#3
BillM Senior Member Join Date: May 2010 Location: Everett, WA Posts: 504	Re: Spark plug clearance I f you want a projected tip plug there is a 7/16" reach for 1954 Fords that are about .605" from the washer to the end of the tip: Champion RH18Y or Autolite 437. Also there is a 3/8" reach projected tip for 1970 Chev 5.0L V8 that is about .530" long: Autolite 85. The NGK plugs listed for these applications weren't projected tip plugs though. I have about the same head and cam lift situation as you and am using the Autolite 85's presently. __________________ My web page: http://myplace.frontier.com/~wgmumaw/

03-26-2015, 09:47 PM	#4
Kahuna Senior Member Join Date: May 2010 Location: NorCal Posts: 2,617	Re: Spark plug clearance Or, just double gasket/washer the plugs

03-27-2015, 03:02 AM	#5
JWL Member Emeritus Join Date: May 2010 Location: Fitzgerald, Georgia Posts: 2,204	Re: Spark plug clearance In come cases I have used 3/8" reach plugs. However I like to chamfer out the inside, exposed, threads before I install the heads. There are plug indexing kits with a variety of plug washer thicknesses from which to add to your existing washers. I do not like to use multiple washers because it makes the plug much easier to foul but it can be an acceptable "get by" solution.

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