The Ford Barn

bchrismer · 06-14-2015, 01:25 PM

I have been monkeying around with my "spare" flathead, preparing to fire it yesterday. It's a 59 block, with a 3 3/8" bore and 4" stroke, and a small lift cam of about .3125 lift. Wearing an OLD set of Offy 400 heads, with an 18mm thread size.

Bought a new set of Autolite 46 plugs, with a tapered seat and .46" reach, and when I cranked it over, 7 of the spark plugs are hitting the valves. (the 8th one was repaired probably 50 years ago and now uses a 14mm flat style plug.)

I'm at a loss, other than to have the 18mm holes converted to a 14mm flat style plug and am looking for suggestions.

Most appreciated.

Pete · 06-14-2015, 01:44 PM

Several alternatives here.
1- Buy a new set of heads.
2- Have the 18's plugged and re-threaded to 14.
3- Buy a set of screw in adapters that convert 18 to 14.

Bob C · 06-14-2015, 03:41 PM

If the heads are OLD are you sure they take taper seat plugs?

Bob

bchrismer · 06-14-2015, 05:03 PM

That is what was in it. I looked at it, this afternoon, and think that I should be able to use some flat crush washer style. Still on the hunt for the right part number to compare with.

VeryTangled · 06-14-2015, 05:40 PM

Hi Everyone,

bchrismer, I am certainly no expert on your subject, but... Wouldn't the spark plug hole be different for the crush gasket type plugs, vs. the tapered seat ones? Are they interchangeable?

bchrismer · 06-14-2015, 07:14 PM

Sponsored Links (Register now to hide all advertisements)

Well...chalk that up for me not looking at the head and just taking the plug up to the store to get the same thing that was in it.

Come to find out, after looking at it, and comparing other plugs on Autolite's website, I ran up to O'Reilly and picked up a set of 386 plugs, with the crush washer.

Sorry for being an idiot and trusting that what was in it was right. Cost me another $20 in plugs. LOL

https://www.youtube.com/watch?v=7qtpL6QmP9A

chap52 · 06-15-2015, 02:02 PM

Any "learning experience" under $100 is great.

Walt Dupont--Me. · 06-15-2015, 02:32 PM

bchrismer . Does these heads have steel inserts for the 18mm plugs or are they threaded in the aluminum heads? Most of the Offy heads I've used 400 and 425 have 14mm and have 3/4 reach plugs. I just installed a set of Offy 375 heads and they had 1/2 reach 14mm plugs. Walt

42merc · 06-15-2015, 04:25 PM

Before Helicoils the fix for stripped spark plug threads was to thread the item to the next larger size.

bchrismer · 06-15-2015, 04:33 PM

Walt,

There's only one with steel insert. It's "#2. The others are threads in the aluminum heads.

The biggest issue that I had with the "new" plugs is that that I don't own a 7/8" long well socket or spark plug wrench. I snugged them down finger tight, then used a short socket and a channel lock to tighten them up about 1/8 of a turn.

Chap, the good news is that I had bought an "extra" starter solenoid, so I returned it and took the refund in spark plugs and a $3 and change credit back into my bank account.

Jack E/NJ · 06-15-2015, 05:40 PM

>>>The biggest issue that I had with the "new" plugs is that that I don't own a 7/8" long well socket>>>

Well, geez! Hurry up and go get one! 8^)

http://www.homedepot.com/p/Husky-1-2...DP78/202934346

Jack E/NJ

06-14-2015, 01:25 PM	#1
bchrismer Member Join Date: Apr 2011 Location: Springfield, MO Posts: 77	OLD Offy heads - 18 mm Spark Plugs hitting valves I have been monkeying around with my "spare" flathead, preparing to fire it yesterday. It's a 59 block, with a 3 3/8" bore and 4" stroke, and a small lift cam of about .3125 lift. Wearing an OLD set of Offy 400 heads, with an 18mm thread size. Bought a new set of Autolite 46 plugs, with a tapered seat and .46" reach, and when I cranked it over, 7 of the spark plugs are hitting the valves. (the 8th one was repaired probably 50 years ago and now uses a 14mm flat style plug.) I'm at a loss, other than to have the 18mm holes converted to a 14mm flat style plug and am looking for suggestions. Most appreciated. __________________ HotRodHundred.com Reliability Runs It's about the drive!!! StreetRodder.Net The FUN is in the RUN!!!

06-14-2015, 03:41 PM	#3
Bob C Senior Member Join Date: May 2010 Location: So Cal Posts: 8,755	Re: OLD Offy heads - 18 mm Spark Plugs hitting valves If the heads are OLD are you sure they take taper seat plugs? Bob

06-14-2015, 05:03 PM	#4
bchrismer Member Join Date: Apr 2011 Location: Springfield, MO Posts: 77	Re: OLD Offy heads - 18 mm Spark Plugs hitting valves That is what was in it. I looked at it, this afternoon, and think that I should be able to use some flat crush washer style. Still on the hunt for the right part number to compare with. __________________ HotRodHundred.com Reliability Runs It's about the drive!!! StreetRodder.Net The FUN is in the RUN!!!

06-14-2015, 07:14 PM	#6
bchrismer Member Join Date: Apr 2011 Location: Springfield, MO Posts: 77	Re: OLD Offy heads - 18 mm Spark Plugs hitting valves Sponsored Links (Register now to hide all advertisements) Well...chalk that up for me not looking at the head and just taking the plug up to the store to get the same thing that was in it. Come to find out, after looking at it, and comparing other plugs on Autolite's website, I ran up to O'Reilly and picked up a set of 386 plugs, with the crush washer. Sorry for being an idiot and trusting that what was in it was right. Cost me another $20 in plugs. LOL https://www.youtube.com/watch?v=7qtpL6QmP9A __________________ HotRodHundred.com Reliability Runs It's about the drive!!! StreetRodder.Net The FUN is in the RUN!!!

06-15-2015, 02:02 PM	#7
chap52 Senior Member Join Date: Jun 2013 Location: Marana Arizona Posts: 1,776	Re: OLD Offy heads - 18 mm Spark Plugs hitting valves Any "learning experience" under $100 is great.

06-14-2015, 01:44 PM	#2
Pete Senior Member Join Date: May 2010 Location: Wa. Posts: 5,409	Re: OLD Offy heads - 18 mm Spark Plugs hitting valves Several alternatives here. 1- Buy a new set of heads. 2- Have the 18's plugged and re-threaded to 14. 3- Buy a set of screw in adapters that convert 18 to 14.

06-15-2015, 02:32 PM	#8
Walt Dupont--Me. Senior Member Join Date: May 2010 Location: Gardiner Me. Posts: 4,200	Re: OLD Offy heads - 18 mm Spark Plugs hitting valves bchrismer . Does these heads have steel inserts for the 18mm plugs or are they threaded in the aluminum heads? Most of the Offy heads I've used 400 and 425 have 14mm and have 3/4 reach plugs. I just installed a set of Offy 375 heads and they had 1/2 reach 14mm plugs. Walt

06-15-2015, 04:25 PM	#9
42merc Senior Member Join Date: Feb 2011 Location: Buchanan, MI Posts: 676	Re: OLD Offy heads - 18 mm Spark Plugs hitting valves Before Helicoils the fix for stripped spark plug threads was to thread the item to the next larger size.

06-15-2015, 04:33 PM	#10
bchrismer Member Join Date: Apr 2011 Location: Springfield, MO Posts: 77	Re: OLD Offy heads - 18 mm Spark Plugs hitting valves Walt, There's only one with steel insert. It's "#2. The others are threads in the aluminum heads. The biggest issue that I had with the "new" plugs is that that I don't own a 7/8" long well socket or spark plug wrench. I snugged them down finger tight, then used a short socket and a channel lock to tighten them up about 1/8 of a turn. Chap, the good news is that I had bought an "extra" starter solenoid, so I returned it and took the refund in spark plugs and a $3 and change credit back into my bank account. __________________ HotRodHundred.com Reliability Runs It's about the drive!!! StreetRodder.Net The FUN is in the RUN!!!

06-15-2015, 05:40 PM	#11
Jack E/NJ Senior Member Join Date: May 2010 Posts: 2,173	Re: OLD Offy heads - 18 mm Spark Plugs hitting valves >>>The biggest issue that I had with the "new" plugs is that that I don't own a 7/8" long well socket>>> Well, geez! Hurry up and go get one! 8^) http://www.homedepot.com/p/Husky-1-2...DP78/202934346 Jack E/NJ