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| | | | Joined: Nov 2000 Posts: 1,966 'Bolter | | 'Bolter Joined: Nov 2000 Posts: 1,966 | Help me remember: do 1948 and older 216 and 235 have 10 mm spark plugs? I should know this. Thanks.
Professional Novice
| | | | | Joined: Feb 2004 Posts: 29,780 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,780 | The 1946 model 216 I just disassembled does- - - - -I'm wondering if it would be possible to drill and tap those heads for 14MM plugs? The 10MM variety are scarce, expensive, and prone to cross-threading. It should be pretty simple to set up my valve seat and guide machine with the air-float work table to do an accurate job of opening up the plug holes to the bigger threads, as long as I don't hit the water jacket in the process of enlarging the holes.
Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
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| | | | | Joined: Sep 2001 Posts: 29,269 Bubba - Curmudgeon | | Bubba - Curmudgeon Joined: Sep 2001 Posts: 29,269 | Help me remember: do 1948 and older 216 and 235 have 10 mm spark plugs? I should know this. Thanks. Yes: the spark plug diameter changed from 10mm to 14mm in 1949 model year. The start/top of a "model year" is not a specified date. | | | | | Joined: Feb 2001 Posts: 1,096 'Bolter | | 'Bolter Joined: Feb 2001 Posts: 1,096 | I think that 10mm plugs were just a war time thing . I know the early 216 , thru to '40 have 14mm plugs . | | | | | Joined: Sep 2001 Posts: 29,269 Bubba - Curmudgeon | | Bubba - Curmudgeon Joined: Sep 2001 Posts: 29,269 | Thanks for causing me to look this up, Dusty
1929-1932 non-metric (7/8" x 18 thread)
1932 18 mm
1933-1940 14mm
1941-1948 10 mm
1949- 14mm | | | | | Joined: Nov 2000 Posts: 1,966 'Bolter | | 'Bolter Joined: Nov 2000 Posts: 1,966 | Thanks Tim. Thanks all. There is so much misinformation on the internet. I’ve probably spread some of it myself. The first motor vehicle I owned was a 40 Chevy car my grandpa gave me when I was a teen. I took the engine partially apart. It had flat top pistons, 14 mm plugs and a tall side cover. I always believed it was a 216. I guess it was a 49-53.
Last edited by Frank50; 11/01/2020 12:49 PM.
Professional Novice
| | | | | Joined: Mar 2005 Posts: 1,636 'Bolter | | 'Bolter Joined: Mar 2005 Posts: 1,636 | Looking at the chart 1940 was 14mm..... the 10mm started in 1941 if i am reading the chart right. (I wasn't around then so I can't tell from personal knowledge). | | | | | Joined: Jan 2020 Posts: 620 'Bolter | | 'Bolter Joined: Jan 2020 Posts: 620 | Personally I would stay with original plug size. I have never had problems with the 3/8ths (10 mm), plugs, granted they may cost more but I have so many AC's in stock. Doc.
Currently making 1954 3100 better than new and Genetics
| | | | | Joined: Sep 2001 Posts: 29,269 Bubba - Curmudgeon | | Bubba - Curmudgeon Joined: Sep 2001 Posts: 29,269 | | | | | | Joined: May 2015 Posts: 11,052 Housekeeping (Moderator) Making a Stovebolt Bed & Paint and Body Shop Forums | | Housekeeping (Moderator) Making a Stovebolt Bed & Paint and Body Shop Forums Joined: May 2015 Posts: 11,052 | Specialty, Marine? I guess Stovebolts are Special. 
Kevin 1951 Chevy 3100 work truckFollow this saga in Project JournalPhotos 1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car) Busting rust since the mid-60's If you're smart enough to take it apart, you darn well better be smart enough to put it back together. | | | | | Joined: Nov 2000 Posts: 1,966 'Bolter | | 'Bolter Joined: Nov 2000 Posts: 1,966 | I think 1940 was the last year 216s had domed pistons. That’s why I think mine (all those years ago) had a 49-53 engine.
I guess a 40 block could have been fitted with flat top pistons and a later head...
Sorry guys, too much time on my hands.
Thanks for all responses.
Professional Novice
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