01-17-2015, 09:20 PM | #1 |
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cylinder head
I just had a cylinder head planed for my Model A ,put it on torqued it down and went to put the spark plugs in and the holes are all over sized. Help, what have I got?
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01-17-2015, 09:33 PM | #2 |
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Re: cylinder head
Oversized as in worn out or just way to big? Are you sure you have the correct plugs? What is the make and number on the plugs and where did you get them? Any pictures of the head and plugs?
Charlie Stephens |
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01-17-2015, 09:40 PM | #3 |
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Re: cylinder head
I actually thought the head looked NOS. They are plugs that should work C4 Champion. I never even thought to check the spark plug holes, they looked good to me (not worn out).
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01-17-2015, 09:49 PM | #4 |
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Re: cylinder head
Have you tried another plug in one of the holes? Quality control is very poor these days. Maybe they are misidentified or incorrectly machined. Have you tried the plugs in another head? Are you saying they are just a loose fit in the holes? Pictures?
Charlie Stephens |
01-17-2015, 10:35 PM | #5 |
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Re: cylinder head
These plugs come out of a Model A, I have had Model A's for years and had a few parts around including heads and I picked this one because it looked NOS . I am not very good on this thing to send a pix but they look like a normal threaded hole but the plug will slip right through, not even close. (The whole plug won't slip through just the threaded part).
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01-17-2015, 11:20 PM | #6 |
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Re: cylinder head
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01-18-2015, 01:23 AM | #7 | |
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Re: cylinder head
Quote:
If the thread looks good then it's obvious that the holes have been tapped for a larger plug. The original holes are 7/8-18. Maybe the holes have been tapped for Heli-coils and the Heli-coils are not there. |
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01-18-2015, 01:43 AM | #8 |
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Re: cylinder head
x 2
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'31 180A |
01-18-2015, 01:56 AM | #9 |
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Re: cylinder head
I found a chart that calls out a 1 1/8" thread for a spark but I can't find any reference for a plug in that size.
As ednondclinton said maybe tapped for inserts.
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01-18-2015, 02:46 AM | #10 |
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Re: cylinder head
This is a Champion RS79N plug. 1-1/8" thread. Only available in heat range 3. $93.99 EACH. Several industrial engine heads used them through the early 50's.
Even if you spend the $$ for a set your connectors will not reach the towers. Get a different head. |
01-18-2015, 07:54 AM | #11 |
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Re: cylinder head
This problem is not holding me up I already have another head on and that one on the shelf with a note. I thought about them being tapped out for heli-coils but why would do all four.
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01-18-2015, 12:40 PM | #12 | |
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Re: cylinder head
Quote:
Many Model Aers would be in for a surprise if they would spray a solution of soapy water around the base of their spark plugs while the engine is running and watch the bubbles pop up. It would not surprise me if someone did all 4. One thinks of using a Heli-Coil only when a threaded hole has been stripped out but it's a different concept when considering having to hold high pressure like combustion. |
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