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I have a set of heads for my 101 and one head has 3/8 head bolt holes with a 5/8 spark plug hole and the other has 7/16 bolt holes with a smaller plug hole around 1/2 or so. Is the smaller bolt hole head an earlier head or is it for 37" engine?
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Travis, I recall reading something about the changeover in headbolt size....hmmm, I'll look! But the 37" Scout heads have 6 bolts, and the 45" have 7 bolts.Pisten Bully is Harry Roberts in Vermont.Comment
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O ya that's right Harry I forgot about the 37" having six bolts. I appreciate you looking into it for me.Comment
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...waiting for someone with better knowledge to chime in, but 3/8" is early 37ci and 45ci, apparently using studs in lieu of head bolts. When the switch to 7/16 occurred is what I was looking for ...but failed to find. The 101 R&O shop manual simply says "The 45 cu. in. cylinder has seven head bolts 7/16 diameter. Early on they were 3/8 inch."
My 37ci from 1930 has 7/16 bolts (6 of 'em)
Happy Thanksgiving Travis!Pisten Bully is Harry Roberts in Vermont.Comment
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Ok it sounds like I have an early and late head,I kind of thought that but wasn't positive. The thing throwing me off is the different plug size.
Harry you have a great thanksgiving also.Comment
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the 750cc motor was originally developed in late 26 and released in 1927 with a 7 bolt head. Specifically made in response to the Police request for something faster. It was still in the short frame i belive. Over here we call them Police specials i do not know if they were sold to the public. These 1st 750 motors had 7 bolt heads and 3/8 bolts. Its my understanding that when the 750cc was released as a 101 the head bolts were upgraded to 7/16 i know i have 6 and 7 bolt head sets in stock with both 3/8 and 7/16 studs in stock. hopefully that helpsComment
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