Head Casting numbers

Classic short-frame models

Head Casting numbers

Postby Otis » Wed Sep 11, 2019 12:01 pm

I recently came across a set of heads that were on a 69 XLCH with casting numbers ending with -57X. Any ideas why the X?
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Re: Head Casting numbers

Postby spacecoast » Thu Sep 12, 2019 7:32 am

Well the 69-71 had bigger intake valves, 1 15/16". Perhaps the x signifies that change.
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Re: Head Casting numbers

Postby sportyparts » Thu Sep 12, 2019 1:35 pm

Do the spark plug holes look raised for a long reach spark plug?
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Re: Head Casting numbers

Postby Otis » Thu Sep 12, 2019 3:19 pm

No, standard spark plug holes unlike XR heads.
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Re: Head Casting numbers

Postby mikeslemmon » Thu Sep 12, 2019 3:46 pm

'70 and '71 heads have 1 15/16 intake valves but I don't know if this has anything to do with the X
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Re: Head Casting numbers

Postby Ferrous_Head » Thu Sep 12, 2019 4:42 pm

I've had several sets of the heads with the "x'. couldn't see any major differences but ...

I think they made changes to the ports in 69. After the race department spent a lot of time looking at port velocities and flow I suspect the results were incorporated into the stock heads. This would have required new cores. But I have no way of verifying that.
"I know only too well the evil that I propose, but my inclinations get the better of me."
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Re: Head Casting numbers

Postby jOe » Thu Sep 12, 2019 4:44 pm

Could be a toolroom I.D. for an engineering sample, prototype or some other sort of non production unit or sample.
I’ve run across similar X markings in gun collecting .
Just a wild guess.
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