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Head Casting numbers

PostPosted: Wed Sep 11, 2019 12:01 pm
by Otis
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?

Re: Head Casting numbers

PostPosted: Thu Sep 12, 2019 7:32 am
by spacecoast
Well the 69-71 had bigger intake valves, 1 15/16". Perhaps the x signifies that change.

Re: Head Casting numbers

PostPosted: Thu Sep 12, 2019 1:35 pm
by sportyparts
Do the spark plug holes look raised for a long reach spark plug?

Re: Head Casting numbers

PostPosted: Thu Sep 12, 2019 3:19 pm
by Otis
No, standard spark plug holes unlike XR heads.

Re: Head Casting numbers

PostPosted: Thu Sep 12, 2019 3:46 pm
by mikeslemmon
'70 and '71 heads have 1 15/16 intake valves but I don't know if this has anything to do with the X

Re: Head Casting numbers

PostPosted: Thu Sep 12, 2019 4:42 pm
by Ferrous_Head
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.

Re: Head Casting numbers

PostPosted: Thu Sep 12, 2019 4:44 pm
by jOe
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.