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After staring at the pictures for awhile, (I'm good at that) I can take a guess at the numbers.
The top picture is the front head. I think the numbers are 16705-80A 242 175 10-81. Looking around on the internet, it appears that 16705-80A is a good number for the front head. Of course 10-81 speaks for itself. The 242 and 175 number makes me think of valve sizes.
The bottom picture is the rear head. The number is a bit easier to see. The number looks to be 16707-80A 12-81.
Your right about the lines. They are not factory. The heads were drilled and tapped for those. So were the extra two holes that are now plugged. They were for dual spark plugs or compression releases I assume.
the right thing to do is to have all the guides changed to the now cast iron that are long lasting and are machined for seals any thing else you will be back asking about smoking
I don't know John. The valves and guides look awful big for a Shovel.
Note the drain back tube.
Been awhile since I've been inside the heads of a Shovel. Maybe everything just seems big. I've got this head striped down and the valve seats are just a hair from touching. So I'm thinking bigger valves and bigger valve guides. If so, not sure I want to change the guides out.
I guess the only thing weird around here is me. I measured the intake and exhaust valves after I cleaned them. They are the stock size. 1.980" intake and 1.750" exhaust.
A friend called me tonight and checked in on how the Shovel is coming along. He said there is a tool that cuts a groove for the valve seals.
Then again, maybe the seals aren't needed. With the original drain back holes still open and the outside drain back holes/hoses added on, maybe the "oil pileup" in the rocker boxes is nonexistent.
Still, I have to admit that the combustion chambers were a bit oily and so were the inside of the pipes. I'm pretty sure the front cylinder had a blown head gasket too.
Overall, it's not a bad idea to have valve stem seals if you have the clearance.
Do what John suggested, dump the bronze guides and have the new cast iron ones put in and yes you want the seals trust me otherwise she'll be smoking all the time and when hot you'll think you have a BBQ going on.
you had to use alloy retainers to get enough travel ( bottom of the retainer to the top of the guide ) to install even an A andrews cam in original guided 81 heads
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