I'd like to add some of my findings regarding the 810 heads.
But first a disclaimer. I've only looked at one set of 810 heads.
These heads, last time they were on an engine, were installed with what might have been fel pro gaskets. This tells me they might have been refurbished at some point, but I really can't tell. And if they where, the inlet valve guides where not touched and are still tight. (which sorta points against them being worked over) The ports where also cleaner than the low mileage 193 heads I compared them to.
Alright.
These particular heads have hardened exhaust seat inserts and pressed in cast(?) valve guides. The exhaust valve stems are as previously mentioned 3/8"
Inlet valve stems are standard size.
Both inlet and exhaust valves have rotators. The casting at the spring pockets are different so the pockets are not as deep as the exh pocket on a 193 head. Another casting difference is that there is way more meat around the exh. valve guide inside the port. Despite that MotorTrend has measured them (the 810 heads) to flow 146 Exh @.500 (& 166cfm Inlet)
Hardened Exhaust Valve Seat insert.
I think
@Schurkey said in another thread of mine that he had never seen a chevy head with a single angle valve job. Well, here is one
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Valve guides look way different, notice how the actual casting appear to just have a small stubb boss which has been machined to take the insert.
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Valve guides and deep exh spring pocket on 193 head.
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