For a stock 383, is it necessary to put hardened valve seats on the intakes, just the exhaust or both?

Since you've gotten no replies, I'll bite. Intake no. Exhaust is debatable and may depend on intended usage. I know of some very knowledgeable/reputable guys who say you don't need it, especially for an engine that won't see too many miles.

I have torn down a 300K mile 383 with 906 heads which had been running on unleaded for the past 25 or so years. It has some noticeable valve depression on 2 or 3 exhaust valves. Not sure if lead additive was used often, but I know it wasn't always used. 300K on a set of heads isn't too shabby.

Whats the background on the situation/what is the engine for?

452 and later heads came with hardened exhaust seats.

I do know that cast iron now days is much harder than it was years
ago(easy to spot by the ring ridge in the bores).. in the old engines
that I tested back in high school both valve would sink.. the exhaust
would go about double the intake.. but if this is just a week end ride
I wouldnt worry a ton about either.. but if you plan on decent mileage
I would do the exhaust seat
EDIT
I wish I could remember when they changed the nickle content
in the iron so I could give you a better answer

Thanks for the responses.

This is my anal restoration car. Wont see a lot of miles. Engine builder says to do the exhaust but not the intakes.

Don't know if I should overrule him and spend the extra $200 to get the intakes done too.

I hope your anus gets well soon after the restoration!

R.

Wouldn't installing stainless steel valves eliminate that issue. ?

It is the seats that get beat out and a stainless valve wont help that. It is a crap shoot on the old iron heads, I have seen some with the exhaust so sunk, it was a miracle it even ran. I would just do the exhaust, it always worked for me.

Put them on the exhaust only. Seen enough of them w/ valves sunk really far into the head that I'd never run a set w/o hardened exhaust seats.