A friend wants to build a turbo engine. Haven't decided on heads yet, might use my old B1 b/s heads, but I though the valve seats and exhaust valves need to be changed to something that handles the heat better. Right now the heads have new Manly Severe Duty valves. They are suppose to be good for 1,400 degrees? I have the standard seats that came with the heads, do I need to upgrade to something like cobalt seats?

How much power are you trying to make?

What fuel? How much boost?

Generally the exhaust valve is the critical one. I run the REV inconel in mine. I got hot enough to sag pistons and crack the iron heads at 20psi on the last motor. Valves came out perfect though and I reused them.

I'm running the stainless that Edelbrock put in the heads when they made them.So far so good. It's a pretty mild set-up with relatively low boost. I will put in the inconel exhaust valves when the heads come off to be put on the "good" engine.One piston in the new 470 is worth more than the whole 383 I have in there now.Don't want to poke holes in them with valve heads.

Manley has a valve that is USA made and they KNOW which alloy to send you for that application--none better Todd at Moparts Connection a sponsor here is best Manley dealer in the country--they will work! As in boats, boosted engines are Murder on exh valves and most turbo/boat engines fail because of exh valve failure--Those Eddy valves will drip off like a marshmellow over a camp fire when exposed to load/boost
Trust Manley tech advice/get part number-- and then order from Todd--they will be on your door step in a couple of days--use them until you retire then sell them

I have a bunch of misc parts I'm thinking of throwing together. A 383, 0.030" over that has old sealed power forged low compression pistons, and not alot of miles on the engine, the B1 B/S heads, a old Crower Compu-Pro cam (I think it is around 220@0.050 duration with a 112 LSA, and maybe 0.500" lift?)
I'd like to use E-85 for fuel, but race gas would be fine. I'd like to run at least 14 lbs of boost, but it's easy to get greedy with boost. The induction will likely be a single plane intake with EFI. I haven't sized any turbos yet, just curious if I will have to change valves and valve seats in the heads I have?
Any input is welcome as this would be the first turbo (gas) engine for me.

Just got done looking for aftermarket connecting rods for a 383 with stock stroke, rod length, and pin size, and the only one that comes up is the Eagle H-Beam rod?