Manley exhaust valves and hardened seats

I have a set of Manley valves I was going to use to rebuild a set of 906's, 2.14 / 1.81

They are Race Series Pro-Flo necked down valves.

Should I have the shop put in exhaust valve seat inserts ?

I don't know if it matters much for longevity on the intakes, but on the exhaust side, maybe so ?

If you use hard seat inserts, what lasts longer, the seat or the valve ?

In my case I'm using a mild hydr cam with light spring pressures, but I'd like the valve job to last.

I think it's always a good idea to install hard seats on the exhaust when unleaded gas is to be used.

Depends on how you want to drive it, and what fuel or additives you run through the engine. Unleaded fuel only cause issues on the exhaust side, no need to install seats on the intake side. What happens is that the valves and seats on the exhaust run hot enough that the valve will pull microscopic bits of metal off the the seat, and eventually you will get what is called valve reversion. The seat sinks in the head. If you run race fuel it has lead in it and fuel additives that have lead in them lubricates the valve face so it will not pull out metal from the seats. also exhaust temps have a big part to play in how much reversion or sinking of the seats, and how fast you will see it. Higher performance and lean fuel ratios advanced timing all will raise exhaust temps. I tell people if you have a show car and drive a couple thousand miles a year, just dump some additive in every once and a while. If you have a race car and run race fuel, don't worry about it. If you want to take your car on the hot rod power tour, then get some hard seats installed. All stock iron heads after about 1974 have flame hardened seats which is supposed to fix the reversion issue, it does NOT, I have torn apart many newer engines with flame hardened seats and many high mileage engines have seat reversion. Hard nickel chrome seats like are used in aluminum heads and retrofitting older cast iron heads solves this issue. One thing is that in a performance vehicle where you want all the flow you can get, sometimes the shape of the hardened seat may cause some issues in the port and reduce flow, so you may loose some performance. I say this because many machine shops will simply cut the old seat and press in the ring and leave a pretty good ridge in the port. A little die grinder work will help, but does not always fix the issue as it really changes the shape of the short turn radius.

Thanks Gents,
I think I'm going with seat inserts.

How much will that cost versus a set of later model heads? Risk of dropping seat?

i have one set of heads with manely valves and seat inserts; no issues. one set of '906's i drive on with ferrea valves and inserts; no issues. all alum heads have some sort of insert. i wonder if seat failure is do more to the installer or how the user treats the head,....

i wonder if seat failure is do more to the installer or how the user treats the head,....



that is a good question.