Small chamber head

[JERSEYJOE]

If I use the early small chamber head with 1.625 exhaust valves on my 401 will the lack of hardened valve seats cause a problem using unleaded fuel? I have long heard that the lack of hardened valve seats would result is a rapid wear and loss of the seat sealing surface. ?????????

Any truth to this? If so when did they start using the hardened seat material??

Is it practical to have all the exhaust seats replaced with hardened ones?????

[tufcj]

I had hardened seats put in my 291-C heads, along with 1.68 stainless valves. I think the hardened seats were $15 each, installed at the same time the heads were done.

AMC used a high nickel content cast iron in the heads (and blocks) and a lot of people get away without running hardened seats.

I know they were using hardened seats when unleaded gas became mandatory in 75-76, possibly before that.

Bob
tufcj

[JERSEYJOE]

Thanks. Not worried about the cost as much as the horror stories I have heard about replacement seats that fell out..


Not sure if I want to risk it. I wanted to run the early heads because I want to run roller rockers. Is it the lack of lead that causes the seats to wear?

[tufcj]

Yep. The lead actually built up on the seat/face area and cushioned the valve as it closed (at least that's what I was told).

I have 2 sets of early heads that have had hardened seats installed. The set in my Jeep have over 50K miles on them with no problems. The set on my AMX are only at about 2K. I think as long as you use a quality machine shop, there will be no problems.

Bob
tufcj