3998993 head question

[Michael C.]

Can anyone tell me whether the 3998993 heads with a C 73 casting date had hardened valve seats? I'd like to know whether I can run them on unleaded fuel without adding an additive or damaging the seats. Thanks!

[John H.]

Re: 3998993 head question

I wouldn't worry about it - valve seat recession with unleaded fuel is pretty much a myth, unless you're towing a trailer at 100mph all day long. The additives don't do anything except eat the plating off the inside of your float bowls and lighten your wallet.