Joined: Thu Oct 13 2005, 04:41PM
Location: Da swamp
Posts: 8
Actually the lead thing is true. The lead combined with the valve heat causes a chemical reaction with the cast iron of the cylinder head forming oxides that locally harden the iron in the valve seat. The depth is negligible, but its enough.
Usually what is happens is that the head previously run on leaded performs fine when unleaded is used, then suddenly goes bad after a fresh valve job. The valve job simply cut away the layer of hardened iron since the depth of the hardening was not much at all.
So if you have old heads that have never had a valve job, either don't give them a new valve job or give them new hardened seats.
BTW - Lead is not a lubricant for valves as some believe, its only function for the valve seats was to be part of the chemical reaction to harden the seat. <span class='smallblacktext'>[ Edited Thu May 11 2006, 04:39PM ]</span>
the victors use an offset intake rocker iirc(i.e. expensive).it is hard to beat the eddies for value.the 452 and 906 have the largest intake runner from the factory.all the open chamber heads(68-up)flow about the same in stock form.
