Reply to "Fuel type"

my 2nd / 3rd hand understanding is that the 351C heads require a shallow seat insert to avoid hitting water during the machining operation. most shops have their own 'go to' seat inserts that are probably fairly thick & substantial & know that those inserts will hit water so they simply say it can't be done

a fellow on 351C.net & other forums, Bill Diehl, runs a stock class bracket racing car is Heavy into reworking his heads within class rules & has successfully replaced all 16 seats as the basis for his air flow work. Steve K has also just recently replicated Bill's valve seat replacement recipe

it can be done with the right inserts, if you need to?

if you have stock valves & are looking to replace them before they dictate your next new engine, you can simply order a slightly larger diameter valve & move the actual seat angle out to fresh material

Yes I've had the displeasure of a valve head separation

and Yes I agree with George that The Sky Is Not Falling in the valve seat recession dept.

the removal of lead from the fuel blend did cause a need to tune differently, as did the introduction of EFI with its' recipe change to optimize fuel atomization from injectors (not necessarily good for carbs) ... now we have another major change to the blend with the various concentrations of ethanol. the fuel blend is constantly changing, watch your Specific Gravity!