My two cents,
Leaded fuel left a lead-based deposit on the exhaust valve and seats,
providing lubrication. When it was mandated out, most companies took
the cheapest way out and inductively hardened their normal exhaust
seats. Inductive hardening is nothing mor than using equipment with a
high radio frequency field to cause the seat to get very hot, very
quickly. It is focused on the seat alone, and does a fair job of "local
heat treating".
This is production equipment, and quite expensive./ Buying a head circa
1972 will get you this feature, plus a larger combustion chamber (lower
compression ratio), ugly bumps in the intake ports, and a exhaust gas
recirculating castings, which need blocking.
I have been told by reliable sources that if the original heads were run
on leaded fuel, the seats are already protected, and don't need
anything. If, however, you are going to grind the surface away, like
putting in bigger valves, you better consider inserts on th exhaust
side. Don't forget the silicone-bronze guides, screw-in ARP studs,
matching ports to gasget on both sides of manifold interfaces, hardened
guides for high lift cams, enough clearance on teh pistons for the new
lift, roller tip rockers, PC seals, new springs, chrome-molly keepers,
chrome stem one piece valves, excess material removal in ports, etc.
Some $900 - $1200 later your going to have a great set of heads, or you
can get some new aluminum ones from Twisted Wedge, Edelbrock, or Ford
Motorsport for a little less.
Oh yes, don't think this can be done with the engine in the car,
especially notching the pistons, so you'll have to pull it. Up or down
is a whole other thread.
Now, as long as the block is on the bench ...........
Steve
--
Steve Laifman < One first kiss, >
B9472289 < one first love, and >
< one first win, is all >
< you get in this life. >
_/_/_/_/_/_/_/
_/ _/_/_/ _/_/_/ _/
_/ _/ _/ _/ _/ _/ _/_/_/_/
_/ _/ _/ _/ _/ _/ _/
_/_/_/_/_/__/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/
_/
_/_/_/
|