Subject: RE: [Healeys] Octane ratings
Steve,
Valve jobs used to be the bread and butter of most repair shops. Since the
advent of unleaded fuel I've done only a few and not due to seat recession.
It's more apt that your head was already damaged from leaded gasoline or by
lead additives. I tell folks to NEVER use lead additives or they will be
doing head repair. It certainly doesn't hurt to use stellite valves and
hardened seats on the exhaust valves. Especially under racing conditions.
However, most old classic cars are never driven hard enough or long enough
to warrant them.
As to your machinist, he too may not have realized that the unleaded
fuel/seat recession scare never panned out. Probably much like the ZDDP
stories may not be a huge issue either. My opinion there is that the oil
companies simply will not sell a lubricant that will cause large scale
damage to consumer's vehicles of any age.
The damage to your pistons (lands) was due to too much ignition advance
causing detonation (which can not always be heard) It is FAR more important
to check for total advance than initial. Have your distributer curve checked
~ every five years for advance performance.
Dave
frogeye@porterscustom.com
Mike, when I had my BJ8 head rebuilt, the machinist told me that I had
significant valve recession. He showed me my head, in which all of the
exhaust valve faces were flush with the adjacent head surfaces, and a
rebuilt head from another type of car where the valve faces were
significantly proud of the head surfaces. When I got the head back, the
valves were like the other head.
I haven't seen any Healey engine head but my own, so I don't know. Was my
machinist correct or not?
I don't know how my car was used before I got it, but I put about 36,000
miles on the engine before I rebuilt it, mostly long distance cruising on
regular leaded until it disappeared and then regular with a lead substitute
until the rebuild (93 octane premium since). I figure the engine had
between 80K and 100K at the time of rebuild. I rebuilt it because I was
losing pieces from the piston edges, apparently due to the rings breaking
up.
Anyway, I went with the no-lead head modifications.
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