I have read some of the debate on lead substitutes and valve recession, and
admit I
don't know the answer. I've seen some head that suffered serious valve seat
erosion, but I don't know that it was due to lack of lead. I play it safe and
use a
lead substitute. It does nothing for the octane, just lubricates the valve
seats.
It's an inconvenience for local driving, but could be a real hassle on a
cross-country trip. The real answer is to have a cylinder head shop install
hardened valve seats.
If the engine doesn't knock, whatever octane you are using is fine, and you
might
even try the next lower octane to save some money. Some of the performance
engines
of the '50s and '60s had high advertised compression ratios, but if you ever
measure
the actual CR, you will probably find it is lower than advertised. Most of the
'50s
engines were actually low compression by today's standards. Again. if it
doesn't
knock, don't worry, be happy. If you hear just a bit of ping on hard
acceleration,
the octane is just adequate. Altitude does make a difference on octane
requirement. Higher altitude requires less. You may be fine driving around
Colorado, but need an additive when visiting Los Angeles.
Joe Mopar wrote:
> Hello all,
> I have a question about how you all handle new fuel in your older cars. Of
> course there is the problem of lead vs. unleaded, but I am also wondering
about
> octane levels. I know that for some of the hotter engines in the fin cars the
> engine compression ratio was very high. (Like 11:1 and more) In Colorado
> premium pump fuel is 91 octane, hardly correct for 11:1 comp. What do you
guys
> do? Is there lead/octane additives that you like? Does anyone know if
altitude
> has an effect on this as well? Am I wrong, and 11:1 does fine on 91? Just
> curious,
> Peter
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