Re: Valve seats and octane level

[jlandry@domain.elided (John A. Landry)]

The black helicopters hovering over the house recorded Paul Beijer +31 40
2736276 <Paul.Beijer@domain.elided> whispering:

>I own a '71 1310 with a 304 engine. The only way to run it on a daily basis
>with Dutch gass-prices is converting to propane. I read somewhere that IH
>offered an LPG factory option for the 304 as well as for the 345. Does this
>mean that my valveseats are allready suitable for propane?

I cannot answer your question as to what IHC did, but I do know that
propane fuels *can* cause valve recession if the air/fuel ratio is not
accurately maintained within a narrow margin.  Because propane burns so
clean, there are no additive deposits to build up and protect the valves or
valve seats.  Propane can heat the exhaust valves to a greater degree than
gasoline.  If you're planning on doing a propane conversion, you really
should insure you have hardened valve seats.  If you cannot afford to
install the hardened valve seats and you retain a duel fuel capability,
then be sure and use one of the several aftermarket additives designed to
reduce valve recession in your gasoline (when you do run it).

>If I run it on gasoline, what octane level should I use?

If you're trying to save money, then use the lowest octane rated gasoline
which will not cause the engine to detonate under the conditions in which
you operate the engine.  If you feel you have to use a higher octane
rating, you should also try different brands of gasoline before you give up
and switch to the next higher octane rating.  Here in the USA, the octane
rating at the pump is the average of the RON (Research Octane Number) and
he MON (Motor Octane Number).  This pump rating is known as the ((R+M)/2)
method.  The spread between the two test methods varies by gasoline
producer and region of the country, so various gasolines do vary in
performance.

When a manufacturer specifies a particular ((R+M)/2) octane rating for a
particular vehicle in the owner's manual, this is the *minimum* recommended
acceptable octane rating derived under careful testing conditions.  It
doesn't necessarily mean *you* can get away with using that same octane.
Also, as an engine ages, usually after only several 1000 miles, the minimum
octane requirement begins to climb.  This is typically caused by carbon
deposits in the cylinders.  Other causes which can lead to increased octane
requirement are things like wear in the distributor advance mechanism.
Every engine is going to be different to some degree, so you just have to
try different gasoline brands and octane ratings and see what works best.
There is no benefit whatsoever to using a higher octane rating than needed
to prevent pre-ignition and detonation in a properly tuned and maintained
engine... with the exception that some manufacturers add better detergents
and fuel system cleaners in their more expensive high octane blends.  But
you can add a bottle of fuel system cleaner to the tank periodically
yourself and save money.

>Compression ratio is
>not that high (8.19:1), so I would expect that I can run it on regular.

If your engine is in good mechanical condition and in proper tune, you
should be able to run on the standard lower octane fuels.  But if you push
the engine hard, you may need to use a higher octane fuel to guard against
detonation caused by higher heat and ignition advance.

Take care,

John
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