Re: Unleaded Petrol

[Glenn Merrell <gmerrel@domain.elided>]

Hello Tim and All,
	Well, I have to agree, as the Triumph Stag Handbook, Edition #9, copyright
1976, published for "all markets" clearly states on page 70:

Recommended Fuel
	The engine is designed to operate on fuel having a minimum octane rating of 97
(Research Method):  This is equivalent to the British Standard 4-star rating.

I believe that BS 4-star rating refers to high octane leaded fuel composition?

In my Humble Opinion, Yours for Speculation

Regards,
Glenn  Merrell
Triumph Stag Register USA VP
*J*O*I*N**Y*O*U*R**L*O*C*A*L**T*R*I*U*M*P*H**C*L*U*B**T*O*D*A*Y*
*Member of:
*VTR, RMTC, TSC USA, TSR, SOC
*73*S*T*A*G*****************************************************



Tim Buja wrote:
> 
> Ian Baird wrote
> > With regard to unleaded  petrol and our stags.
> >
> > It has now been confirmed in the S.O.C. magazine, that the stag 3.0L
> > engine was designed to run on unleaded.
> >
> > This has been confirmed by Jim Parkinson, Chief Engineer for design
> > and developement of all Triumph and Rover engines, upto 1976.
> >
> > The only thing he says is that the later MKII engines may need their
> > timing retarded, but for the rest of us MKI drivers, it's safe for
> > unleaded driving.
> >
> > So maybe this will put an end to the rumours of valve seat and valve
> > deterioration, and expensive non-essential modifications.
> 
> Sorry, but I'm afraid we can't just ignore what Triumph had to say
> about this.  The following quoted material is from the Emission Control
> System Warranty (for 1973 models), and is bound in the center of my
> Stag Driver's Handbook, publication part number 545106/73 (c) British
> Leyland Motor Corporation Limited 1972, 1st edition 5M/11/72 (North
> American Type Market):
> 
> "Use of Unleaded Fuels.  Regular use of unleaded or low-lead gasolines
> may cause difficulties with the engine and will result in malfunctions
> of the Emission Control System.  The anti-wear additives found in
> leaded gasolines are necessary to avoid difficulties of this type.
> While an occasional tankful of unleaded or low-lead fuel is unlikely
> to cause such problems, conditions attributable to sustained use of
> such fuels will not be considered 'defects'."
> 
> Also mentioned in the text preceding this paragraph is the statement
> "engine valves must be regularly inspected, and replaced where
> necessary, in order to make sure that emissions will not rise to
> unacceptable levels."
> 
> The Emissions Warranty requirement for valve inspection may actually
> be a check for recession, since this was written at a time when
> low-lead fuels were about the only thing on the market.  Lead levels
> in US petrol were significantly reduced starting in 1971. Unleaded
> fuels began appearing about 1974 in preparation for the 1975 models
> which could no longer meet emissions standards for the warranted 5
> years/50,000 miles without the use of a catalytic converter, which
> would be poisoned by the use of even low-lead fuels.  Leaded
> automotive fuels seem to have disappeared in the early 1980s,
> leaving 100 octane low lead fuel only available for aviation use.
> 
> Everything I've seen so far seems to indicate that the Stag heads
> are suitable for unleaded fuel, but the OEM exhaust valves are not.
> Replacement of the OEM exhaust valves with TR7 exhaust valves, part
> number 155524, will make the engine mechanically compatible with
> unleaded fuel.  You may have to retard the timing to avoid spark
> knock under load.  My Stag (.040 over bore) knocks (pinks) at part
> to full throttle with 87 octane (R+M/2) unleaded fuel when using
> the 4 deg ATDC dynamic / 10 deg BTDC static timing settings per the
> ROM.  Knocking is significantly reduced with the use of 89 octane
> fuel and the same timing setting.
> 
> As I've previously posted here, TR7 exhaust valves have the part
> number stamped on the valve stem just below the groove for the
> valve spring retainers.
>   _________  <---top of valve stem
>  /         \
> |           |
> |___________|
>  \_________/
>  /_________\
> |           |
> |1 5 5 5 2 4|
> |           |
> ~~~~~~~~~~~~~
> 
> Tim Buja - Rockford, Illinois, USA - 80 TR8, 73 Stag, 72 TR6