Re: Unleaded Petrol

[Glenn Merrell <gmerrel@domain.elided>]

Hello Ian,
	As to the question of hardened seats vs not, it is a crap shoot.  Regarding the
use of unleaded, you might want to visit the VTR Web site
http://www.vtr.org/maintain/valve-seats.html 
for an article titled "Triumph Valve Seat Recession and Unleaded Fuel" by B.
John Mitchell, designer of the Rover/Buick 3.5L V8 engine, written 15 March
1996.

	You may experience a hotter running temperature since unleaded burns hotter. 
Expect a reduction in power and throttle response. 

	Warning signs, well, if a valve burns through, the engine will misfire under
load.  In my humble  inexperienced opinion, I do not believe you are going to
have a problem unless you race the car and keep the rev's up over 5k RPM.

	Timing will need to be slightly retarded a few degrees from spec.  UK spec is
12 degrees advance (Before Top Dead Center BTDC), where in the US, timing is
more like 6-8 degrees BTDC.  You may need to experiment a bit depending on your
fuel preference and driving habits.  I advance the timing until it pings, then
back it off a couple of degrees, my preference.

In My Humble Opinion, yours for Speculation...

Happy Holidays,
Glenn  Merrell
Triumph Stag Register USA VP

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Ian Baird wrote:
> 
> Hi Guys
> 
> Sorry about the subject name, but I don't wish to start a revolt again, I
> just need some advice.
> 
> Firstly my Stag is an early 1970 model, and I have just started to use
> unleaded petrol, so far so good.
> 
> What I need to know is should I alter the timing, and if so by how much ?
> 
> Also does anyone know if early stags, engine no. 114,  have the hardened
> valves/seats, as has been suggested, in other circles from here, that it
> may, because the stag was designed for America principally.
> 
> Also what are the warning signs I should look out for if there are any
> problems with unleaded.
> 
> Thanks in advance.
> 
> Ian Baird
> MK1 '70 Stag