Hi Frank,
I've been running a lucas PI for around 5 years on unleaded. The only
problems I had were at the change over between the leaded and unleaded
fuel. The mixture of the two different sorts of fuel melted every o-ring
and seal between the fuel tank and engine. I had to do a complete rebuild
of the system. Fortuanately, the fuel company paid for it. The only ones
that weren't damaged were the hardened rubber in the banjo's on the
metering unit.
Friends of mine who don't use their cars as regular transport made a clean
switch from leaded to unleaded and had no problem with damaged seals.
There are a couple of companies in the UK capitalising on the unleaded
changeover by suggesting that the metering units need the lead for
lubrication and that owners will have lots of trouble unless they get a new
"lead free" metering unit. My understanding is this is basically rubbish.
The Tetraethyl lead in the fuel only lubricates after combustion.
There is a special seal for the PI pump motor shaft which may need to be
removed. This is available from the UK. Pretty much all the other orings
are available from the local engineering outfit.
Since replacing the damaged o-rings and seals, I've done around 100,000
km's with no further problem on the unleaded.
Personally I think unleaded fuel is an improvement over the leaded. My only
real gripe is the petrol companies in NZ buy unleaded fuel with very high
quantities of aromatics (benzene, xylene, tolulene etc) which evaporate
lowering the octane of the fuel. One has to be careful where one fills up,
because if the petrol station tanks are getting empty, the octane may be
lower than what it should be and on the high compression PI cars this can
be a real pain. The other down side to the aromatics is they are fairly
carcenogenic which is a bit of a worry to those living in smoggy areas.
Since the change, the car exhaust system lasts longer. With leaded fuel, I
would have to change the rear muffler at least once a year (the leaded fuel
is full of wonderful scavenging by-products like sulphuric acid which
doesn't do the exhaust much good!).
As far as the engine valves seats, the general advice seems to be to run on
unleaded with a suitable additive (Valvemaster is the most common brand
here in NZ). I have had a couple of problems with the valve master as a
major component is kerosene which fouls the plugs if doing a lot of round
town running. There is another brand (whose name evades me) which is
basically a pill which one drops into the tank. This seems to burn a lot
cleaner than valvemaster.
I have not been able to convert my PI to unleaded valves and seats due to
the large size of the valves. As I understand it, the later cars
(CRxxxx)had smaller valves and can be re-machined with no problems. The
earlier cars (CPxxxx) had larger valves and as a consequence, it is
difficult to fit the valve seats reliably. The problem is that due to the
lack of metal, the interference fit of the valves can fail (leading to very
bad things happening to the internals of ones engine).
Sorry this has been a bit long winded, but I hope it is helpful.
Regards
Bernard Robbins
71 2500PI
73 TR6 PI
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