Morris Minor Owners Club

My A Series 1098 pinks under load when using unleaded fuel. I do use a castrol additive with octain boost. I have tried adjusting the timing between 5 deg B.T.D.C & T.D.C. with no luck. The engine was rebuilt 8000 miles ago & is fine when using original 4 star fuel. Any info on this would be a great help. Thanks Alex
E-mail: alexm2499@aol.com[ This Message was edited by: Alexm2499 on 11-03-2002 22:21 ]

Lo, the timeing for the 1098cc engine is
3degrees static,6degrees stroboscopic.
This is only a starting point, if it pinks there then retard it until it doesn't pink,
(eleven clicks on the knurled nut equals one
degree. When you reach a 'pinkless' setting
the question then is,does it drive well,does
it overheat,and is the consumption normal?
If so then it's set for your engine. (my 1098
on unleaded, with NO additives, is fine at
one degree BTDC).
Have you tried a different make of fuel?
If problems persist then check the springs
on the advance weights on the distributor,
one may be off.
Willie

Hi
I agree with Willie. I remember when they changed from 948cc to 1098cc and at that time Petrol was being rationlised(Goodbye Benzol?). The 1098cc engine did not like it!
A major guarantee job was to remove cyl/head and grind off "Peak" of heart shaped combustion chamber. Apparantly this "Peak" used to glow and ignite unburnt fuel at the WRONG time causing pinking! Also engine would "Run on" after being switched off!
I suspect there are still some cyl. heads with this design fault around. The 1295 head stopped this altogether.
Another "Happening" was the introduction of "Long nosed" sparking plugs,the self cleaning type. Some engines really hated them and would cause "Pinking" and missfire.
The old Champion( They reckon BMC. lived on Champion) plug N5 was OK. But we had to resort sometimes to the 1/2"reach ones. Weslake desgned the "Heart" shape chamber but it has problems at times.
The "Spherical" chamber designed in the
30`s was and still is the best?(Riley,Jaguar etc;).....Sorry for the Book...Ivor

Pinking can occur when the cylinder head needs decarbonizing. However it is fairly unusual for it to be that bad after only 8000 miles.

So to sum up if you retard it until pinking
ceases and it drives well then ok, but if it
then drives like an old pudding then the
pinking is probably caused by something in
the chambers glowing enough to pre-ignite the
mixture. Tuning 72 has probably hit the nail
on the head. I thought it was to improve flow
when the 'peak was ground off but it seems it
was to reduce preignition. This is probably
why you are having trouble because I understand that unleaded fuel makes an engine
run hotter which would make it more likely
to pink. Have you tried 'lead replacement
petrol'? Are you running a high thermostat.
Willie

So to sum up if you retard it until pinking
ceases and it drives well then ok, but if it
then drives like an old pudding then the
pinking is probably caused by something in
the chambers glowing enough to pre-ignite the
mixture. Tuning 72 has probably hit the nail
on the head. I thought it was to improve flow
when the 'peak was ground off but it seems it
was to reduce preignition. This is probably
why you are having trouble because I understand that unleaded fuel makes an engine
run hotter which would make it more likely
to pink. Have you tried 'lead replacement
petrol'? Are you running a high thermostat.
Willie

Thanks for the info. I have just dismantled my dissi and it has 18 deg. on the cam base!
I have read the topic on the degrees & printed off the 25D section on lucas web page.
The small springs on the advance weights were different sizes and one was loose. I have replaced them with 2 identical springs from another dist. I'll refit tommorrow. (sunday)

STOP!!! the springs SHOULD be different sizes and one at least is 'loose' i.e. it
relies on the end loops being tight enough
to keep it connected.
willie

Contained within the article at this website is an explanation of why the two springs are different and how the centrifugal mechanism works.

www.telusplanet.net/~chichm/tech/lucastuning.pdf