Help! Ignition Timing 2.25 Petrol

Recently been having running trouble with a IIa 2.25.

Checking the ignition timing, i have conflicting data from workshop
manuals:

II Manual Says:

7.0:1 engine
75 RON 3deg Before
80-85 RON 6deg Before

IIA manual says:

7.0:1 or 8.0:1 engine
75 RON TDC
80-85 RON 3deg Before
90-95 RON 6deg Before

III Manual says:

7.0:1 engine
75 RON TDC
80-85 RON 3deg Before

8.0:1 engine
80-85 RON 3deg AFTER
90 RON TDC

Considering all these engines are the same, use supposedly the same
distributor, and have the same valve timing, why the hell is there so
much difference? Some of the figures i can accept as being "optimal"
and varying slightly (vis 3deg or 6deg for 85RON) but how come the
setting for a IIa with 90RON is 6degrees before, but for a III with
90RON it is TDC?

To complicate matters further I have a 1965 IIa engine which has a
Lucas 45D distributor fitted, from a 1975 vintage engine. Now what do
i set it to?

Cheers

Alex

"Alex" <[email protected]> wrote in message
news:[email protected]...
> Recently been having running trouble with a IIa 2.25.
>
> Checking the ignition timing, i have conflicting data from workshop
> manuals:
>
> II Manual Says:
>
> 7.0:1 engine
> 75 RON 3deg Before
> 80-85 RON 6deg Before
>
> IIA manual says:
>
> 7.0:1 or 8.0:1 engine
> 75 RON TDC
> 80-85 RON 3deg Before
> 90-95 RON 6deg Before
>
> III Manual says:
>
> 7.0:1 engine
> 75 RON TDC
> 80-85 RON 3deg Before
>
> 8.0:1 engine
> 80-85 RON 3deg AFTER
> 90 RON TDC
>
> Considering all these engines are the same, use supposedly the same
> distributor, and have the same valve timing, why the hell is there so
> much difference? Some of the figures i can accept as being "optimal"
> and varying slightly (vis 3deg or 6deg for 85RON) but how come the
> setting for a IIa with 90RON is 6degrees before, but for a III with
> 90RON it is TDC?
>
> To complicate matters further I have a 1965 IIa engine which has a
> Lucas 45D distributor fitted, from a 1975 vintage engine. Now what do
> i set it to?
>
> Cheers
>
> Alex

You could do it the old way get the engine nicely warm slack off the pinch
bolt and slowly adjust for best revs then tweak the throttle to make certain
she doesnt bog down if alls well nip up the pinch bolt and have a test run
if she pinks retard the ignition a couple of degrees and check again. I
admit its not a book accurate way to do the job but if you are running
non-standard equipment or there is wear in the dizzy you are likely to get
the best result that way .
Derek

In message <[email protected]>
Alex <[email protected]> wrote:

> Recently been having running trouble with a IIa 2.25.
>
> Checking the ignition timing, i have conflicting data from workshop
> manuals:
>
> II Manual Says:
>
> 7.0:1 engine
> 75 RON 3deg Before
> 80-85 RON 6deg Before
>
> IIA manual says:
>
> 7.0:1 or 8.0:1 engine
> 75 RON TDC
> 80-85 RON 3deg Before
> 90-95 RON 6deg Before
>
> III Manual says:
>
> 7.0:1 engine
> 75 RON TDC
> 80-85 RON 3deg Before
>
> 8.0:1 engine
> 80-85 RON 3deg AFTER
> 90 RON TDC
>
> Considering all these engines are the same, use supposedly the same
> distributor, and have the same valve timing, why the hell is there so
> much difference? Some of the figures i can accept as being "optimal"
> and varying slightly (vis 3deg or 6deg for 85RON) but how come the
> setting for a IIa with 90RON is 6degrees before, but for a III with
> 90RON it is TDC?

The engnes are very similar, but the disrtibutors are not necesserily
(Early Lucas, Late Lucas & Ducellier, plus any aftermarket ones fitted).

Setting it to TDC will get it running, after that ensure the points gap is
correct and move the distributor until it runs nicely!

>
> To complicate matters further I have a 1965 IIa engine which has a
> Lucas 45D distributor fitted, from a 1975 vintage engine. Now what do
> i set it to?
>
> Cheers
>
> Alex

Richard

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try the engine with 6 degs advance , if it pinks under heavy load [ ie
uphill or full throttle] or runs on after you stop it then go to 3
degs advance .

if this runs ok then leave it as it is and carry on timing it this way
..

basically the more advance you use the more power it will make and the
cooler it will run , but you need to combine this advance figure
against the octane rating of the petrol used.

i think unleaded is 95-97ron but with a 7-1 comp engine you can run it
on almost anything as thats a fairly low compression and will run
unleaded just fine , but if youre worried about using unleaded and
valve recession then buy a fuel additive something like MILLERS VSP or
CARPLAN NITROX .

you need higher octane for higher advance settings , but really this
only means in high compression [above 9-1 ] and race type engines .

the higher octane rating is for high compression engines to stop them
pre igniting and melting pistons .
basically lead used to be used to make higher octane , higher octane
gives fuel a deadening effect to stop the high comp engines from firing
before the piston reaches top dead , ie trying to make engine fire
before piston reaches top and then trying to force piston backwards in
effect .

youre 1975 distributor is pretty much same as the old one , it may have
different advance curve on it but that shouldnt cause you any problems
..

what you get when you set the static advance is the engine at a
particular revs and advance setting .

as soon as you push throttle and the inlet manifold vaccum drops ,
this will then pull the advance diaphragm on the distributor and add
more advance to the timing , it may add say something like 38degs at
2000rpm .

so for instance at 2000rpm youll have 38degs distributor advance and 6
degs static advance , which gives you 44degs total advance .

this is the point at which the ignition sparks before the piston
reaches top dead , so that the fule is ignited at the right time in
order to maximise power etc .

the more advance you run , the more likely you are to get "pinking"
occurr .

pinking is a problem because it can make the engine "diesel" [like and
air rifle if you put oil in chamber] , and very high pressures and
temps can occur within the combustion chamber which melt the piston
tops or etch/burn them away , and this is not what you want to happen .

so basically if you have a timing light , set the static advance when
engine is ticking over to 6degs advance and see how it runs .

if it runs fine , doesnt pink when under load etc and doesnt overheat
then you can keep it as it is .

if you find it does pink then back off the advance 3 degs until the
time comes it does run ok .

you also need to set the dwell angle but this will be shown in the
manual and is in effect the same range for all the 4cyl engines .

you could do with a gunsons dwell meter and a good strobe light , it
will pay for itself time after time .

there is probably a hex nut sticking out the side of dizzy for
adjusting the dwell angle of the points while engine is running , if
not youll have to set the points gap using feeler gauges and then check
the dwell , and adjust gap as necessary in order to get correct dwell
angle .

the tuning needs to be set at whatever the handbook says idle revs
should be , then adjust the advance and set/check dwell angle, and
adjust either as reqd until correct values are for both .

the gunsons autoranger dwell/tachometer can be used to set revs ,
dwell etc , 58 quid approx .

www.mgocaccessories.co.uk/acatalog/Gunsons.html


hope this helps you .

"Alex" <[email protected]> wrote in message
news:[email protected]...
> Recently been having running trouble with a IIa 2.25.
>
> Checking the ignition timing, i have conflicting data from workshop
> manuals:
>
> II Manual Says:
>
> 7.0:1 engine
> 75 RON 3deg Before
> 80-85 RON 6deg Before
>
> IIA manual says:
>
> 7.0:1 or 8.0:1 engine
> 75 RON TDC
> 80-85 RON 3deg Before
> 90-95 RON 6deg Before
>
> III Manual says:
>
> 7.0:1 engine
> 75 RON TDC
> 80-85 RON 3deg Before
>
> 8.0:1 engine
> 80-85 RON 3deg AFTER
> 90 RON TDC
>
> Considering all these engines are the same, use supposedly the same
> distributor, and have the same valve timing, why the hell is there so
> much difference? Some of the figures i can accept as being "optimal"
> and varying slightly (vis 3deg or 6deg for 85RON) but how come the
> setting for a IIa with 90RON is 6degrees before, but for a III with
> 90RON it is TDC?
>
> To complicate matters further I have a 1965 IIa engine which has a
> Lucas 45D distributor fitted, from a 1975 vintage engine. Now what do
> i set it to?
>
> Cheers
>
> Alex

You could do it the old way get the engine nicely warm slack off the pinch
bolt and slowly adjust for best revs then tweak the throttle to make certain
she doesnt bog down if alls well nip up the pinch bolt and have a test run
if she pinks retard the ignition a couple of degrees and check again. I
admit its not a book accurate way to do the job but if you are running
non-standard equipment or there is wear in the dizzy you are likely to get
the best result that way .
Derek