Morris Minor Owners Club

Confused... Again.
My Haynes and BL manuals disagree on which piston (either 1 or 4) should be at TDC on the compression stroke when you insert the distributor drive. Which one is it? (948cc - not that it should matter!)

And...If the timing marks on the cam drive gears line up,the valve timing is right, correct?

And, if you have no. 1 piston at TDC on the compression stroke then shouldn't the distributor rotor be pointing at no.1 firing point on the dist. cap?

If all that is correct, the baseline ignition timing (and the valve timing) is right, isn't it?

1) #1 or #4 depends on which cylinder is under compression.
Have a look at the rocker arms on #1 at TDC. If they are at the point of rocking (one opening as the other is closing) then #4 is under compression. If both valves are fully closed with freeplay, then #1 is at the top of the compression stroke & so the rotor button should point to #1.
2) If the cam timing is correct, then the valve timing will be correct also. On some reground cams, the valve timing might be out slightly which is why vernier gears are used to optimise it in some cases.
3) Yes, taking into allowance a bit of advance.
4) Yes. the engine will fire up on these settings. Once you know it starts, then set the ignition timing more accurately.

Is this a new camshaft ?
If so, it will have to be run/bedded in.

It's a secondhand cam from a mini 1100.

If I follow the instructions from the manual(s) - I've tried both the Haynes and BL - I'm getting the rotor pointing to the cylinder following the one it should be (ie for No 1 @ TDC comp - rotor points to No 3 in dist cap)

I've always taken No 1 on the dist to be the upper-forward quadrant. - (ie the first contact after the low tension lead in the anti-clockwise direction of rotation)

In that case, you need to rotate your distributor drive shaft. Be aware that the slot is offset (not dead centre).
If you don't want to do that, the just swap your HT leads around to suit the new rotor position.

Ok, I've double checked for the fourth time...

timing dots on the camwheels line up
notch in crank pulley lines up with TDC - big pointer on front cover
both valves on #4 closed
Valves on #1 rocking

therefore cyl No.4 is at TDC on compression

...and I insert the dist drive with the slot vertical and the small offset forward (I think that means the smaller 'half' of the circumference of the drive gear head to the front of the block)

the distributor winds up facing square on cyl 3 contact.

Looking at the distributor's offset drive, the stated 11 o'clock position, which is where it finishes when you insert it, 11 o'clock can't possibly be cyls 1 or 4 - is the manual wrong?

Shawn wrote:timing dots on the camwheels line up
notch in crank pulley lines up with TDC - big pointer on front cover
both valves on #4 closed
Valves on #1 rocking

therefore cyl No.4 is at TDC on compression

...and I insert the dist drive with the slot vertical and the small offset forward (I think that means the smaller 'half' of the circumference of the drive gear head to the front of the block)

Yes, the BMC manual has it like that.


When the manual goes on to fitting the distributor, it says fit the distributor when #1 is on TDC (so rotate the engine 360deg).
The pictures then show the rotor button pointing to the upper rear quadrant which must be the correct (original) #1 position which appears to be your #3 position.

Happydance!!!!! - the good ol' Scientific Publications (Australian) Manual had it right!

Working on Cyl No. 4 @ TDC on compression stroke, insert the distributor drive gear with the slot HORIZONTAL and the small offset uppermost. Rotor aims straight at No. 4 contact!!!

Thanks for your help Scott! - Saved me losing patience with the bugger a lot earlier than I nearly did!

It really doesn't matter where the slot is - just set the HT leads to suit. Does the engine start ok ?

Don't know yet - working on the bench at the moment - Will fit it in the next couple of weeks.

Once you have lined up an engine so that the number one piston is at TDC on the compression stroke the distributor drive in the 1098 engine goes in at a different angle to the distributor drive in a 948cc engine.

No logical reason why that should be - it doesn't matter!