Dynamic timing conundrum

[Grumpy21]

Something is very odd here

Car runs ok but vac advance has gone and I’m intending to fit electronic so I’ve got a nice replacement dissy from a source I trust and have used before in lots of classics.

As Morris put the timing marks in a daft place at the bottom of the crank pulley I’ve always followed a similar procedure. Get the engine at TDC zero degrees and make two marks at a more convenient place, one on the crank pulley the other on the timing chain cover. Much easier to see and accessible for a strobe. Then I can simply dial in my advance.

Now I’ve done all that I’m getting 20 degrees advance - that can’t be right can it? Engine doesn’t pink and it pulls as good as I expect it should. That’s at 600 rpm too. Timing is scattering so there is wear hence changing the dissy.

Nothing removed yet. Want a decent base setting before I change anything.

Cheers

Gary

[Grumpy21]

Even more peculiar. Old fashioned static timing (turn the engine until the light across the point just comes on) shows 15-20 degrees advanced.

Wonder if it’s had a different front cover or pulley wheel at some point?

Any other ideas?

[philthehill]

Remove the distributer drive shaft (the one that mates with the camshaft) and check the condition of the skew gear on the bottom of the shaft. I have seen the skew gears so worn that the timing is all over the place.
The other area of wear is the timing chain & gears - excess wear can also cause the timing to wander.
A photo of your crankshaft pulley would be beneficial.

[Grumpy21]

Thanks Phil

There’s a little play in the dissy but not enough for me to think the skew gears are over worn. I’ll try to get a pic but access isn’t great is it? Anything in particular?

Mechanical advance seems ok but vac advance is certainly kaput holding no vacuum or movement in the baseplate.

[philthehill]

A picture of the pulley to determine its style would be sufficient.

[Grumpy21]

Just taken these. Sorry but the access isn’t great. In the first you can just make out the notch on the pulley and see it’s well advanced on the 10 degree pointer

[philthehill]

Thank you for the photos. The pulley looks to be standard Minor.
All I can further suggest is that the distributer drive shaft has been fitted one tooth out. You will have to remove the distributer to check whether the shaft has been fitted correctly. See wksp man for details of correct fitment.

[Grumpy21]

Hmm, guess that’s a possibility. Thanks Phil

[geoberni]

I must admit I have around the same, about 20 ish deg.
I've always felt the Dissy was a bit out, but as the car runs fine I've never got around to trying to mess with it.
I've loads of experience years ago with 'regular' Dissy fitment on Fords & Vauxhalls, where the cog is directly on the end of the Dissy, but this system of having to set up a drive gear/shaft first is all new ground. So I've just left it along for now.

I plan on taking the engine out to change the rear plate, something I intended to do 2 years ago and still haven't, a long story that phil many remember ( viewtopic.php?f=4&t=67378&hilit=engine+ ... 20#p642783 ).

Perhaps I'll investigate the Dissy drive set up then.

[Grumpy21]

Just had a look at a couple of pics of the drive gear. Looks like it has 10 teeth so each tooth = 36 degrees. Can’t work out any number of teeth out that would result in a reading of 20 degrees advanced.

[Grumpy21]

Update. New electronic dissy in and running. Made no sense in the end so just set it to tdc and swapped everything over and set it to 20 degrees on the strobe.

Much smoother and pick up is much crisper too.

Have to wait until Thursday for a little drive.

Thanks all

[Grumpy21]

update to the update

Just driven a very happy 30 miles and the improvement is very noticeable. Much smoother idle, vastly improved pickup and acceleration and more torque for those uphill struggles in North Wales.

Highly recommended upgrade!