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Crankshaft ignition pointer

Posted: Sun Mar 16, 2025 9:31 pm
by Boxprod
Every factory manual I have seen, as well as Haynes and Clymer, shows the ignition timing being set with a strobe and a special pointer screwed into the end of the crankshaft.
Does anyone actually have one of these factory-supplied pointers?
Does anyone still make or sell such a simple thing?
I only ask because it would make timing my 1974 350 a complete doddle. I've got a timing disc, but I'm not completely sure about running the engine with 6 inches of spinning disc close by (although you could say that a small pointer isn't far from the knives that stuck out of Boadicea's chariot).
I have had a go at making my own, but I reckon that a degree or two out of whack between the tip and the tang which fits into the slot on the crank would render it pretty useless...
So what I thought is that if anyone has one, then maybe I could get a replica made - even 3D printed.
Then again, after static timing it, I could go back to the old-fashioned, seat of the pants road test, tweak, road test, tweak and so on.
Enjoy the spring sunshine while it lasts.
Pete.

Re: Crankshaft ignition pointer

Posted: Sun Mar 16, 2025 10:15 pm
by LaceyDucati
Pete
I have one, but I'm not convinced it is a very accurate device. It relies on the slot in the crank being machined accurately and being a good fit to the tool. Add to that the tools accuracy of manufacture and the relative small radius and parallax error to the cover. I prefer an accurately set disc or pointer to TDC.
Never used the original tool, maybe I should try one day just to see.

Regards Nigel

Re: Crankshaft ignition pointer

Posted: Mon Mar 17, 2025 10:53 am
by Jordan
This is my home made strobe timing tool. Disc diameter is 80mm.
I made pin-prick sized depressions on the clutch cover after determining TDC, so there's one for that and another at the required full advance position. Nobody has ever mentioned noticing these marks, but they are adequate for the purpose of timing.

Re: Crankshaft ignition pointer

Posted: Mon Mar 17, 2025 11:28 am
by ranton_rambler
I printed a disc from the internet on paper which I glued to a bit of aluminium sheet. I use a piece of M8 threaded bar screwed into the end of the crankshaft.
Once it's screwed in I can find TDC with my piston stop and then set the disc and lock it in place with a couple of nuts. There are no markings on the clutch cover so I just draw an arrow with a marker pen and wipe it off afterwards.
It needs to be quite close as it tucks in behind the brake pedal.
Ian

Re: Crankshaft ignition pointer

Posted: Mon Mar 17, 2025 11:52 am
by Boxprod
Thanks for the help.
I take Nigel's points about potential inaccuracy coming from both manufacturing error and parallax - so probably best to set the static timing as accurately as I can with a degree wheel.
To which end, can anyone confirm (or estimate) the static figure for my engine, which is a '74 Mototrans-built 350, rebuilt by John Wittman with a green-and-white cam and a 32mm Dell'orto (and a 32mm inlet tract)...?
I've got a proper degree wheel and a piston stop, so it should all be a doddle.
Fingers crossed.
Pete.

Re: Crankshaft ignition pointer

Posted: Mon Mar 17, 2025 12:56 pm
by mrkprsn
In this post I described how I time two different NC singles. The timing data for all single are in there. I also use an unconventional way to time.

viewtopic.php?f=3&t=3846&hilit=timing

Re: Crankshaft ignition pointer

Posted: Mon Mar 17, 2025 1:28 pm
by bendik
LaceyDucati wrote:Pete
I have one, but I'm not convinced it is a very accurate device. It relies on the slot in the crank being machined accurately and being a good fit to the tool. Add to that the tools accuracy of manufacture and the relative small radius and parallax error to the cover. I prefer an accurately set disc or pointer to TDC.
Never used the original tool, maybe I should try one day just to see.

Regards Nigel


I first used a stopper to set TDC at the degree disc and then actually checked the timing turning the engine over using the dyno and a strobe light to accurately see where I was. The markings on the electronic ignition was off so it was nice to know exactly where I was.