I have access to a distributor machine however in this instance it's more convenient to do the testing at my garage rather than where the machine is.
Has anyone tried to lock the centrifugal advance mechanism at 0 degrees? I'd like to do some testing on the vacuum advance using a hand held pump but I need the mechanical advance to keep from coming in while I'm testing on a running engine. This way I can see the point at which the advance starts and is complete as well as the total amount.
I've thought of using cable ties or electrical tape to bind the distributor shaft and advance plate together but I'm not sure if that would work or not.
Any ideas would be appreciated.

 

Why not just remove the weights and springs? The weights are what provide the centrifugal advance, if you don't have the weights in there, there is nothing to push on the advance plate.

 

Interesting that you whould suggest that as it was in my original post but I waited too long to submit it and was logged off. I forgot to include that bit when I re-wrote the question.
I had thought of that too but the two components of the distributor would still have to be bound together in the zero postion. Certainly it would be a lot easier with the weights and springs out of there.
Thanks.

 

Are you trying JUST to test the vacuum advance canister's curve? Then at idle the distributor shouldn't be 'into' the mechanical advance and simply hooking up the handheld vacuum pump should be all you need to do - if you're really that worried about it and have the lightest springs installed - either swap to the heaviest springs in the tuning kit or replace the spring with some safety wire (or similar) - then the weights won't move for sure.

 

take the weights off... make a sheetmetal plate to hold the pins in the same place relative to each other like the drag racers do when they lockout the timing..

it will look like this image i found after 2 seconds of typing into the google search box:



hell, a small zip tie holding the posts tight would probably be good, and you might have to only remove the springs to do it..

 

Thanks for the replies everyone.
Removing the weights/springs and securing the pins with a bit of safety wire or a cable tie sounds like it'll do the trick. It IS only a test as I'm suspicious of the calibration of the old Sunnen distributor machine at the shop. I have a fully adjustable vacuum advance mechanism for both set point and total amount. A run through the machine indicated that there was 12° of advance available with maximum vacuum applied. That's 24 crankshaft degrees. I'm not certain if there's that much available. So another test is required.

Yes I could have googled it but I like this method of searching too. It engages the 3rd gen community and I enjoy the interaction.
Thanks again.

 

Why take off the springs and weights at all...just wondering. If you have springs in it that don't start mechanical advance until - say, 1200 RPMs or so, couldn't you just hook up the vacuum can to full manifold vacuum at idle (well below 1200) and see how much advance it's giving with a timing light?

 

I've been experimenting with different springs and the current setup has 0° at 1200 rpm and 2° at 1400. I'm trying to determine the point at which the advance can starts to work and how much vacuum is needed to bring it all in. I would also like to verify the total supplied and compare it to the the distributor machine data.
With the mechanical advance active, what I found was that as I brought on the vacuum advance (using a hand held vacuum pump) the rpms would increase as you would expect and that was getting well into the mechanical advance side of things. I couldn't get definitive results.