Ignition: timing help on a 1947 m-5

[rocketshoes]

I am putting in the distributer and plug wires, and setting timing on a rebuilt six. Here is what I think I must do, so please correct me if I am wrong. This is the stock straight six in this 1947 M-5 pickup. I want to find the timing mark on the damper. There are two center punch marks one above the other, toward the edge but on the front of the damper, inline as if you drew a line from the center out. These seem to coincide with the release of compression from number one cylinder past my finger held over the spark plug hole on the compression stroke as the marks come to the pointer. there are no marks on the side of the damper that would help with a timing light. I was going to put a mark on the side to help me, right where the marks are on the front. I have another old straight six, same vintage, same center punch marks, no markings on the side. Also have an M-15, bigger six in it. this has the center punch marks and on the side of the damper it has coinciding marks, at the same spot, saying IGN, which is where I am reading is the spot to set the timing, not necessarily TDC, correct? So, is this right? the center punch marks are the IGN spot? If so, why the front of the damper, how did they set the timing back in the day?

Also, why do some say to disconnect the vacuum advance, and bring the idle down to the lowest it will run to set the timing, I have always set timing with the proper idle, with the vacuum set up, like real running conditions...!!??

I am setting my distributer body and cap / wires with the mark at the pointer in front, and the rotor pointing to #1, with the points just starting to open. Lock down the vacuum advance collar. Run the wires to the plugs. Start it, and then adjust the idle then timing. I have set the points already.

[tbirdtbird]

When you time a motor you are setting the baseline timing only, usually somewhere between 5-10 degrees BTDC. The vacuum advance and the centrifugal advance add extra advance on top of the baseline timing, that is why the vacuum line is disconnected to set it. And at idle, the rotational speed of the distrib shaft is too slow to kick in the centrif. advance, thus insuring you are setting the baseline properly. Some later carbs had ported vacuum going to the distrib, which means you didn't have to disconnect the vacuum line, but most of the earlier ones did *not* have ported vacuum, and if you are not sure, you can *never* be wrong to disconnect it, and BTW be sure to plug the line temporarily else you'll have a vacuum leak and it will idle poorly if at all

[rocketshoes]

ok thanks. Well explained. However, still would like to know if the punch marks are the timing mark to set too, or just a TDC mark.

[nvonada]

I thought in 47 the timing marks were still on the flywheel. I could be wrong. I do mine with the vacuum advance disabled

Nathan

[rocketshoes]

wow maybe your right. never thought of looking at that. I was wondering what that hole was for. awesome. also, still wondering why disable the vacuum, if the original manuals for studebaker dont tell you to.

[rocketshoes]

also, I will probably figure this out when I get down to the shop, but is there just one mark on the flywheel for the timing? or is there marks for tdc, etc.? Thanks!

[tbirdtbird]

don't disable it if you don't want to, but it won't be right. back then it was universal knowledge to disable the vacuum amongst mechanics; kinda like people knowing they have to breathe to stay alive

[nvonada]

On mine there is one deep mark with "IGN" stamped next to it. There is another smaller one that might not be factory for TDC. Find the IGN mark and just line it up with the pointer. Which is a bit harder than it should be. There is probably a 3/8" gap between the plate and the flywheel so it is easy to get parallax errors. My 12V timing light works on the 6V system but it is very dim so I usually try to do this out of sun. I used a yellow paint pen to highlight the mark which helped too.

I tried timing with the vacuum connected and it was not right. If you got the idle down enough it might be close enough but it only takes a second to disconnect the advance.

[tbirdtbird]

Nathan, when I run into the issue of a 12V timing light on a 6V system I grab my jump box or maybe a spare 12V battery is laying around and run the light off that.dave

also the best way to time a motor is by ear, meaning keep advancing until it pings under load and then back off slightly

[rocketshoes]

I am not fighting for keeping it connected by any means. I appreciate all the advice. I feel dumb for going this long in my life and not knowing that. Thanks! Also, i did find the marks when i went down to the shop as far as the timing marks go.