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TSM Timing Specs

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67 Marlin View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 67 Marlin Quote  Post ReplyReply Direct Link To This Post Topic: TSM Timing Specs
    Posted: Oct/18/2017 at 10:45pm
My 1967 TSM cites distributor degrees for mechanical advance. Does it really mean distributor degrees or was the number cited actually the crank degrees? I have the high compression 343 to the right in the photo below. A forum member advised me to be careful with too much initial advance because the stock distributors had about 30 degrees of advance built in, which got me thinking about my TSM. Strange things happen when you start thinking...

My dial back timing light reads 17 degrees of mechanical at 2,500 RPM. I have initial set at 10 and it works pretty well, though I thought it would be nice to have more than 27 total when the distributor is rebuilt. If the TSM's 13 to 15 distributor degrees equates to 26 to 30 crank, then how come I'm not even close to that? I assumed the TSM was citing crank degrees because 17 is close and the RPMs are close. Figured maybe it's worn a bit at the stop and allowing a couple extra degrees. If anything is sticking or too grubby in there (it's the original assembly), could the mechanical be reduced by as much as 9 to 13 degrees?

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FSJunkie View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote FSJunkie Quote  Post ReplyReply Direct Link To This Post Posted: Oct/19/2017 at 11:23pm
Those specifications are in distributor degrees and RPM, both of which are HALF of what the crankshaft sees. If the distributor is advanced 5 degrees at 1000 RPM, then that is 10 degrees and 2000 RPM at the crankshaft.

For those specs given, your maximum advance in crankshaft degrees and RPM is 26-30 degrees at 4400 RPM. With that advance curve, you will want an initial timing setting of 5 degrees, no more than 10.

The factory timing specs given there are actually really close to optimal for all-around performance.  
'66 Marlin: 327/T10/3.54 Twin Grip
'72 Wagoneer: 360/TH400/3.31
'73 Ambassador: 360/TF727/3.15
'77 Hornet: 232/TF904/2.73
'84 Eagle: 258/TF904/2.73
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67 Marlin View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 67 Marlin Quote  Post ReplyReply Direct Link To This Post Posted: Oct/20/2017 at 10:07am
Thank you FS. To follow up on this so I advance my knowledge (pun intended)... when I adjusted it to 10 degrees advanced by viewing the timing marks, that was going by crank degrees, correct? So, if the mechanical was working right, I'd have 36-40 crank degrees of total timing (too much). My dial back says only 17 mechanical, so I'm okay with 27 total at 10 initial. This is the first time I've had a dial back timing light. I'm assuming it reads crank degrees. If so, I have to figure out why the mechanical advance isn't working right. I revved it up to about 3,500 RPM and it wouldn't go beyond 17 mechanical at about 2,400 RPM.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ccowx Quote  Post ReplyReply Direct Link To This Post Posted: Oct/20/2017 at 10:16am
The distributor mechanism has a number stamped on the underside of where the weights are that gives the total in crankshaft degrees. Usually it is three digits such as "724" or "530" or similar. You can see this number with a mirror. The last two digits are the total degrees advance. See the distributor sticky at the top of this message board for photos of what I mean.

I would clean the advance mechanism for sure. With all of the whining about points that goes on, I have personally had far more trouble with this mechanism than I have the points!

You want to have your total timing be around 34-38. The stock dissy is probably advancing around 30 degrees or so. That is why they usually suggest around 5 degrees btdc initial timing, ie 5+30=35 total.

It is intended that you will have it hooked up to manifold vacuum for the vacuum advance. This will give you an additional 12-16 degrees of timing at idle for a total of around 17-20 initial and a similar increase at cruise. Many prefer ported vacuum for all out performance, but with a stock set up it should work well with manifold vacuum.

If you have left the rest of the engine stock, that should put you in the ballpark. You might want to consider getting an aftermarket spring and weight set such as Mr. Gasket 927G to increase the rate of advance a bit. Performance seems best if the timing comes on fully in the high 2000 rpms to low 3000's.

I hope that helps!

Chris
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ccowx Quote  Post ReplyReply Direct Link To This Post Posted: Oct/20/2017 at 10:25am
Just a quick add in to answer your questions. Your timing light and marks read in CRANK degrees, your TSM lists DISTRIBUTOR degrees, as FS says.

Again, check here(http://theamcforum.com/forum/distributor-1967-to-1974-application-info_topic32011.html) for a better understanding of what distributor you have. It may not be the original, as I discovered when first trying to time my car, back when the earth was young.....

Chris
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