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PostPosted: Sun Oct 02, 2016 9:30 pm 
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As i posted in my build thread nobody reads anymore i had an issue with an ebay distributor with a crappy adjustable vac canister that had a mis-shapen allen head so i couldnt adjust it and it threw all the timing in as soon as i touched the throttle.
Disconnected the vac advance and it runs great on just the bit of mechanical advance built in.
Wondering if i am better off getting a quality adjustable vac advance canister or going full mechanical advance? Any reasons why any of you prefer one to the other?

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PostPosted: Mon Oct 03, 2016 1:24 pm 
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Are you still running the stock computer?

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PostPosted: Mon Oct 03, 2016 1:31 pm 
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I went back and looked at your posts and I guess not. With the cam you have you should just stay with mech advance and taylor it to your needs. You can add springs and/or heavier weights to come in early. You should be running about 8 - 10 BTDC at idle and up to about 28-31 by 3200 rpm. You'll have to play with the springs and weights to get there but it's easy.

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PostPosted: Mon Oct 03, 2016 3:07 pm 
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Yeah i am at 10* at idle right now. Need to check where it goes at full advance gonna rig up a template to match the toothed 0-12* marker on the 4.3 and extend it to about 36* so i can see just where it goes now and with vac.
No computer just a carb and a distributor.
I am starting to think you are right. I have a mechancal secondary carb im worried that the big changes in vacuum would make tuning a vac canister a pain.
Any real downsides to mechanical? Little less sensitive to throttle?

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PostPosted: Mon Oct 03, 2016 3:37 pm 
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You don't have to rig anything. Figure out the size of the dampner then divide 360 by the product of 3.1416*dampner diameter. if it's a 7" dampner then 3.1416*7=22.9912 then 360/22.9912= 15.6°per inch. So if your looking to be around 30° by 3200rpm make a mark @ 2" off TDC. Don't get this confused with crankshaft degrees as that is 720 because of the stroke. The timing is measured in degrees before top center which is relative to one turn of the crank as opposed to cam timing which is relative to 2 turns. It is also demonstrated this way in that when you check every cylinder for it's firing position it will be 90° behind the previous piston accounting for 2 full turns of the crank although they respectively fire before top dead center.

8"= 14.3°/inch
7"= 15.6°/inch
6"= 19.1°/inch

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PostPosted: Mon Oct 03, 2016 4:01 pm 
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Good idea that makes a lot more sense

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