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Discussion Starter #1
i have a 327 engine my 67 camaro, 9.1 CR, comp cam xe274, vortec heads, edelbrock vortec performer rpm, 650 dp, flamethrower hei, turbo 350 trans, 2800 stall, 4.10 gears. i set my timing with vacuum plugged at 18 initial, when i plug vacuum advance back in, it goes to 43, i use manifold vacuum, does 43 seem high, i was thinking around 30 or 32 at idle would be good with vacuum, do i need a different vacuum can? thanks
 

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Discussion Starter #3
it runs so much smoother with manifold vacuum.
 

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If you add another 18° of mechanical on top of the 43° initial+vacuum you could have problems. I would limit the vacuum advance to about 15°, about 10° less than you have now. This will provide you with about 51° advance under light loads, and it should work well.

You don't need a different vacuum can, you just need a method of limiting the travel of the can you already have. You can see some examples at:

http://www.kendrick-auto.com/ignition.htm
 

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Discussion Starter #5
i contacted kendrick, they suggested a 10 degree can. would that be 10 at the distributor or the crank?
 

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i contacted kendrick, they suggested a 10 degree can. would that be 10 at the distributor or the crank?


This was more in line with what I was thinking. It limits the travel of your existing can. Vacuum cans are usually rated in distributor degrees.
 

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Discussion Starter #7
i asked kendrick about the limiter, he said it would be easier just to change the vacuum can? if the vacuum advance is a 10 degree can, it would be 20 at the balancer, is that right, i just need to add about 15 degrees to my 18 initial.
 

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Discussion Starter #9
i actually have a pertronix flamethrower hei on my motor, i will have to check number on can, i know i have a 25 degree increase when i hook vacuum advance up, it goes from 18 to 43 when its at idle, way to high.
 

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If you hooked it up to ported vacuum where it is usually connected (above the butterflies), it would not jump that much at idle since there would be no vacuum until the throttle opened. It's odd that yours would run better on full manifold vacuum as that usually causes issues.

Also, adjustable vacuum cans are cheap. Yours may already have one. Look in the hole in the can with a flashlight and see if you can see a hex head for an allen wrench.
 

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Discussion Starter #11
motor runs alot better with manifold vacuum, smoother idle, quicker throttle response, read john z and lars timing articles, im just trying to find a vacuum can that will give me about 12-15 more advance at idle
 

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motor runs alot better with manifold vacuum, smoother idle, quicker throttle response, read john z and lars timing articles, im just trying to find a vacuum can that will give me about 12-15 more advance at idle
What's your manifold vacuum reading at normal idle? You want a can that's fully-deployed at least 2" Hg. less than that. If your existing can really adds 25*, it's a real oddball - most only add 14*-16*, which is what you want.
 

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Discussion Starter #13
i have my initial set at 18 with vacuum plugged, and when i plug into manifold vacuum it goes to over 40 at idle, thats what i thought, kinda odd, i know it would run alot better with a different one, is there a part number for vac advance that would give 14-16 at idle. thanks.
 

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i have my initial set at 18 with vacuum plugged, and when i plug into manifold vacuum it goes to over 40 at idle, thats what i thought, kinda odd, i know it would run alot better with a different one, is there a part number for vac advance that would give 14-16 at idle. thanks.
You can put a mechanical limiter on it and make it anything you want at idle.

What kind of distributor do you use?
 

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Discussion Starter #15
pertronix hei
 

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Discussion Starter #17
i will double check and see if it does.
 

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Discussion Starter #18
onovakind67 was right, i do have a adjustable vacuum advance, so i fired motor up and got it warm, with vacuum plugged i made sure i had 18 initial, then plugged in vacuum and it went to 43, so i turned down vacuum advance with 3/32 allen wrench until i had 32 at idle, i still have to check total advance, am i doing this right or going in the right direction?
 

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I thought when you adjusted the vac. can with the allen wrench you were limiting the mech advance, if I read the pertronix owners pamphlet right?
I thought the only way to change up vacuum advance was buying a can rated for what your motor pulls at idle (vacuum).
 
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