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post #1 of 32 (permalink) Old Jul 16th, 09, 05:08 PM Thread Starter
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to much advance

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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post #2 of 32 (permalink) Old Jul 16th, 09, 05:09 PM
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Re: to much advance

Why are you using manifold vacuum?

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post #3 of 32 (permalink) Old Jul 16th, 09, 05:19 PM Thread Starter
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Re: to much advance

it runs so much smoother with manifold vacuum.
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post #4 of 32 (permalink) Old Jul 16th, 09, 05:22 PM
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Re: to much advance

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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post #5 of 32 (permalink) Old Jul 16th, 09, 05:51 PM Thread Starter
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Re: to much advance

i contacted kendrick, they suggested a 10 degree can. would that be 10 at the distributor or the crank?
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post #6 of 32 (permalink) Old Jul 16th, 09, 06:23 PM
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Re: to much advance

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Originally Posted by rkmjbad67 View Post
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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post #7 of 32 (permalink) Old Jul 16th, 09, 06:40 PM Thread Starter
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Re: to much advance

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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post #8 of 32 (permalink) Old Jul 16th, 09, 08:20 PM
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Re: to much advance

My Pertronix distributor came with a B-22 can - I recently switched to a B-28 can
What kind of vacuum are you seeing at idle and what kind of vacuum at steady cruise?

Lars paper will help you select the right canister
http://www.corvette-restoration.com/...c_Adv_Spec.pdf

you can cross reference the NAPA part number to ACDelco, etc

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post #9 of 32 (permalink) Old Jul 16th, 09, 08:54 PM Thread Starter
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Re: to much advance

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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post #10 of 32 (permalink) Old Jul 16th, 09, 09:16 PM
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Re: to much advance

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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post #11 of 32 (permalink) Old Jul 16th, 09, 09:58 PM Thread Starter
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Re: to much advance

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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post #12 of 32 (permalink) Old Jul 20th, 09, 02:09 PM
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Re: to much advance

Quote:
Originally Posted by rkmjbad67 View Post
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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post #13 of 32 (permalink) Old Jul 20th, 09, 02:30 PM Thread Starter
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Re: to much advance

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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post #14 of 32 (permalink) Old Jul 20th, 09, 02:57 PM
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Re: to much advance

Quote:
Originally Posted by rkmjbad67 View Post
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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post #15 of 32 (permalink) Old Jul 20th, 09, 03:01 PM Thread Starter
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Re: to much advance

pertronix hei
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