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Author Topic: timing without a timing light*  (Read 28462 times)

Offline Grim 82

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Re: timing without a timing light*
« Reply #15 on: December 08, 2010, 04:29:09 pm »
This can explain it a lot better than I can: http://www.hotrodders.com/forum/distributor-tuning-theory-part-1-a-59033.html?highlight=DISTRIBUTOR+TUNING+theory

A full manifold source will be pulling vacuum at idle, a ported source will not. Unplug the hose and if it whistles and sucks air and engine rpm changes, it's full vacuum. That vacuum to the distributor will advance your timing a few degrees. There is a debate about using full or ported for the vac advance. My motor prefers a ported source, so that's what I use.

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Offline txchainsawgogi

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Re: timing without a timing light*
« Reply #16 on: December 08, 2010, 06:07:24 pm »
Seems to be pulling nonstop. Are there downsides to keeping the advance capped off? I've fiddled with it in the past and everytime I connected it, the engine ran like crap. I figured the new distributor would help but no.
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Offline txchainsawgogi

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Re: timing without a timing light*
« Reply #17 on: December 08, 2010, 06:20:48 pm »
Ahh ok so it needs to be hooked up. But why does it make the engine run so poorly when I connect it?
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Offline TexasRed

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Re: timing without a timing light*
« Reply #18 on: December 08, 2010, 09:22:35 pm »
Define poorly? If you mean detonating, then you've prolly got too much initial advance.
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Offline txchainsawgogi

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Re: timing without a timing light*
« Reply #19 on: December 08, 2010, 09:41:34 pm »
When I hook up the vacuum advance it makes the engine shake, and feels like its about to die. Driveable, but it feels off. It even sounds rough.
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Offline txchainsawgogi

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Re: timing without a timing light*
« Reply #20 on: December 08, 2010, 09:46:53 pm »
when you were explaining how to turn the distributor CCW until it pings, was I supposed to do this with the vacuum advance hooked up? Or capped off?
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Offline TexasRed

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Re: timing without a timing light*
« Reply #21 on: December 08, 2010, 09:54:35 pm »
Something sounds amiss. Did you also cap off the vacuum port on the carb when you cap the vacuum advance on the distributor?
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Offline Grim 82

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Re: timing without a timing light*
« Reply #22 on: December 09, 2010, 12:43:23 am »
Quote from: txchainsawgogi on December 08, 2010, 09:46:53 pm
when you were explaining how to turn the distributor CCW until it pings, was I supposed to do this with the vacuum advance hooked up? Or capped off?

If you are using manifold vacuum you would want to leave it hooked up when turning the distributor. If using ported vacuum it doesn't really matter because it won't be pulling in any advance at idle. You can get this to work, but I suggest that when you get the time, install the timing tab, verify TDC, and get a baseline on your timing to save yourself some trouble in the future.

Quote from: TexasRed on December 08, 2010, 09:54:35 pm
Something sounds amiss. Did you also cap off the vacuum port on the carb when you cap the vacuum advance on the distributor?
Agreed. The vac advance on the distibutor only reacts to the vacuum applied from the carb. It needs to be capped coming from the carb, not at the dist.
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Offline txchainsawgogi

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Re: timing without a timing light*
« Reply #23 on: December 09, 2010, 07:35:36 am »
My vacuum advance line goes to the three pronged thing that screws into the thermostat housing. Should it? That's how it was when I got it :/
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Offline burbboysgc

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Re: timing without a timing light*
« Reply #24 on: December 09, 2010, 09:03:32 am »
Im pretty sure that three prong port on therm housing has something to do with vacum activating once engine gets to certain temp.
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Offline Grim 82

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Re: timing without a timing light*
« Reply #25 on: December 09, 2010, 09:19:54 am »
Do you have any ports on the carb that are capped off and not being used? I'm not sure but I think there is only 1 port on most q-jets that are ported (no vacuum signal at idle). Find it and hook it to your dist. Some engines don't respond well to full manifold vacuum, and if that's what you were running it could be why it runs rough with it hooked up. You can change the hose routing and optimize it later but for right now I would just get a dedicated timed vacuum supply to the distributor from the carb if you can. Just make sure you don't bypass any vital systems. You may have to use a tee connector.
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Offline txchainsawgogi

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Re: timing without a timing light*
« Reply #26 on: December 09, 2010, 01:05:13 pm »
Ill take pics of everything when I get home so I can explain it better.
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Offline TexasRed

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Re: timing without a timing light*
« Reply #27 on: December 09, 2010, 04:36:11 pm »
Get me a decent job in Austin, and I'd come help ya out  ;)
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Offline txchainsawgogi

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Re: timing without a timing light*
« Reply #28 on: December 09, 2010, 04:40:19 pm »
Haha id have to get me one first. There are actually a lot of places hiring right now.

Pics on the way!
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Offline txchainsawgogi

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Re: timing without a timing light*
« Reply #29 on: December 09, 2010, 06:16:47 pm »
Ok here they are. Middle prong blocked off and distributor blocked off. Not sure if the tubes are how they should be...that's how they were when I got it.




« Last Edit: December 09, 2010, 06:21:59 pm by txchainsawgogi »
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