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07-04-2017, 03:32 PM | #1 |
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Adjustable vac advance for Chevy L6 distributor
Greetings
Does anyone make an adjustable vacuum advance for a stock Chevy L6 distributor? I've looked at all the usual suspects and can't find one that is similar to the one shown below. Notice the hook shaped arm: I annotated the image to indicate where an adjustable stop might possibly be added. Worst case scenario would be to fabricate an adjustable stop near the canister-arm interface per the pic above. |
07-04-2017, 03:58 PM | #2 |
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Re: Adjustable vac advance for Chevy L6 distributor
I've seen them for hei's but not for a six.
Curious!! Why do you need to limit it? |
07-04-2017, 04:00 PM | #3 |
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Re: Adjustable vac advance for Chevy L6 distributor
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07-04-2017, 05:41 PM | #4 |
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Re: Adjustable vac advance for Chevy L6 distributor
A stop there will limit Total vacuum advance, but it won't change the amount of vacuum needed for vacuum to begin the advance.
>>Too much vac advance at idle/<< If you are having vacuum advance at idle, the idle rpm is too high and/or the carb isn't adjusted properly. Have you checked for vacuum leak? What is base timing?
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'67 GMC 2500, 292, 4spd, AC |
07-04-2017, 05:55 PM | #5 |
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Re: Adjustable vac advance for Chevy L6 distributor
! You have the dizzy vacuum hose connected to the wrong carby port ~ if you do simple testing you'll find a vacuum port with ZERO VACUUM @ IDLE BUT IT'LL BEGIN PULLING VACUUM THE *INSTANT* YOU OPEN THE THROTTLE .
This is very important on i6 engines to give proper idle and max power right off idle . Remember to re set the base timing @ 700> RPM after you've corrected this vacuum mistake and be amazed at how much power you gained whilst still being buttery smooth and not run hot .
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-Nate Geezer '49 3100 235 W/ Muncie SM420 SOLD '69 C/10 shortbed sidemount survivor 250 L6 W/ 350TH |
07-04-2017, 05:58 PM | #6 | |
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Re: Adjustable vac advance for Chevy L6 distributor
Quote:
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07-04-2017, 06:06 PM | #7 |
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Re: Adjustable vac advance for Chevy L6 distributor
It's called a vacuum advance for a reason.
>>The ported vacuum doesn't retard timing enough << Using a vacuum advance for an off-idle vacuum retard is a Band-Aid for incorrect timing and poorly adjusted carb. There is no reason to set a stock six cylinder idle above 600. Depending on engine condition, oil pressure can drop off too much as it gets closer to 500.
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'67 GMC 2500, 292, 4spd, AC |
07-04-2017, 07:06 PM | #8 |
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Re: Adjustable vac advance for Chevy L6 distributor
I know you're frustrated here Carl but it was designed to run best on ported vacuum, you're forcing it to ping using manifold vacuum .
Once you try the correct way you'll see and we can set about fine tuning it for max power and economy both . I;m a Geezer who grew up working on/with i6 powered farm machines long before your truck was designed much less built, one thing I know is how to tune InLine engines . I wish I was closer (and not in this wheelchair) as I could do it for you before lunch .
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-Nate Geezer '49 3100 235 W/ Muncie SM420 SOLD '69 C/10 shortbed sidemount survivor 250 L6 W/ 350TH |
07-04-2017, 07:25 PM | #9 |
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Re: Adjustable vac advance for Chevy L6 distributor
All's good:
The dwell was way off. Once that was set correctly (and timing adjusted) the old 6 is running great. Thanks for all of the suggestions and offers of help. I'm going to leave the vac advance on the manifold for now as it's running really well under a variety of load conditions. Note: This engine has always had part throttle ping issues when using the ported vac line. |
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