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Set Timing Using Vacuum Gauge yes or no

#1 User is offline   Rollbar 

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Posted 24 December 2007 - 07:10 PM

U lost your timing light? The timing can be set with a vacuum gauge. Hook the gauge to manifold vacuum and run the engine at curb idle. Rotate the distributor clockwise to retard the timing. Now slowly rotate it counter-clockwise to the point where you just reach the maximum vacuum reading. Back off (clockwise) until the vacuum drops by 1". Lock the distributor down. Timing can be set to within 1? using this method.

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1. Now, would this be more accurate in combination w/a timing light.
2. What is the best desired vacuum for a 258 CI engine?
3. Would you be better off setting your engine to the specific vacuum instead of what the book says (i.e using the marks on the flywheel).
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#2 User is offline   JeepinIan 

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Posted 26 December 2007 - 07:21 AM

I rarely use a timing light for initial timing, as any upgrades, changes, etc. affect the timing. I generally go by ear. Set it so it runs pretty good, drive and check under load, no pings, great, ifi it pings I adjust it a little bit until the pinging goes away. Then I check where the timing is and write it down somewhere I can find it it later.
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#3 User is offline   nero004 

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Posted 26 December 2007 - 02:21 PM

yea i usually go by ear its faster but i know its not super precise
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#4 User is offline   Rollbar 

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Posted 26 December 2007 - 04:41 PM

View PostRollbar, on Dec 24 2007, 07:10 PM, said:

2. What is the best desired vacuum for a 258 CI engine?
3. Would you be better off setting your engine to the specific vacuum instead of what the book says (i.e using the marks on the flywheel).


So, what about #2, 3.


View PostJeepinIan, on Dec 26 2007, 07:21 AM, said:

I generally go by ear. Set it so it runs pretty good, drive and check under load, no pings, great, if it pings I adjust it a little bit until the pinging goes away. Then I check where the timing is and write it down somewhere I can find it it later.


Ya, I to usually do that also Ian & it helps get it close. I was just wondering about #2, 3 to see if there were specifics.
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#5 User is offline   JeepinIan 

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Posted 26 December 2007 - 07:36 PM

I dunno what the "best" desired vacuum would be as there are variables, cam timing, valve overlap. Setting to a "specific" vacuum would have the same variables.
That's why there are timing marks. Otherwise everyone would use a vacuum gauge
Ian Stewart

If you don't fight for the trails, there won't be any trails to fight for.

What you get by achieving your goals is not as important as what you become by achieving your goals.
Zig Ziglar

"War is an ugly thing, but not the ugliest of things. The decayed and degraded state of moral and patriotic feeling that thinks that nothing is worth war is much worse. The person who has nothing for which he is willing to fight, nothing which is more important than his own personal safety, is a miserable creature and has no chance of being free unless made and kept so by the exertions of better men than himself." ....

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#6 User is offline   TranyDoctor 

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Posted 26 December 2007 - 08:24 PM

if there is no computer the most accurate method is by ear.
all timing marks are adequate not actual. all fuel is not the same.
so for the best performance with the acquired fuel do it by ear and make sure it cranks over easily for every day use.

#7 User is offline   Rollbar 

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Posted 26 December 2007 - 08:39 PM

View PostTranyDoctor, on Dec 26 2007, 08:24 PM, said:

......all fuel is not the same.


:bounce: like tranny fluid :beach:

P.S. Ian, I should have specified with great specificity, stock engine/config w/a carter 2bbl. I for got what I was pull for vacuum (18-20" if memory serves), my gauge is down South. I use to run a vacuum gauge/meter in my old car I had @ high school, I raced a lot. :sneak:
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#8 User is offline   TranyDoctor 

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Posted 26 December 2007 - 08:49 PM

View PostRollbar, on Dec 26 2007, 08:39 PM, said:

:cool1: like tranny fluid :roll:


:beach: :bounce: keeps me roll-in-roll-in-roll-in rahide

View PostRollbar, on Dec 26 2007, 08:39 PM, said:

P.S. Ian, I should have specified with great specificity, stock engine/config w/a carter 2bbl. I for got what I was pull for vacuum (18-20" if memory serves), my gauge is down South. I use to run a vacuum gauge/meter in my old car I had @ high school, I raced a lot. :sneak:

18-20 is great for idle, but what happens with throttle :sunny:

#9 User is offline   Rollbar 

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Posted 26 December 2007 - 09:02 PM

View PostTranyDoctor, on Dec 26 2007, 08:49 PM, said:

, but what happens with throttle :unsure:

(If memory serves, or the gauge drops to....) but, I'm thinking it drops to zero when I punch it by hand @ the linkage. I have to get it up here & check it but the wife wouldn't know where to look.
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#10 User is offline   TranyDoctor 

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Posted 26 December 2007 - 09:12 PM

View PostRollbar, on Dec 26 2007, 09:02 PM, said:

it drops to zero when I punch it by hand @ the linkage.

yes it should go to low vacuum.
at 18-20 inches of vacuum at an idle you will have a good idle................
once you turn on the butterfly it changes (this reminds me of a woman)

#11 User is offline   JeepinIan 

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Posted 26 December 2007 - 10:33 PM

The only thing I ever really used a vacuumgauge for was to set multiple carbs. What pain!
Ian Stewart

If you don't fight for the trails, there won't be any trails to fight for.

What you get by achieving your goals is not as important as what you become by achieving your goals.
Zig Ziglar

"War is an ugly thing, but not the ugliest of things. The decayed and degraded state of moral and patriotic feeling that thinks that nothing is worth war is much worse. The person who has nothing for which he is willing to fight, nothing which is more important than his own personal safety, is a miserable creature and has no chance of being free unless made and kept so by the exertions of better men than himself." ....

John Stuart Mill

#12 User is offline   TranyDoctor 

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Posted 26 December 2007 - 10:39 PM

View PostJeepinIan, on Dec 26 2007, 10:33 PM, said:

The only thing I ever really used a vacuumgauge for was to set multiple carbs. What pain!

i concur :unsure:

#13 User is offline   Rollbar 

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Posted 26 December 2007 - 10:42 PM

Ya, I had a three carb set up on a old Triump TR6, PIT :unsure:

P.S. Thanks guys
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