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Hey all,
I got 1 question for all of u:
I was talking to the dude at the trans shop, and he was telling me the best way to set engine timing is to run the engine at 1200 rpm in park, witht the vacum advance on the distributor plugged, and put a vacum gauge to manifold vacum, and to turn the distributor until u get the highest reading, and that is where u should put the timing at, and that I should ignore the timing marks on the engine. Is this true???
 

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I personally don't see how that could be true. In order to get a higher vacuum reading, you would have to increase the engine speed without moving the throttle position. This would mean that you would set the timing for the highest idle speed. I am almost positive that this would advance the timing too much. You could try it and see then put a timing light on it to see what the actual timing was. Who knows, the guy may be right.
 

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That's why the guy works in a transmission shop, not an engine shop. Timing is set with a timing light, not a vacuum gauge. Hope he doesn't breed.....


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JohnZ
'69 Z28 Fathom Green
 

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Say you need 37 deg. of total timing for best performance. How in the world would you know where your total timing is??? The guy is full of it!


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67RS STREET CAR, 502 PUMPGAS, HYD. ROLLER, TH350 w/ATI 10" 12-BOLT w/373 - [email protected] ON MOTOR, ET-STREETs w/MUFFLERS
 

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Sounds like the right procedure for adjusting your idle mixure screws, but not the timing....




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Son's 67-327, Dad's twistin' wrenches again after 25 yrs.
 

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Well guys this method of setting timing is older than all of us, actually I believe it is done at an idle and this gives you your best running at idle, as a matter of fact if you do this to a stock engine and you check it with a timing light it is very close to factory spec makes you wonder how thay get a factory spec. but once you change cams, intakes and all that you timing requirements change.
If you would like to get the most out of your engine like me, find where you engines max timing is (where it runs the best and is not detonating) lets say 37 deg and then find you optimum idle vacuum timing lets say 17 deg then you set your mechanical advance for 20 deg, and then you come back and find the curve (springs) that work best and you will have your ignition system set up good.
Some of these old time methods still have there place in the electronics age
 

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Adjusting timing and carb with a vacuum gauge is accepted practice in drag racing. But you would still have to ensure that total advance does not cause run-on or detonation. I quess the 1200rpm start point is to negate the vacuum advance from affecting the initial setting. If a car is only used in parades and parking lots you probably don't need it.
 

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I don't run in drag racing circles and I'm not a mechanic by trade but IMO if you're gonna use a vacuum guage to set your timing you might as well do it buy ear and look for the highest idle!! Setting the initial timing on anything but a stock vehicle to factory spec's doesn't cut it. Total mechanical timing requires a timing light! A vacuum guage is used to adjust the idle mixture. When there are millions of cars in the world and they have been around for a century or so you will find many things will have been tried...

It was my understanding that timing is locked on drag cars and timing curves and vacuum advance are not used... Mind you there are various classes and the closer you get to street it might be different!!

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...Dennis
'69 RS Convertible w/SS trim
'96 Z28SS #1679 of 2410
"The Club"
 
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