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Author Topic: Vacuum advance  (Read 2818 times)

KenBourque

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Vacuum advance
« on: October 22, 2011, 02:04:57 »
On the 1970 28SL, at 2400RPM the two-way valve closes and eliminates the vacuum retard which was in effect at lower RPM's.  Does anyone know just how much advance is introduced at this point?  Should I be able to perceive a slight surge in power?
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Benz Dr.

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  • Canada, ON, Port Lambton
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  • Benz Dr.
Re: Vacuum advance
« Reply #1 on: October 22, 2011, 03:30:26 »
The mechanical portion is about 10 degrees and the vacuum is about 20 degrees. The system is set up so that the vacuum cuts in just as the mechanical portion is finishing its advance. It's more or less seamless so you really won't feel it.

If the vacuum portion isn't working, and they often aren't, the engine will lack power and use a lot more fuel.
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1966 230SL 5 speed, LSD, header pipes, 300SE distributor, ported, polished and balanced, AKA  ''The Red Rocket ''
Dan Caron's SL Barn

1970  3.5 Coupe
1961  190SL
1985   300CD  Turbo Coupe
1981  300SD
2013  GMC  Sierra
1965  230SL
1967 250SL
1970 280SL
1988 560SEC

jeffc280sl

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Re: Vacuum advance
« Reply #2 on: October 22, 2011, 16:55:35 »
The fact that your two way valve operates as it does indicates  the emission control system or at least part of it is operational.  There are two relay boxes located on the inner fender near the battery that are the brains of the system.

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