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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: bluetarger on October 25, 2012, 09:01:47 pm

Title: Vacuum... modulator?
Post by: bluetarger on October 25, 2012, 09:01:47 pm
Hey Team,

1981 Chev Scotsdale K10

First of all I am curious to the purpose of the vacuum valve and steel line that are attached to the exhaust manifold with a bracket. The steel line then goes behind the engine block. (to transmission?)  I have attached a picture. Needless to say it looks terrible where it is and I would like to remove or relocate when I change my intake next week. I would like to clean up and eliminate as much of the vacuum lines as possible with my new Edelbrock performer intake and Performer 600 cfm carb.

If I have to keep this mystery valve set up, I would like to relocate it out of sight. Is the steel line necessary or can it be replaced with rubber? I'm guessing it is steel to protect from heat.

Any advise on what it is I am dealing with and ideas on how to relocate or eliminate it would be appreciated.
Title: Re: Vacuum... modulator?
Post by: bd on October 25, 2012, 09:32:55 pm
That's an image of the Early Fuel Evaporation (EFE) actuator.  The EFE actuator is a vacuum operated exhaust heat riser that forces hot exhaust through a passage in the floor of the intake manifold to heat the intake charge when the engine is cold, improving fuel atomization.  The 'steel line' is actually a solid rod that attaches to a butterfly valve mounted between the outlet of the right exhaust manifold and the inlet of the headpipe.  Assuming the butterfly valve is not seized in a (partially) closed position and can rotate freely, on a stock or nearly stock engine, removing the EFE may cause cold drivability issues, especially in freezing temperatures.  However, on a moderately modified engine EFE will detract from engine power and becomes impractical.
Title: Re: Vacuum... modulator?
Post by: bluetarger on October 25, 2012, 09:36:53 pm
Thank you sir, thats exactly what I needed to know!