Engine Speed Switch Delete

[AKguy]

1981 C20, 454, new Holley Sniper EFI with Hyperspark mudule and Dual Sync distributor. I am assuming that since I removed all the emissions equipment, ditched the Quadrajet and the old distributor I can delete the engine speed switch since the speed valve is gone. I cannot see any other connection on the wiring diagrams to indicate any other function will suffer. Thoughts before I modify the new harness?

 

[Blackbeard44]

is that a dummy light for an over rev??
never heard of an engine speed switch, what does it do?

 

[bucket]

I believe you are correct, you can ditch it because everything it had to do with is gone already.

 

[Matt69olds]

Speed switch????? Are you asking about cruise control parts? No clue what a speed switch is.

 

[Matt69olds]

Stepper motor or fast idle solenoid? Post a pic of what your asking about.

 

[Craig 85]

Stepper motor or fast idle solenoid? Post a pic of what your asking about.

I think he's referring to #3 on the driver's side valve cover.

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[AKguy]

I had not heard of one either, but my new harness from American Autowire had specific instructions to save the old plug because mew ones are not avbl. I wired it in, but questioned the need. Here is another pic from the service manual shown below what Craig 85 posted:

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[Matt69olds]

If it’s in American Autowire harness instructions, and listed in the service manual, it’s pretty obvious it’s a real part on the truck.

What isn’t obvious is it’s purpose? What is it for? What is it suppose to do? Learn something née every day.

 

[Craig 85]

I think it has a couple of purposes, but haven't verified it all. I believe it ties into the cruise control system, but for sure triggers the throttle kicker on the carb (#1). The one on my truck has the similar placement to that of SBC truck with A/C. My understanding is the valve is triggered at certain RPM's (1600-2000?) to prevent backfiring when decelerating. That speed control module connects to #4 as seen in photo #3.

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[AKguy]

Looks right. I removed all the cruise control as well. I will get into the harness and terminate what I do not need any longer. Thanks.

 

[cptsnoopy]

I thought I read that the speed switch worked with the A.I.R. system. I’ll try to find it again.
Update: the speed switch is part of the TRC (throttle return control) system. My manual said it should tell the throttle actuator arm to extend above 1890rpm (might not remember that number correctly) and retract if the rpm is 1700 or less. From what I gather, it’s to prevent backfiring during deceleration.
If you have the option to shut off the fuel during deceleration with the Holley Sniper then you should not need the TRC system.

 

[AKguy]

Thanks! I am confident that the Sniper will take care of deceleration. As a side note, I left both the heavy pink distributor wire and the smaller pink/black wire in the harness as both are a good 12v ignition source and plan to route the heavy pink into a relay prior to feeding the needed ignition source(s) for the Sniper/Hyperspark.