Jake Brake valve cover question

[chessie4905]

Have never seen one. Ask Luke. How would know if the ever made one.

[luvrbus]

I have a question what is the purpose of a fast idle/buffer switch using a manual transmission

[richard5933]

I have a question what is the purpose of a fast idle/buffer switch using a manual transmission

I'm not sure I understand the question.

I'm not an expert by any means on how Jake Brakes work, but wouldn't I still want to be able to have fast idle work and to have the Jakes turn off when I depress the accelerator pedal? If you have something behind your question that would help me, then I'd appreciate some more information. It was explained to me that this was necessary to still have the fast idle function and have the Jakes properly turn off when they should.

Perhaps I'm using the wrong terminology, perhaps I don't fully understand, but this was part of the set of parts I was told were necessary.

[luvrbus]

I was just asking because I don't see many GM,Eagle.Mci.or Prevost with manual transmissions with the high dollar combo buffer switch all they have is the 5 to 40 buck micro snap switch mounted on the throttle linkage at the engine to keep the fast idle.Some have foot pedal control,clutch control, toggle switches and cruise control you name it there are dozens of ways to control a jake    

[bevans6]

My MCI has what I presume is the factory setup, a fast idle buffer switch (air cylinder and a micro-switch combined screws into the buffer hole).  Electrically it goes power to dash switch (I set it up for both sides on, not hi/low) to clutch switch (jake only on when clutch is up) to buffer switch to solenoids.  The alternative arrangement is for hi/low, and its power from the rear bus to buffer switch to hi/low/off dash switch at the front, back to the solenoids.  My wiring harness had all the wires to do it either way.  I never considered the fast idle to have anything to do with the jake function, I thought is was so you could idle fast and run the air conditioner or heater when idling.

[richard5933]

Bevan6 - We're planning to go with the type of setup you have. Sounds like you've got the same combined switch.

[luvrbus]

I have maybe a 1/2 dozen of the combo fast idle buffer switches ,I just do it the way the customer wants to pay for,some go with the King Cruise with fast idle option you can buy those cheaper than the combo unit then they have cruise and fast idle .
Me personally I don't care for the fast idle on those old engines even with a fast idle under no load they still build gunk in the air box.I have a 8v92TA in the shop now from a MCI C3 the engine has been fast idled to death,Fast idle is on there just to keep the oil pressure and volume up, a DD will not oil good at the rear at 500 to 600 rpm.All highway DD engines come with a fast idle the military and industrial engines don't you shut it off      

[TomC]

I took the stock engine door bulge off (not big enough for the Jake brake valve covers) and just let the valve cover exposed. Paint it, and sometimes I draw a face on it. Good Luck, TomC

[luvrbus]

I saw a neat bump out on a GM it was polished Stainless wire mess the guy had polished valve covers too

[RJ]

Richard -

Don gave you the measurements of the bump out on his 4905's tailgate, the cutout area on your 4108 should be identical.

FWIW & HTH. . .

[richard5933]

Richard -

Don gave you the measurements of the bump out on his 4905's tailgate, the cutout area on your 4108 should be identical.

FWIW & HTH. . .

I think you are correct - the bump I got from Luke was off a 4905. Got it installed this fall just before the weather turned cold.

There is another thread about the same topic which I replied to with some photos of my install:

https://www.busconversionmagazine.com/forum/index.php?topic=33651.0

Might be some confusion because I linked to this thread in one of my replies.

[chessie4905]

Yours is identical to mine except your ends are sealed.