idle speed

[AUSMHLY]

What is considered a good idle speed for a bj8 when not moving. No choke, warmed up.
Thanks, Roger

 

[bighly]

800 to 1000

 

[Dave Russell]

Hi Roger,
I think the idlespeed is mostly personal preference. Factory specs usually call for about 500 rpm.

My personal preference is an rpm that is high enough that the engine won't stall at any temperature encountered. The idle speed tends to get a bit slower under very hot stop & go traffic conditions. Other considerations with the original generator is that the idle be high enough to prevent battery discharge during prolonged idle conditions. Also, the cooling system usually works better at a somewhat faster idle. I think a lot of folks try for something like 800 rpm.

The faster idle also brings in some of the distributor's centrifugal advance which tends to promote less combustion heat rejection to the engines cooling system.

I don't know about your car, but my BN2 is set up so that the first part of choke knob travel only affects the idle speed, doesn't really apply any choke, just fast idle. This allows convenient temporary resetting idle speed to anything needed for the conditions, ie. very hot driving conditions, altitude changes, fuel quality, etc.
D

 

[Keoke]

800 to 1000

/bcforum/images/%%GRAEMLIN_URL%%/iagree.gif-- /bcforum/images/%%GRAEMLIN_URL%%/hammer.gif-With both of them----------------Keoke- /bcforum/images/%%GRAEMLIN_URL%%/laugh.gif

 

[Dave Russell]

It appears that you may not care about long winded explanations about what or why. If so, just set it at 900 & be done with it. Sorry to clutter up the board.
D

 

[Keoke]

Yeah Dave, I thought that might be mistooken and I was just about to fisit. But on the BJ8 if the chokes are set up properly the first 1/4" or so will vary idle speed without applying any choke. Sorry it didn't just pull your leg a bit.---Keoke- /bcforum/images/%%GRAEMLIN_URL%%/smile.gif

 

[MarkA]

If you set the idle speed to 800-1000, then what speed do you use for the fast idle speed (choke pulled just before mixture richens up)?

 

[Dave Russell]

If you set the idle speed to 800-1000, then what speed do you use for the fast idle speed (choke pulled just before mixture richens up)?

The fast idle is a linkage operated cam. The more the choke is pulled, the faster the idle. I would set the fast idle to about 1,500 rpm when the choke is fully pulled.

If you set it up correctly, when the choke knob is pulled, the first part of the travel will increase idle speed without actually applying any choke. You can watch the carb linkage as you pull the choke to see the action. The shop manuals give pretty complete details on setting.
D

 

[Patrick67BJ8]

It appears that you may not care about long winded explanations about what or why. If so, just set it at 900 & be done with it. Sorry to clutter up the board.
D

900ish is perfect and that's if you can believe the tach. Not all car engines idle the same at the same tach speed so set the speed to whatever feels good.