SBC idle speed

[BobE]

I’ve a couple of questions directed to those with SBC motors and air con. I’ve been sorting out the starting and running of my car which has a 6.3L American Speed engine with 550bhp on their dyno and is fitted with a Holley carb and an electric choke. The previous owner had dismantled and cleaned the entire fuel system but either didn’t understand how the choke works or gave up trying. I’ve sorted this out and now got the car so it will start fine from cold or hot first time and run reliably. When the electric choke comes off I’ve set the idle speed at 700rpm which is about as low as it wants to go and still maintain a good running condition. When the engine is fully warmed through the idle speed rises to 900rpm which again I think is fine. Is that what others with similar set ups have done?
I’ve now also got the cabin circulation fan operating correctly and the aircon - the latter is extremely effective. Now when I turn on the aircon the idle speed drops by about 200rpm as the compressor and fans cut in. You can also notice the slight ‘drag’ when driving the car as the compressor cuts in. Is this what others experience? It also means that until the engine is warmed through I don’t really want to turn on the aircon - it’s fine with a 900 idle but the engine struggles if it is cold and has the initial 700 idle speed. Again comments?

[Ultimike]

Yes that's normal. I suggest having a chat with Charles Dunn he has a very handy mod for the Holley carb which raises the idle a little when you turn on the Air Con

[BobE]

Ultimike said:

Yes that's normal. I suggest having a chat with Charles Dunn he has a very handy mod for the Holley carb which raises the idle a little when you turn on the Air Con

Thanks for the response - I’ll contact Charles Dunn.

[Ultimike]

Tell him I sent you.

Regards

Michael

[Mr Pid]

There is a standard Holley solenoid part for this... I fitted mine a few years ago to fix the same issue. It simply adjusts the throttle stop at idle when the a/c compressor clutch is engaged. Simple, effective and easy to adjust. I now have no idle speed change when a/c is on.

Not the best picture but gives the idea.



Ps... Seems I have the very special inverted engine arrangement !

[BobE]

Mr Pid said:

There is a standard Holley solenoid part for this... I fitted mine a few years ago to fix the same issue. It simply adjusts the throttle stop at idle when the a/c compressor clutch is engaged. Simple, effective and easy to adjust. I now have no idle speed change when a/c is on.

Not the best picture but gives the idea.



Ps... Seems I have the very special inverted engine arrangement !

Thanks Stu - I will sort the issue out over the winter.