Fast Idle Setting?

[colnago]

I have a 352 with an Edelbrock 1405 4BBL carb. I just rebuilt the block, so I'm going through the adjustment processes for everything. With the cold mornings, it's been a beast to start. One of the things I have never looked into (even on the old block) was the fast idle speed when using the manual choke. I've done searches on the forum and on google, but came up empty. Does anyone know what idle speed I should aim for when adjusting the fast idle screw on the carb? Edelbrock said ~1500RPM, but I was wondering if it's different for different engines.

Joseph

[1972hiboy]

It kinda ends up being a compromise of what the engine wants and what you want, and the engine needs will probably change as it breaks in so periodic adjustment will probably be required. I usually shoot for a lower fast idle speed around a thousand rpms or even less. with automatics i like this so if you go into gear on fast idle it doesn't slam into it. kinda the same deal for the manuals, its kinda funky to try and take off with the engine on super high idle. I think the idea behind the higher fast idle speed spec is getting the engine to warm up as fast as possible for emission reasons. but ive always never liked starting a cold engine and having immediately spin up that fast.

p.s with the choke working correctly so you have a over rich mixture to get a cold engine to start up you can get the lower fast idle speeds. with a fresh engine you gotta find the sweet spot of what it likes with the choke butterfly. This can be difficult with a new tight engine. but I would think if its hard to start its either not enough choke to get an easy smooth start or even possible to much choke and its not getting enough air. I would set the choke up so full choke still has a crack open to let some air through.

[Ranchero50]

You set the fast idle to whatever it takes to keep the carb fueling (vaporizing the fuel when cold) until it warms up. It's a balance between choke flap closure and throttle plate opening that gives it a clean slightly rich cold idle mixture.

It's also vital that the thermostat is closed fully and add a 1/4" restriction in the heater hose so the water doesn't flow through the motor too fast with the T stat closed (takes longer for the engine to warm up).