Oldsmoswede

I’m considering doing a carb rebuild (Rochester 4-Jet) for the first time ever. Have been watching some YouTube videos about it and doesn’t look that difficult.

My carb has electric choke on it, are there any advantages with a electrical one? Otherwise I might put a “manual” one with the bimetal spring. As I understand those chokes works automatically so I don’t need to install any wire to it?
Anyway, this car will never be used in cold weather as it is only a ”summer car”.

Any opinoins about electrical or not?

Olds64

If you convert to an OE hot air choke you will have a choke stove going to the carburetor instead of 12V. If you're running an aftermarket intake manifold it might not be able to accommodate a hot air choke. You can always go with a manual choke which is operated with a cable under the dash (like a lawn mower). I don't think GM offered manual chokes in the 60s and 70s though, they had all probably gone to hot air chokes.

I would just keep the electric choke.

joe_padavano

A "manual" choke is one that you control manually with a **** and cable under the dash. Functioning of the choke would be unrelated to engine temps, only where you position the ****.

The original choke was an automatic hot air choke. A bimetallic spring is heated by air that warms up as the engine warms up and opens the choke. The electric choke simply uses a resistance heating element instead of hot air to perform this function. Likely the original hot air choke was replaced with electric when the hot air tube rusted out. Unless you care about a totally stock appearance, and assuming the electric choke is working properly, why would you remove it?

joe_padavano

Actually, Jetfires came with manual chokes from the factory.

Olds64

Interesting.

If the OP is interested, you can still get manual choke kits from Dorman.

Oldsmoswede

Ok, thank you for your thoughts and advise👍

Oldsmoswede

I was just thinking that it would be a way to keep it simple and reliable. But maybe it came with that electric choke, as it is a “Deluxe” model?

joe_padavano

Again, the original choke would have been the hot air choke. The carb was converted to electric by a previous owner. This is the same thing I told you on FB a couple of days ago.

Oldsmoswede

Ok sorry, as it’s not my account on fb I’m having a hard time to keep on track there sometimes.
But I can’t really see the point with a electric choke, that is adjusted of the heat it gets from being heated up by electricity. Maybe it is me missing out something here, but shouldn’t the need of a choke be dependent of the engine temperature and nothing else?

joe_padavano

Ideally, that would be the case, and there are actually aftermarket electric choke kits that include a temp sensor that bolts to the engine. In reality, that extra complexity isn't necessary. The engine heats up at a pretty constant rate. As a result, an open loop system that simply heats the choke based on a heat source (either hot air or an electric heater) is good enough. In addition, the bimetallic coil in the electric choke also sees radiated heat from the engine, which keeps the choke open on a hot engine that's been sitting prior to restart. And finally, a properly wired electric choke will use an oil pressure switch so that the choke is only heated when the engine is running. That at least precludes the chance that leaving the key on will prematurely heat the choke. These systems have been working on production cars for half a century. They're reliable.

Oldsmoswede

Thanks Joe, appreciate it 👍
That part with the oil pressure explains it better for me, haven’t seen if there are any kind of oil pressure connected as well yet.

joe_padavano

Most people don't bother using one when they retrofit. The factory electric choke installations did use them. See this thread for more info.