454 CI carburetor question

[VicB]

Each 454 on my 3807 has Rochester carburetors. This is the interesting part. They have divorced chokes. Meaning they have a separate metal coil mounted to the manifold that is attached to the choke plate. When engines start choke is fully closed. When the manifold heats up, coil expands, lifts the rod and the choke plate opens. Seems cave mannish, but maybe it was a tried and true method in 88?. Just had the carbs cleaned and rebuilt. Still have the issue of when started, there’s a smell of raw gas, a little blue smoke in the exhaust and a bit of sheen can be seen. Engines start and run well, just very rich and I guess take a while before the choke opens. Is there something I should do? Is it any big deal that they run rich for a bit? I think the adjustment is to bend the rod so the choke plate is not so closed. Here is a pic of the choke thermostat. Any thoughts would be great. Just not sure if this is normal or an issue I should look at.
Thanks,
Vic

[bud37]

You can adjust a bit, but really where you live and boat I cannot see any reason for a choke.....Myself , i would just block the plate open and move on. Generally there may be a small tab that will not allow full throttle when the choke is on, make sure to check that out. It may require some playing with the throttle on a very cold morning but that would only be a few seconds.

Just my opinion...

[VicB]

Bud37, that’s what I was wondering. I wouldn’t think a choke in north Alabama would even be really needed. The other issue is what had me have them cleaned. If the choke doesn’t fully open, your secondaries won’t open. I took the thermostats and put them in boiling water while the carbs were being rebuilt, just to see them work. They moved, but I just don’t have the confidence that they open the choke all the way. If that’s the case my other two barrels of the carb haven’t opened. Interesting!

[bud37]

Easy enough to check the operation.....just warm engines and look at the choke plates to see if they are wide open.

[km1125]

When you say you "took the thermostats and put them in boiling water", did you mean the engine coolant thermostats or the choke thermostats?

Look at that pivot pin in the center of the divorced choke thermostat. Make sure it is not loose. Mine were loose and would cause erratic choke operation. Once I re-crimped them, they worked just fine. Make sure you clean the manifold where they bolt down to also, as you want good heat transfer there. There is an exhaust passage through the intake manifold right below the divorced choke thermostat, which heats the area. Your engine temp doesn't have to be very high but the choke will open up because of this exhaust passage.

The choke should snap shut when the engine is cold and should fully open when warmed up. However, there is also a choke pull-off diaphragm that pulls the choke open just a bit once the engine starts. It has a small vacuum line to it that may be faulty, or the diaphragm might be faulty. You can use a small vacuum pump the check these. They would be mounted on the carb just forward of the divorced choke linkage.

[VicB]

Good thoughts. They have new choke pull offs. They were included in the rebuild. One thing I did wonder was that my engine runs about 110 degrees and the cooling thermostat opens. They are raw water cooled. I wondered if the thermostat would get warm enough to work correctly. If there is an exhaust passage just below them, I’m sure it gets plenty of heat right there.

[bud37]

Vic , not sure what is going on there.....engine controlling at 110 F ??.......seems a touch cold to me.....even in salt ,the raw water spec would be around 140 F.

Maybe get an IR temp gun and double check those temps at the thermostat housing.

[tomschauer]

At 110 degrees, I would check to make sure you have engine thermostats installed. Those motors will run a bit better at 140 or 160.

[VicB]

The thermostats are definitely there. I’ve had the housing covers off. Interesting about the temps. I wondered if it is the correct thermostat. I’m guessing they may be wrong. I just chalked it up to raw water cooled. That’s what both gauges read when they reach operating temp. Just read in the manual they call for 140 degree t’stats for raw water cooled. Do you think it’s hurting anything to be running cooler ones? I have a vacuum gauge coming tomorrow and plan on fine tuning the carbs Thursday or Friday. I will check temps with a IR gun.

[mjk1040]

Replace both thermostats, the colder one is bad. You need 2 new 140 degree thermostats if you have raw water cooling with no antifreeze (closed cooling system). If it's closed cooling system you'll need 160 degree thermostats. The lack of correct operating temps would throw the choke thermostats off. Personally I would remove the chokes all together and just pump my throttles one stroke before starting if needed.