AFB Choke thermostat Spring

[Harry S.]

Lets use a 63 3461S carb and choke as an example.

Looking through past threads I noticed folks are looking to align the hash mark on the bakelite cover with the choke body. I've also had this problem. I pulled from the parts box several springs on the choke thermostat and noticed they are different sizes ( number of windings ). I tested with a spring with minimal windings and I could get the hash mark to align ( + or - a few degrees ) the mark on the choke body.

Anyone have a picture of a setup that they know works. As soon as I get a picture I'll post it.

Thanks

[Arland D.]

What is the motivation to get the hash marks to line up if the choke is working properly?

[Timothy B.]

It's my understanding, to properly set the spring at approx 68-70* then turn it to rich until the choke blade just closes.

I don't know how that answers your question about lining the marks but you may or may not get it close.

[Harry S.]

I would think the hash marks on the choke body and the bakelite cover were put there for a reason. Depending on the spring used it's doable. I'll get some picture up later today.

[Tim S.]

I've had the same observations Harry. I'm interested to see what comes of this discussion.

Tim

[Harry S.]

The spring on the left allows the hash marks to align.

IMG_6704.jpg

[Duke W.]

I don't understand what "lining up the hash marks means". There is an index mark on the plastic choke housing cover and hash marks on the choke housing. This is equivalent to the timing notch on the front torsional damper and the hash marks on the timing tab.

The 1963 Corvette Shop Manual (page 6M-4)says to set the index on the plastic cover to the center notch on the housing with PG and one notch lean with synchromesh. This is for a new carburetor.

Over time the choke vacuum break piston gets sticky, especially with the OE type oil-wetted polyurethane PoS filter. The method of adjustment mentioned in post #3 might help, but it's a crutch. The real solution is to remove the choke housing, which can be done with the carb on the car, clean, inspect, and lubricant with a dry lubricant like graphite (Lok-Eze), and be sure to have a tiny O-ring to seal the vacuum passage from the choke housing to the main body. At least one should be in any zip kit.

Use a modern cellulose filter on '63-'65 engines. Save the urethane PoS for judging.

Duke

[Harry S.]

The attempt is to get the two hash/index marks close. Depending on the spring it could be close, per the spring on the left or 180 degrees out. Just trying to understand what the engineers had in mind.

All parts are clean and the o-ring is in place.


I don't understand what "lining up the hash marks means". There is an index mark on the plastic choke housing cover and hash marks on the choke housing.

[Duke W.]

Maybe the problem is you don't know which spring is original. On my 3461S which is original other than a couple of minor rebuilds it's just a matter of installing the choke housing cover and, ensuring that the spring end hook engages the lever, then rotating the cover so the index mark lines up with the one notch lean hash mark on the choke housing, lightly securing the three hold down screws, and all is well.

Duke