I've got a new one that I've changed the throttle plates for ones without holes. I've also sorted the choke.
I've now learnt that the Venturi Size and step up piston are different after reading a Chrysler Tech articles that Reed kindly directed me too. It went on to say that the carb should not be interchanged.

It works on the car ok, but now I'm wondering if I'm better off just looking for a 225 solid fuel BBD to replace it with.
Fuel economy is the most important to me, followed by drivability and lastly power. Can someone explain the improvements that I would notice with a 225 solid fuel BBD instead, so I can decide whether it is worth sourcing another carburetor?

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1967 VC Valiant

A friend of mine has done some pretty thorough testing of BBD's on an engine dyno. His finding was that there is very little difference between the S6 and V-8 carbs. The V-8 one actually ran a touch leaner stock.

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Official Cookie and Mater Tormentor.

When was running carbs I liked the BBD with the adjustable fuel metering rods best of all carb 2 bl options. Does yours have the removable plate over the rods?

Sam

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This is just the sort of information Im looking for thanks. Im pretty happy with how it is running on V8 one, but I dont have anything to compare it with, so dont want to just run it and find years down the track that it could have ran better, or used 10% less fuel if I had the right carb on it.

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1967 VC Valiant

Yes it does have the adjustable rods. Do you recommend that I set them up as per factory manual, or do you have a different method.
Looking at the Chrysler tech article, they have limited the rod travel, because they mention it prevents the mixture becoming excessively rich

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1967 VC Valiant

You can play with them and optimize your set up. If you had a wideband, you would know exactly what was happening. The goal is to have the metering rods sit at the right height in cruise, high vacuum conditions, and raise at the right time to meet the fueling needs of increased load. The factory specs would be a good starting point. I do not know if you can get different metering rods now. That would increase your fueling options.

Sam

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I adjust the rod height often, on my BBD.
I set them just off "full lean" for my around town commute and move the setting to the middle of the range, for track or highway use.
The biggest problem I find when set on the lean side... I get a lean-out "flat spot", when quickly moving into the throttle.
DD

Just to make sure we are talking about the same adjustment here, you mean adjusting the small hex screw on the top of the step up piston assembly. This is the assembly that the manual says not to touch Right?

Are there any more comments about whether to limit the step up piston travel like the 6 cylinder ones and also to modify/ change the toggle rod that activates it like the 6 cylinder one.

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1967 VC Valiant

I got my truck and the super six carb was already replaced- guessing its a 75 318 since thats the carb kit that fit it.Using a manual choke.And just set the metering rods and accelerator along with step up piston to specs.I ran mine so rich that he plugs would carbon foul with a gm hei ignition at about 50kv.Droped the meter rods down with seat of the pants feel when driving a steady flat road road it lagged then brought them up a bit.Then tweeked the step up piston travel so it didnt flat spot up grades.Then as long as you have a good acerelator pump shot and it doesnt stumble on hard accel your done.With a manual choke in the summer once it starts it will idle with no choke and stuble cold with no choke- at 100 degerees it does not matter on a cold start a choke is not needed.With 2.97 gears - a833 od trans and 28.5 tires I get a consistent 19 mpg. Just locktie the carbe mounting nuts and throttle body to bowl body screws so you wont have a drive ability problem when they loosen up and create a vacuum leak,

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I may be slow,but I"m ahead of you.