73 Thermoquad 6319SA Factory Jets

[73LemonTwist]

I have a stock 73 6319SA on my 340. The metering rods installed are the stock 1966 rods. The jets are 4098's (98 thousanths jet size I believe), which I believe are the stock ones.

I read that the old jet sizes should be reduced to lean out the mixture with the quality of the gasoline we get today vs the '70s. Anyone have experience with how much to reduce jet size to accomplish this?

 

[idrivemopar]

I have run the same 6319 on my 73 RR, but it was running way lean just setup stock, but my motor is built up a bit so that is most likely why, so I am messing with a 6322 currently. I am curious why you need to lean it out, are you at a high elevation or is it having a problem with stumble or something like that?

Also, have you checked out the thermoquad guide on the site here, there is a ton of information on it about the functions of the thermoquad. Its located here.

 

[73LemonTwist]

I have run the same 6319 on my 73 RR, but it was running way lean just setup stock, but my motor is built up a bit so that is most likely why, so I am messing with a 6322 currently. I am curious why you need to lean it out, are you at a high elevation or is it having a problem with stumble or something like that?

Also, have you checked out the thermoquad guide on the site here, there is a ton of information on it about the functions of the thermoquad. Its located here.

The car seems to be running rich, and it does tend to stumble when you hop on it. The biggest tell seems to be fuel consumption - it definitely chows down the gas even cruising light throttle. Will know better once I get the car on the road this spring - waiting for the winter salt to get washed away. Have played a bit with the metering rod tree position as well - dropping the rods into the jets further than they were previously. Will see what that does.

 

[idrivemopar]

I have read, that you shouldn't adjust the metering rod positions, however, I have done the same thing and it can help, although, if that is the case, then smaller jets may be in order. I would also double check the accelerator pump position and maybe try a lower position as well as make sure the rod is adjusted properly. If you are experiencing the stumble, and this is a long shot, but there is a service bulletin out about this issue but it was only typically found on early carbs.

 

[73LemonTwist]

The accelerator pump is set to the highest hole on the arm, which I believe maximizes the pump stroke. I will try dropping it down as you suggested and see what happens. Its an easy adjustment.

Last fall I messed around with the secondary air valve spring tension, and that seemed to have an effect on the off idle performance when you hopped on it as well. In the end, I stuck with the recommended 1.5 turns on the spring adjuster.

The engine is totally stock, and never been opened up, so who knows how this affects the picture.