Yesterday i checked the rods of my thermoquad strip kit and I found something odd.

If i get it right, the rods consist of three parts: the upper part which is of the same diameter, the middle part that narrows downwards and the lower part that is of the same diameter again.

when comparing the different rods of the strip kit side to side, the middle, narrowing part starts in different locations (lengths) of the rod (hope you understand what i mean).

Am i correct that it is the middle part that is responsible for part throttle mixture?

If so, then wouldnt the rod tree have to be adjusted to the individual rod, so that the beginning of the narrowing part sits in the right spot of the jet?

Am i correct or do i get something wrong?

just trying to understand how this stuff works.

If some of this doesn't get answered I will be in the shop later. I will check.

The rods are not 3 differeint parts by default, like really depends of the rod model and specs. Diff rods to diff aplication and throttle response. There are rods with steps, rods with slopes, rods allmost straigth down

Check numbers stamped on Rods and will notice that probably you have two diff model of rods, so you are having diff response on each side of carb

i tried to make some pictures, unfortunately its pretty hard to make good pictures of such small parts. those are all different rods, compared next to each other. i hope you can see that the narrowing (middle) part is always in a different location.

VERY nice pics .... what type of camera do you have ?

Yes indeed ... there are a few rods like that but they are rare.

Yeh I know what you are talking BUT all those simply looks like non matching sets. Have you checked numbers stamped ?

all sets I have had are totally matched

If I understand the OP correctly, yes they are different rods. He was asking about the location of the part throttle step varying between the different sets.

IE: a 1966 set of rods has the part throttle step further up from the WOT step than a different set like a 2159.

It's normal for the steps to vary, I have a few here that have a noticable difference. It allows tuning the carb for better responce and drivability.

I've always found that the tree needed to be tuned to the specific rod for correct operation when switching between numbers.

HTH

I don't know t-quads, but if they work somewhat like the AFB's, where the "transition contour" between the wide part of the rod and the narrow part of the rod will determine when you get power enrichement and slightly vary the a/f curve as you go from high vaccuum part throttle to no vaccuum WOT.