TR6 What's wrong with this carb '73 TR6

[TR6oldtimer]

Take a look at this carb, which is the rear one on my car. Can you see what is wrong?

The '72-73 TR6 have a vacuum driven ignition retard feature that would kick in on high temperature. The vacuum tap came off the rear carb, you can see the pipe in the top of the picture.

What is missing is they did not drill the hole through the body into the throat. I always thought my car never hit the point where the ignition retard feature would kick in, but now I know it was not because the condition to activate it ever happened.

Not that I miss or had a problem without it, I had to laugh at all the times I looked for a vacuum leak there.

 

[poolboy]

Are you sure ? I believe I see it. The hole in the throat is not nearly as big as the external nipple.
Run a straight pin size wire thru the nipple and see if it's just plugged with crud if you can't blow thru it.
And, BTW, from 72 thru 74, the vacuum line from the carbs go to a thermostatic vacuum switch (TVS) which is in the top radiator hose.
When/if the coolant reaches about 200 degrees the TVS blocks the passage of vacuum to the dizzy retard.
That advances the timing at idle and causes the idle to pick up about 200 rpms, both of which are supposed to assist in coooling down the engine
I might add that above about 1100 rpms there's not enough vacuum to have an affect on the dizzy retard. Above that the centrifugal advance weights "take over".

 

[tdskip]

Can you blow air through the pipe Ray?

 

[TR6oldtimer]

What day is today? April 1!

Actually there is a hole there. After I posted this, and just before diner, with my reading glasses on, I found the hole. Darn, I thought, how could I get the post off the forum?

Anyway, thanks for the feedback and correction on the ignition retard function.

I did note that the gasket for the bypass valve on the front carb did not have the two holes joined as in this picture, but the rear carb did. I also noted that the rear carb's mixture trim screw was all the way in.

Back to the bypass valve, there is no channel or difference between the two carbs I have, so I am inclined to build the rear carb just like the front, that is with the gasket that seperates the two holes.

 

[poolboy]

Ray, if you mean the idle trim screw on the right side of the carbs, I'd screw them all the way down. They really don't have much affect except tap a very little bit of air from the Temperature Compensator's ports when they open. It's even recommended in the manuals to close it off (Clockwise) after the engine has broken in.
If you have that machined channel between the mixing chamber and the manifold ports like the picture I'd put the gasket with that opening in place. If there is no channel cut, then do use the gasket that separates the 2 holes
Here's a tip about adjusting the spring tension on the throttle bypass valve (TBV).
The spring tension adjustment screw has numerous threads, as many as 22, so, see how many you have by turning the screw fully clockwise then fully counterclockwise intil the nut is free and then make your initial setting mid way.
That should insure that the TBV opens on deceleration downshifts and closed when you've reached idle speeds.
You mentioned 72 and 73 carbs in your first post, which ones are you using on your 73 car? There is another difference that bears checking if the carbs are 73 versions (brass tag# 3508 for 73's).

 

[TR6oldtimer]

The car is a '73 with a build date of 11/72. No tags on the carbs. Also, the choke housing on the carbs are different, but function the same.

 

[poolboy]

The Anti Run-on Valve (ARV) came into being in 73 and continued on until the last 76 and the particular lever that opens the port for the ARV on the left side of the carb is unique to the 73's.
Seems to me that a lot of 73's have had a problem with this port opening.
Not only does the port open at idle for the ARV to work when you turn the ignition key to "OFF",but much more importantly that very same port (nipple) is the only vent for the float chamber when the engine is at idle speed.

If you haven't already, make sure that the lever operated, brass, spring loaded plunger for the transition valve is free to move both in and out of it's housing.
I like to put a few drops of oil into the float chamber's vent port on the carb's air box mounting flange and work the brass plunger to cleanup any debris or oxidation that may prevent the transition valve from working properly.

 

[TR6oldtimer]

I had one float bowl vent that was totally siezed, so I tapped and pulled the brass tube and cleaned the vent stopper. Once I did it to one, the second was simple.