T-Series Can't get idle below 2000

[drooartz]

I'm helping some friends get a MG TC back on the road. It's a beautiful restoration, but there are some mechanical things we're trying to sort out.

The car fired up yesterday, but we could not get the idle down below 2000 RPM. We did a quick check of the butterflies and they seem to be seating properly in the bores (we didn't pull the carbs, just looked in from the front). Idle screws are all the way out. We were struggling with the mixture. We ran the jets all the way up but they didn't seem to go far enough -- were not level with the bridge in the carb bore even with the nuts all the way up. The number on the needle was a 158.

The fellow I'm working with has a bunch of TC experience, I have none but have played with SUs for a number of years. We've wondered if the jets are incorrect, or are not correctly installed.

Looking for some suggestions on other things to try or to consider. No one involved did the actual restoration, so we're a bit blind as to what is in there.

 

[DrEntropy]

Check that the needles are not "hanging" somewhat in the jets. Checking the centering of the jets may be a good idea.

Seems the jets should be able to go flat to the bridge, too.

 

[drooartz]

Thanks. We were wondering if the jets are either the wrong part or are installed wrong. Unfortunately no one involved with the actual restoration is currently involved or available, so it's a bit of a black box until we really dig in there.

Makes me really appreciate what professional mechanics deal with when trying to sort out someone else's work.

 

[JPSmit]

can you disconnect the cable? It might be binding and not returning fully

 

[PAUL161]

Have you checked for vaccume leaks on the intake manafold or carb gaskets? PJ

 

[DrEntropy]

Have you checked for vaccume leaks on the intake manafold or carb gaskets? PJ

A spray bottle with water and spray around all joining gasketed parts of the manifold & carbs. RPM will react if a vacuum leak sucks in the water mist.

 

[drooartz]

Update: my friends were able to get things set a bit better. They reset the needles and jets and were able to get the idle down to about 1200. Still a bit high, but drivable which was the goal.

Good thought in the water bottle, will suggest that if we get working on it again.

 

[PAUL161]

Drew, my TF idles at 1000rpm due to the Crane cam profile, any lower then a roughness starts to appear, but saying that, at 1000 rpm the engine is as smooth as silk, so a couple of hundred RPMs makes no difference in sound and shifting. Just saying. PJ

 

[drooartz]

That makes sense. The goal was to get the car to where it could be driven, and they seem to have done that. Happy times.