View Full Version : TR2/3/3A tr3 carburetor rebuild question

03-27-2005, 12:32 AM
I just rebuilt 2 TR3 H6 carburetors and on the carb closest to the fuel pump, on the bottom of the carb I found a threaded hole that went all the way into the carbs center. I don't remember anything being threaded in it and all the pictures I took never showed anything in it. It almost seems like it might act as a vacuum hole if something was in it. The second carb does not have this hole. Can anyone tell me what this hole is and am I missing a part. Everything else seemed to go back together without any problems, except this hole /ubbthreads/images/graemlins/confused.gif

03-27-2005, 12:43 AM
It's for the vacuume advance on the distributor. Very small threaded ferrull on the end of a metal tube.

03-27-2005, 12:44 AM
It's the connection point for the vacuum advance line that should connect to the vacuum advance piece on your distributor. At least that's the way my TR4 w/ H6 carbs is set up, and I assume the TR3 is similar.

Ive heard that these are sometimes disconnected; however, Id think youd want to plug the hole if that was the case.

03-27-2005, 12:49 AM
Is there a connection or something that should be screwed into the threaded hole. I certainly want to have my vaccum advance to be connected.

03-27-2005, 02:18 AM
Aloha Scott,

As other have said it is the connection for the vacuum advance on the distributor. The fitting is illustrated as part # 80 on this page from the Moss Catalog:


The vacuum line and fittings are shown on this page:


The threaded hole you ask about seems to take a 7MM 1.0 pitch male fitting. I don't know a source for the proper part, perhaps some else does. On my car, some PO found a brass fitting to accept the 1/8" compression nut on the vacuum line and filed the other end down to fit in the carb body. They then epoxied it into the carb. If you decide to not use a vacuum advance distributor, I would recommend plugging the hole with a set screw or modified machine screw.

Safety Fast,

03-27-2005, 02:18 AM
Take a look at a Moss or Victoria British catalog (page 124). In my Vicky Brit, you need part 12-8485 and 18-718.

03-27-2005, 02:22 AM
I was 15 when I rebuilt the SU's on my '59, but I remember distinctly ordering a new vaccuum advance line from Moss, one of my first LBC parts purchases about 20 years ago, but the line should be threaded on the carb end and have a fitting that connects to the distributor end. Nothing that isn't already on the line should be needed.... it has been twenty years, but I am very sure it's a direct connect... check the Moss catalogue online for the TR3, there should be a diagram that would show the parts, even if they are no longer available.. www.mossmotors.com (https://www.mossmotors.com)

Brings back some great memories! The SU rebuild is like a day at Disneyland compared the Zenith Stromberg nightmare on the Auto Choke Jag I've been attemping. I used to think British carburettors were fun to rebuild and tune.... those were the days. Enjoy your car, I'm looking for another Triumph currently, missing the small roadster tinkering.

Brian /ubbthreads/images/graemlins/cheers.gif

03-27-2005, 02:35 AM
I need to get some kind of memory supplement first thing in the morning... There is a fitting, says no longer available for the SU, but when you search the TR2-4A for "advance line" it will link you to the Zenith Stromberg page for Triumph.. I do now remember that part, and I believe it was brass with about an eight to ten millimeter Hex surrounding two small threaded ends... if you can't find yours call Moss and ask if there is a substitute, they have some numbers listed that look like Jaguar part numbers or maybe it is the same fitting used on the Zeniths for the TR4s. Sorry for the wrong info, and for skimming the replies and missing the fact that someone had already linked you to the correct page on Moss's site.. only 35 and the mind is already slipping. /ubbthreads/images/graemlins/blush.gif


03-27-2005, 04:02 PM
Its for the vacuum advance. Hey if I had seen this post last night this would have been helpful.

03-27-2005, 07:42 PM
Thanks for all the help. After reading all the replies, I went and searched the parts box that came with the car and guess what I found. The previous owner must have taken the advance hose off for some reason. Anyways, it fits perfect and will certainly help with the cars driveablity. Once again, thanks alot for all the help and I certainly will be coming back to this site for more information in the future, as I'm in the middle stages of restoring this TR3. Thanks