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MG TD TF 1500 - H4 SU carb and needles!

My 1250 engine is running waaaaaay to rich. Thus, I'm attempting to tune the carbs and am going square eyed reading the prolific quantity of "how to" articles on the subject. One thing that would help is the for someone to refer me to a SU H4 diagram that clearly identifies what the "Bridge" is and what the meaning of setting the "jet" height at 30 or 40 thou below the bridge means? A basic line drawing/description would be much appreciated,
BEST REGARDS
Rod Murray 54 TF #3006
Rodney G Murray

https://m.youtube.com/watch?v=R1ns8yg66Mo


This one seems pretty good for carb set up. Although on first glance I did not see float setting.

Regards, Tom
tm peterson

The detailed instructions from Dave Braun are the best you're going to get.

https://www.dbraun99.com/SU%20Carburetor%20tuning%20gen%20rev%20d%20161127.pdf

After that, you can browse numerous detailed examples of SU rebuilds.

https://www.dbraun99.com/MGTD15470/Engine/Carburetors/

https://www.dbraun99.com/SU_Carburetors/

That's 15 rebuild projects with a total of 1590 photos.

This attached copyrighted image is an example of what you'll find, thanks to Dave.



JIM N

I pulled these two images off the MG Experience BBS.




JIM N

Many thanks for the replies!Now understand the "bridge".
The Resto Nation video is perfect for what I want to do.
The first URL for Dave's items did not show up as now being available; however, his photo shows 70 thou on the verniers which is another number I've seen. 30,40 and now 70 thou, if that is the number he suggests rather than a number he found indicating how far it was out!
Just to confound things if you use turns/flats then I have seen a large number of different suggestions but I would believe that is probably a function of the massive number of variables like temp, altitude, humidity and not least the variable wear conditions of these carbs.
I will find mine through trial and error.
Again thanks for the help!
Rod Murray (loving driving TF 3006.)
Rodney G Murray

Rod---Probably no use to you , but i do a few MGA/MGB carbs and set them at 2 turns down/12flats and that gives .065" and that usually ends up where they stay within a flat or two fine adjustment----Of course none of this fine adjustment will be relevant unless the shoulder of the needle is dead level with the bottom of the piston---Take time to get the needles set correctly and that makes jet adjustments more accurate/equal-

willy
William Revit

This thread was discussed between 07/05/2022 and 08/05/2022

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