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TR6 1 & 3/4 SU's on a TR6

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K

karls59tr

Obi Wan
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What size jet needle is used on a TR6. Asking for a friend who is replacing the Strombergs on his TR6 with SU carbs from a TR3. Wonder if TR3 linkage would work for that application or would something have to be fabricated?
 
I'll be working on this same question later when I convert to HD6s. APT Performance in Riverside, CA does a lot of Triumph dyno tuning and sells many needles for SU carbs. I'll be wanting to know what needle is spec'd for the HS6 conversion kits for the TR6, which they sell. Guessing the same needles would work on the H6 TR3 carbs you're mentioning.

https://www.aptfast.com/
 
Karl,
I believe your biggest problem with using the H6 carbs from a TR3 on a TR6 is going to be the linkage. The H6 carbs use a bell crank located at the front of the carbs and is located on the exhaust manifold. You will have to do a lot of fabricating to establish that. The TR6 uses a bell crank located between the carbs. However the HS6 carbs (used on a few late TR4s) use a bell crank located between the carbs.
 
Also, the SU H6 carbs are "thicker" (flange to flange) than the ZS or SU HS6 carbs. There may not be enough room for the stock air cleaner. What would be gained from the switch?
Berry
 
APT got back to me . BAG is the Swing needle used in the HS6 TR6 conversions. Won't fit in earlier carbs - HS6 and HD6 require a fixed 100 needle for the 100 jet. These are comparisons of the jet area with the needle. Note the TR3 is richest of all:

NeedlesTR6_2.jpg


From Ian Hamilton's "Needles.ods" spreadsheet
 
Steve-Just remove the cap on the swinging needle, lightly file the knurls on the shank, and the needle can be used in a fixed needle piston. I have also found that the recommended BAG needle (used with the 8 oz yellow spring) was too lean).
Berry
 
titanic said:
Steve-Just remove the cap on the swinging needle, lightly file the knurls on the shank, and the needle can be used in a fixed needle piston. I have also found that the recommended BAG needle (used with the 8 oz yellow spring) was too lean).
Berry
Click to expand...

Berry,

Thank you for the input. Looks like the Healey normal CV might be a good starting point after all.

Edit: Healey BJ7 HS6 normal (BC) added. Healeys run the 12oz Green spring - that would make the BAG run a little richer.

NeedlesTR6_4.jpg
 
The short answer is I am using a KN needle with red springs. It was recommended by a person who had a wide band AF meter and similar mods as my engine, which are an increase in CR to about 9.5, 150 hp PI cam, and the dual outlet exhaust from a later TR6. He found that the lighter (4.5 oz) red springs gave better acceleration. He also gave me a modified profile for this needle for better performance-it is .001"-.002" thinner starting at station 2.
Berry
 
titanic said:
The short answer is I am using a KN needle with red springs. It was recommended by a person who had a wide band AF meter and similar mods as my engine, which are an increase in CR to about 9.5, 150 hp PI cam, and the dual outlet exhaust from a later TR6. He found that the lighter (4.5 oz) red springs gave better acceleration. He also gave me a modified profile for this needle for better performance-it is .001"-.002" thinner starting at station 2.
Berry
Click to expand...

Good info, Berry!

Question - if one is going to shave the needle for all positions above idle, couldn't the jet be dropped a few thou instead?
 
Steve-I suppose you could, but the idle would be pretty rich. I think that is what Kastner suggested in his competition prep manual, but he wasn't concerned with anything but the upper range.
Berry
 
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