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Difference Between Carburettor Models

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glcaines Avatar
glcaines Silver Member Gary Caines
Hiawassee, GA, USA   USA
I have a 1973 TR6 that currently has SU carbs on it. I found a set of Strombergs already mounted on an intake manifold for a very cheap price, so I bought the set in case I or a future owner wanted to switch back to original. I know the 1973 TR6 is supposed to have 175CDSCV (3508L and 3508R) carbs. The set I bought are 175CDSCVX (3613L and 3613R). I know the ones I bought are Federal Spec carbs. Does anyone know what the physical differences are? Are the differences important? If so, I'll likely sell the ones I bought and look for the correct carbs.



Current: 1973 TR6 W/Overdrive

Previous:
1963 TR3B W/Overdrive
1962 TR3A
1961 TR3A
1960 TR3A
1960 TR3A

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poolboy Avatar
poolboy Ken D
Sandy Hook, MS, USA   USA
73 carbs were unique.. the mechanism that controlled the transition of the float chamber vent outlet was unique and I suspect "experimental".
A more robust mechanism was adopted in 74 and continued on throughout the remaining life of the TR6.
3613 were also unique...the only post 69 carbs to have Throttle Bypass Valves with an external vacuum sensing port...And, the rear 74 carb had a provision for a vacuum breaker for the EGR valve.
Vacuum port for activating the distributor's vacuum RETARD module was on the 73's rear carb and on the 74's front carb.
Any difference between 73, 74, 75 or 76 carbs can be compensated for.
If you want to keep a working Anti Run-on Valve, you'll need one of those years....If not a 71 or 72 carb would be my choice.



Edited 1 time(s). Last edit at 2018-02-13 08:52 PM by poolboy.

glcaines Avatar
glcaines Silver Member Gary Caines
Hiawassee, GA, USA   USA
Thanks Ken. I sent the same question to Burlen technical service in the UK and just received their reply. I didn't think I would receive a reply from Burlen based on the disclaimer on their website. I've copied the Burlen reply below. Based on what both you and Burlen provided, I'll keep the set of carbs that I bought, although they very much need to be rebuilt. I'll leave the SUs on the TR6 for now at least. Thanks again for your quick reply.

"The basic way of seeing these is that the more letters then the more emission devises are involved.
The two specification numbers given are the some bore size and have the same central metering needle should behave the same.
For the vehicle details provided I think you have the correct carburettors fitted as the original drawing attached is first dated April 1973.
We can no longer supply complete carburettors however we can supply service and rebuild kits to suit that specification."

Gary



Current: 1973 TR6 W/Overdrive

Previous:
1963 TR3B W/Overdrive
1962 TR3A
1961 TR3A
1960 TR3A
1960 TR3A

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poolboy Avatar
poolboy Ken D
Sandy Hook, MS, USA   USA
Your 73 does not have the facilities to activate the type of TBV's that are on the 74 carbs...but that's something that's easily taken care of, though.
I think if you compare the 73 with the 74 in this illustration, you'll see a far more complex system of plumbing connections to and from the 74 than the 73.
https://mossmotors.com/triumph-tr6-250/fuel-intake-emissions/emission-control-vacuum-system
If you need any carb related services, contact me...I can probably help.



Edited 1 time(s). Last edit at 2018-02-14 12:23 PM by poolboy.

glcaines Avatar
glcaines Silver Member Gary Caines
Hiawassee, GA, USA   USA
Thanks again, Ken!



Current: 1973 TR6 W/Overdrive

Previous:
1963 TR3B W/Overdrive
1962 TR3A
1961 TR3A
1960 TR3A
1960 TR3A

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