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TR4A SUs - Proper Air Filter Mounting

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smdl Gold Member Shaun Laughy
Courtenay, BC, Canada   CAN
Hi, folks.

I'm currently working on completing the rebuild of the SUs that are on my TR4A, and hope I can get some opinions about the best way to mount the air filters. The car currently has a set of K&N filters on it, and they are mounted using pieces of threaded rod, nuts and lock washers through the holes in the carb mounting flange (see pics). This is a pain in that the rod is as likely the unthread from the rear nuts as the front ones, meaning that it all has to be fitted back in place before remounting the air filters again. Also, the rear nuts can easily drop off, disappearing under the car. I had thought to use a bit of loc-tite blue on the nuts at the rear to discourage this, but that might be a pain if I want to take the studs out completely. Also, the positioning of the nut on the rear carb causes interference with the choke mechanism, so I thought I would pause for a moment to get some ideas as to what might be a better way to mount these. I'm sure I had seen something that said bolts should thread into the carb flange, but there aren't any threads there on these carbs.

Any suggestions would be appreciated.

Cheers,
Shaun

Edit: Attachedpics



Edited 1 time(s). Last edit at 2017-11-12 05:49 PM by smdl.

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Perdido Avatar
Perdido Gold Member Rut Rutledge
Tuscaloosa, Alabama, USA   USA
Shaun,
The original air filters fit the same way, but with bolts and thin nuts on the back of the carbs. Studs might be a good way to eliminate the nut and bolt arrangement.
Rut

Milpitas, California, USA   USA
1963 Triumph TR4 "Merlin"
Shaun,

The factory fitment was a bolt a plain washer a lock washer and a plain nut.
With the K&N 1 3/4 inch filters on my Tr I'm using a 5/16" X 3" bolt a 5/16" plain washer a 5/16" lock washer and a 5/16" UNF plain nut.
Depending on which K&N filter you are using you might have to use a longer bolt.
The arrangement is as follows:
Insert bolt thru plain washer then thru filter (and inner filter spacer) then install on carb (make sure the filter and gaskets are oriented correctly) and then the whole mess is inserted thru the filter boss and the lock washer and plain nut secures them.

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Tr4 air filter attach.jpg    20.9 KB
Tr4 air filter attach.jpg

smdl Gold Member Shaun Laughy
Courtenay, BC, Canada   CAN
Thanks, gentlemen. Very helpful.

Shaun

TR3driver Randall Y
Confusion, Los Angeles, USA   USA
FWIW, on my earlier SU carbs, I installed a Helicoil in the holes and used a bolt and lockwasher from the front of the filter. Much easier to R&R the filters.
Should work the same on HS6, but I haven't tried them yet.



Randall
56 TR3 TS13571L daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild

smdl Gold Member Shaun Laughy
Courtenay, BC, Canada   CAN
Good idea, Randall! I might just give that a try.

Cheers,
Shaun

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