Strombergs / SUs

Engine Oily Bits, Ignition, Fuelling, Cooling, Exhaust, etc.
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Alec
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Re: Strombergs / SUs

#11 Post by Alec » Tue Jun 12, 2018 8:22 am

Hello Charles,

"Strombergs MUCH better built!!"

I do see this sort of comment from time to time but wonder on what basis ?

Alec
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tony
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Re: Strombergs / SUs

#12 Post by tony » Wed Jun 13, 2018 5:25 am

And much more complicated, and rubber parts which, today anyway, degrade. :shock: Love my S.U's
Tony.
1976 2500 TC.

Lots of bits

1999 BMW Z3.
2003 BMW 525i Touring.
Hopefully not needing too many bits.




.
Hopefully don't need bits !

brianthesnail96
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Re: Strombergs / SUs

#13 Post by brianthesnail96 » Wed Jun 13, 2018 9:47 am

I'm sure this is a silly question to the old hands (and not quite the right place to ask but it is related) but what is actually involved in swapping from one to the other? I've got a bit of a bitsa- originally a Mk2 PI (so pre facelift) but with the engine from a post facelift 2500TC (from memory), with a pair of 150 Strombergs off of a 2000 (and so I'm told the matching cam). I'm more familiar with SUs and I suspect it's probably losing out a bit with the current set up so fitting SUs and a more suitable cam is a tempting option, but I've seen mention of different crossmembers, engine mounts etc? It certainly looks like there's not a lot of room for the SU manifold looking at my current set up...

Cheers,

Matt

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Re: Strombergs / SUs

#14 Post by johnnydog » Wed Jun 13, 2018 10:09 am

The basic difference is the orientation of the mounting studs for the carbs on the inlet manifold.
HS6's have four mounting studs per carburettor, whereas HS4 only have two per carb. The other issue is that Stromberbs also only have two stud mountings per carb, but they are at a different orientation than the HS4 carbs.
Also the air filter box off Strombergs won't fit HS4's; if may look identical, but the through bolt holes are in slightly different positions. The thread of these mounting bolts for the air filter box varies between the HS4's and Strombergs too.
Personally, I would get the complete set up of the carbs of your choice off a donor car - then you will get the inlet manifild, linkages, throttle / choke cable, air filter box and the carbs which hopefully will be straight bolt on bolt off job. You probably may have to change the needles to fit your particular engine.
Strombergs also varied quite considerably through the production of our Triumphs, so if you went for Strombergs, I personally would get the ones relative to the age of your car. The inlet manifold varies relative to the carbs fitted too. I'd avoid the later ones though with the internal mixture adjustment and breather outlets - go for the earlier type with the simple adjustment at the bottom of each carb.
Sounds like you have a bit of a mish mash on your car. You really need to identify exactly which engine you have, and also equally importantly which cam is in it.
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1967 Mk1 2000 in Gunmetal Grey
1969 Mk1 2000 in Royal Blue
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1972 Mk2 2.5 PI in Triumph White
1973 Mk2 2.5 PI in Sienna Brown
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brianthesnail96
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Re: Strombergs / SUs

#15 Post by brianthesnail96 » Wed Jun 13, 2018 11:02 am

Cheers!

My train of thought was to fit HS6s with, as you suggest, the matching manifold, linkages etc. that I believe should be on my engine anyway- I'll look up the engine number when I'm back with the car. Hadn't even thought about HS4s but I imagine they are more suited to a 2000?

The engine should be coming out this weekend to investigate the erratically slipping clutch issue it has (it's halfway there...) so a cam change to one suited to the HS6s wouldn't be too tricky, especially as I've no idea what is currently fitted. The car was running with the injection kit on this engine, but I'm sure the cam was changed when it was carb converted as there's a cam in the box with the PI bits (that I should check the spec of as well, although it's knackered).

From looking at it I wasn't sure if the long HS6 inlet manifold + carbs would fit in the place of the Stromberg set up.

To be honest there's not too much wrong with it as is (other than suffering badly with fuel evaporation) but it doesn't feel as lively as I suspect a 2.5 should- I'm sure a tune up would make a big improvement mind.

Charles H
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Re: Strombergs / SUs

#16 Post by Charles H » Wed Jun 13, 2018 5:21 pm

Alec wrote:
Tue Jun 12, 2018 8:22 am
Hello Charles,

"Strombergs MUCH better built!!"

I do see this sort of comment from time to time but wonder on what basis ?

Alec
Alec
The Stombergs have a lot of brass fittings and are much better engineered albeit with the diaphragm rather than the solid piston. SU's have cheaper plastic and steel bits and pieces. Just pull one apart to compare! I have an old scrap broken Strommy if you want to look. Can bring to the National if you are going!
Charles Harrison
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Alec
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Re: Strombergs / SUs

#17 Post by Alec » Thu Jun 14, 2018 2:39 pm

Hello Charles,

I've worked on both and do not really see that Strombergs are better engineered. The tightest bti of engineering on the S.U. is the very close fit of piston and chamber.
I personally prefer S.U.s, especially the H.D. series; after injection, of course.

Alec
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torque2me
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Re: Strombergs / SUs

#18 Post by torque2me » Fri Jun 22, 2018 1:31 pm

Alec wrote:
Tue Jun 12, 2018 8:22 am
Hello Charles,

"Strombergs MUCH better built!!"

I do see this sort of comment from time to time but wonder on what basis ?

Alec
Supposedly from data available in the era.

Strombergs were designed and built by Triumph as an alternative to the SU which they believed the factory was being overcharged for. They had, at the time, experienced designers in this field as they used to design and produce carbs for the bombers of the Forties. Old press and magazine tests suggest that performance wise there was only a fag packet paper between them with the Stromberg being more fuel efficient. Over time wear has a big say on the performance and which wears quicker I would not like to say!

Kev

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