Inlet manifold

[marki]

Hi All.

 For various reasons I’m considering fitting SU’s back on my 4a I have Webbers at the moment. Which manifold should I be looking at as I see there are various ones, long neck ?

  Cheers Mark

[Lebro]

The original 4A manifold is reckoned to be the best. Yes it is longer than the earlier ones.

Bob

Edited May 9 by Lebro

[RogerH]

see item #3  https://www.moss-europe.co.uk/shop-by-model/triumph/tr2-4a/fuel-system-induction-controls/carburettors-manifolds/inlet-exhaust-manifolds-tr2-4a-1953-67.html

 

Roger

[rcreweread]

Mark - the photo below shows a 4A SU set up with the correct manifold:

U

Unfortunately I haven't got any of these sets spare  - however I do have a Stromberg set up spare - these were fitted as standard on Tr4s, apart from the early ones where they were using up the left over TR3 H6 sets with the short stubby manifold, and were fitted to TR4As until the latter part of production in 1966 when they reverted to the HS6 set up - the Strombergs used the same manifold as the SUs, the only difference between a TR4 and 4A manifold being the triangular bump on the balance tube for TR4s and two "ears" ( see above photo) rather than the bump on 4As.

Below are some photos of the Stromberg set up which is available for a bargain price of £550  - Strombergs have arguably obtained an unfair reputation over the years for being inferior to SUs but this isn't necessarily true - what was true some time back was that spares availability for Strombergs was much inferior to SUs so it was easier to switch to SUs if they were worn etc - the situation today is completely different and spares availability is on a par with SUs, but mud sticks!

PM me if this could be of interest

Cheers Rich Crewe-Read

 

[ianc]

If Mark's engine is modified, and his mention of Webers seems to suggest this could be so, then standard Strombergs might need to be set on a rolling road and would likely require different needles, for which I believe there is a far greater range available for SUs.

Perhaps someone who has Strombergs on a modified motor could comment.

Ian Cornish

[stuart]

Also FWIW you need a different choke cable for Strombergs, its a longer one as it works on the front carb.

Mark theres always the EFI set I have

Stuart.

[marki]

Thanks for the replies guys.

 Rich thanks for the offer but I’m sticking with SU’s, tempting Stuart but I’m after something a bit cheaper and simpler. 
I will have it set up Ona rolling road as the engine is modified, so I should be looking for a long neck manifold ?

cheers Mark

[marki]

Would I be looking 1 3/4” SU’s ?

[rcreweread]

Mark - ideally, you want a long neck ( or swan neck as they are sometimes described) manifold as shown in my first photo with the SU's and you want 1 3/4" HS6 SUs - don't get H6 SUs as they are longer, more prone to leaking and more costly to restore.

Cheers Rich Crewe-Read

[stuart]

As your engine is modified why are you going away from the Webers?

Stuart.

[marki]

Thanks Rich, due to the fuel consumption and setting up, not sure if I’ll loose any power?

cheers Mark

[ianc]

HS6 carbs are fine to 5000, but if you want to go higher, then Webers are the answer.

Which is why the Comps Dept made the change on the Works' TR4s later in 1962.

Ian Cornish

[Lebro]

5000 will do me !

Bob

[Motorsport Mickey]

1 hour ago, ianc said:

HS6 carbs are fine to 5000, but if you want to go higher, then Webers are the answer.

Which is why the Comps Dept made the change on the Works' TR4s later in 1962.

Ian Cornish

You are right Ian, the SUs give plenty of go up to the 5000 area, and of course you need some clear roads (or significantly higher ratio rear axle) to want to be cruising at 5000 revs or more. Do you know, did the factory fit the then current Weber 42s or did they go to 45s ?

Mick Richards

[david ferry]

Mick,

Different sets of FIA homologation papers haver a different answer to your question. Perhaps the answer is 42s until they became unavailable, and 45s were used.

Papers under FIA recognition number 98 show the option of 42 DCOE carbs.

Papers under FIA recognition number 133 show the option of 45 DCOE carbs. 

David

[Motorsport Mickey]

3 hours ago, david ferry said:

Mick,

Different sets of FIA homologation papers haver a different answer to your question. Perhaps the answer is 42s until they became unavailable, and 45s were used.

Papers under FIA recognition number 98 show the option of 42 DCOE carbs.

Papers under FIA recognition number 133 show the option of 45 DCOE carbs. 

David

Thanks David.

Mick Richards

[marki]

That’s interesting 

[ianc]

David was quick on the draw there !

The Works' team soon started to fit 4.3 ratio so as to make use of the full potential of the modified engines, which proved able to sustain 6000 rpm without failures.   And without the modern contingent of flying mechanics, who can completely re-build a car in next to no time, the cars had to be reliable.  The Triumph crews were using Atlas vans, which do not fly !

When one considers the tough regime involved in the Rallies, with many ascents of Alpine passes and some circuit tests thrown in, the engines were a credit to the mechanics in the Comps Dept.

The TRs, with all the modifications incorporated, proved very quick in ascents, especially with Jean-Jacques Thuner (a Swiss) as driver - he would beat more exotic machinery, such as Ferrari !

Ian Cornish