Su carburettor issues

[Adrian Fuller]

Hi all, the engine is getting machined so I have moved onto the carbs. Unfortunately the piston is sticking badly (almost solid) in the suction chamber. See photo with engineers blue mark, I have tried the other piston and that sticks in the same place. Is there a standard way to sort this out?. I was thinking of 2000 grit wet and dry then scotch bright cloth or is this just wasting my time?. If new carbs are required should I upgrade from h6 to hs6 as these are a lot cheaper. 

 

Many thanks for any help

Adrian

[ianc]

The jet arrangements on HS6 are much better as the age old problem of leakage from the cork seals has been eliminated.

If HS6s are cheaper too, it's a no brainer!

Ian Cornish

[BlueTR3A-5EKT]

1 hour ago, ianc said:

The jet arrangements on HS6 are much better as the age old problem of leakage from the cork seals has been eliminated.

If HS6s are cheaper too, it's a no brainer!

Ian Cornish

On a sidescreen car it is not a quite so simple a swap.   It will need  all the linkage changing and the heater elbow on the bulkhead that the float chamber of the HS almost touches......  and the choke cable may not be long enough.  Buy a full manifold and linkages if you are going that route.  

I’d try the polishing trick to start with.   An used matched pair of one piston and dash pot chamber could be bought cheaply and substituted.   

Perhaps put a request in “For Sale, Swap or Wanted, maximum value £250” and see what turns up.  Or try Turner Carbs. http://www.su-carbs.co.uk/

 

 

  TR 4 A manifold and HS carbs is a nice set up. https://www.tr-register.co.uk/classified/3076/Pair-of-175-HS6-SUs-on-TR4-4A-Manifold-fully-refurbished-with-all-Linkages

 

[Ralph Whitaker]

2 hours ago, Adrian Fuller said:

Hi all, the engine is getting machined so I have moved onto the carbs. Unfortunately the piston is sticking badly (almost solid) in the suction chamber. See photo with engineers blue mark, I have tried the other piston and that sticks in the same place. Is there a standard way to sort this out?. I was thinking of 2000 grit wet and dry then scotch bright cloth or is this just wasting my time?. If new carbs are required should I upgrade from h6 to hs6 as these are a lot cheaper. 

 

Many thanks for any help

Adrian

It has obviously had a knock on the outside if the suction chamber. Bad news is I dont think you will recover this as to polish that out and maintain the ultra fine limits of clearance needed will be almost impossible. Good news is that they are available as a matched pair of piston and chamber and they are among the cheaper ones ( £200 or so) bad news again is they are currently out of stock.

Ralph

[Adrian Fuller]

Hi all I have decided to replace my damaged H6 carbs with Hs6, following a discussion the the distributor doctor he suggested that it would be better to fit the longer tr4 manifold as the HS6 are shorter than the H6 which results in a shorter distance from inlet valve to venturi and this impacts the torque at lower revs, he did say he was not sure so I thought it was worth a post on here. Also if the longer manifold is required does anyone know the Stan part number. 

 

Once again thanks in advance for your help

 

Regards

Adrian

[Peter Cobbold]

I would grind/polish that high spot. And clean out the labyrinth seal grooves in the piston. The pressure difference across the piston is not great, about 8" water and the effect of locally removing that ding will be undetectable. But do not touch the rest of the dome or circumference of piston. Peter

[BlueTR3A-5EKT]

3 hours ago, Adrian Fuller said:

Hi all I have decided to replace my damaged H6 carbs with Hs6, following a discussion the the distributor doctor he suggested that it would be better to fit the longer tr4 manifold as the HS6 are shorter than the H6 which results in a shorter distance from inlet valve to venturi and this impacts the torque at lower revs, he did say he was not sure so I thought it was worth a post on here. Also if the longer manifold is required does anyone know the Stan part number. 

 

Once again thanks in advance for your help

 

Regards

Adrian

These are still available I think and include the TR4A inlet manifold

https://www.tr-register.co.uk/classified/3076/Pair-of-175-HS6-SUs-on-TR4-4A-Manifold-fully-refurbished-with-all-Linkages

 

Peter W

[barrytr4]

Hi Adrian

I would keep going to make it fit, I tried fitting HS6 on my tr4 but gave up ( I never had the right linkage) and got some H6 carbies , The car  would look better w/ the right carbies at least you can see what you need to do, increase the grit size, or use a small scraper

barry

[BlueTR3A-5EKT]

15 hours ago, Peter Cobbold said:

I would grind/polish that high spot. And clean out the labyrinth seal grooves in the piston. The pressure difference across the piston is not great, about 8" water and the effect of locally removing that ding will be undetectable. But do not touch the rest of the dome or circumference of piston. Peter

+1

Press on with very localised polishing and scraping inside the dash pot to remove the high spot.

Peter W

[roger murray-evans]

15 hours ago, Adrian Fuller said:

Hi all I have decided to replace my damaged H6 carbs with Hs6, following a discussion the the distributor doctor he suggested that it would be better to fit the longer tr4 manifold as the HS6 are shorter than the H6 which results in a shorter distance from inlet valve to venturi and this impacts the torque at lower revs, he did say he was not sure so I thought it was worth a post on here. Also if the longer manifold is required does anyone know the Stan part number. 

 

Once again thanks in advance for your help

 

Regards

Adrian

Adrian, as you must have already realised, there are those who know what they are talking about and those who don't. Just stick with what you have and what the car was originally built with.You know that the H6s fit, and with a bit of tlc and perseverance will do the job well, as they already have done so for many decades.

Good luck

Roger M-E

 

[Ian Vincent]

I swapped my H6 carbs for HS6s with a TR4a manifold. It was pretty straightforward and I sold the H6 carbs for more than I paid for the HS6s. The alterations to the linkage are simple and all of the parts are available from Moss. 

The trickiest bit was refabricating the heater hose bulkhead connection behind the rear carb to avoid the float chamber but there is an alternative solution using a TR connector for both pipes on the LHS of the car. 

Rgds Ian

[Hamish]

These are my H6 and the longer (later) inlet manifold. On my 3a

interestingly the division inside the manifold to the front and rear pair is a lot sharper better separating the flow to each port.

 

 

[BlueTR3A-5EKT]

Here is a manifold from a TR4A for sale

 

https://www.ebay.co.uk/itm/Triumph-TR4-TR4A-Inlet-Manifold-307455-Dry-Climate-Rust-Free-for-Restoration/274672762846?hash=item3ff3c5bfde:g:y~MAAOSwT9dgHVwa

Peter W

Edited April 20, 2021 by BlueTR3A-5EKT