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Grinnal

HS6 SU carb vacuum setup

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Hi Guys,

 

After more advise :)

 

I have fitted SU HS6 to my RHD car.

 

I am now am trying to understand how I should link up the vacuum hoses and the Servo pipe.

 

Should I link the two cards and then "T" to the distributor (type 22D) and then link the rocker cover to the brake servo?

 

Thanks in Advance

 

Mike

 

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Not sure what was in the picture but the distributor vacuum take off should come from just behind one of the throttle plates, a small push on connector.

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Sorry, Pete - good point.

 

Posted this picture - not glamorous, but seems to work. Distributor vacuum take-off is hidden in the picture, but it comes off the rear side of the rear carb (microbore woven tubing).

 

Paul

 

IMG_0093.jpg

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As Peter and Paul say, there should be a small bore tube that links the take-off in the photo to the vac advance capsule on the disy:

http://0.tqn.com/w/experts/MG-Car-Repair-3786/2010/07/SU-HIF44-Carb.jpg

It provides 'vacuum' that advance the spark only at cruise, no at tickover or wide throttle openings. Vac advance compensates for the slower combustion at cruise, d gives the best consumption.

Peter

Edited by Peter Cobbold

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Hi Paul,

 

Thanks for the pictures

 

The bit I am struggling with fitting the throttle linkage, the linkage I have looks the same as yours,

 

I cannot see how to mount it without it hitting the steering arm.

 

There are two threaded holes on the manifold which I assume are its mount point but as I say it hits the steering arm did you have to modify yours?

 

Thanks

 

Mike

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I'm not sure if the 6 setup is like the 4 but it looks very similar from the top. If so, the bracket that carries the bell crank is mounted to the two lower innermost carb fixing studs.

 

On second thoughts, yours will be cable operated I imagine, and Paul's is LHD so no steering arm in the way.

Edited by peejay4A

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I'm not sure if the 6 setup is like the 4 but it looks very similar from the top. If so, the bracket that carries the bell crank is mounted to the two lower innermost carb fixing studs.

 

On second thoughts, yours will be cable operated I imagine, and Paul's is LHD so no steering arm in the way.

 

Mike, Pete is right and I'm afraid that my set-up isn't going to help you. Hopefully, another of the RHD HS6 conversion owners will come up with a suitable image.

 

Alternatively, there are some decent images of a RHD HS6 conversion here - the images are small, but if you right-click and select 'view image' from the menu, they open at excellent resolution. They might give you some useful references for the throttle linkage.

 

Cheers

 

Paul

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Interesting, I can see the choke cable but it looks like that one has a rod operated throttle using the bellcrank like yours Paul.

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Hi Mike

Mine is set up as follows;

The 1/2" vacuum pipe to the servo runs from a connection on the balance pipe on the inlet manifold.

The microbore pipe to the distributor runs from a small connector on the rear carb only, adjacent to the butterfly.

The rocker breather is a 1/2" pipe from the rocker cover to a home made connection on the back of the standard Stromberg filter box.

It seems to work OK, never had any problems with it.

If you need a photo, pm me

RonA

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I think I see a Vacuum Retard module on that Blue car in PaulAA's post.

If the vacuum going to that module is coming from a vacuum nipple on the top of the rear carb, that would not be correct.

The Vacuum at that location is suitable for a Vacuum Advance module, but not a retard.

Hooked up to a retard, the timing will be retarded while steadily cruising along with a relatively small throttle opening.

On the other hand if the vacuum is coming directly from the manifold and not the carb, then it would be appropriate for the retard module..It's just hard to make out exactly where the vacuum is coming from in that picture but the module being on the cockpit side of the distributor makes it a retard.

Edited by poolboy

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Poolboy,

Difficult to tell for certain from the angle of the photo, but it does look like that capsule would pull the points-plate anti-clockwise when vacuum is applied. Making it vac-retard unit as you say.

Did USA carbs have vac retrad without vac advance- I thought they all had two capsules.

Vac advance capsules should be connected to the butterlfy edge take-off to pisck up venturi depression at cruise. This ensures there's not enough vacuum to advance the spark at tickover nor at wider throttle openings. And to advance the capsule must pull the points plate clockwise, since the dist rotor turns anticlock.

Peter

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Peter

 

Below is an image of the distributor before it was cleaned up. Single capsule, currently connected to the vacuum feed on the rear carb.

 

Paul

 

IMG_0094_adj.jpg

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Retard capsule for sure and no micrometer adjuster either.

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Paul

Disconnect the pipe.

It might be possible to swap the capsule over to the other side to make it vac-advance. The vac retard you have now is not needed.

There are other solutions too.

Peter

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Poolboy,

Difficult to tell for certain from the angle of the photo, but it does look like that capsule would pull the points-plate anti-clockwise when vacuum is applied. Making it vac-retard unit as you say.

Did USA carbs have vac retrad without vac advance- I thought they all had two capsules.

Vac advance capsules should be connected to the butterlfy edge take-off to pisck up venturi depression at cruise. This ensures there's not enough vacuum to advance the spark at tickover nor at wider throttle openings. And to advance the capsule must pull the points plate clockwise, since the dist rotor turns anticlock.

Peter

Hey Peter.

After 71 our distributors only had a retard module..Up until then they did have both an advance and a retard.

There's a fellow who does make a conversion module that actually replaces the Retard module..

He places the vacuum on the opposite side of the diaphragm which pulls the points in a clockwise direction...BUT the vacuum nipple on the carb that supplied vacuum for the retard can not be used for the reason you described.

Here's what I'm talking about..I haven't installed one, but I have read reports from a couple of folks who have..they say it works as advertised.

https://www.britishvacuumunit.com/Ported_Vacuum.html

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Hey Peter.

After 71 our distributors only had a retard module..Up until then they did have both an advance and a retard.

There's a fellow who does make a conversion module that actually replaces the Retard module..

He places the vacuum on the opposite side of the diaphragm which pulls the points in a clockwise direction...BUT the vacuum nipple on the carb that supplied vacuum for the retard can not be used for the reason you described.

Here's what I'm talking about..I haven't installed one, but I have read reports from a couple of folks who have..they say it works as advertised.

https://www.britishvacuumunit.com/Ported_Vacuum.html

Poolboy,

Brilliant link that - thankyou !! bookmarked.

 

Looks like he has the answer for Paul's disy.

https://www.britishvacuumunit.com/Special_Advance_Unit.html

 

cheers,

Peter

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Poolboy,

Brilliant link that - thankyou !! bookmarked.

 

Looks like he has the answer for Paul's disy.

https://www.britishvacuumunit.com/Special_Advance_Unit.html

 

cheers,

Peter

 

Many thanks for this.

 

It looks good, but I'm guessing that the HS6 would require a new vacuum take-off to be drilled into the carb body - the existing outlet appears to be too far forward to draw the correct vacuum.

 

I'll contact the manufacturer, but it begs the question whether the easier solution is to replace the dizzy with a reconditioned 22D6 with the correct advance unit.

 

Cheers

 

Paul

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Many thanks for this.

 

It looks good, but I'm guessing that the HS6 would require a new vacuum take-off to be drilled into the carb body - the existing outlet appears to be too far forward to draw the correct vacuum.

 

I'll contact the manufacturer, but it begs the question whether the easier solution is to replace the dizzy with a reconditioned 22D6 with the correct advance unit.

 

Cheers

 

Paul

Paul

I have an HS6 with the t/edge drilling - can take a measurement from that.

Peter

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