SU carbs on 67 gt6 mkl

[xtbearx]

I am planning to switch my gt6 from stromberg cd150 to HSU4 carbs. The engine is MKl. Has anyone done this switch? I would appreciate any info you can provide.  Thanks 

[iani]

4 minutes ago, xtbearx said:

I am planning to switch my gt6 from stromberg cd150 to HSU4 carbs. The engine is MKl. Has anyone done this switch? I would appreciate any info you can provide.  Thanks 

It's more common to go to HS6s, by going to HS4 you're going from one pair of 1.5" carbs to another, what's the benefit?

[RobPearce]

I don't believe there's a readily available manifold for SUs on a Mk1. And as iani says, what's the point? You're going from a well-engineered system with thousands of hours of development behind it, to a hotch-potch of your own guesswork and rumour. All you're likely to gain from the change is a LOT of grief and trouble.

[iani]

Just now, RobPearce said:

I don't believe there's a readily available manifold for SUs on a Mk1. And as iani says, what's the point? You're going from a well-engineered system with thousands of hours of development behind it, to a hotch-potch of your own guesswork and rumour. All you're likely to gain from the change is a LOT of grief and trouble.

I don't know Rob, I've got a ported Mk1 inlet manifold going spare here 😉, opened out to 2" and it worked fine with HS6's when I had a Mk1 engine in the car. My car had a PI cam and was putting out 113BHP, not bad for a Mk1 car.

[xtbearx]

The reason for wishing to switch hsu' is I am tired of the stromberg cd150 's. I have tried two sets of cd150 's. They leak out of the float bowel (3 carbs). The linkage is 50yr old plastic and easily cracks. Plus good luck setting the fuel/air valve in the bottom of the float bowel (plus these routinely leak). So the hsu's simply can not be worse then the cd150 's.

I would be interested in the mk1 manifold mentioned

Thanks

 

 

 

[RobPearce]

6 hours ago, xtbearx said:

So the hsu's simply can not be worse then the cd150 's.

Oh yes they can! I had no end of trouble with the (refurbished!) SUs on my Spitfire. I have NEVER had any trouble with the Strombergs on my Vitesse or my GT6 (or my previous Vitesse).

Leaks from the float bowl or the adjuster are nearly always fixable with a couple of 5p O-rings and a new gasket. The plastic bits of the linkage can be replaced with readily available UJs (sold for RC models) if need be.

[iani]

7 hours ago, xtbearx said:

 

I would be interested in the mk1 manifold mentioned

Thanks

 

 

 

Pics & PM sent re manifold

[Dave Clasper]

After a bit of basic/cheap sorting, never had any probs with Stroms on my car in 9 years, 

[david langrick]

On 10/11/2022 at 19:47, iani said:

It's more common to go to HS6s, by going to HS4 you're going from one pair of 1.5" carbs to another, what's the benefit?

Don't do it Ian. An early engine is far better on CD150's..

SUs will make no difference.

Contact Burlen Fuel systems to repair or refurb your existing Strombergs. They will be able to sort you out.

Consider the flowed / balanced inlet manifold from Chris Witor and you will have a good reliable set up.

 

 

 

[Tim Bancroft]

Got to agree with Dave, stick with the Strombergs, in many ways they are superior to SUs, mainly due to the integral float chamber. 

Re-furb and stick some MED stub stacks after the carbs have been re-built, then fit an ITG filter with a cold air feed and you will be surprised at the torque gain.

MED Stub Stacks: Check with them to see that they will fit:

https://www.med-engineering.co.uk/ancillaries/stub-stacks/med-stub-stacks

ITG filter example:

https://www.merlinmotorsport.co.uk/p/itg-megaflow-air-filter-jc40-sausage-domed-type-itg-jc40-s-25

As Dave states, Chris Witor does a nice flowed inlet manifold. Also thin down the throttle spindles in the throat of the carb and make sure you have a smooth flow through the carbs into the manifold (port match). Good old fashioned UK sports car tuning. You will be surprised.

 

[iani]

3 hours ago, david langrick said:

Don't do it Ian. An early engine is far better on CD150's..

SUs will make no difference.

Contact Burlen Fuel systems to repair or refurb your existing Strombergs. They will be able to sort you out.

Consider the flowed / balanced inlet manifold from Chris Witor and you will have a good reliable set up.

 

 

 

It's not me Dave, I've gone to 2.5l as you know. Chris Witor doesn't do the manifold now, I believe the machinist stopped doing the work some time ago