Modifying a Stromberg 175 Carb

[Burdekin]

Has anyone done the SU mods to a Stromberg 175 as outlined by David Vizard in his book; "Tuning the A-Series Engine"? If so what were the results? I have a dyno session next Friday to see what my car is running at currently and would like to do the mods to measure the effects. Not much time to get them done though.

[Laird Scooby]

For those of us who haven't read the book, what mods are you talking about specifically? The Stromberg is a different animal to the SU in many ways although they work and perform in a similar way.

[Burdekin]

Squaring off the internal casting post bridge, reducing butterfly shaft, knife edge butterfly, dome head butterfly screws and taper piston leading edge and back edge at full up position. Want to see if the additional flow will increase or hurt low to mid torque or just give a bit of extra high end HP. Not sure if there is a rich enough standard needle though so that might also need modifying, currently running one of the richest needles and that is just with a stub stack and K&N filter fitted which gave a good increase in flow.

[Laird Scooby]

Originally Posted by Burdekin

Squaring off the internal casting post bridge, reducing butterfly shaft, knife edge butterfly, dome head butterfly screws and taper piston leading edge and back edge at full up position. Want to see if the additional flow will increase or hurt low to mid torque or just give a bit of extra high end HP. Not sure if there is a rich enough standard needle though so that might also need modifying, currently running one of the richest needles and that is just with a stub stack and K&N filter fitted which gave a good increase in flow.

On an A-series with a relatively short inlet manifold that would help, not so sure you'd even notice the difference on something twice the size in terms of capacity and with a relatively larger inlet manifold.

What oil are you using in the damper?

Also if you want to really increase power/flow capability, have you considered an SU HS8?

Gut feeling says you'll lose driveability by modding your Stromberg that way but i've not tried it so can't be certain.

[Burdekin]

Originally Posted by Laird Scooby

On an A-series with a relatively short inlet manifold that would help, not so sure you'd even notice the difference on something twice the size in terms of capacity and with a relatively larger inlet manifold.

What oil are you using in the damper?

Also if you want to really increase power/flow capability, have you considered an SU HS8?

Gut feeling says you'll lose driveability by modding your Stromberg that way but i've not tried it so can't be certain.

80 90 gear oil, works a treat but will also try 75 80.

The mods to a SU6 will result in it flowing similar to a HS8.

The stromberg is a good cheap carb and personally think it is better than the HS SU carbs. Mine works really well. I just want to see if the extra flow will give increased performance and if I can get performance close to the B20B. Just having a play.

[Laird Scooby]

Originally Posted by Burdekin

80 90 gear oil, works a treat but will also try 75 80.

The mods to a SU6 will result in it flowing similar to a HS8.

The stromberg is a good cheap carb and personally think it is better than the HS SU carbs. Mine works really well. I just want to see if the extra flow will give increased performance and if I can get performance close to the B20B. Just having a play.

I've always used Dexron II-D in Strombergs and SUs as well. Given that you're running a bit lean at the top end, 80W90 would work well too.

The limiting factor on an HS6 will always be the 1 3/4" diameter, the HS8 will give that vital extra 1/4" diameter or you could opt for twin carbs of a Weber 38DGV conversion which is in effect twin HS4s in terms of flow area but are easier to alter the jetting.

What other mods have you done to the engine?