• Hey Guest!
    British Car Forum has been supporting enthusiasts for over 25 years by providing a great place to share our love for British cars. You can support our efforts by upgrading your membership for less than the dues of most car clubs. There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Upgraded members don't see this banner, nor will you see the Google ads that appear on the site.)
Tips
Tips

Su carbs 1 1/8 to 1 1/4

Share this page

The Weber/Pierce I had on my Bugeye had been jetted correctly by the PO and the performance was good, no flat spot either. From everything I've read the Weber has a little better wot, the dual HS2s are better all around, and the single SU is somewhere mid pack. David Harrison (Gundy) probably has the most experience with all these carb combinations since I think he's tried everything! Iirc, he has gone back to the dual HS2s on his modified 1275.
Rut
 
Rut said:
The Weber/Pierce I had on my Bugeye had been jetted correctly by the PO and the performance was good, no flat spot either. From everything I've read the Weber has a little better wot, the dual HS2s are better all around, and the single SU is somewhere mid pack. David Harrison (Gundy) probably has the most experience with all these carb combinations since I think he's tried everything! Iirc, he has gone back to the dual HS2s on his modified 1275.
Rut
Click to expand...

As I recall, David has a high modified 1380, not your ordinary street car. He also used HS4's as I recall, not the HIF44 I have traditionally used. I qualified my comments in that regard, but I have done a wide variety of builds for myself and others, and stick by my experience. Also, there's no question HS2's will not flow like a single HIF44. If you understand how the dual carbs work on our cars, you'd know that even with two 1.25" carbs you're still limited to 1.25"... they are not cumulative.
 
Area of a 1.25 carburetor throat = 1.23sq". Area of a 1.75 carb = 2.40sq". If you think about it, it doesn't matter what your engine displacement is but how much correct fuel to air mixture you can pump through it in a given amount of time. Its why formula 1 engines run at high rpm's with a tiny displacement and tractors with huge displacement run at a low rpm to put out small amounts of power. There carburetor area's will correlate with the power they put out. Not directly but they will.

Kurt.
 
nomad said:
Area of a 1.25 carburetor throat = 1.23sq". Area of a 1.75 carb = 2.40sq". If you think about it, it doesn't matter what your engine displacement is but how much correct fuel to air mixture you can pump through it in a given amount of time. Its why formula 1 engines run at high rpm's with a tiny displacement and tractors with huge displacement run at a low rpm to put out small amounts of power. There carburetor area's will correlate with the power they put out. Not directly but they will.

Kurt.
Click to expand...

Thought this might help illustrate some of this conversation

 
Back
Top