I’ve been told that XJ6 in ENGLAND had the two HD8 (2”) SU. Carbs. If that is correct what is the market price of those and who is a source I can find some decent used ones from?
I’m putting a supercharger I have on a V12 and would like the carbs to be SU’s.

 

Depends on the years. Early cars would have had HD8, by the 70's they has HS8 and some later cars had HIF44. I have used all 3 on various cars, I prefer the HIF44, just make sure to change the choke valve O ring to a viton or other material that is compatible with modern fuel.

You can get any of these on Ebay UK. They don't have to be a Jaguar application, late Mini's used a single HIF44 for example.

 

Thanks you. I already have 4 HD8’s and I’m looking for 2 more. Are they rare and expensive in the UK ? Or reasonable?

 

I've never shopped for HD8's, so I don't know what they sell for now. E Type stuff is very expensive, not sure about the other applications.

 

Burlen Services in Salisbury are the manufacturers of SU. They have HD8s available new:

https://sucarb.co.uk/pair-of-hd8-yje...l-1968-71.html

 

You want 6 carburetors on a supercharged V12? That sounds like a tuneability nightmare, but you do you!

 

Sounds well over carburetted too. On the injected engines, the throttle ares is about 9.8 square inches, and that can support in excess of 500hp. 6 HD8 carbs is double that area, so seems overkill to me.

 

Two things.
1. Supercharging requires at least 40% more air than normally aspirated. In addition I’ll be using E85. (85% ethanol) that requires as much as another 50%. (It both cools the heated intake charge and adds significantly to the intake requirement.).
2. Alcohol is extremely tolerant fuel mixture wise. ideal gas is 14.7 parts of air to 1 part of fuel. Deviation over 1% is a serious problem.
Alcohol ideal is 9.8 parts of air to one part of fuel but will tolerate as lean as 11.5-1 or as rich as 8,6-1 without any serious issues.
Since the Venturi is variable SU’s tolerate being oversized and adjusts itself according to actual need.
3 HD8’s on a 4.2 XKE is seriously oversized but works very well.
With a race car I will likely be able to get real close to the full potential of a 5.3. V12.
If they don’t work I’ve got 6 Strombergs and worst case 6 1&1/2 inch SU’s.
Now for on the street using gasoline the Six 1&1/2 inch SU’s would probably work best.