Hi, changed from the Strombergs to HIF SU's and the garage is having difficulty getting the jetting correct.

Can anyone give me a fighting chance to get the jetting correct or near the correct air/fuel ratio?

Thank you for any assistance.

 

I dont know.

The HIF is not a common swap on these, however, it is what it is.

I use HS8, with manual choke conversion.

The people at SU Midel in Sydney have always helped me over many years.

Might be worth a call.

Home

 

From the book i have "Tuning SU Carbs" by G Wade,

needle NZX 8013 or 8023

jet WZX 1456

Thats for S2 4.2 XJ

Good luck,

Rob

 

Hi all,
Are SU carburettors substantially better than Strombergs?
If so, why?
I ask this question because as they both are of very similar design and on observation it is hard to see why the SU would deliver a better performance.
Certainly the SU has the name and nothing looks better to my eyes than set of polished SUs. Having said that Strombergs seem to be more technically advanced in the sixties and early seventies by having the float bowl integral with the carburettor rather than remote like the SU. The cold start enrichment seem more sensible compared to moving the main jet, in my opinion.
Was the Stromberg a cheaper option?
Ive got 'no skin in this game' as our American friends say, it's just something that has always interested me
Al

 

The HIF SU has the float bowl the same as the Stromberg, under the main body.

I only changed over to the SU's on the recommendation of the local Jaguar expert who said that I may experience some trouble with the Strombergs in the future due to the small O rings and perishing rubber. When I told him I had access to a pair of new HIF's or HS'8 he advised the HIF's. What he forgot to mention was that he had never done this conversion before. The whole operation has been a disaster thus far, with the vehicle going back to them three times for jetting and further modifications. It is now running OK performance wise but is running far too rich at low speeds. On a pleasant drive cruising at 40>60kph I am using 28l/100km (that's 10mpg) on a brisk country drive cruising at 100kph I return 13.78l/100 (20mpg) To me that indicates that they have got the top end correct but hopeless at low RPM.

IN so deep now I do not want to change back to the Strombergs, also they have been sitting in a box in the shed for the past 12 months while this ongoing saga continues.

 

Hi Landdfall,
good luck with it.
It is hard for a non- expert to believe there is not an answer to your mixture problems with the range of needle and jets available.
As Gary mentioned my first 'port of call' would be Midel or another specialist.
SUs have been around a long time, I'm sure that there are no mysteries to those who make their living from them.
Good luck, I will be interested in hearing any performance difference once it is sorted.
regards
Al

 

Alan, Landdfall,

Main reason from MY point of view, and waaaaay before Computers and stuff.

The Strombergs were CD175, and that is 1 3/4".
The SU HS8 is 2".

The Strombergs were installed as part of the Ozzie Emission Scandal back then, as the SU's were deemed by someone as not able to meet these reqirements. Stayong rightof teh Politics, to silly for me at any time.

The Strombergs have a diaphragm inside, that gets a hole in it and basically screws your day.

The USA also got Strombergs on the V12 engines, in the "E" and the S1 cars, and that was purely related to California proposed emissions requirements, or so we were told at Jaguar at the time.

My 4.2 cars all returned about 18MPG for local driving, and in the 26+ MPG for Interstate cruising.

The rest is trial and error, unless those Jets/needles mentioned are pretty close for the OZ cars.

Mate here, put 4 HIF on his V12 E, and spent months trying to get the settings right for the balance of driving, so much so, he ditched them for Fuel Injection a very long time ago, and that sorted the thing 100%.

I have NO notes etc in my shed on HIF, never fitted them myself, as I do prefer the simplicity of the HS8.

 

The SU reference book gives NZX8023BDY as the standard needle and AUD4355 as the piston spring. I found that the spring(yellow coded was important.

 

Thanks Alan, I have finally got the correct needle BDY, had the spring but the garage changed it to green, will go back to yellow.

We were so close yet so far.lol

 

Update on the forever going saga of the HIF carbies.

Changed over to the other recommended needles BDN with yellow springs and what a huge difference.

Thank you to those that posted recommendations, it all helped, either by practical means or just encouraging me to keep on.

Now very happy with the car and its performance.

Cheers

Ken

 

hi Grant, how did you set up the manual choke on HS8s?