Which spring and needle ? – SU HS6 For Landrover series

For those who have not read my set up of SU HS6 carburetor for land rover series 3 you can read it Part 1 here and Part Two here:

As you may aware, I bought the carburetor SU HS6 as a complete unit, it comes with BAK needle and green spring, and that what I use for the initial set up… It works but may be not optimal… from the forum and discussion, they are few suggestion:

  1. Copy ACR set up with BGB needle and Black spring
  2. BDM needle with red spring
  3. BDB or BBW but not sure what spring they use..

Just to remind you on the profile of the needle, you can see below  that BGB is very rich needle, BBW second, BAK third, BDM fourth and BDB is the leanest…

needle su

Actually I want to copy ACR set up, however after having discussion with Burlen… there is no such thing as black spring for HS6, I think they do not want to be copied, and may be they change the color of the spring to hide the their set up…

Finally I ordered BDM and BDB needle and  red spring, hence I have three needles and 3 springs (one spring is from old SU)… it will be interesting the try all possible combination.. :).

Here some photos when I am tried needle and spring combination

Three springs SU HS6

Three springs SU HS6 : the Green, the red and the unknown.. (from right to left)

 

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Needle BDM and BDB fro burlen

 

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Off the Dashpot, and we can easily change the spring and needle

IMG-20140409-01855

Replace The spring with the another spring we want

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Off the old needle and the new needle is ready to be installed

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The needle center lead… its funny because actually the needle is slightly not centered even using this centering aid..

To make it apple to apple, first I have to make sure that the ignition timing is at 6 deg BTDC as suggested by ACR using their Cyl head.

So.. after the few tries… I finally concluded that the setup is best using green spring and BDB needle... The others also works but at high throttle it missed fire or blow back… or severely lost power compare to this one.  it is quite strange… ACR set up is using the richest needle, I am using the same head from ACR but it best using the Leanest of the option…

Bit confuse, but I find it very smooth and have more power using this set up, it capable of going uphill at 3rd gear,  previously it need the second gear to climb it… So thats it for now, any questions please write it down below.. hope it can be useful for you

 

Cheers for now..

 

Other set up is OK, but in the open throttle, I experienced a missed fire… even if I tried my best to adjust the

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Everything About Tuning The 2.25 Petrol Engine – ACR, Turner & others perspective

engine2.25petrolWarning: Long article but worth it..! There are a lot of information about how we upgrade our old engine… some says.. : drop in the 2.5 cam, milled the head by 0.02 inch, ported and polish etc etc.. all is good advise but I read this discussion (or debate) with great interest and decided to put it here in case we need  reference lets start (I deleted conversation that are irrelevant), and unfortunately, I can not see the poster names unless it stated at the end of the post.

Someone: I think that these engines have a specified max rev limit of 4600. Though going over 4000 for anything short of a few seconds is probably not a good idea. My tachometer has the occasional misbeat but in no way does it wander like yours does. If its something to do with the ignition and not a bad connection it’ll show up on a vacuum guage as well, they’re cheap, easy to fit and very useful.

Roland (ACR): We set the Power Plus engine red line at 5200RPM this will give plenty of safety margin as they will run to 5700 on an intermittent basis with no problems. There is little to be gained by running much over 4800 as the power falls off rapidly over this point. However if you enjoy using the power e.g. racing rush hour traffic, off road competition etc it is useful to be able to run past maximum power so that the engine drops into a more favourable part of the power band on changing up a gear as the spacing between gear ratios on the 4 speed box is large. Regarding oil temperature the red line is around 250 however Mobil 1 will work safely well beyond that . We would keep the 250 as the upper maximum it is very unlikely even desert temperatures will push the temperature this high.

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