Lotus Elan

Just how adjustable are Non Adjustable Needles?

PostPost by: terryp » Mon Jan 12, 2015 8:21 am

Hello
Since rebuilding the car , it has not run as well as my previous Dellorto powered cars.
I had set the needles as per all the instructions i.e with the shoulders of the actual needles level with the housing.
On reading a few posts in the archives I thought I would try them a little lower.
The transformation is amazing!
My question is how adjustable are they, how low can I go or is it just a case of lowering them until the plugs blacken (or use Colourtune) and then adjust back a bit?
Thanks
Terry
(Currently set at about 0.33mm below)
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PostPost by: miked » Mon Jan 12, 2015 11:20 am

Terry, I presume you are talking about Strombergs. There are generally 3 turns in total then the top bit of the needle unscrews. If set in the centre you can go up 1 ? up and 1 ? down . Everything is however dependant upon the brass jet position that the needle sits in. These, as I recall, are meant to be nominally 100 thou (was told 96) down from the area the jet sits in the carb. As I understand the 1 and a 1/2 up and down allows you to dial in were you need to be. There is not a lot of info' around about this.

This worked for me and I found the jets in the wrong position (60 and 80) and could not achieve what I wanted until they were set right. Also I later saw this in an article in one of the classic car mags confirming the 100thou.

PS it is worth having brand new jets and needles as the side bias wears mark in these (meant to be) very accuarte metering devices. Have a look under a magnifying glass. A groove can also wear into the jet.

Mike :)
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PostPost by: terryp » Mon Jan 12, 2015 11:27 am

Mike
I have new needles and the car had only done 32000 miles
My needle housings are not adjustable with any turns. I bought the tool but there is nothing to turn :-(
My only adjustment is to remove the dash pot covers , expose the needles and loosen the grub screw and alter.
Thanks
Terry
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PostPost by: miked » Mon Jan 12, 2015 11:34 am

Fair enough Terry, you have the earlier type of needles. The same still applies re the jet height. You can only move the needle so far up and down in the slide. Check the height of the brass jets in the body of the carb with the tail of a vernier caliper. That sholuder setting stuff with the ruler relies upon the jet being in the correct position to start with, thus allowing you a window of adjustability. Mike
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PostPost by: terryp » Mon Jan 12, 2015 11:37 am

Thanks Mike, I'll check the jet but I suppose I am left with trial and error only

Terry
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PostPost by: miked » Mon Jan 12, 2015 11:45 am

I would not think of it like that Terry, if you get the position right on the jet then the ruler gives you a "there abouts" starting point (almost right) and then you can coulortune test to get your mixture dead right. Until I got the jet height right I kept running out of adjustment. Frustrating until I dropped up on the jet setting on a Triumph site. I may be able to find the mag article somewhere.


Mike :)
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PostPost by: terryp » Mon Jan 12, 2015 11:52 am

Mike
I think my frustrating bit is there is so much to alter to get to a point to try it.
i.e there is not just a handy screw with the engine running!
Thanks
Terry
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PostPost by: miked » Mon Jan 12, 2015 11:59 am

See what you mean. A bit of PITA to keep doing it.
There was an article on the net about converting from those internal adjustable needles to the top adjustable ones. Involves some drilling and tapping etc. Again I think it was a Triumph site. Mike
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PostPost by: terryp » Mon Jan 12, 2015 4:17 pm

I don't suppose anyone has tried the Southern Carbs conversion to adjustable jets?
Thanks
Terry
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PostPost by: miked » Tue Jan 13, 2015 6:20 pm

Terry,

Steve WW who used to post on here had a set with bottom adjustable jets but he had taken them off later CD175's and retrofitted. I looked at this about 2 year ago for my friend but we only found the new kits on a site abroad and they were over ?120 each, as I recall. I had a look on the Southern site but did not see any prices, except "buy it now" button. Do you know as they would be the way to go IMO. Not sure about any problems with the rear carb and the clearance underneath? I don't have a stromberg car anymore.
How about talking to somebody like Paul Exon, he must have done quite a few hot Stromberg motors and would not want to keep whipping lids off.

PS I am a bit of a plonker, I did not notice the non adjustable bit in the title, sorry.

Mike :)
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PostPost by: collins_dan » Tue Jan 13, 2015 7:00 pm

This was almost 5 years ago, but this is what I did.

Went to Gower & Lee and got:
2 x B1BT metering needles @ ?10.82 each
1 x B20379 adjusting tool ?9.99
2 x second-hand pistons, chemically cleaned and fitted with new adjusters & fixing screws @ ?35.00 each (new pistons were ?69 each)

Made a huge difference. Before it was either too rich at idle or too lean at higher rpms.

Good Luck.
Dan
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PostPost by: terryp » Wed Jan 14, 2015 7:14 am

Dan / Mike
Presumably that is to move needle up and down rather than move the Jet for the Southern Carn Conversion, which could be an alternative if I can get the pistons
I think the problem with the Jet conversion is that there is a potential for a fuel drip. My old Ginetta had Strombergs for a while and despite new O rings every few weeks (!!!!) they still dripped out from the adjuster. The other thing was that the adjusters moved and they were constantly going off mixture (May have been a Ginetta vibration problem)

Well at the moment its running OK but with a rough idle. I may try to lower the needles in the pistons a tad again to see if that improves before going to adjustable needles .... or jets

Thanks
Terry
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PostPost by: miked » Thu Jan 15, 2015 10:03 am

Terry,

Yeah, needle goes up and down, that business I mentioned with the 3 turns. The whole lot is held down there with one of those star type washer things (digs in the tube sides) and there is also an O ring on the threaded adjuster so the dashpot oil does not run down. If you get a second hand pair I would pull them apart and fit new O rings. You know you have a particular needle for your Spec' which has a bigger brass insert and a thread in the top for the aforementioned adjuster screw. Mine were not as Dan's. B1Y comes to mind. It will be on here.

Getting the pistons should not be a problem from old carbs (Ebay) so long as you check with the seller that they have the top adjuster parts. The side screw in the pistons is also spring loaded. I believe the carb and lid are matched machined pairs but think the pistons are not. I have changed them in the past when the side thread was messed up and also the spring loaded side screw was damaged.
Don't know about leaks on the jets.

Mike :)
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PostPost by: 106500 » Wed Jan 21, 2015 9:06 am

terryp wrote:I don't suppose anyone has tried the Southern Carbs conversion to adjustable jets?
Thanks
Terry

I have installed these and I can recommend them as giving plenty of flexibility for adjustment. Make sure you change the needles at the same time. One problem is that I had to drill a hole in the pedal box to allow for clearence.
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PostPost by: terryp » Mon Feb 29, 2016 1:10 pm

Just thought I would give a bit of an update ........

I managed to get some new pistons and new B1BT needles posted to France all for ?87.50

I think someone must have found some new old pistons as they were not avaialble!

http://www.ebay.co.uk/itm/321648731696? ... xe,ext=ext

or phone Bob at Chatsworth Motor Spares

Just got to fit now ..........AND ADJUST :-)
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