Lotus Europa Community
Lotus Europa Forums => Garage => Topic started by: TurboFource on Tuesday,December 01, 2020, 03:23:29 PM
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The needle in one of my slides seems to be spring loaded as it will pull slightly from the slide and then go back in, you can also twist it freely in the slide. My other slide the needle doesn't seem to be spring loaded and you can't twist it with your fingers. Which one is correct? How do you get the needle out of the slide? I would rather ask than mess something up....
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(http://www.lotuseuropa.org/LotusForum/gallery/1_01_12_20_3_33_13.png)
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If you haven't found it, yet, the Buckeye Triumph site has a fantastic series of pages on the Strombergs. The snippet below from that should help with your specific question, but worth a read. I rebuilt a set for my Elan a couple years ago and have several spare bits so can grab pictures of anything "internal" should you need. Also, the burlens site is quite valuable.
https://www.buckeyetriumphs.org/carburetors
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The Stromberg needle comes in a holder (as shown in SENC's photo). If it is a fixed needle, then there is a screw on the side that holds it in place. The needle holder has a corresponding flat spot for the retaining screw to bear upon. If it is an adjustable needle, it's a bit more complicated. The screw on the side is a guide pin that fits in a slot cut in the holder. In order to remove the needle, you first use a special tool down the damper tube and turn the adjuster until the holder sticks out the bottom. Now remove the guide screw, hold the needle holder and turn the adjuster until the needle holder is free.
Lotus TCs never came with adjustable needles but it is a better way to go. You can get the pistons for adjustable needles from a TR6 or TR7. Then order replacement UK spec needles and swap them into the adjustable needle holders. I would also change the needle jets at the same time.
More info here:
http://www.lotuseuropa.org/LotusForum/index.php?topic=3619.msg37946#msg37946
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Thanks JB!
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Are there different size "jets" available or is all fuel metering requirements handled by changing to a different needle with a different taper?
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The needle jets do not come in a range of sizes.
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But be aware that jets do wear from needle contact over time - and depth of jet impacts air/fuel mixture, just as raising/lowering the needles. There is a Lotus Service Bulletin describing correct depth.
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The Lotus Elan S4, non-Federal, had adjustable needles and different carburetter adapter blocks, connected by a balance pipe. This is the setup to get, if you can.
Apart from a Weber head, that is....
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My Early TCS 2758R came with Stromberg Carbs and adjustable needles. I know a couple of guys with Fed-spec Sprint Elans with Strombergs and and they have adjustable needles. I was under the impression that the only Fed-spec Twin Cams with Strombergs that had fixed needles were the Fed-spec Elan S4s. That all Big Valve Stromberg versions had adjustable needles and that the early non-Big Valves TC Strombergs had fixed needles. The Twin Cam supplement mentions only fixed needles but doesn't reference the Big Valve.
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I stand corrected :huh: Fed-spec Europa TC and TCS's with adjustable needles like mine are retrofits. My Carbs are the original. Just didn't know that they were modified. Sorry to question you JB :beerchug:
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Eh? Question a way. We all learn that way. I can assure you that I make mistakes and have been mistaken many a time.
Adjustable needles with the Euro spec profile makes for a sweet set-up.
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I have read you can modify the stock air valve/slide/piston to accept the adjustable needles.
If I can't find Triumph ones I will give it a try.
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Turbo - I'm fairly certain I have a spare piston/air valve for fixed needles in my spares box if you decide to modify and want 1 to experiment with. Just pm me when you get to that point.
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Thank you SENC!
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To the general discussion of models, etc., I found this a few years ago when rebuilding mine for my Elan. They are from the Burlens website for the Zenith Strombergs. I went back this morning to see if they had anything for the Europa - they don't, and as suggested above I suspect Lotus used the same on all twinks fitted with Strombergs based on what they had on hand.
You can match the markings on your carbs to this to see which spec - then you can find the spec on the burlens website to see exactly what components were in it. Mine were 3296, but I rebuilt them to the 3322 spec to incorporate adjustable needles.
I looked back in my notes and at the time had found a Chatsworth Motors that had pistons.
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The fixed needle and adjustable needle pistons are different. Can you modify the first into the second? I suppose so. It would require some very careful machining. There are/were lots of used TR6/7 carbs out there. Seems a simpler way to go.
If you are not concerned about originality and just want better performance, go with motorcycle/snowmobile Mikuni sidedrafts. They flow way, way better than Strombergs and even Webers/Dells.
(modified to clarify I'm not talking about period Mikuni Weber-clone carbs)
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Mikunis would be excellent at some point but I have a lot to do before that would ever happen!
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I received a B2AR needle in an adjustable holder today, that CW found and mailed to me.
One of the slides I have seems to be adjustable (there is a definite hole at the center bottom of the damper tube that is probably 3/16 deep)..what size is the Allen wrench that fits
in the adjuster?
Remember I am only running one carb due to the draw through turbo setup. If I have one adjustable
slide that will work for now....just gotta get the thing apart without tearing anything up.
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The adjustable pistons (it's not a slide as there is still a separate throttle) mostly use a 1/8" or 3mm allen key. The proper tool has a holder that prevents the piston from twisting. It's not critical but it is helpful. Both piston types have a hole in the bottom. One is simply an empty hole and the other has a threaded screw visible.
If you are using your turbo set-up, who knows what needle will be best(!?!).
Random advice: do not use engine oil in the damper. That will attack the diaphragm, use Dexron automatic transmission fluid.
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The hole for a non-adjustable needle is about 5mm or so, adjustable is about 8mm. The threaded screw is held in place by a spring clip which can be removed with a fine pick, or driven out with a length of steel brake pipe.
Some have counselled against this method, but I was advised by Joe Curto, and that seems good to me!
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https://static1.squarespace.com/static/5c6dec53b10f25d4edf0b3f7/t/5d0191966981d30001198d1e/1560383895133/TR250_TR6+Carbs+-+Adjustable+Needles.pdf
https://static1.squarespace.com/static/5c6dec53b10f25d4edf0b3f7/t/5d0191191376fd00017521ed/1560383774528/TR250_TR6+Carbs+Part+II.pdf
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I ran across that before, thanks for putting the link here SENC!
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These appear to be adjustable to me! They are out of the carbs on my '73 TCS and I know they are original as I bought the car from the original owner.....
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Excellent!
Fit new o-rings to the needle adjustment screw!
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Will do!
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Painting some stuff for presents, so between coats decided to increase the flow of my fuel needle. There were European Volvos available with blow through turbos using a Stromberg. On a Swedish site I saw to drill out the needle to 2.5mm , I am close at .094" (about .030" increase). I removed the inlet screen and used a pin vise to drill it out, I then used a small hammer and tapped lightly on the end of the needle to form a new seat. It passes the "blow" test 8). I will need to reset the float height as the needle moves farther now. I want to ensure adequate flow as I will be using just one carb with the turbo....more upgrades to come....According to an Aussie site a single CD175 is good for 250hp draw through and even more blow through....
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Large bore needle and seats are used in gravity fed applications. Smaller bore in pressure fed. The reason is that the larger hole allows pressurized fuel to spray in like a power washer. This makes the fuel in the float bowl turbulent and the level inconsistent. I think 30 thou should be fine. Just something to watch out for.
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I would think it would be the opposite.....
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Nope, common problem with two stroke tuning when you switch over to using a fuel pump. You have to fit a smaller needle/seat or fuel bowl turbulence will make it impossible to set-up.
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I can easily change back if there is an issue. I am concerned the fuel bowl will run dry as there is now just one carb feeding what was estimated as 200hp. On the R-Sport Volvos theyincreased the needle size and I think they were rated at 145hp.
On the two-strokes you referenced, did the electric pump increase fuel pressure requiring a decrease in surface area at the needle seat to prevent overriding the float?
The stock needle will flow enough fuel at 2.5psi for approximately 115hp (based on .5lbs of gas per hour per horsepower). My modified needle should flow enough fuel at 2.5psi for 220hp. (This is based on flow rate for water through an orifice, there would be some slight difference for gasoline.)
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Basically, yes. Most two wheeled carbs used to be fed by gravity so needle and seats were large as there was minimal pressure. Performance 2T mostly use diaphragm pumps. Pressure changes in the crankcase move a diaphragm which pumps the fuel.
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It seems there is an easy way to tell if you have adjustable needles.
It was hard to see down my damper tubes and there was a bunch of crud down there and the adjustment screw was stuck and wouldn't turn anyway so I wasn't sure if mine were adjustable until I took them apart....
So it appears that only air valves with adjustable needles have the top of the damper tube machined with the small slots for the adjustment tool to engage to prevent damage to the diaphragm during adjustment.