Stromberg question

[SENC]

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.

[jbcollier]

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)

[TurboFource]

Mikunis would be excellent at some point but I have a lot to do before that would ever happen!

[TurboFource]

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.

[jbcollier]

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.

[Roger]

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!

[SENC]

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

[TurboFource]

I ran across that before, thanks for putting the link here SENC!

[TurboFource]

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.....

[jbcollier]

Excellent!

Fit new o-rings to the needle adjustment screw!

[TurboFource]

Will do!

[TurboFource]

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  .     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....

[jbcollier]

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.

[TurboFource]

I would think it would be the opposite.....

[jbcollier]

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.