Lotus Elan

Stromberg Needles

PostPost by: david.g.chapman » Mon Jul 05, 2004 1:06 pm

I have just had the cylinder head reconditioned for my +2 twin cam, with new valves, guides and seats. At the same time,
I had my standard cams replaced by CPL2 cams - roughly equivalent to Sprint cams, I believe. With the extra air flow through
the engine, I though that new needles would be in order, so I askes Burlen Fuel Systems for their advice, and they
recommended the B2AF type instead of my original BIG type.

After trying out the new needles, there seemed to be a little more power, but I found a flat spot at around 3500 rpm.

I have tried everything to eliminate this, but can only do it by going back to the old needles.

This seems strange, because the B2AF needles have a thinner profile to give you a richer mixture. The flat spot
(I thought) would be due to too lean a mixture!

Using a colourtune on both needles does not reveal anything (looks OK).

Has anyone had a similar experience? Any ideas?

Dave Chapman.
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PostPost by: steveww » Mon Jul 05, 2004 4:39 pm

My S4 SE which has the same cams as the sprint 26/76 0.36" has B1Y needles as per original spec and there is a bit of the lean flat spot between 2300 and 3500.

I have uploaded to Yahoo groups files section a file called needle100.xls which is a spreadsheet of all the .1" needles I know about. The spreadsheet has some graphs so you can compare two different profiles. The only sure way is to find a good rolling road and a large stock of needles and "suck and see". A good carb shop can take a stock needle and reprofile it for your engine.
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PostPost by: patrics » Mon Jul 05, 2004 9:05 pm

Hi Dave / Steve,
I have B2AR needles fitted to my S4 which has L2 cams. It has a slight flat spot at 2500 rpm which I could get around this by advancing the timing but then it tended to run on.
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