Lotus Elan

Removing Crossover Tubing

PostPost by: 72plus2 » Tue Mar 01, 2005 3:00 am

I have a federal Plus 2 with the stromberg emissions carbs and crossover tubing. I have read that the engine will be much more responsive without the crossover tubing. Does anybody have any advice regarding removing this piece of the equipment?


Thanks


Chris
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PostPost by: "Whit Davis" » Tue Mar 01, 2005 3:29 am

Chris, the crossover tubes can be removed and freeze plugs inserted
in the AL secondary throttle bodies. I also removed the butterfly
plates and shafts and plugged the shaft bores. One can also purchase
a high-balance tube manifold. I went another step further on one of
my Europa's, I removed the secondary throttle body completely and
heliarched an AL, 5/8" ID, tube across the branch manifolds and
mounted the carbs to the four bolted flange. I have never foam the
fuel in the bowls yet, 3 years later.

Whit
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PostPost by: lotuselan2 » Tue Mar 01, 2005 3:56 am

Whit or others,

I sold my Europa a few yeas ago with its Stromberg carbs. My plus 2 has a
BDR with Delorrto's so this discussion is irrelevant to it.



Has anyone ever pulled off the Stromberg carbs off and simply installed two
motorcycle carbs, Nikuni or equivalent. Bikes do some awesome things with
carbs, flat slides or barrel; slides? I think Nissan prep shops put bike
carbs on cars.

Ken
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PostPost by: daves56 » Tue Mar 01, 2005 4:07 pm

Ken,

About two years ago I pulled the Strombergs, built a simple custom
manifold and installed a Holley 5200 downdraft carb on my Plus Two.
Works fine. Still have it on. Starts a lot easier. Throttle response is
clean. The only downside is that it's a little small for the engine. So
it's missing some of the high end power. On my "to-do" list is to try a
Ford 4300(?) two-barrel carb. They're made for larger engines so it
should be a good choice.

The point is........ Motorcycle carbs might work great if you can find
them for a decent price. I thought about it, but a new pair of S&S
carburetors are about $700.

Dave Sutcliffe

69' +2

77' Esprit V8
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PostPost by: twincamracing » Wed Mar 02, 2005 2:01 pm

Has anyone ever pulled off the Stromberg carbs off and simply
installed two motorcycle carbs, Nikuni or equivalent.

not yet, but I have kicked around doing some 52mm EFI throttle bodies
and building a DIY EFI like Megasquirt to run them

Scott




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PostPost by: steveww » Wed Mar 02, 2005 2:09 pm

Not sure you would get bike carbs big enough. I am looking at using SU
HIF44 carbs as they are a bit bigger and flow better than the Strombergs.
Additionally parts availability, range of needles etc is better for the SU.

On a Weber head bike carbs would work great and give much better
performance. I will go with this route when I replace the Stromberg head
with a Weber one.
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PostPost by: Tim Dafforn » Wed Mar 02, 2005 3:13 pm

In a previous life on another list one of the listers spent 6 months
installing and sorting out a set of 4 Nikuni carbs on a 1500 cc triumph
spiotfire engine.
The car seemed to run well and gave about 5% more power on the dyno,
although he also inevitably made some other changes during the
installation of the new carbs.
His biggest head ache was the linkage and balancing all 4 in terms of
air flow and mixture..
Food for thought though
Tim
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PostPost by: lotuselan2 » Thu Mar 03, 2005 2:59 am

Bike carbs can be pretty big when you can get 80 HP from a 250 cc 2-stroke.
I believe there are Nikuni kits for Nissans, so they should be plenty big.
As for set up, rent a bike racer for a day, maybe every day! My son raced
250 cc GP bikes.

Ken
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PostPost by: "denicholls2" » Thu Mar 03, 2005 1:59 pm

Jay Mitchell on the Europa list competes in autocross at the national
level with a Europa S2 [Renault] fed by four Mikunis. The system is
well enough sorted not just to keep him competitive at that level
with a heavily penalized car, but to keep him from pursuing his fuel
injection project as a next priority. I believe he eBayed the carbs
for around $150.

I'm no flow expert, but the Stromberg vs. SU vs. Weber debate in
Europa-land usually devolves to the Stromberg being a more than
competent carburetor that's hard to improve on unless you're willing
to go to one dedicated barrel per port. The high-level science makes
sense to me.

There are also some projects underway to add injection to Stromberg
heads. The better ability to map fuel mix to varying conditions
makes this strategy more sensible in my opinion if you feel the need
for change, particularly with the distribution issues Stromberg
manifolds are reputed to have between cylinder pairs.

Doug Nicholls, 54/1822 Ma~ Happy with her DCOE
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