johnemms
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| posted on 24/6/10 at 07:33 AM |
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Carb Question
Got a 1700 crossflow - fast cam - light flywheel - electric dizzy - type 9 box ...
I have a Lynx 'single' 40/45 side carb manifold... I figure a single carb is easyer to start with also better for IVA & emissions
etc.
Whats the recomended carb?
Do i use a 40 DCOE or a 45 DCOE ?
cheers 
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atspeed racing
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| posted on 24/6/10 at 07:46 AM |
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You would need to use a 45 DCOE for the best all round performance. I would select a 34mm choke with a 4.5 aux vent. With this setup you should get a
good idle and still obtain good power. I used this set up in the eighties quite alot on 2.0 pintos, but havnt seen it for a while. Fashion I guess.
Alan
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johnemms
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| posted on 24/6/10 at 07:53 AM |
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I got a pair of delorto's - twin 40 DCOE on a 3 inch manifold but they seriously cramp the dizzy .. Would there be much benefit over the single
45 or would it just be a pain in the vaccum sensor and constantly filling the fuel tank... cheers
[Edited on 24/6/10 by johnemms]
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atspeed racing
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| posted on 24/6/10 at 08:34 AM |
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Just to add a reply for the above poster with the comment about fuel consumption.
Multiple carbs will not use any more fuel than a single carb provided both are setup correctly.
Let me explain.
If your car needs 30BHP to propel it along at say 60MPH, it does not matter if you use four carbs or one carb, you still need 30BHP to propel youself
along, infact the four carbs should give you better fuel consumption as you should have a direct shot down each port. But the problem is really the
driver. You now have more BHP due to the bigger carbs, so, you use all the power, and so more fuel.
So. It is the drivers fault the car uses more fuel and not the carbs fault. This is why the vehicle manufactures use multiple injection where economy
is needed.
So endeth todays lesson
Alan
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britishtrident
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| posted on 24/6/10 at 08:56 AM |
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With Twin 40DCOE's Lotus Elans even the Plus2S/130 would quite easily return 40+mpg on motorway trips provided the speed was kept just below
70 above 70mph the main jets would come start to come into play and fuel consumption dropped as the air/fuel mixture ratio in the change over
region between the main and idle jets tended to be a bit rich.
The Lynx crossover manifold was a a bit iffty certainly no majorl improvement over a single down draught -- istr David Vizard in old CCC articles
wasn't a fan of it..
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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johnemms
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| posted on 24/6/10 at 09:22 AM |
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So irrespective of size or number of carbs - the 1700 emissions/iva should be similar if tuned correctly?
Infact a set of twin 40's may be more economical and give better control over emissions with increased bhp?
Therefor would 40's give good pull and 45's give more rpm?
cheers
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atspeed racing
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| posted on 24/6/10 at 09:25 AM |
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Regarding the Lynx over the standard manifold.
The standard weber carb and manifold on the X/flow and the Pinto are very good, we have seen over 150BHP @ the flywheel from a 2.0 pinto. The only
advantage I can see over the Standard versus Lynx is the saving on height and the fact that they sound REAL good.
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