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Can't seem to adjust the engine correctly

Started by vielle568, October 15, 2015, 16:25:42

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vielle568

Hello,
I've just sold my two "regular" 2CVs and bought a souped up camionnette.  It has a special Visa engine from André Jacques, with a Weber 40DCOE carb, electronic ignition, a special camshaft, large stainless exhaust, lightened flywheel, etc.  Unfortunately I am not familiar with this type of engine and I can't figure out how to adjust it correctly.  Sorry, but I don't want to use the vehicle for racing but for street use. 
At present it starts first time and ticks over smoothly.  There are no obvious faults such as mechanical noises or smoke from the exhaust.  When driving there's a kind of dead zone.  As soon as you put your foot on the accelerator the engine seems to fade; it doesn't have any energy at low revs to power the car, but at higher speeds the it will pick up energy and run fine. 
I've spent time fiddling with the carb, I've set the valves and I know that the ignition/plugs are working fine (although I haven't checked the timing).  Is this kind of performance normal with tuned up engines or should I be able to get some horsepower across the entire speed range? 
Any suggestions would be most welcome.  Thanks.

Nick clarke

Sounds like idle jets maybe a bit small going lean before on main jets. Or it could be if cam is very wild it's just off cam and it pics up as you come 9n cam higher in rev range, this is less Likely I would say jets first. An hour on a rolling road may prove fruitful

vielle568

The idle jets were initially 45F8 and I've tried 50F8 without much sign of improvement.  The venturi is 32 mm and the main jets are 115 with 200 air correction.
The cam has been modified to a type K4 > 90° which doesn't mean a great deal to me but perhaps it could explain the engine's behaviour?

Bart van Wijngaarden

does/do your accelerator pump(s)/enrichment work as should?
I once rebuild a big single choke solex carb and had put the lever for the accelerator pump the wrong way around, causing the enrichment to come in later/at much more throttle opening and that gave a similar engine behavior as you describe.   

vielle568

That's a possibility.  The accelerator pump works OK but if it's linked in sync with the throttle mechanism is another matter.  I'll take a look and see what I can find out.  Thanks for the suggestion!