A Carb Queation?

[Motor-Mouse]

I have a 30VM-5 fitted to my Nippy, it has an unmodified Speedy engine, 3/8 lift cam etc, when setting this engine up I tried a range of alternative 30VM carbs, the larger choked versions did not appear to improve performance. So from from my experience with this car I would be inclined to agree with Jon that a std engine would be best with a 19mm or less choke size.

PS as I posted this I saw Bob's comment about choke size on a VM5, I am talking about a 19mm C855 not a 23mm Jowett Carb, as I mentioned my experience is that even with a high lift cam these are to large.
 

Wow, I really do need to do my research some more it seems, but loving this information overload....


Thanks all...


S.

[Steve Berg]

I have a 30VM-5 fitted to my Nippy, it has an unmodified Speedy engine, 3/8 lift cam etc, when setting this engine up I tried a range of alternative 30VM carbs, the larger choked versions did not appear to improve performance. So from from my experience with this car I would be inclined to agree with Jon that a std engine would be best with a 19mm or less choke size.

PS as I posted this I saw Bob's comment about choke size on a VM5, I am talking about a 19mm C855 not a 23mm Jowett Carb, as I mentioned my experience is that even with a high lift cam these are to large.
 

Ian, I have the same set up on my Speedy-engined Nippy so I'm comforted by the fact that you found that there seems to be nothing better :-)
One thing that has puzzled me is the vertical gap between the float chamber and the caburettor body. It seems to me that air would leak here into the choke tube below the beak when I would have thought that ALL air should flow past the beak.
I'd be grateful for anyone's thoughts on this. Have I missed something?