Weber question about 31

[miked]

Could someone help me here. I am building a twin cam that will be mildly tuned to about 135 ish BHP. Just a well balace bottom end with some head works and some new cams. Looking in Miles Wilkins book about Webers etc he mentions the 40DCOE 18 and 31. He states that the later cars with more HP used the 31 and it is good for up to 140BHP. I am building the car from bits and have not specifiaclly got to the carb bit yet. I do however have a pair of 40's that I picked up from my brother. Upon checking them I found one to be an 18 and the other to be a 31 (shucks).
Has anybody got a 31 they want to part with or even swap for an 18 if that an idea?. Also after the 31's what number would do for my build if I struggle with finding a 31. As I watch ebay it all looks very confusing with 40's. Didn't realise there were so may. Any advice welcome

Mike

[types26/36]

Although I am not 100% sure, I think the 18 and the 31 share the same basic body, the only difference is the "state of modication" that is the settings,jets,cold start, needle valve etc.etc,etc are different. Check that the progression holes are the same and I dont see why you couldn't match them up.
The 151/152 series are a different construction.
Ofcourse I could be wrong!
Brian

[miked]

Brian,

I suspect you are right. I dont know much about webers. Are the progression holes the ones drilled in the butterflies?

Mike

[types26/36]

Are the progression holes the ones drilled in the butterflies?

No, on the top of the carb near the mixture screw there is usually a brass plug, if you take that out you should see some small holes, these are uncovered by the opening butterflies. I seem to remember there are usually three although I think I have seen four, check these are in the same position, size and the same number of them.
Not all the carbs have these removable brass plugs, some carbs are not threaded and are just blanked off.
Brian

[miked]

Brian,

I had a look at the carbs last night. They have the brass screw cap. They both have three holes in and as far as I can see with the magnifying glass they are the same. I did notice that the 31 has a drill hole in each butterfly near the bottom.

thanks Mike

[type36lotus]

Not sure about webers, but I read somewhere that Dellortos are serial numbered and should be used in matched pairs (sequential numbers). Does it really matter? Beats me, but mine are sequential in number.

[twincamman]

mine came off an alfa----numbers are 260 apart--rejetted to 7 manual specs 150 correction and a 117 emulsion tube- and a 50 air --as the dpo of the carbs removed the jets when I looking at his car-----ahhhh the joys of dealing with some peoplw who advertise in bargan hunter press --ed