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Bob_pipedream

Active Member
Hi all,

Got my jet in front of me - it is a 47-773 from an MA-4SPA 10-3678-32 carb.

Everyone's drill the jet sites say that I should go (drill) from something like #40 hole to #39. I don't have a #39 drill at the moment, but a 2.5mm #40 drill feels very slack in the hole (i.e. so slack that it must already be a #39).

Now this is in a new engine and with a new carb - I doubt very much that any one has already drilled the jet.

Would anyone be able to tell me the diameter of the #47-773 jet when new?

Thanks
 
Hi would anyone have a parts list for the 10-3678-32 or something that would tell me what the part number for the locking tab on the jet is?

Can not find it anywhere and the only numbers I can find are for the O-360's carb...

Thanks
 
BTW...

The 10-3678-32 is one of the richest running carbs for the O-320, you should not be having any issues as set-up factory. I'm thinking you have another issue as to the problem you have discribed.
 
update

Hi All,

Just to say that I found my #47-773 jet to have a #38 hole already ? my carb was new and I do not think it had been touched by the engine builder. This some what confused me as it should be stock and I expected a #41 or 40.

I left the jet alone as I had already found an issue with the sump where Superior supplies one sump for either the O-320 or O-360. Problem is that the sump favours the wider diameter carb on the O-360 so on an O-320 there is a step that causes all kind of turbulence and mixture distribution problems ? see Lycoming SB258 and other thread.

I may still need to drill the jet, but it is now clear that the main issue was the sump as she is now very much smoother and faster?
 
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