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jetting for standard 3.9
Posted: Mon Aug 10, 2009 7:39 pm
by v8 pete
any one know what are the best jets and needles for a 3.9 on the weber 500.
was running 4.6 but cant get it through the sva test[long story] so i have fitted another engine 3.9 lump.
i have the rejet kit so whats the best combination please
regards pete
Re: jetting for standard 3.9
Posted: Mon Aug 10, 2009 8:18 pm
by sidecar
v8 pete wrote:any one know what are the best jets and needles for a 3.9 on the weber 500.
was running 4.6 but cant get it through the sva test[long story] so i have fitted another engine 3.9 lump.
i have the rejet kit so whats the best combination please
regards pete
Standard primary jets (86) and 67-55 rods, won't be far off.
Or 83 jets 63-47 rods.
Some light reading:-
http://how-to-build-a-pilgrim-sumo.wiki ... ing-system
Posted: Mon Aug 10, 2009 8:26 pm
by mgbv8
Pete!
I'm in Majorca at the mo so I cant get to my notes. But I have just set up my 4.6 on a dyno just a week ago. I did 4 carb rebuilds during the day. And got the part throttle afr's a bit lean and the wide open throttle afr's just a tad on the lean side of ideal with the jets in the Weber kit.
Was it emmissions on the SVA for the 4.6 or something else?
Have you got the jet and needle kit with the book?
If so, start by fitting the stock jets and needles listed on the 1404 carb table. You should find this will be a good starting point. Mine was a bit rich with these settings on the 3500.
I have found that good afr's on the dyno dont always give good performance on the road. But if it keeps the MOT man happy they can be changed back after its passed.
Perry
Posted: Mon Aug 10, 2009 8:32 pm
by v8 pete
problem with 4.6 is i dont have orignal engine number. so they want latest emssion rules0.3 co and 200hcc . never in a million years.
engine is modified and cant get anywhere near.
3.9 now fitted and already in in the ball park with out trying.
3.5co and 800hcc without trying. ignition not set or new plugs yet