Join Date: Jul 2006
Location: Northfield, Illinois
Yes, still different. The 151 and many other "emission " Webers have a pair of extra adjustment needles located over the throat barrels, (italian version covered with grey caps unless lost). They are fitted with very fine air correction needles before the butterflys in back.
In use, those over the barrels are used to get a rough air correction setting and locked down with provided 8 mm locking bolts, caps then reinstalled. The final idle air correction is done with the fine needles rearmost, with exhaust analizer.
To use these as you would old style DEOE32's, the needles over the barrels are competely closed, and all air correction at idle is done with the rearmost needles.
Now to add more confusion, there were at least three types of rearmost air correction needles. I call them coarse, medium and fine. They DO NOT interchange in different bodies as the bore holes through the throats are different sizes as are the seat designs. The coarse ones are the about 60 degree taper you see on DCOE2's 32's and most the rest. The medium have a much more tapered point and are seen in those Jim mentioned. The fine are actually a tapered needle crimped into the screw and very fine.
Obviously each requires it's own type of adjustment and "starting" number of turns out from seated.
This is a TERRIBLE oversimplification. I can get more technical, but for MOST use that's unnecessary. If anyone feels they want to address this in more complex terms, please feel free.
Now, some of the high numbered Webers, like those Jim mentions, also have a VERY NEAT self adjusting accelerator pump bleed-back or exhaust jet in the bottoms of the float bowls. The purpose here is to avoid pumping unnecessary fuel into the pump jets under different types of acceleration (light throttle tickle vs "FLOOR IT!"). It consists of a brass spring loaded piston valve, that with varing pressure bleeds back or exhausts more or less fuel from the pump. If you have these, (they work quite well) DO NOT lose any of the small parts! No replacements are available easily, and they do not easily convert to the older style ball ckeck bleed back jet.
There are several other less noteworthy variations with notched butterfly plates, butterfly plates with holes drilled through them, 2, 3, 4 and even 5 progression holes and the list continues. Most variations were application specific, but "emission" variations were not only application specific, but adjustable within that application for a cleaner idle circuit than earlier Webers. The use of emission Webers on performance engines is common, particularly with the 45 mm Spanish Webers. They can all be made to work just fine, though the emission type may require a bit more fine tuning work for some performmance street applications.
I did not want this post to get into unnecessarily complicated technical detail, so it IS simplified.
On the picture below, note the grey cap over the coarse air correction needle on my customers restored 40DCOE44&45 Webers for his 1600 Junior Z.
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