Thanks to Tambox for lending me the Weber Carburettors book. Great info into how the carbie actually works.
A little while ago I bought a brand new 38/38 weber synchronic. Forget it. I went against the tide hoping I'd get even more low down torque that what the new 15/55 cam would give me. It is virtually untunable for the ea81/ea82 as it is only suited to high performance highly modified engines and these engines have a head design that is not modifiable to that degree.
I recently purchased the Gunson colortune unit that came in handy. For 100 bucks its a great addition to your toolbox. Search for it on youtube.
Briefly, my newly reconditioned ea81 has 9.5:1CR, 15/55 cam for high torque at low revs, and SPFI manifold. This manifold is 6mm greater in diameter so about double the volume capacity. To install this manifold (if you go to the trouble to get one from the USA) you need to grind 2mm off the centre of the crankcase halves to give clearance, ream the 6 mounting holes at each end of the manifold (if the block/heads are shaved the holes wont meet up) and you'll need to splash some $400 on a aluminium adapter. Unlike other manifolds the SPFI one has an angled face and a large circular hole. You need to cut away at the hole to make the weber butterflies fit.
The carbie- the 32/36 comes in a number of models with different chokes. I've had both my 32/36's without chokes fitted and its argued that these no choke carbs have a little less air restriction. However when starting from cold you'll need to pump your pedal 5-6 times in order for it to start. The redline 32/36 conversion kit is sold with the following jets.-
Primary/secondary mains 140/140 airs 170/160 idles 50/55
Don't be fooled, if you want the best output and cleanest engine then you'll need to change your jets.
Unlike a lot of logic the idle jets for the primary circuit operates up to 3000rpm when the idle for the secondary jet comes in. So it is critical to get that primary idle jet correct in size. So how do we do it? There are two ways.
I'll assume all other aspect of your tuning has been done- leads, plugs, timing (10-12 degrees BTDC) etc
Firstly the A/F mixture screw. This works in conjunction to the idle jet. If your idle jet is of the correct size the mixture screw should be wound out from all the way in between 1-2 turns. If it is over 2 turns then consider going down one size on your idle jet. Don't know where your jets are? google images weber 32/36 jets and you'll get a view.
The other method is as follows. Allow your engine to idle. Tune your mixture screw to its preferred best running point (I used my colortune here) then raise your idle speed to 2000 rpm. Now, slowly screw out your mixture screw...if the engine speed rises then you need to go up one size on your idle jet. Repeat this each time you change a jet. Eventually you'll get to an ideal size...in my case 60 idle was it. My mixture screw was wound out 1.5 turns.
Go for a drive. Do you have enough power on the primary? are there flat spots?
Hesitation from primary to secondary should not occur. If it does try a larger secondary idle jet. Go for a drive. Enough power? If not enough try larger main jets. in the end I got my ideal jetting at-
primary/secondary mains 145/150 air 180/180 idles 60/55
redline is...............mains 140/140 air 170/165 idles 55/50
notice that all jets are one or two sizes from redline? No great huge changes but massive change in performance. This engine is seriously improve. I did, while doing this found a stuck vacuum advance diaphragm. Had a spare handy and all was fixed.
Some comparisons. The 38/38 was dyno tuned. It struggles to get past 120kph (private road ok) The tuned 32/36 140+ and quickly to 130.
I hope you guys that want to go weber or have done so and you aren't happy with your performance try these basic methods to get it ok. Feel free to add, criticise. cheers.
I have a 34 ADM weber (ford six cylinder 3.9 or 4.1 motor) sitting in a box now because as much as I tried I couldn't get it to be economical 
