Weber 40 IDA Pump Shot Spec

[John912]

I'm going through a set of Weber 40 IDA 3C/3C1 with stock 30 venturis and jets (125 main, 180 air correction, F26 emulsion, .55 idle). Does anyone know what the injection quantity for the accelerator pump shot is for today's gasoline? 0.5cc for two strokes? Thanks in advance for any help

[1QuickS]

Here you go:

[John912]

Thanks Paul, thought I read/heard somewhere that characteristics of today’s gasolines require amounts different than was first established 50+ years ago?

[1QuickS]

Not that critical for acceleration squirt, fuels for today want larger fuel jet sizes to richen mixture. Webers adopted adjustable pump rods to fine tune acceleration fuel delivery starting in late 1967 for the 1968 year model, this was to allow tuning of squirt amount based upon driving evaluation.

If you compare the specs for IDA and IDAP you will see a large difference in squirt output. The engines were identical and so were the Webers, the only difference between IDA and IDAP is the IDAP had a casting change to provide a vacuum tap in the base flange to. accommodate the vacuum retard distributor for that year model and all subsequent Webers had that feature. The reason for the decreased squirt was for emissions reduction.

[John912]

Thanks Paul, I'll stick with original setting.... 0.8cc per stroke

[1QuickS]

Hi John,

A stock 2.0 with Solex cams or "Normal" cams likes jetting as you have selected. If you are working on IDAs for your 66 then your pump rod is non-adjustable however, the early lever arm associated with this pump rod typically provides adequate squirt amount.

[John912]

Duh! Well, I learned something. The last set I did was a 67 that had pump shot adjustments so I assumed the 66 was the same. Funny how you don’t see something when you assume something else. I replaced the diaphragms and will check the output to see what I get. Thanks again Paul for all the help and education.