Zenith jetting questions on 2.7
 

Hi, guess this is my first post despite being a frequent reader…great source of information and inspiration!

I´m rebuilding the Zenith carbs (2nd time in 4 years) on my -75 2.7 and want some input on jetting size.

The engine has the euro “RS” cylinder/piston kit (8.5:1) and the heads are ported with bigger valves,
backdated exhaust and a cam grind somewhere between E and S.
The engine mod. was made in the mid 80s by a local Porsche guru.

I have trouble with intake popping during light load/cruising around 2500rpm and I think I´m a bit lean on WOT
because it feels like the engine has more to give.

This is my current carb jetting:
Venturis 36mm
Main jet 150
Air correction 160
Idle jet g65
Idle air corr. 155 (approx)

What should I do? Increase the Mains to 155-160 and leave the idle circuit alone or also increase the idle jet one step?
The squirt from the acc. pumps are 0.5cc/stroke now, should I increase the squirt volume? Drill air bleed hole in the butterfly?

I can´t find any leaks on the intake/exhaust and the idle isn´t affected by an ether spray (engine starter gas) around the
throttle plate shafts…
Float level is ok. The rebuild now is because a leak in three acc. pump membranes, the rubber was dissolved,
if it´s because of the ethanol mixture in our 95oct gas or just poor rubber quality I don´t know?!

Thank´s!
/Daniel