Weber settings?

[kandhmfg]

I am having considerable issues getting car to idle without either spitting or backfiring at idle and also prevalent in transition between 2-3k. Foot to the floor everything seems to operate as it should.

I have cleaned, blown out passages, etc. etc. etc., set float levels and checked 3 times. Plugs are new NGK BP7ES. Using standard bosch CD and standard plug gap. Plug wires are good, cap and rotor good, timing set to 36 deg BTDC at full advance.

The car seems okay while under about 170 degress, but once it hits 180, then erratic backfiring, popping through carbs shows up. Had it on a CO monitor and was good, but still having issues. That is why I was thinking, maybe the setup is wrong?

Engine is now a 2.7L with 8.5:1 RS P/C, Webcam 104/102 mod S-Cams, but running heads from a 2.2L so a little more compression possibly. Heads are ported to 36mm intakes, standard 32mm exhaust, running old style factory heat exhangers.

Weber 40IDA3C with the following
60 idles
145 mains (hard to read, but I believe that is what they are)
F26 e-tubes
180 correction jets

Other things done recently before the problems arose were the anti-percolation mod using the PMO drill fixture and the Float Bowl modification. Did this while rebuilding the motor, which ran mostly fine prior to rebuild. Could these mods cause issues? I am going to take it in for a compression test just in case later next week. I am at my wits end. And I have read about every post twelve times, tried all those things, still having problems. Both sides seem to have issues.

Any thoughts are appreciated.

Erik

[2.70Racer]

Erik,
60 idle jets may be a bit big for your application. 50-55mm will be closer.
Further they should be checked. A 60 idle jet is 0.60mm dia. or .024"
It is common to find these out of spec. Usually larger than marked.
With older carbs, the shafts are worn and leaking air. These worn carbs will not idle properly.
Any perceptible motion from the shafts will leak air. Fix this first.
The main jets, if they are 145, should be fine. They really play NO part in the idle.
To check the mains the dia s/b 1.45mm or 0.058"
Another fairly common problem with old Webers is leaking O-rings at the idle jet holder and at the idle mixture screw. These carbs after all are typically 20 years old or more.
I assume you have the carbs mounted on the insulators. If not the carbs can and will percolate.
Float height is best determined with the sight glass screwed into the side of each bowl and running. This will show you the actual running float height.
PMO knows how important this is and installed a sight glass into each PMO bowl to see at a glance the float level.
The sight glass float bowl tool may be available from Pelican.
Fuel pressure s/b 3.5 psi. Again a permanent gauge is best.

[JohnJL]

Doug is right on all counts. I have the same carbs as you with the exact same setup, with 57 idles and it runs like a raped ape. But my engine is a ported-out, twin-plugged, DR60 cammed, high compression 3.0. So I suspect you are a bit overfuelled.

[kandhmfg]

Yes, carbs are mounted on insulators. I have a Holley fuel pressure regulator, but have not verified for sure the exact fuel pressure. This thought had crossed my mind and need to check. Interesting with the float level guage being checked while running. I might do that next. Maybe I am getting too much fuel and some spillage when the carbs/fuel warm up. The idle jets read 55, but we measured them with whatever tool and came up with about a size of 60. Can move down and see if that helps. However I am getting the spitting up through the right bank of carbs on occassion. Which indicates lean??

Again, the only change I have made since the engine ran fine before, was the anti-percolation holes drilled using PMO tool and the Bruce Anderson float bowl mod. Re-thinking if this might have been a mistake.

The shafts are tight. I have a 67 with Webers and they are definitely loose, wobble around when idling and warm. So, I am sure these are in much better shape and tight.

Sounds like a full day back in the garage checking things over again. Thanks for the replies.