PMO idle circuit stumble at 1,800 rpm

[Number1_dog]

I have a 1979 SC with PMOs and the car will accelerate slowly with no stumble but if I floor it, it stumbles between 1,800 and 2,000 rpm then takes off.

Engine has max moritz 98 mm P&C, 9.3 compression, 964 cam grind, lightened flywheel, M&K 2 in 2 out exhaust, MSD ignition, 46 mm PMOs. The PMOs have 4.5 AVs, 36 vents, 150 mains, .55 idle jets, 130 idle air jets, 190 Airs, F11 tubes, 50 FBCUs and HB f1 high I hope I got the categories right.

I initially had E3 plugs in and the problem started at 1,800 rpms, I went to ngk heat level 8 plugs and my mechanic said to gap at .028. The stumble was then at 2,400 rpm. Looking at het MSD web site they recommended a gap of .05, the stumble dropped to 1,800.

Is the problem the idle set up, or should I adjust jets, ie idle jets .60 ? Richard set up the carbs when I purchased them in 2009. I just installed them in 2000.

[Number1_dog]

And Barry H recurved my distributor

[911 SLANT]

I just went threw this on my 46mm PMOs. Richard helped me out. Carbs have a smooth transition now. I run
110 Idle air
175 Main air correctors
155 mains jets
55 idles
38 Venturis
F16 emulsion tubes

[GG Allin]

Make sure your air cleaner base plate(s) aren't on backwards. I made the mistake last summer and had a similar running issue, among other things.

[911 SLANT]

When I had my base plate backwards it just made my floatbowls drain in minutes once the car was shut off. Richard at PMO knew right away what it was when I explained to him that my right carb fuel window on bowl was draining after shut down.

[snbush67]

Double check the fuel pressure, 2.5 lbs at the gauge is a guide, some like a little more, some like less.

[thor66]

fuel dirty - plugged something

try 3 psi on the regulator

progression holes were often an issue on the Webers, not sure if Richard used them for transition or not

IIRC, he has a FAQ of issues to look at on his web site

[911 SLANT]

Also make sure you have the updated accelerator hatches. If you purchased new from Richard recently, you have them already.

[Joe Bob]

accelerator hatches...I have to admit, that's a new term on me.

[911 SLANT]

I never heard that term before until Richard at PMO called them that.

[Joe Bob]

Reducer cams for the throttle throws...?

[snbush67]

Hatchets. ��

[Number1_dog]

Fuel pressure is a little over 3

How do you know if the air cleaner base plates are backwards. I took off the cover and air cleaner and front and back looked the same. Do I have to remove the base plates?
And is there something underneath that will show front back?

[GG Allin]

Wrong.

[GG Allin]

Right.

[Number1_dog]

I figured it out after looking at the instillation instructions, the idle air holes on the outside. Checked both sides gasket seemed off on one side and flipped it the other side was perfect. Put me good glasses on and saw that the fuel pressure was at 4.

Time to go to a local expert, I think he is close to my age, thanks for us old folks, gota teach the new kids!