idle mixture setting 3.0 GS PNCA holley 2 BBl carb

[aerobat]

hey gents !

i would like to tune up the idle mixture on my engine . as far as i understand you will find two screws each side of the carb and you start with a warmed engine idling in gear both screws one turn out . the you turn out ( enrichen) both srews until the smoothest idle is reached and then turn back ( lean) 1/4 turn . is that right?

maybe real pro,s like don ,bond or other could confirm this procedure or correct me before i mess something up.

thanks very much gents !

 

[ewenm]

Re: idle mixture setting 3.0 GS PNCA holley 2 BBl carb

yep thats what i understand,however for me i need to get the plugs out that cover the screws.

 

[Silvertip]

Re: idle mixture setting 3.0 GS PNCA holley 2 BBl carb

There is no exact "one setting" fits all. But if that's what the manual says -- do it. However, to ensure it is right, start with the screws at any setting that allows the engine to stay running. Turn one screw in in 1/8 turn increments until the engine begins to bog or run rough. Note that setting. Then back the screw out in 1/8 turn increments. At some point you will pass through the point where the engine runs smoothest and then begins to run poorly again. The best setting is somewhere between the in and out positions. Repeat for the other screw, always adjusting "idle speed" to spec. If from whatever setting you started at the engine immediately runs worse then back the screw out until the best idle is achieved.

 

[aerobat]

Re: idle mixture setting 3.0 GS PNCA holley 2 BBl carb

There is no exact "one setting" fits all. But if that's what the manual says -- do it.

and thats exactly the problem... the adult site gives a workshop manual for the fuel system on the NC series engines but just page 2-52 with the specs for tune up of the 3.0 is missing so i have no verified information about the initial setting of the mixture screws for this engine :facepalm:

 

[Don S]

Re: idle mixture setting 3.0 GS PNCA holley 2 BBl carb

Odd that page is missing from the manual. I checked the manuals before and after and they both have the same information, and I know they used the same carb as you have. The only thing that changed in the specs is the main jet size. The MD and HU model had a 75 while the LK (shown below) had a 71. Since those don't normally change during a rebuild, you can look at yours and see what you have from the factory.

 

[aerobat]

Re: idle mixture setting 3.0 GS PNCA holley 2 BBl carb

thank you so much don, thats exactly what i was looking for- you are the best !

odd that the port and stbd needle have different initial settings, but when the manual calls for it i will start with this !

 

[aerobat]

Re: idle mixture setting 3.0 GS PNCA holley 2 BBl carb

ok, i played on the mixture needles and adjusted the mixture, on my carb there are no caps preventing this. but the old setting was pretty close to my new one . the new one is very slightly more in the lean direction, maybe 1/8 turn .

the engine responds relativly abruptly to changings on these needles. is maybe half a turn between rough lean or rough rich on my carb .

thanks again for all your help !