when to replace SU CARBURETORS SM NEEDLES?

[jalexquijano 93]

Ztherapy refurbished both of my 3 sscrews roundtop SU Carbs and install Brand new SM Needles on them. My car engine is not stock it has been upgraded to 2.6 L with oversized pistons and a Shneider 274F Camshaft. Should i consider changing the needles to another type to get a better performance at idle?

[240260280 2,089 1 Vehicles]

Idle is Idle is Idle.  The only thing to worry about is too rich a mixture that stinks and fouls plugs.  Anything from 13 to 16 usually works. 14 to 15 is the least stinky.  13 is  more tractable and sounds better.

[jalexquijano 93]

okay. I´ll stick with the SM needles provided by them! sorry what do you mean by 13 to 16?

[Jarvo2 63]

Talking about the Air/Fuel ratio that can be measured by a wideband oxygen sensor.

https://smile.amazon.com/AEM-Combo-30-4110NS-Bosch-30-4110/dp/B01F46VJ4U/ref=sr_1_2?ie=UTF8&qid=1497022242&sr=8-2&keywords=wideband+o2+sensor+kit

[jalexquijano 93]

Nice! But quite expensive! im using the gunson colortune. Ill let the car warm up and race the car for 10 to 15 mins and then pull the plugs out to see if i can achieve the dark Brown color on the plugs.

Edited June 9, 2017 by jalexquijano

[Jarvo2 63]

I had a colortune and it was nice at idle but couldn't see what was happening while driving on the street. Also with modern unleaded gas it's difficult to base everything on the color of the plugs.


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[Patcon 1,872]

That's not expensive...especially if you consider how long you have been chasing drive ability problem s and the associated mechanics fees!

[jalexquijano 93]

anyone else bought this a/f sensor?  i want to see which is the correct spark plug color i must achieve

Edited June 9, 2017 by jalexquijano