Carb Jetting issues

[pcarb]

I am having issues jetting my carbs after an engine swap, rebuild, etc.

I am running a 1976 2.7 911S engine, with a cam grind for Weber carbs. I have an M&K MKM29 muffler with SSI heat exchangers. I have backfiring and carb popping especially on decel, and even some when simply lifting off the gas. Does anyone know where to begin? Trial end error with the multiple possible combinations of the various jets would take me forever.


I have read through countless posts on here and cannot find my specific build to use as a guide. I appreciate any guidance the pros on here can provide.

[Dpmulvan]

What’s the carb history? Are they new, old, rebuilt? I suggest going to Paul abbots site,
Performance Oriented And read through all the tech sections so you understand what your up against.

[pcarb]

Originally Posted by Dpmulvan

What’s the carb history? Are they new, old, rebuilt? I suggest going to Paul abbots site,
Performance Oriented And read through all the tech sections so you understand what your up against.

Thanks for the reply. The engine and carbs are rebuilt. Paul is great and helped me out a few years ago with a different build. My issue is that I do not know where to begin related to the jet sizes, venturi measurements, and the emulsion tubes. Trial and error will take forever, and cost a fortune. I will surely check out Paul's site again to see if I can get any intel.

[Dpmulvan]

https://forums.pelicanparts.com/porsche-911-technical-forum/999539-porsche-2-7-weber-jetting.html

[Dpmulvan]

https://forums.pelicanparts.com/porsche-911-technical-forum/421589-2-7-weber-jetting-baseline.html

[pcarb]

Originally Posted by Dpmulvan

https://forums.pelicanparts.com/porsche-911-technical-forum/421589-2-7-weber-jetting-baseline.html

I appreciate you.