[DMSALKOWSKI]

Walter, I am not certain who selected your venturi size..but I can assure you.... that they are much too small for your 347ci motor. In particular... if you plan on making peak power at 6000rpm and using a redline of 7000rpm. I see this all the time. The typical seller of these units always steers the customer towards smaller venturi's because the motor is considerably easier to tune this way. Higher velocity= stronger signal=easier tuning. There is just one big caveat. While the motor will certainly be streetable with great low speed throttle response and torque...your horsepower numbers are going to be very disappointing. I have worked on Webers for over 17 years. Most of the engines I have worked on are very large cubic inch engines that are dramatically more difficult to tune than your particular set-up. I have run some mathematical calculations and have determined that you need a minimum of a 40mm venturi to adequately feed the air your engine needs at 6000rpm. For the record... your engine is running out of air with your current 37mm venturi's at just 5000rpm. This is not conjecture on my part. It is a mathematical fact. Remember you are now 347ci... not 289ci like these carbs were originally designed for. I would highly recommend that you see if it is possible to exchange your venturi's for the larger size. By the way... you would need a 42 mm venturi to satisfy your engine at 6500rpm. At 7000 rpm you would need almost a 44mm venturi. The problem you will notice with this larger choke size is that without a good deal of compression your air velocity will slow sufficiently and negatively effect your bottom end. Regardless...40 mm appears to be the smallest size I would run. If you have compression over 10 to 1... you should seriously consider the 42mm chokes. Most people will steer you towards the smaller sizes....this is typically because they have know idea how to properly tune these carbs! Let me know if I can be of further help. David