If you are using bladder pressure, you can run these engines without the carb. Just drill a new hole for the NVA. I modded one this way after the glued-in carb (an older model engine) fell out in flight and was lost. I made a venturi extension out of the standard alum tubing found in most hobby shops, epoxying it in place. I picked up 1500 RPM's with this set-up! If you can find a VA fine-thread NVA to replace the Norvel NVA, that is even better. Larry Driskill used to carry them, but is currently out of stock. He may have a new batch in the future. If you are running suction, you can still go the above route, but will need to have a smaller venturi extension made.