hubeerjw
Well-Known Member
I started crunching some numbers today after having taken off my carbs and intake and noticing the oval shaped intake ports. The stock carbs are 35mm (and if I am wrong with anything I say, please correct me) and the top/circular part of the intake is 36mm. The intakes then "blend" into an oval shape that I measured to be 30mm by 40mm. This is the same shape/size as the intake on the heads. If we take the area of these openings we will get the following:
35mm Circle (diameter) = 9.62cm^2
36mm Circle (diameter) = 10.17cm^2
38mm Circle (diameter) = 11.34cm^2
30mmx40mm oval = 10.07cm^2
I threw in the 38mm circle because I recently purchased some 38mm carbs off eBay hoping to get them installed on the VMax at some point. I wanted to know if anyone knows what the intake and exhaust valve sizes are and where the most restriction would be located? If it is at the valves, then I will not bother with trying to remove material in the oval parts of the intake and head. If the valves will allow more flow, then I would think it would be in my best interest to try and match the carb size with my intake/head size. I have calculated that an ellipse measuring 36mmx40mm would match almost perfectly with the 38mm carbs. That would mean removing only 3mm of material at the center of the intake at both the top and bottom. If you throw V-Boost into this, all my theoretical numbers go out the window. I talked with Shawn a while back and I believe he had his heads flow tested to 120CFM. Shawn if you are willing to read through this whole thing, do you know if they tested your heads at 28inches of water depression and what did they use for exhaust restriction (diameter of exhaust pipe?) Now I'm no way an expert in any of this and will take in any comments or criticism. I have also read how port size and velocity all play an important part with HP, throttle response, etc. Maybe I am over-complicating things, but if I'm going to spend the time on certain projects, I would like to get as much out of it as possible. Sorry for being so longwinded.
Thanks,
Jeff
35mm Circle (diameter) = 9.62cm^2
36mm Circle (diameter) = 10.17cm^2
38mm Circle (diameter) = 11.34cm^2
30mmx40mm oval = 10.07cm^2
I threw in the 38mm circle because I recently purchased some 38mm carbs off eBay hoping to get them installed on the VMax at some point. I wanted to know if anyone knows what the intake and exhaust valve sizes are and where the most restriction would be located? If it is at the valves, then I will not bother with trying to remove material in the oval parts of the intake and head. If the valves will allow more flow, then I would think it would be in my best interest to try and match the carb size with my intake/head size. I have calculated that an ellipse measuring 36mmx40mm would match almost perfectly with the 38mm carbs. That would mean removing only 3mm of material at the center of the intake at both the top and bottom. If you throw V-Boost into this, all my theoretical numbers go out the window. I talked with Shawn a while back and I believe he had his heads flow tested to 120CFM. Shawn if you are willing to read through this whole thing, do you know if they tested your heads at 28inches of water depression and what did they use for exhaust restriction (diameter of exhaust pipe?) Now I'm no way an expert in any of this and will take in any comments or criticism. I have also read how port size and velocity all play an important part with HP, throttle response, etc. Maybe I am over-complicating things, but if I'm going to spend the time on certain projects, I would like to get as much out of it as possible. Sorry for being so longwinded.
Thanks,
Jeff