godheadcustoms
Well-known member
I know lots of people have ran dual and triple offy (or whomever) intakes over the years, but my question is really about running an IR set-up on the half independant port/half siamese port configuration of the early Ford's. Even the 235 Chevy's with their all siamese port intakes make more sense from a logistics standpoint. In theory they should all flow equally good (or bad).
I understand the benefits of an IR intake over a plenum style intake, but the wacky port arrangement has me scratching my head a little. I know the factory 1 barrel log intake can be improved upon by a large margin, but I don't just want to throw more CFM's at the problem. I want to improve the whole intake system as a cohesive package.
What I'm after is better fuel distribution by directly improving the flow with straight shot intake runners, and indirectly by limiting intake charge reversion as much as possible with the IR set-up. On the one hand, the distribution should be better with only the paired, center ports potentially affecting each other and the end ports being completely independant. But will that, in effect, actually make things worse since now the cylinders are out of "balance" vs. a plenum intake where they can all be equally bad (or good)? And will I end up with a nightmare of stagger-jetting trying to get this thing to balance out somewhat?
My current thinking is: 4 small 1 barrel carbs (Corvair carbs that flow about 90cfm ea.) on a longish set of sweeping tubes (probably about 10" or so- I haven't done any calcs yet to see where the 2nd reflection comes in strongest) with only a small plenum at the carb mounting, mainly just for ease of fab work and making the carbs fit/transition. No interconnections or common plenum at all, although the carb mounting would probably be one long piece to help tie everything together structurally. The only thing I might do is a small plenum just to dampen the pulses going to the vac adv. in the dizzy.
So am I crazy, or would this be feasible? Or for that matter, am I better off going with basically the same set-up only using a plenum chamber at the carbs and saying to hell with intake charge reversion? Maybe this is all academic since it seems like the reversion problems would only have a noticable negative impact at higher intake velocities and I don't plan on spinning this motor much past 4500-5000 rpm?
Thoughts? Ideas? Theories?
I understand the benefits of an IR intake over a plenum style intake, but the wacky port arrangement has me scratching my head a little. I know the factory 1 barrel log intake can be improved upon by a large margin, but I don't just want to throw more CFM's at the problem. I want to improve the whole intake system as a cohesive package.
What I'm after is better fuel distribution by directly improving the flow with straight shot intake runners, and indirectly by limiting intake charge reversion as much as possible with the IR set-up. On the one hand, the distribution should be better with only the paired, center ports potentially affecting each other and the end ports being completely independant. But will that, in effect, actually make things worse since now the cylinders are out of "balance" vs. a plenum intake where they can all be equally bad (or good)? And will I end up with a nightmare of stagger-jetting trying to get this thing to balance out somewhat?
My current thinking is: 4 small 1 barrel carbs (Corvair carbs that flow about 90cfm ea.) on a longish set of sweeping tubes (probably about 10" or so- I haven't done any calcs yet to see where the 2nd reflection comes in strongest) with only a small plenum at the carb mounting, mainly just for ease of fab work and making the carbs fit/transition. No interconnections or common plenum at all, although the carb mounting would probably be one long piece to help tie everything together structurally. The only thing I might do is a small plenum just to dampen the pulses going to the vac adv. in the dizzy.
So am I crazy, or would this be feasible? Or for that matter, am I better off going with basically the same set-up only using a plenum chamber at the carbs and saying to hell with intake charge reversion? Maybe this is all academic since it seems like the reversion problems would only have a noticable negative impact at higher intake velocities and I don't plan on spinning this motor much past 4500-5000 rpm?
Thoughts? Ideas? Theories?
