What would it take to make 1.44 lbs-ft per cid ?

One thing I think I've learnt from this is too little velocity is a lot harder to get than people make it out to be most heads seem to be in the acceptable range calculated 260-310 fps with 285 fps being considered optimal.

And examples of 260 fps the lowest recommended fps and would give the largest ports for a given cfms is very unlikely to come across 225 cfms = 170 cc, 250 cfms = 190 cc, 275 cfms = 205 cc, 300 cfms = 225 cc, those are some very large ports for each given cfm and there still would be considered very acceptable velocities for very good hp and torque. You would have to add like 15+ cc to these to be considered slow port with possible reversion, it seems like too high of velocity is far more likely above 310 fps being the highest recommended, 225 cfms = 140 cc, 250 cfms = 155 cc, 275 cfms = 170 cc, 300 cfm = 190 cc. Any thing like 5+ cc smaller and run the risk of too much velocity.

It seems like ports generally for a given cfm automatically fall in the ranges acceptable velocities as long you build for the right rpms range for a given cid for each head. Which might be why we generally focus on cfm numbers.

Minimum csa might be more of an issue.

Calculated recommended head flow cfm for a given cid and rpm.


RPM. 4,500.....5,000....5,500....6,000....6,500....7,000

273. 150.........167......184.......200........217......234 cfm

318. 175.........194.......214......233........253......272 cfm

340. 187.........208.......229.......250........270......291 cfm

360. 198.........220.......242.......264........286......308 cfm

408. 225.........250.......274.......299.........324.....349 cfm