Lower breathing, lower cfm heads are less likely to have high cam duration low to mid range torque loss problems than higher flow heads.
I know its prudent to under cam, and follow CI advice. However, a too low stall converter problem causing idle and off idle problems is easy fixed with a 300 to 500 dollar torque converter upgrade if it ever happens, and our sixes have four really important factors which avert low speed torque loss.
In all cases, I'm sure we therefore tend to be too conservative.
Due to
1) small porting,
2)the poor exhast flow,
3)the tendancy for all of us to worry about how a 264/274 will deal with a c4'S stock low stall ratio (always factory rated at 1650 rpm by Ford),
4)the 200 and 250 is a quasi Pontiac 455/Chev 400/Chev 396 style stump puller 1.5:1 rod ratio engine which really drags the peak rpms down and keeps the low rpm air speeds up
These four things I'm sure make it impossibly hard to screw up low speed torque on a 200 and 250 engine.
Based on what I've experienced with a 1.65:1 rod ratio 280 degree cam 3.3 liter 1-bbl engine (9 port Holden 202, 215 degrees duration at 50 thou on both intake and exhast, headers, but no other mods but cam, 8.8:1 compression, BW wide ratio 5-speed, 3.9:1, 2700 pound) and my old 1.5:1 rod ratio 4.1 2-bbl Holley 500 engined Falcon (252 degree Heatseaker cam, headers, 3-stage auto, 9.65:1 compression, 2.77:1, 1650 stal, 3000 pound), i'd say a log 200 or 250 needs a cam of at least 215 degrees at 50 thou to do anything. At lash figures vary so much, but I'd not even consider a 260 degree at lash cam as a valid swap based on the time consumed doing the swap verses the overall results through the rev range.
Most cases, compression ratio is going to go up over 8.5:1, with even a later 62 cc cylinder log head, as most people have a log head shaved. Most times, we go for better carburation, most times extractors/headers or better exhast, most times electronic ignition, most times, a better manual or a rebuilt C4.
I know it's dead easy to over cam a car, but that fourth factor with our little sixes is they always come with a stump puller 1.5:1 rod ratio engine which really drags the peak rpms down and keeps the low rpm air speeds up. You don't end up with a loose torque car like you do with, say a 289, 302 or 351 when you go from a 256 degree at lash cam to a 280 degree cam. These engines never got L/R (Lenght of Rod to stroke ratios ) of less than 1.65:1, and were always higly responsive to cam changes
If a heavy 1-bbl 3.3/200 car can cope with a 280 degree at lash, 215 degree at 50 thou cam. And a higher flow cross flow 2-bbl or EFI 4.1/250 can take a 280/215 cam with 8.7:1 compression, then I don't think a poor flowing log head will have any issues. Generally, low end torque loss would be accentuated with bigger port 2V and CI heads, where over camming would show a low speed torque loss. Due to the crappy rod ratio, even a Classic In lines head with 8:1 compression, stock exhast on with a 500 Holley 2-bbl and a 3.3 engine would propably take a 264/274 cam, and make it work from off idle to red line.
Only issue I've ever heard is that when you go to bigger Holley 2-bbl carbs and bigger than 215 at 50 thou cams with stock transmissions, you have to be very carefull not to go too high with duration, or else you get fuel standoff/carb spit back/reversion. The factory 1971-1974 250 cube 2v engines had 1.65" diameter ports, bigger than any 200/250 combo, and with a 280/215 at 50thou cam, 500 cfm 2-bbl 4412 Holley and stock C4, you can get problems with off idle torque. Well known problem. Due to mixture motion and the work done with the latter alloy CI head, it would be unlikely tohappen with a C1 HEAD with the same combination.
