The drone is resonance frm your exceptionally well made, large diameter primary exhaust system and induction system. The rest you can control by slapping a dual pipe final exhaust with conventional mufflers.
George Striegel at Clay Smith has been the man to get cams from in the past.....vast experience means he just sort of listens to what radio station your on, and whammo, you have a cam.
Smetimes Clay Smith or Schneider screw up, just like any. Your actual results vary. I don't like low lift, low duration cams on turbos. The 256H is in my humble opinion quite the wrong cam for a cut off log head with good intake and exhausting manifolds.
Lobe center discussions are all very good and well, but camminess is based on cold cranking compression with your pump gas octane, and how you trim the air fuel curve. The cam's actual dynamic compression ratio is mellowed by the total cfm flow with all the EFi and exhaust bolted up.
Your bare cylinder head casting with the iron head has similar flow figures to a 2V 250 Head with better exhaust flow. The intake flow figures are compromised at low rpm by port which are a little to big, and at high speeds by shape which is a little too far off the idealised apple port with the bottom of the port the wrong shape, and the top of the intake port to flat and square. So peak rpm looses power, and at low rp, you loose torque.
The reverse slpit cam is the right one, and going up in off the seat duration betweeen 30 and 50 thou is okay on a 3.3 six with opened up ports and better exhaust.
I don't doubt a Schneider 256H will idle better, but the problem is with ignition and fuel tables, not cam size or LCA. Lobe splay is better to be wider, but 115 is best for EFi, going back to narrow lobe splays isn't gonna help much.
A real disease with cam selection in the US is using benchmarking of existing mild cams on engines that aren't the same. The Schneider 256H and other cams like it have been used on 2V 250 headed 200's and Classic Inlines heads, and give great results. Period.
Georges "Turbo Expriement" was a 250 X flow Cortina with a 291 duration, 220 degree lift at 50 thou cam that others like Mike 1157 ran... a solid lifter cam on a 250 with a very good breathing head with more than 200 cfm at 25" H20.
All the 250 engines with turbos lap up extra duration and lift, and the little 200 needs a lot more duration and lift than the milder cams. The Lobe split angle recomendations for I6's are all wrong.Port EFi needs wider lobe centers to time the low speed pulses. All good programs give you crank angle at maximum piston speed, and that governs how you set up your injector pulses. Below 3000 rpm, the Fuel Injection world is sequential, and you really need to avoid narrow lobe centers.
Peak power rpm is defined by the traditional three or four emperical formulas, but low speed behavour is defined by injection and advance set up and cold cranking compression values. Yo9u can pull out valve lash and advance or retard cams to adjust, but it won't alter the peak power rpm much because thats set by the total cfm at 4500, 5000, 5500 and 6000 rpm zones. If you have 180 cfm at 520 thou valve lift with the intake manifold on, then your peak power rpm will be 5714 rpm with a 210 cubic inch engine, and as cubes go downwards, rpm goes up.
For a 30 thou over 200, that's smack dang on 5800 rpm. If your total cfm is lower at 520 thou lift, then peak rpm will drop, but there aint no way I'd ever undercam a 200 turbo with EFi with as little cam as that. Everyone these days is wanting to run power Steering, A/C, and high stall converters, and the common recomendations Jerry makes is for something a little less than the ideal. With bigger head flow CFM's, carb duration and lift don't need to be as high, but as the head become less efficent like our log heads, then cam duration and lift become CRITICAL.
Balancing off overscavanging is likewise ultra important, because Ford's engineers decided to restrict intake flow and adjust exhaust flow to 65% of the intake figure on all its engines. Cleveland 351 4V's are the worst, as are FE 390's and Lima 460's.
Anytime you got a great intake, Ford always restricted the exhaust hump. Mainly becasue they were lumped into little uni body X chassis 60's Falcon sedan based platforms with coil over A arm or Modified McPherson strut suspension Foxes that you couldn't swing a spanner in.
So all the Ford cams up till 1985 were ground for restrictive exhaust flow, while a turbo 200 with a cut off log needs a reverse cut intake and duration split like 300/290 or 280/270. Especvailly Aussie X flow alloy heads, the most unbalanced Ford head ever, with perfect exhaust ports, and very , very small intakes, becasue it was designed by Honda in Japan to a Ford Australia brief, using all the inputs from the old Lean Burn Four Cylinder project Ford and Honda did togehter in the mid 70's.
Everything changed in 1984-1/2 with th advent of headers and low restriction four catalyst exhausts, and then with roller cams. Ford did some great work on the V8 EFi engines, and changed the intake to exhasut split, the lobe angle, and from 1984, started using the Power Control Module to run the ingtion advance to control idle speeds and smoothness in adverse conditions. At lash duration went up, so did 50 thou figures, and they used electronics to tune out bad idles. Or, in the case of the few Saleens than came with the E303 roller cam, tuned in the B-A-D idle, and thats what everyone loves about a bad a$$ 5.0 Mustang. Idle chop!
I've seen Jerry Cantrell's latest cam recomendations, and they are generally very conservative. One done on Feb 7, 2018 was in my opinion, wrong for the combination supplied. ITB EFi, approx 220 cfm intake flow, 250 six with 4 stage auto. It was so far off Georges, and way, way off the Australian Dean Tigue cam. US cam selections use too much V8 histronics that don't relate to full house street in line sixes with Holley or Megasquirt port EFI control systems.
Having said all
that, I love Schneider. Schneider cams back up and its cam selections appear to be based on the over rIding issue that nearly all US in line six cylinder guys have...."my Ford in liner won't idle smoothly." If its gonna take out a V8 on the street, then idle shouldn't be concern No 1 fellas.
I'm convinced that Schneider under recommend duration, lift and lobe center, not because they don't
understand full house cams, but because they know
that 90% of Ford Six Cylinder guys are a heck of a lot more conservative than Ford V8 guys, and that a smaller cam won't suffer break in and low speed drivablity problems, a primary issue for aftermarket cam buyers today.
All the recomendations I've seen leave a lot of power and mid range torque on the table, instead on in your in line engine. Use Fuel and Igntion EFi manages air fuel and idle tip in to fix off the cam issues. If a 2-bbl CFi 1985 Mustang used a cam milder than your Schneider 256h recomendation, then the Schneider recomendation isn't man enough for the job. Any time you loose two cylinders, 102 cubic inches,and add a turbo, you'll need to have a much racier than a good Ford 302-361 V8 "benchmark"cam.
A traditional Cobra Jet or Torino 73 351 Marine cam was what the 5.0 GT's and the non Saleen SVT R351 1994 Mustang used....
the D3OE-6250-AA cam for 1973 Torino/1982 GT 5.0/ 1984 5.0 GT or RS HO CFI / 1985 HO AOD/ 5.8 Lightening 260° intake, 278 (or 274 by another source)° exhaustviewtopic.php?f=5&t=71872
84-85 5.0L CFI
Cam OE Number Type Int Lift Exh Lift Int Dur Exh Dur Int Dur@.050 Exh Dur@.050 Lobe Centerline
D3OE-6250-AA Hydraulic .416 .445 260 274 198 208
Split lobe cams were Fords total solution to getting cars to make low end torque while still giving okay emmissions. The culmination of them was the 1985 to 1993 Ford Motorsport "Deadly Letter" Roller Cams.
The cam choices sugested are just too conservative for me, and they typically over scavange like all Ford performance cams from 1968 to 1985.
Ford learned to widen the lobe center and not be affraid of extra 50 thou duration with the advent of EFi.
We should be doing the same thing, even with solid lifter flat tappet cams.