Kelford Camtech is my supplier from 1993, ex Christchurch, South Island shareholdership.
Its a Danger Will Robertson Cam. Checking durations off the ramp can be 6 thou, or 10 thou for earky SB Chevies. 20 thou is used by some companies. 50 lift has become industry standard.
David Vizard gave exceptionall clues to cams, camminess, and turbo synchronisation in his Ford S.O.H.C Performance book in 1988. Let he who has wisdom understand....pmuller9 s cam calcs are just like Vizards Isky 134 example.
He discussed lobe centers, off boost and C4 automatic torque holes off idle and how to fix them with reducing duration when both intake and exhausts are open 30 thou.
Google SCRID xctasy Ford S.O.H.C, and you'll get my three posts.
Re-read the EAO/Pinto stuff. What works on those worjs better on Ford Sixes.
The "at lash" duration is calculated below using the standard calculations pmuller9 has posted(see below).
The cam is a lot more intense off the seat than Mikes; CMA's is down around the 235 mark for 50 thou duration. A 250 engine has a 25% stroke increase that dulls that savageness, but 253 at 50 is exceptionally savage, and a turbo 200 wont work at all well with it off boost.
Its very similar aside.
Im touch screening this, so cannot re-edit wrongly pushed "fat fingered fone fugg ups" without constant re-edits, so any words miss-spelt, im truley sorry.
I use Thou as a short hand slang term, and the System Internationale 0.552 when I see .552. I blurt out 30 thou over when I see a .030 over 351C.
Sign conventions like net and gross valve lift are like negative and postive wheel offset. They vary from place to place. My conventions might not be the same as proper US convention
The first readings are at lash durations, intake and exhaust. The second, at 50 thou (.050) durations intake then exhaust, the third brace of numbers, the average lobe center angle, the average of two, intake and exhaust. The forth set, the with 1.73:1 rocket ratio gross lift, minus the lash setting.
The grind is just like Mike1157's.
The total duration is a little less than the part race solid lifter cams from the early 1970's used in 265 Hemi Six Pack Chrysler Valiant Charger E49's, and the Phase II and Phase III GTHO 351C 4v Falcon four doors. The intensity, second figure, is far, far higher, so it reakky has a much more savage load stress curve, making it very noisy, with more noise than Mopar or Ford would ever except. At more than 220 degrees at 50 "thou", the engine will be unsympathetic to vacuum advance, low stall converters, a/c compressor cut in, and powersteering or 130 amp alterntor or electric fan cut in, so electronic or manual idle kick-in "throttle kicking" and "ignition ramp tip in" stratergies might be needed to tame ragardness from engine catch at 650 to create a stable 900+/- 50 rpm idle. The LCA average governs how the engines cam duration melds in with the cylinder size. Turbo engines with big cames should have 4 degrees more LCA than a cammed up carb engine. Most modern EFi engines start with 5 degrees more LCA from the factory to favor emissions and tame liw speed ragardness. 113 indicates its designed for an EFi engine, but LCA is not a band aid, its a mandatory requirement to manage reversion in the intake charge. In my opinion, its purpose is to allow pulse tuning.
On small 200 and 250 engines, Ford used the same 109 degree lobe center as the bigger 302C and 351C engines, and then just retarded the cam chain sprocket or crank sprocket for emissions compliance. In the 1985 speed density EFi era, Ford Europe and USA added LCA, and removed built in cam retard. In Australia, everything was VAM Meter EFi till the OHC in line, but the bottom end cars were CFi speed density, and Multipoint EFi still used the tighter lobe center.
Early in, FoMoCo had limited cam master profiles, cam changes were costly, and Fords late sixties Cobra Jet and Super Cobra Jet split duration cams were designed to save Ford money in reconguring the exhaust systems on emissions vehicles with thermactors. For LeMans, example is the GT40 289 and 427 LeMans Total Performance cams the intake exhaust duration was split with 18 less duration on exhaust; overscavening was provided by a special bunch in bananas exhaust.
Different philosphies to the days when cam grind cost was immense, now, its a growth industry which allows American cam grinders to rule the world with. Just remember, it was Clay Smith and heavy fuels and Hillbourne injection that got things moving. Everyone else then the world over copies USA cam grinders.
For gross lift at the valve, the normal max of the intake valve times (x) the curtain area are calculated using a factir of 0.30. If your lobe lift is 0.325, your solid lifter lash 6 thou (0.006) becomes lost motion and thats just 0.319 at the lobe and your rocker ratio might be measured as 1.75 instead of 1.73:1 advertised, then your lift at the valve is .319 x 1.75, or .558 at the valve. With a later larger intake valve of 1.84, your active .30 curtain area is bang on .552. Any lift over that isnt wasted lift, but you need to know that huge 2nd, 3rd and 4th factors need to be managed.
Very importantly, Ford Australia used 15 cc dishes in the little 200 cross flows instead of 5.5 cc pistons in the US 200 and 250. Peak lift at the valve was just 0.435, and any 200 with a 0.558 intake lift might get close to needing more than 8.5 cc of piston relief. The angles of the Aussie X flow valves are different and flatter than the Boss 302 and Cleveland 351 heads, but Be Carefull. The Boss 302 engines needed relief cuts with the 505 cams to avoid piston to valve contact in 8000 rpm situations.
The 250 cross flow used 21.9 to 27.9 cc piston dishes. The US 250 added another 18 cc by a 0.103 or greater piston shortfall.