quote:
Originally posted by Danford1:
Hi George. I'm resurrecting this thread. I'm thinking of having
one of these Cobra Jet cams ground for solid rollers in a 357 C ...
In the process of penning a cam for another person I needed a
different intake lobe, which after I penned the cam I decided
I liked it better, its more universal, so the spec has changed
a bit. The benefits are two fold, increasing the intake duration
means that engines with non-4V heads, i.e. smaller ports, shall
still peak at about 6000 rpm; and both lobes now have the same
lift, so having different rocker ratios for intake & exhaust is
no longer necessary.
No 351C with 4V heads has a "smooth" idle, because of the big valves.
But this low overlap cam will have an idle about like the 351 Cobra
Jet, maybe just a bit "rougher". The engine shall have a slight lope,
a nice 1960s burble. I don't do rough idling cams, there's a million
of them already I don't need to add to the list. I uniquely pen street
cams that people can't find in the aftermarket. That's where my usefulness
lies. Lowering the engine's idle speed increases the lope, raising the
idle speed decreases the lope.
Here's the revised spec:
Ford 351 Cleveland solid roller tappet street cam
Grinder: Comp Cams
Lobes:
High Energy Street Roller
Intake #1474
Exhaust #1476
112° ATDC intake lobe mathematic centerline
117° BTDC exhaust lobe mathematic centerline
280°/288° advertised duration (284° average)
236°/244° duration at 0.050"
Indicators
44°/44° intensity (advertised duration – duration at 0.050)
35° major intensity claimed by Comp Cams
Overlap at 0.050” = 11°
Lobe separation angle = 114.5°
0.3666"/0.3666" lobe lift
0.020”/0.020” lash
0.634”/0.634” theoretical valve lift (1.73:1 ratio)
0.614”/0.614” net valve lift [(lobe lift x 1.730) – lash]
0.603”/0.603” factual valve lift [(lobe lift x 1.70) – lash]
EVO = 81° BBDC
IVO = 28° BTDC
Overlap = 55°
EVC = 27° ATDC
IVC = 72° ABDC
Suggestions:
• Install tappet bore bushings having 0.062” orifices. A do-it-yourself installation kit is available from Wydendorf Machine.
• Utilize Isky solid roller tappets #3972-RHEZ (they roll on solid bushings instead of needle bearings and they feature forced lubrication instead of splash lubrication).
• Valve springs, Manley Nextek #221432. Dual valve springs plus damper. 1.53” diameter, 1.90” installed height, 150 lbs. seated force, 435 pounds per inch spring rate (412 pounds over the nose), 0.630” max. lift, 0.730” coil bind.
• Utilize a steel distributor drive gear for steel roller cam cores (never a bronze gear). They are available from Crane Cams and Ford Racing.
• Best possible rocker arms are T&D Machine #7200 individual shaft mount rocker arms, 1.70:1 ratio, having rocker arms manufactured from steel. Yella Terra YT6321 would be a less expensive substitute.