Dave McLain built and dyno'd another Pantera engine. This time it's a solid
roller cammed 438 cubic inch short block with unported CHI 3V Cleveland
aluminum heads and matching single plane intake. It made 666 HP (yes, the
Mark of the Beast, how appropos) at only 6300 RPM and 627 lbs-ft at 4700 RPM
through the mufflers running on premium pump gas. That's on a dyno that reads
4 to 5% low compared to the calibrated Engine Masters Competition dynos.
666 * 1.05 = 699 HP. Dayum! Details of the build:
Heads are stock 225cc runner CHI 3V's. They have PBM stainless valves with
30 degree back cuts on the intakes only. 2.190" diameter intake and 1.75"
exhaust. All that was done to the heads was to finish the seats, hone the
guides to get the correct clearance and machine them for 0.502" diameter
Viton seals and ID style spring locators.
Cam is a solid roller ground by Steve Demos that uses Reed ULX lobes with
durations at 0.020" of 290 degrees intake and 292 degrees exhaust. At 0.050",
it's 254/258 degrees. Lobe lift is 0.400" intake and 0.405" exhaust. With
the Yella Terra 1.73:1 roller rockers, the zero lash lift is 0.692" intake
and 0.700" exhaust (minus lash of 0.024" to 0.026" hot). Intake centerline
is 104 degrees with a 108 lobe separation.
Springs are Erson E915043 with 235 lbs on the seat and 610 lbs at 0.700" lift
on both intake and the exhaust sides. Titanium retainers are from PBM.
Carburetor is a Competition Carburetion built 950HP with 76 jets front and 88
jets rear (no power valve in rear). CHI 3V 4150 style single plane air gap
intake. Both a 1 inch open spacer and a 1 inch HVH merge spacer were tested
and were virtually identical (open spacer made 664 HP and 630 lbs-ft torque,
HVH made 666 HP and 627 lbs-ft). Best power came at between 28 and 30 degrees
total timing.
Headers used on the dyno are the Mustang Hooker Super Comps we used on the
dyno project 351C engine with 1 3/4" primaries and 3 inch diameter collectors
that are about 6 inches long with a 12 inch extension into 3" inlet/outlet
Magnaflow mufflers. 180 degree Pantera headers will be used in the car.
A Dart SHP block with a 4.125" bore was fitted with a Scat 4.1" stroke forged
crank for 438 cubic inches of displacement. Rods are 6.2" in length from RPM
and the pistons are from Diamond with a dish giving the engine approximately
10.5:1 compression. Dave didn't deck the block. Instead he bought a Cometic
head gasket in a 0.031" compressed thickness to give the desired quench
distance.
Lifters are from Morel, pushrods are 3/8" diameter 0.080" thick wall from
Trend. Balancer is a Power Bond. A stock Melling 351 Windsor oil pump
was used though the bypass spring plug was pressed in a little deeper to
raise the relief pressure slightly over the stock 60 PSI. The engine has
about 70 PSI above about 4000 RPM and it idles with about 45 PSI hot. Dave
set it up with moderate bearing clearances and feeds the valvetrain through
a 0.075" restrictor. Oil pan is an Armando Pantera road race style pan.
Oil is 15W-50. Filter is a 2 quart Hastings LF 426.
Gaskets except for the head and intake are Felpro, stock rebuilder.
Timing cover is a new aftermaket stock replacement piece. Timing set is a PBM
billet gear set with a Torrington thrust. Dave retained the eccentric so an
engine mounted fuel pump can be run.
Dan Jones
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