An update on the dyno testing. We're currently testing the unported iron
4V heads. As a quick re-cap, we previously tested the CHI 3V aluminum
heads along with the Pro Comp copies. Fitted with the Scott Cook dual
plane intake, the CHI 3V heads made right at 400 HP and 400 ft-lbs
of torque (420 HP and 420 ft-lbs when corrected for the dyno absorber)
through the mufflers. We had some trace detonation so backed off the
timing a few degrees which dropped the uncorrected HP to 395 (415 HP
corrected). Switching to the single plane CHI 3V intake manifold picked
up 20 HP (436 HP corrected). The stock ANSA Pantera mufflers cost a
whopping 50 HP compared to the 3" inlet/outlet Magnaflows.
For the second round of testing, we replaced the CHI 3V aluminum cylinder
heads from Australia to the Pro Comp knock-offs from China. We tested
the same intakes (Scott Cook dual plane and CHI 3V 4150 pattern single
plane). On the flow bench the Pro Comps were down considerably to the
CHI heads and this was backed up on the dyno. The best pull with the
Pro Comps was 378 HP and 381 lbs-ft of torque (397 HP and 400 ft-lbs
corrected). What worked on the CHI as far as timing (32 degrees) and
carburetor spacer (4 hole 1 inch) also worked the best on the Pro Comp
heads.
For our third round of testing we switched to unported iron 4V closed
chamber heads. Interestingly, the unported iron 4V's made better power
than the Pro Comps. Fitted with a Holley Strip Dominator single plane
and a 1" HVH spacer, the 351C made 397 HP and around 380 ft-lbs (417 HP
and 399 ft-lbs corrected). The Parker Funnelweb was tested next. It
picked up around 10 ft-lbs in the mid-range but was down about 6 HP at
the peak. An Edelbrock Torker was tried next which performed about as
well as the Parker for HP and the Strip Dominator for torque. The Parker
worked best with a 4 hole 1 inch spacer, while the Strip Dominator and
Torker preferred the HVH. The final test for the evening was with the
Torker intake manifold but with the 1 3/4" diameter long tube headers and
Magnaflow mufflers replaced by the OEM 351C-4V cast iron exhaust manifolds
and a short elbow of pipe (no mufflers). The result was 366 horsepower
and 351 ft-lbs of torque (uncorrected), a nearly 30 HP/30 ft-lbs drop!
The engine also sounded rather odd and the increased back pressure upset
the idle quality noticeably. Combine this test with the muffler test,
and it's easy to see you can throw away a bunch of HP on a 351C with a
poor exhaust.
Dave noted the 3.5" stroke 351C with iron closed chamber 4V heads required
more timing than the 4" stroke 408C strokers he's tested with the same type
iron heads.
Rather than mill and drill the unported iron heads for studs and guide
plates, we used the bolt-down roller rockers from Randy Malik at R.M.
Competition. These are fully adjustable aluminum roller rockers
manufactured by Harland Sharp to Randy's specs which are dedicated Ford
351C/351M/400/429/460 rocker dimensions. Randy says they will withstand
spring pressures in excess of 475 pounds open and over 625 pounds open
when using the option Jesel bolts. These rockers are not the old style
flat top Harland Sharp rockers and are shaped more like the Crane Gold
units.
We've got a bunch more intakes to test with the unported iron 4V heads
but I thought it was time for a quick update.
Thanks,
Dan Jones
Original Post