Reply to "Suggestions on Cam for '71 351c 4v motor"

> Would like to stick with hydraulic lifters, no roller cam!

Hydraulic or solid lifter cams can be either hydraulic or roller.
We are currently dyno testing a hydraulic roller on the 351C dyno
project engine. I assume you mean you want to stick with a hydraulic
flat tappet cam. If so, are you aware of the wear problems with
flat tappet cam lobes and low ZDDP content oil?

> Current engine config; Holley 750 DP, Performer intake, pertronix 3, etc.

Do you have closed chamber heads and flat top pistons?

What exhaust are you running? We lost 50+ HP through the stock and
Euro GTS mufflers. Gained 10 HP and 10 ft-lbs back by gutting the
Euro GTS mufflers and replacing the baffles with a Y-pipe. We gained
all 50 HP by running 3" inlet/outlet Magnaflows.

> As the title suggests, looking for recommendations on a new cam for my
> '71 351c 4v motor. The car is mostly driven in the canyons, not too
> much city driving... but have to get to canyons.

Okay.

> You want a dual pattern cam, different on the intake and exhaust events.

I think it's a fairly minor effect. You trade some low RPM performance
for some peak power that doesn't drop off as quickly. If you run extended
duration, be aware that extra lift is of no benefit. On dual pattern cams,
we've actually picked up a few HP and ft-lbs of torque running a shorter
1.65:1 ratio rocker on the exhaust side and 1.73:1 on the intake. Granted,
it's not a big effect. Ideally, a 351C with 4V heads (2.19" intake valves
and good exhaust) wants a narrow lobe center (107 or 108 degrees, 108 is
available off-the-shelf, 107 is custom order). If you have a restrictive
exhaust (lik most Panteras), you may want to widen the lobe centers a couple
of degrees to 109 or 110. Crower has a few cams in there "390 Series" for
351C with dual pattern, shorter exhaust lift and 110 lobe centers that might
fit the bill:

P/N LSA advert 0.050" lift cubes low peak peak top
duration duration intake/exhaust rpm tq hp rpm
15173 110 280/287 219/225 0.530/0.524 351 2300 3800 5700 6300
400 2000 3500 5200 5700

15174 110 289/295 227/233 0.550/0.547 351 2400 3900 5900 6400
400 2100 3600 5500 6000

For your application, assuming restrictive exhaust, I'd recommend the 15174.
I'd only go with the 15173 if the compression were low. Also, check with
Bullet on their pricing. All of Bullet's cams are custom ground. For only
a few dollars more, a cam tailored to your specific engine can be ground.

On 351C-4V's, I personally prefer 108 lobe centers but few Panteras have
an exhaust efficient enough to really utilize the narrow lobe center cams.
From our dyno testing, there is more to gain in the exhaust than in
aftermarket heads or intake manifolds. If you have an efficient exhaust,
there are several 108 lobe center grinds from Lunati, Isky, Crower etc.
that will work well.

In the "Be the Camshaft Expert" article, David Vizard presented the results
of a lobe separation test:

http://www.bacomatic.org/galle..._comparison.jpg.html

Ideal LCA for that engine was 108 degrees. Narrowing to 105 degrees made
similar power but had noticeably worse idle and low speed characteristics.
Widening to 111 degrees lost power most everywhere. At low speed, lots of
overlap is bad as it hurts low end but overlap helps power as the RPM
increases. To a degree, you can offset overlap with static compression.
For most V8's with reasonable heads, the ability to raise low speed torque
with compression increase holds to around 285 to 290 degrees (at lash point)
of cam duration. After that, drop off is faster than an increase in
compression can recover. In another article ("Compression Comprehension")
about running up to 12:1 compression on pump gas, Vizard presented the
results of a compression test:

http://www.bacomatic.org/galle...peed_output.jpg.html

"When used in conjunction with a bigger cam, increased compression can
work wonders for the entire curve. When a 265-degree cam (gray curve)
was substituted for a 285-degree cam (blue curve), a substantial drop
in low-speed output was seen. Raising the CR from 9:1 to 12:1 recovered
almost all the lost low end and gave a further increase in top-end
output"

When used with the right amount of cam overlap, you can run closed chamber
heads and flat top pistons in a 351C and have an excellent street motor
that runs on pump gas. In a dual pattern cam, the Crower 15175, looks
good:

15175 108 298/303 236/241 0.574/0.567 351 2500 4000 6100 6500
400 2300 3800 5800 6300

In a single pattern, Isky has the Isky 280 Megacam (the 270 Mega would be
good for a lower compression engine):

Isky 270 Mega 221 deg @ 0.050" (270 deg advertised), 0.542" lift, 108 LSA
Isky 280 Mega 232 deg @ 0.050" (280 deg advertised), 0.565" lift, 108 LSA

Lunati also has a couple:

Lunati 07111 225 degrees @ 0.050" (275 advertised), 0.550" lift and 108 LSA
Lunati 07112 235 degrees @ 0.050" (285 advertised), 0.560" lift and 108 LSA

Dan Jones