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

> I have closed chamber heads and free flowing headers and exhaust

What mufflers are you running?

> Comp Cams part# 32-000-8

That part number indicates the cam is a custom grind street roller grind
using an austemprered cast ductile iron cam core. It is a roller cam but
may be either a hydraulic roller or a street solid roller. From the short
duration, I'll assume it is a hydraulic roller but please verify that.
Be aware that the cam material is supposed to be compatible with cast iron
distributor gears. In the past, I would recommend either a Ford Motorsport
or Crane steel distibutor gear but with Crane's demise, those are no longer
available. Do not use a parts store iron gear. A friend Rockwell (B scale)
tested several distributor gears. A generic auto parts cast iron gear tested
at 70, a bronze gear at 90, and the stock Ford cast iron gear was 102. Note
the soft bronze gear was actually harder than the generic auto parts cast
iron gear. Mallory makes a distributor gear for their distributors that is
made specifically for "austempered ductile iron billets" and "proferal billet"
cams. You may want to look into that gear.

Do you have the cam card for that cam? I'd need it to figure the total
overlap. From what you've provided, I'd guess the overlap is around 64
degrees. That is less than the 68 degrees of overlap of the cam I'm
currently testing in the 351C dyno mule. That cam has specs of:

228/232 @ 0.050" lift (280/284 @ 0.006)
0.588"/0.588" lift
107 LSA

Our cam peaks at around 6000 RPM and holds the peak past 6500 RPM
with the Crane link bar lifters. Your cam has specs:

220/230 @ 0.050" lift (276/290 advertised)
0.591"/0.588"
106.0

will likely peak around 5500 RPM, perhaps a bit less. Figure it will
have a noticeable idle and start pulling well at 2500 RPM or so.
Depending upon your intake and carb, it may take some fine tuning (carb
and distributor) to smooth out below 2500 RPM. If I were re-designing
your cam, I'd increase the intake duration at the expense of the exhaust
duration and widen the LSA slightly to 107 or 108 which would (not
coincindentally) end up looking more like the cam I'm testing. Extended
exhaust duration adds overlap but the duration is better used for power
on the intake side. Extended exhaust duration is primarily a drag race
trick to keep the power from dropping off quickly after power peak.
Ideally, you want to use the minumum extra exhaust duration that keeps
your cam from dropping off at your shift point. Extended exhaust duration
can also hurt fuel economy and low RPM performance but your total duration
is still moderate so that may not be big deal in your case.

Be aware that Comp uses a reduced base circle on their 351C hydraulic
roller cams. If you are using the spider and dog bones to retain the
lifters (like the OEM 5.0L hardware), there can be clearance issues in
Cleveland blocks. It seems to be hit or miss. Some Cleveland blocks
can use the OEM style, others need the link bar lifters. One one 351C,
we were able to use the dog bones, ona another we could not. Apparently
the lifter bore height varies enough in production 351C blocks to make
some of them too short for the Ford lifters. The Crane link bar lifters
fixed the problem in the block with clearance issues. Crane is no longer
in business but the lifters are still in inventory last time I looked.
Also, Comp makes a link bar lifter now. We trial fit those on our
351C dyno engine but they would not work due to a different problem.
With our standard base circle cam, the oil feed hole on the lifter comes
out of the bore at max lift due to the chamfer at the top of the lifter
bore. The same lifters worked on a previous 351C engine but that engine
had a block that was machined differently (by Ford). Comp uses reduced
base circle cams so you should not run into the problem but check it
anyway. Also, Dennis at Reed Cams said that, as a rule, irregardless of
how much lift that a camshaft has, the lifters generally all stop in
approximately the same location at the top unless the base circle is
deliberately reduced which can cause problems at the other end of the
lifter bores.

If you go with the OEM Ford style lifters, Alex Denysenko at MoneyMaker
Racing (http://moneymakerracing.com/) can get you Sherman modified lifters
that can be worth 500 RPM.

Dan Jones