Stock Camshafts

351C 4V Factory Cam & Street Cam Info

Here's the factory cam specs:
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1971 351C-4V (M code) camshaft, D0AZ-6250-C

268°/280° advertised duration
duration @ 0.050” not available
0.427"/0.453" valve lift
118.5° lobe separation angle
Int lobe mathematic centerline = 116° ATDC
Ex lobe mathematic centerline = 121° BTDC

Exhaust valve opening = 81° BBDC
Intake valve opening = 18° BTDC
37° overlap
Exhaust valve closing = 19° ATDC
Intake valve closing = 70° ABDC
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1971 Cobra Jet (Q code) camshaft, D1ZZ-6250-A

270°/290° advertised duration
205°/220° duration @ 0.050”
0.481"/0.490" valve lift
117° lobe separation angle
Int lobe mathematic centerline = 117° ATDC
Ex lobe mathematic centerline = 117° BTDC

Exhaust valve opening = 82° BBDC
Intake valve opening = 18° BTDC
46° overlap
Exhaust valve closing = 28° ATDC
Intake valve closing = 72° ABDC
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1972 through 1974 Cobra Jet (Q code) camshaft, D2ZZ-6250-B
(Same as the 1971 camshaft except the camshaft timing was ground 4° retarded to reduce the dynamic compression ratio)

270°/290° advertised duration
205°/220° duration @ 0.050”
0.481"/0.490" valve lift
117° lobe separation angle
Int lobe mathematic centerline = 121° ATDC
Ex lobe mathematic centerline = 113° BTDC

Exhaust valve opening = 78° BBDC
Intake valve opening = 14° BTDC
46° overlap
Exhaust valve closing = 32° ATDC
Intake valve closing = 76° ABDC
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If you're considering replacing a factory cam with an equivalent cam, the Cobra Jet cam is still available. This cam was rated by Ford for 29 additional horsepower over the M code camshaft, the basic RPM Range is rated as 1700-4200 rpm. To the best of my knowledge these modern versions are ground on 115° lobe separation angles, and I recommend timing them for intake lobe mathematic centerline = 115° ATDC.

Blue Racer #972227
Melling #SYB-29
Clevite #229-1883
Sealed Power #CS-650
Manley #MS700
Lunati #11104LUN
Crane #C580
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There were 2 other well liked cams sold by Ford in the 1970s and 1980s, and reproduced by many aftermarket companies. These are both a little hotter than the Cobra Jet cam.

The 505 cam (1970s) D1ZZ-6250-BX
Described as having a fair idle with lope, and a wide power band – its a hydraulic version of the Boss 351 cam. This camshaft was rated by Ford for 50 additional horsepower over the M code camshaft, 21 additional horsepower over the Q code camshaft, and 7 additional horsepower over the Boss 351 solid tappet camshaft.

290°/290° advertised duration
219°/219° duration @ 0.050”
62° overlap
0.505"/0.505" valve lift
114° lobe separation angle
Basic RPM 2100-5000

Blue Racer #972803
Melling #24224
Clevite #229-2072
Sealed Power #CS-173R
Lunati #11101

The SVO A341 cam (1980s) M-6250-A341
Described as having a good idle with lope, and good low to mid-rpm torque. This cam does not have as much high rpm pull as the 505 cam.

280°/290° advertised duration
214°/224° duration @ 0.050”
61° overlap
0.510"/0.536" valve lift
112° lobe separation angle
Basic RPM 2000-4800

Blue Racer #972836
Melling #24204
Clevite #2055
Sealed Power #CS-1021R
Crane #523941
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If you're considering a modern performance cam with specs similar to the factory cams the Crane Cams H-278-2 hydraulic flat tappet camshaft or the Crane Cams HR-216 hydraulic roller tappet camshaft are modern off the shelf cams with similar drivability characterisitics (but higher lift and more horsepower).

I can also provide specs for custom cams ground by Bullet Cams that emulate the 1971 M code cam and will provide excellent drivability, excellent intake manifold vacuum, excellent low rpm power with even better performance and horsepower than the cams from Crane Cams. They use somewhat hotter cam lobes but not so hot to cause exessive valvetrain wear.

Here's feedback from someone running one of the cams ground by Bullet Cams

quote:

"... My engine is a 393 stroker, 10:1 compression, dished pistons, iron 4V closed chamber heads, 66cc polished chambers, blended bowls, hand ported by me, 2.19/1.71 valves, 7/16 studs, guide plates, beehive springs w/steel retainers, roller rockers, all good Comp Cams stuff; Edelbrock RPM AirGap intake, Demon 750 vac sec (annular boosters) carb, Pertronix ignition, 8° initial, 34° total advance. The exhaust uses 1-7/8" headers, 2-1/2" intermediate pipes, and magnaflow mufflers.

I was running a Comp Cams custom hyd roller 224°/230° @ 050, 0.572"/0.584" lift, 110° LSA, 110° ICL. The motor switched on @ 2200 rpm and was all done by 5600. 10" vac idling @ 1000 rpm; The motor had difficulty passing the smog idle test.

I installed the hyd flat tappet cam you specified, ... I needed a 9 way timing set to get the timing correct (straight up), but it installed perfectly and matched the cam card; the Bullet guys had it done in 3 days.

Anyway, I am ECSTATIC about the results so far! The motor will even idle down at 650 rpm now (wouldn't idle below 950 before) Vacuum at idle has jumped from 10 to 17 inches! And it idles cleanly (couldn't stand beside the car before at idle, it stunk so bad due to emissions) It has a nice lope to it, but still idles very well. I'd recommend this cam to anyone.

... the motor "turns on" at 1700 rpm now (was 2200 with the other cam) and pulls hard past 6200; just blipping the throttle, it revs so freely now to 4500 it makes me laugh; and it melts the tires at will and even breaks them loose shifting into second gear now (never did that before); its been all you said it would and more! I'm going to need more tires under it though (laugh) ..."

Regards!"

351C 4V Street Camshaft Shopping
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A motor equipped with 4V cylinder heads is capable of excellent low rpm power and throttle response with the right cam and with a dual plane intake manifold. If somebody is having problems with the lower rpm performance of their 351C 4V it’s not the cylinder heads that are the problem, it’s the camshaft selection, the intake manifold design, the tune of the carburetor, the tune of the ignition, or the general condition of the engine (i.e. rings & valves).

The other small block in-line valve motors people are more familiar with have small ports and small valves for the given displacement of the motor, thus pushing the motor’s power band into the very lower end of the rpm range. Such motors rely upon camshaft and intake manifold design to widen the power band and promote mid and upper rpm power. The 351C 4V is just the opposite, the intake ports and valves were sized to give the motor response to 7000 rpm, the 351C 4V relies upon the camshaft design and intake manifold design for its lower rpm performance.

Camshaft selection for a street driven Cleveland motor with 4V heads should be limited to camshafts with advertised intake duration in the range of 270° to 290° (advertised duration) to prevent pushing the powerband too high in the rpm range. Overlap should be in the range of 50° to 62° for good low rpm power and good manifold vacuum. Exhaust valves should open approximately 78° to 84° BBDC (based on advertised duration) for good upper rpm performance and/or to help the motor cope with restrictive exhaust systems. Intake valves should close approximately 68° to 74° ABDC to steer clear of reversion. Camshafts having 112° to 115° lobe separation provide best drivability and compliment the design of the cylinder heads in supporting a wide flat powerband. Cams with 8° to 14° split duration (more exhaust duration than intake duration) allow the cam designer to center the overlap event around top dead center, thus aiding low rpm power. Many of the most popular 351C camshafts were (and still are) Crane Cams grinds.

Street Cams
LSA ...... Average Duration ........ Overlap

115° ... 280° through 292° ...... 50° through 62°
114° ... 282° through 290° ...... 54° through 62°
113° ... 284° through 288° ...... 58° through 62°
112° ... 286° ........................... 62°

average duration = (advertised intake duration + advertised exhaust duration) ÷ 2

The heads will provide good upper rpm performance as long as they are not strangled by restrictive intake or exhaust systems. The 351C 4V will make peak horspower at 6000 rpm with cams varying as widely as the Cobra Jet cam (270° advertised intake duration, 205° intake duration at 0.050), the Boss 351 cam (290° advertised intake duration, 235° intake duration at 0.050), the Crane HR-216 cam (278° advertised intake duration, 216° intake duration at 0.050) or the Crane H-278-2 cam (278° advertised intake duration, 222° intake duration at 0.050).

With the 4V heads and powerbands up to 7000 rpm the cam is the tool for shaping the motor's low rpm performance, but it takes a back seat to the induction system in regards to shaping high rpm performance. The way to increase horsepower at higher engine speeds is to improve the volumetric efficiency. Valve lift, cam lobe design, and the associated valve train play a part in that. But so do the heads, the intake manifold, the carburetor and the exhaust system.

To make my point, there is a Pantera owner whose Pantera is equipped with a standard displacement 4V Cleveland that makes over 500 BHP at 6000 rpm with the very small Crane HR-216 hydraulic roller cam! Only 216 degrees @ 0.050" intake duration. The Pantera's motor has independent runner induction and a bundle of snakes type exhaust with very open mufflers. The cam is obviously not responsible for all that power ... its the intake & exhaust systems, plus the iron 4V cylinder heads (which are mildly ported). The volumetric efficiency of his Pantera's motor is very high. The 4V heads are capable of very high volumentric efficiency, the intake and exhaust systems of that Pantera's motor are not hindering that performance.

-G

George,

Thanks very, very much for an informative answer way beyond what I'd asked!

Mike

Ford always had the policy for street cars that idle quality and drive-ability were paramount and it was an edict that could not be circumnavigated internally for a STREET PRODUCTION VEHICLE.

All of these camshafts fall into that category.

None of them, including the Boss 351 cam, are capable of producing the magic 500hp number in the Cleveland.

The Boss 351 comes the closest with around 400hp at the flywheel.

They all have a nice idle to them and the CJ even though it is a mild grind, has a nice rump, rump idle in the Pantera.

One thing about it though, in the Mustang, the CJ idles at about 775 rpm. In the Pantera, it's 1,000rpm. Same engine though.

I always wondered why?

We're spoiled by modern hot rod parts (especially the camshafts) and modern dyno equipment, desk top dyno, etc. So many big numbers get thrown around.

The Boss 351 made about 290 rear wheel horsepower on the chassis dyno I used back in the Jurassic era. That's with the rev limiter disabled, high rpm points in the distributor, headers and Cadillac mufflers. That's equivalent to about 360 flywheel horsepower. The Boss 351 gained 10 BHP if you tossed the Autolite carb & installed one of Ford's over-the-counter 780 Holley carbs. The Boss 302 made the same power, although the rpm was higher.

The 351C in my 1971 Mach I read 305 BHP on the same dyno; it was equipped with the Shelby intake manifold, a Ford/Holley carb, headers, the 505 cam, a Motorcraft breakerless ignition conversion. We thought that was tremendous horsepower back then. The car ran like stink and passed smog tests too. That same motor hit 390 BHP later on with a custom ground solid lifter cam, milled and ported cylinder heads (10.5:1 compression). The dyno owner figured 390 on his chassis dyno equated to an honest 485 BHP at the flywheel; pretty close to 500 BHP, I was proud. The drivability suffered though and I ended up putting it back into the 380 BHP state of tune, the car was my daily driver. That was just before I wrapped the car around a light pole one rainy morning, on the traffic circle in Long Beach California (that was about 1981 or 1982).

The idle rpm spec for a Pantera is the same as the idle rpm spec for the 351C in a Mustang or Torino with a manual transmission for any given year. The Mustangs & Torinos equipped with automatics idled around 600 to 800 rpm (depending upon year) when the transmission was in drive.

The 351C 4V like any performance motor from its era, has a burble in the exhaust note from the early opening of the exhaust valve. The Pantera's burble is lower in frequency and louder because there is no cross-over in the exhaust between the banks of cylinders. The exhaust cross-over doubles the frequency and dampens the amplitude of the exhaust note.

I can get mine to idle with the Comp Cams solid 605 lift at 650. Of course at that speed and that cam the sound is...interesting.

600 with a CJ should be easy.



What does the Pantera tag mean that says advance is 16 degrees and idle speed is 1,000 rpm? You do have that tag, do you not?

I never had this car new, so I don't really know what it idled like new.



Since the Pantera was an import, it wasn't required to have the same emissions equipment as the Mustang did with an air pump.

It also has headers with dual exhaust and no exhaust balance tube like the Mustang does.

This effects the idle rpm and the idle quality. Makes it a little rougher, so to compare the 73 Mustang and the 73 Pantera, all things are not equal.



The Ford Muscle Parts carb recommendation for a 351c was the 4781, 850 double pumper. Said it was good for 15hp gain.

Having run the CS Shelby intake and the Edelbrock Torker on a Boss 351 in a Mustang, the intake of choice to me was the Torker.

I ran a 4779, Holley DP, and the Shelby manifold did not like it. the Edelbrock loved it.



Personally I think that a 2x4 Holley vacuum secondary carb set up would respond to the best of both worlds.

Keeping the engine vacuum up in a big port Cleveland is very helpful and makes the engine pull hard at all rpms. Too bad this never came to be with a Cleveland?

Works really, really well on a 347 with two 600cfm Holley 1850s.



Also ran a Boss 302 780cfm Holley and a 735 428 CJ Holley on the car. Neither was worth the effort.

Didn't try the Holley Track intake back then but seems that was a true hp gain and held the key to flow vs. velocity?



The first CJ hydraulic cam actually is a very decent cam for everyday street driving.

As George states, everyday drivability suffers with aftermarket cams of that era.

The CJ cam will also reduce the valve train wear that you will get from a higher lift cam.
The combination on that cam doesn't exist for no reason.

For it's idle quality alone, the CJ is worth putting up with it's upper rpm limitations.(about 6,000rpm +/-)

A good carb match for it would be a Holley 1850 600 cfm carb. That's all a stock 351c CJ needs.