[b-man]

I recently acquired a NOS 421 Super Duty cam and thought I'd share a few pictures of this piece of Pontiac racing history.

Pontiac part number 541596, made by the Melling Tool Company who was the OEM supplier for all of the Pontiac cams under part number RPC-2.

This is a solid lifter cam known as the 'McKellar #10 cam', named after Pontiac engineer Malcolm 'Mac' McKellar who was the camshaft designer during those glory days.

The valve timing specs are pretty much identical to the RAIV '041' hydraulic lifter cam with 308/320 advertised duration, but with lower valve lift values of .445" intake and .447" exhaust using 1.65 rocker arms.

The 421 SD engines running this cam were rated at 405 HP but were probably making closer to 500 HP.

Ancient racing camshaft technology at its best, just leave it to Pontiac.





Here are a few pictures of the long-duration low-lift cam lobes, first 2 pictures are the intake lobes.





Exhaust lobes.

[Tom Vaught]

I ran one of those in college (and afterwards) for several years in a 64 389 "Mule engine", the original 389 TRI-Power engine was in storage. It has a marvelous sound to it. Instant rpm and held lash just fine over thousands of miles to Niagara Falls and other places from Michigan. I installed the 7/16 straight screw in studs in the heads I used. I also had a set of M/T Aluminum rockers with a bit more RA Ratio.

Tom V.

[David Jones]

Interesting B-Man, thank you.

[68WarDog]

Tom, because of #10 long valve lift duration , were very high >12:1 compression required to maximize its performance?

[Tom Vaught]

Maybe "maximize its performance" but the Mule never had over 10.5 CR and ran great everywhere. Course I also ran a 4:33 Gear in the car too.

Tom Vaught

[gtofreek]

Back in the 90's we purchased a Melling 068 blueprint cam for a customer engine. It had lobes just like those, except the intake lobes flat was narrower than the exhaust[about 1/8" wide compared to 1/4" wide for the exhaust]. Years later, I saw another supposed 068 blueprint cam, but it didn't have the flat lobes. Now I wonder if the 068 cam we bought was boxed wrong and actually had this cam in it. It went into a stock 455 with 5C heads, tri-power, and 1.65 stamped steel rockers. It ran out of steam around 4200 RPM.

[Stan Weiss]

Has anyone ever Cam Dr one of those cams? Looking at the pictures it looks like it was designed with a huge amount of "dwell" over the nose.

Stan

[Stan Weiss]

Paul,
This is from an old H-O manual. Look at how flat the exhaust of the H (744) cam is.

Stan

[Old Man Taylor]

Those are the only two Pontiac OEM cams that I know of that have the flat nose. The H (744) looks even flatter. It's my understanding that the reason for this was that a fixed ramp rate was used on all their cams, so when the duration got big enough the lift had to be limited to not exceed what the heads could use - resulting in a flat nose on larger duration cams. The first cam that had a new computer profile was the T (041).

[gtofreek]

So, is the "S" cam, the 068?

[b-man]

Originally Posted by gtofreek

Back in the 90's we purchased a Melling 068 blueprint cam for a customer engine. It had lobes just like those, except the intake lobes flat was narrower than the exhaust[about 1/8" wide compared to 1/4" wide for the exhaust]. Years later, I saw another supposed 068 blueprint cam, but it didn't have the flat lobes. Now I wonder if the 068 cam we bought was boxed wrong and actually had this cam in it. It went into a stock 455 with 5C heads, tri-power, and 1.65 stamped steel rockers. It ran out of steam around 4200 RPM.

I would seriously doubt that it could have been a misidentified 421 SD cam if it quit pulling at 4200.

Originally Posted by gtofreek

So, is the "S" cam, the 068?

Yes, and it has a flat nose lobe design that looks similar to the #10 421 SD cam.

'S' identifier stamped on the nose of the '068' cam.



Intake lobe.



Exhaust lobe.

[Craig Hendrickson]

Good thread with accurate info. Nice close up pix of the lobes B-man. The only thing I can add is the specs for the other McKellar cams.

# - P/N - Int dur - Int lift - Exh dur - Exh lift - L/C - Adv - note
6 - 524886 - 283 - .406 - 293 - .406 - 114 - 2 - 1956 to 1962, lift w/1.5:1
7 - 535480 - 300 - .445 - 304 - .447 - 113.5 - 1.5 - 1959 to 1961
8 - 540233 - 308 - .445 - 312 - .447 - 113.5 - 1.5 - 1961
9 - ? - 308 - .445 - 312 - .447 - ? - ? - no production
10 - 541596 - 308 - .445 - 320 - .447 - 113.5 - 1.5 - 1961 to 1963 421SD
11 - 542992 - 312 - .445 - 324 - .447 - 113.5 - 1.5 - ditto, OTC
12 - 545319 - 308 - .445 - 324 - .447 - 113.5 - 1.5 - ditto, OTC

Stan is correct as far as I know, i.e., the duration changes were due to constant lift dwell change over the nose. That makes for terrible dynamics, but it seemed to work.

[b-man]

While we're on the subject of factory cams and how the lobes looked, here are some pictures of the 9779067 cam (273/289 advertised duration) which is the same profile as the 524009 'C' cam. The '009' cam is best known for its use in both the 1964 GTO 389 325 HP 4-barrel and 348 HP Tri-Power engines

'P' identifier stamped on the nose of the '067' cam.



Blue-green paint swabbed on the back of the cam along with what looks to be a 'C' stamp that might be connected to the previous designation for this grind, perhaps a '009' camshaft identifier.



Intake lobes with no flat across the nose.





Flat nose exhaust lobes that look pretty much identical to the intake lobes on the '068' cam, 289 duration for the the '067' as compared to 288 duration for the '068' intake lobe.

[68WarDog]

Craig, would it be simple to state that extreme flat lobes substituted for high lift of today's cam design?

[Craig Hendrickson]

68WarDog

Craig, would it be simple to state that extreme flat lobes substituted for high lift of today's cam design?

Short answer: yes.

In 1975 I had a conversation in my office with Harvey Crane (while he stilled owned Crane Cams) about the Pontiac cams and what he and his company could do for H-O Racing in the private label and custom grind arena.

One of Harvey's main points during that discussion was that if one does a computer design and analysis (lift, velocity, acceleration and jerk) to produce a "smooth" profile, then one gets the extra lift "for free." This is due to not having "too much" deceleration on the opening side approaching max lift. The downside of course is that one has to check for coil bind, etc to account for the extra lift.

All Crane's cams even in that era were computer designed. Harvey spoke well of the Pontiac 041 cam as being well designed and of course it had extra lift compared to the McKellar #10 even though the advertised durations were the same.

[77 TRASHCAN]

Craig,
Did you ever have any dealings w/ Mr. McKellar, in the day???
Boy, I wish he was still around!, and many others!

[72LuxuryLeMansLa.]

I have a Performance Trends Engine Analyzer Plus and in the cam specs menu it has a setting for "Dwell Over The Nose". This cam is an example that would require entry of a number for dwell to get an accurate (for a sim) prediction.
B-Man, do you have a cam card with all the specs including dwell over the nose? I'd love to enter that cam in to my very limited library.

Also, does anybody know how much dwell over the nose you see on a Stump Puller HR cam like SD sells?

Performance Trends call these "Cheater Cams" and says the use of Dwell over the nose helps in racing classes where lift is limited.

[Craig Hendrickson]

77 TRASHCAN

Craig,
Did you ever have any dealings w/ Mr. McKellar, in the day???
Boy, I wish he was still around!, and many others!

No, I did not although I certainly wish I had.

[b-man]

Originally Posted by 72LuxuryLeMansLa.

I have a Performance Trends Engine Analyzer Plus and in the cam specs menu it has a setting for "Dwell Over The Nose". This cam is an example that would require entry of a number for dwell to get an accurate (for a sim) prediction.
B-Man, do you have a cam card with all the specs including dwell over the nose? I'd love to enter that cam in to my very limited library.

Also, does anybody know how much dwell over the nose you see on a Stump Puller HR cam like SD sells?

Performance Trends call these "Cheater Cams" and says the use of Dwell over the nose helps in racing classes where lift is limited.

I seriously doubt this cam ever came with a cam card, but if it did it is certainly now lost to the ages.

Just the fact that this cam survived in pretty much new condition in the stash of a long-time Pontiac enthusiast until I was able to buy it is pretty lucky in itself.

[Craig Hendrickson]

Originally Posted by 72LuxuryLeMansLa.

(snip) Performance Trends call these "Cheater Cams" and says the use of Dwell over the nose helps in racing classes where lift is limited.

Back in the 1970s, H-O Racing had a manual "Cam Doctor" measurement fixture that Kern put together, so we could profile any lobe on any Pontiac cam.

H-O Racing customer and NHRA Stock Class racer Billy Joe Moravitz in Texas did not have such a device so he used his "calibrated eyeball" to "measure" the dwell over the nose on cheater cams. Basically, it was "the fatter, the better." It seemed to work for him.