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The Gentleman's Express: Tech-Tips from the JIOC

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Author: CFF

Rebuilding the engine of your Interceptor? Having problems finding the original Magnum Cam that the car came with? Talked to a lot of people lately that have a SUPER CAM that is almost the same? Ever wonder what the difference was? Well, I am, have and did! And here is the story:

I started looking’ for a new STOCK cam for the ’72 440 that I’m rebuilding to put into my ’74 MK III after Bob, at J S I, had given me the part number 4071002 for the cam that Chrysler was offering as a replacement for the original. Finding it no longer available from my local Chrysler dealers, I phoned a parts locating service (1-800-633- 3637) that gave me the phone numbers for two (2) Chrysler dealers that showed that they had the cam in stock. After phoning them and finding out that neither did, I was referred to a dealer in Texas, who in turn referred me to another dealer in another state (by this time I no longer asked which state, just what area code), who assured me that this other company in another area code had it! They didn’t, but during the course of our conversation it came to light that the replacement cam I was looking for did not have the same specs as the cam that came with my car in the first place. The duration was different, as was the valve lift and overlap. It seems that Chrysler had offered a cam that was used on a 350 HP 440 as a replacement because “it would work.”

Of course it would work, but would it work as well as the original? I did not want to wait until I had the engine back in the car and running before I found the answer to that question so I started calling some of my friends (yes, even old CCF has some friends) in the Industry. First I called Roland Osborne of Chrysler Performance Parts Association (a Chrysler Direct Connection dealer), then Ed Neino at Camonics Camshaft Co and Mike Landy at Dick Landy Ind. (See, I told you I had a few friends). After more than a few hours spent on the phone with these gentlemen and bent over various parts books, catalogs, Chrysler racing manuals and etc. this is what I found out:

Camshaft PN 3512907

This is the cam originally used in our Interceptors and is commonly referred to as the MAGNUM CAM and was first introduced in the 1967 375hp / 440 Magnum engine. It was then used as a stock cam in all Road Runner 383’s, the ‘67-70 375hp/440, the ’71 370hp/440, the ’71 300hp/ 383, the ‘72-76 400-4 bbl HP, and all ‘68-70 335hp/383’s. With a duration of 268 degrees (intake) - 284 degrees (exhaust), this is called a split profile, a 0.450" lift with 46 degree overlap, this cam is a very versatile performer.

I also found out that the Magnum Cam is no longer available, and not just from Chrysler but from every manufacturer that I was able to contact. Aftermarket manufacturers do try to sell you a replacement cam which is almost the same, but not quite. The closest replacement cam available is commonly called a 272/455 cam, which means that the cam has 272 degrees of duration, on both inlet and exhaust, with a 0.455" lift. Now you say to yourself “What’s a poor restorer, that wants to keep his car running the way it was meant to, to do?”. Not to worry! I am having the Magnum Cam manufactured locally and I will be offering a Magnum Cam Kit complete with new HP lifters very soon or, if you wish, you can purchase the cam by itself.


The very next step up from the Magnum Cam according to Chrysler is the Hemi Profile Cam. This is available from Direct Connect PN P3690214. This is a 284/470 cam (duration is 284 degrees and lift 0.470"). This cam has radical idle characteristics to go with its increased performance. Although not required, it is recommended that you replace the stock valve springs with those used on the 440 Six Pac engines. These are available from Direct Connection PN P3690933.

Best Performance

The best performance hydraulic cam for the B engine is purported by Chrysler to be a 286/485. With a 286 degree duration and a 0.485 lift you will have to use the springs suggested above. This cam is also available from Direct Connection PN P3690933.

440 Six Pac Cam

This cam has the same duration and lift as the Magnum Cam but it is a low-taper cam which requires that the lifters be around on a much larger radius resulting in a flatter face on the lifter. Because of this low-taper design feature, these cams require that you use special hydraulic lifters, PN P3420039. The 440 Six Pac Cam does not offer a horsepower-performance increase over the standard Magnum Cam.

NOTE: Camshafts with a duration greater than 286 degrees will require valve clearance pockets in the top of the pistons. It is very important that a new camshaft be installed with new lifters and be liberally coated with the special cam break-in lubricant found in the cam kits.

Valve Timing for the Magnum Cam

Intake opens at 21 degrees before top dead center
Intake closes at 67, degrees after bottom center
Exhaust opens at 79 degrees before bottom center
Exhaust closes at 25 degrees after top dead center

Thanks are due to Ed Neino, Mike Landy, Chrysler Direct Connection and especially Roland Osborne for their help. Roland (at Chrysler Performance Parts 818/303-6220) is more than willing to help with the right decision and can provide all the Chrysler high performance parts that might be needed.

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Contents copyright 2008, 2009 - Jody F. Kerr

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