V8 Cams Problem and Solution

By Don Mallinson

Updated info:

Here are pictures of a known bad cam and some more explanation, be sure to go to the bottom of the page for the newest pics:

What you see below is the back head (nearest the firewall) with the intake cam being the driven cam, the exhaust cam being the slave cam.  Note the main sprocket is bolted onto the passenger side end of the intake cam.   The problem sprockets are the slave sprockets just behind (to the left in this photo) with the chain between the two cams.
(picture courtesy of Paul Nimz)

In this view below, you see the same head with the cams removed.   Note that the cam bearing surface between the lobes is very small.  Also these heads do not use cam bearings as such, the cam rides on the head material itself.   This has not been a problem.
(Picture Courtesy of Mike Frey)

Below you see the front of the main cam sprocket in detail showing the way it is bolted on to the end of the cam.  Note that the slave exhaust cam has the mounting and locating pin the same as the intake, but it is not used.  The slave sprockets and chain are right behind the main sprocket.
(Picture courtesy of Paul Nimz)

NOW we get down to the nitty-gritty!  In the view below, note that a good cam (on the left upper) is next to a failed cam (lower right).  Look right at the point where the slave sprockets meet the cam.  The gold tone sprocket on the cam on the left meets the cam and you see all the cam material looking the same.   On the cam on the right, notice the lighter colored area at the junction of the cam and sprocket.  This is where the cam sprocket has spun severely on the cam.   Creating grooves.   Note that the sprockets and even the lobes, have this splined area.  The way the cams are put together is that the parts are located on the smooth cam shaft, then a device is forced through the opening in the cam itself, forcing the parts into an interference fit.    Apparently the parts are just not on tight enough to take the forces over time.  It remains to be seen if ALL cams will fail or just a few.   The fix as we understand it from FPS in Atlanta is to spot weld the slave sprocket to the cam in at least three locations right where the little openings are where the sprocket and cam meet.
(Picture courtesy of Mike Frey)

Below is the same pair of cams.  In this view, we see the good cam on top, and the failed cam on the bottom.  Note the large amount of scoring where the slave sprocket has "walked" back and forth on the camshaft leaving the "screw" like appearance that should NOT be there on the cam in front of the sprocket.
(Picture courtesy of Mike Frey)

Jim Merriman sent the following two pictures of the cams and valves in his V8 SHO.   He wrote: "Attached are digital JPEG pictures of my SHO's left hand bank camshafts. I got clarification from the mechanic (Crestwood Ford) who is working on the car that the primary camshaft which is driven off the timing chain broke at the slave sprocket joint. The sprocket now spins around the camshaft effortlessly. The mechanic said that the secondary camshaft (it has the water pump pulley on it) is out of round by 2 1000ths of an inch. He wants to replace that as well."

Below is the close-up of his two front head (as you look at the motor when standing in front of the car) cams, set on the head with the head upside down so you see the valves under the cams.  It is hard to tell, but the top cam is probably the one that has spun, you can see some horizontal marks, probably put there when the mechanic or Jim moved the sprocket around.

Here we see a close-up of the bent valves (intake) on Jim's front V8 SHO head.

So now you have seen the "beast" that can eat a V8 SHO motor.  SHO Club and various people/vendors continue to work towards a solution.

SHO Club

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