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Cam Sprocket - Part 2

Sheriff Buford T. Justice - new 9/4/01

On Thursday August 30, 2001 I called Doug Lewis of "Ford Performance Specialists" of Atlanta Georgia to discuss the cam sprocket failure issue. Doug was magnanimous with his time and wisdom and has a good handle on this situation having fixed several V8 SHOs with this problem.

As you may know the rear most camshaft on each bank is motivated by the primary chain, then in turn drives the forward most camshaft. So on the rear bank the exhaust cam drives the intake cam but on the forward bank the intake cam drives the exhaust cam.

It is these master-slave chain sprockets that are failing. The primary chain sprockets are bolted on and not failing. No indication of engine lock or lubrication failure is evident. The cams are not twisted, the bearings are not damaged in any way. Without valves to open the damaged camshafts turn free in their bearings and are true.

All four master-slave sprockets have identical construction and all have been known to fail. The sprockets are swedged or shrunk fit onto a splined area of the hollow shaft. As far as I know a ball or piston expands the hollow cam tube from the inside and all the lobes and presumably the sprocket are also glued in place.

Lubrication, high mileage, heat so far don’t seem to be direct causative agents. It is NOT an indication of driver abuse but an unproven design gone to production before all the bugs were ironed out.

Doug admits tig welding may be better than mig welding in this situation but mig is what Doug has and what he has used successfully several times. In this case, in my opinion Doug’s’ skill and experience are more important that choosing between mig or tig choice. I would not let just any rube try this repair. To weld the sprockets the area must be very clean and grease free. Doug puts (3) small ¼" long evenly spaced welds on each sprocket. Much care must be taken in welding to get good penetration with out putting so much heat into the thin (tube is 3/16" thick) tube as to cause it to distort. The small welds in addition to the grip that the factory design sports are ample to guarantee a permanent fix.

Camshafts do not have the same balance issues as crankshafts, they are far lighter, less eccentric and have no massive reciprocating pistons. (A valve is a lot smaller load than a connecting rod, piston & cylinder ignition.)

Doug told me he has never seen an engine do this without a lot of audible warning. I told him we may have had an engine "just go" and he tactfully told me that he has never been his experience and some SHO owners may be less perceptive than others.

Cost of welding the cam sprockets at FPS automotive is $400 "while you wait." If the engine has more than 70,000 miles new gaskets may be called for and can add about $100 to the total cost.

If a V8 SHO has at least 80,000 miles it may be prudent to do the 100k tune up (valve shims and new spark plugs) and weld the cams at the same time. A 100k tune up costs $600-$700 but doing the cams at the same time only adds about $100 more since you must expose the cams anyway for a turn up.

I guess what is the most worrying prospect is that of a second sprocket failure. Say a sprocket starts making noise and unlike most dealerships this one diagnoses the cam sprocket correctly and does not tell you to drive it to failure. Instead of welding the cam you replace the whole camshaft at a total cost of ~ $1,500 - $2,000 using all new Ford parts. Great now you have one good cam sprocket and 3 others waiting to trash your engine at any moment. Yikes! You could spend $6000 four times, once for each sprocket, with this sprocket design and still have a problem.

I had a 50k pm done at FPS last summer as reported in SHOCLUB and can vouch for the quality of work at FPS. If you going to visit Doug you might do well to first call and talk over all your needs. If you are going to pilgrimage to Mecca you might as well make the trip worthwhile.


Timothy Wright
aka Sheriff Buford T Justice

Ford Performance Specialists
8810 Bright Star Road
Douglasville GA 30134

(770) 949 – 7191



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