Nylon-Clad Cam Sprockets

[EmTee]

I was over in the Riviera forum and spotted a thread regarding use of the dreaded nylon-clad cam sprocket on the 430 Buick V8 (1967).  I was thinking that my '64 GP was safe until someone mentioned that other Buick engines (Small block) used them as early as 1964.  Does anyone know for certain when Pontiac started using them?  Is my 1964 389 steel or not...?

[PONTIAC1953]

i'm not sure that pontiac ever used the plastic gear, been going to pontiac swap meets for 43 years, never seen one, read of one, or heard of one in a pontiac V8 engine.

[Guest]

  I will check tomorrow, however I do know when Oldsmobile introduced the 2nd Generation V-8 in 1964 for the F-85 / Cutlass, the short deck Gen 2, 330" V-8 had nylon coated aluminum cam gear. Will find out tomorrow when Pontiac started using them, but all of GM and Ford used them.

Well a day later and I have no beginning date for Pontiac. I do know first hand that a 67 326 has the nylon gear. My guess is 1964. Contrary to popular belief that they were designed for a quieter operation, they were actually designed for better cam harmonic's. Factory high performance FE 427 Fords also came with them. 

It seems that heat and age are the downfall of the sprockets.

Edited April 20, 2016 by helfen (see edit history)

[EmTee]

I do remember growing up that my father had the timing chain and cam sprocket changed on our 1970 Catalina (350 2 BBL) shortly after it hit 50K miles.  It had a nylon cam sprocket.

[GMPARTSMAN]

The dreaded Pontiac cam sprocket.

Replacement parts (steel gear) 483047 cam sprocket, 532993 timing chain, 9772517 timing cover gasket,9794125 oil pan gasket. Still remember those part numbers from 1971. About 1965 or 66 they started using the nylon and aluminum cam sprockets IIRC. Pontiac finally quit using those in production about 1972. It was not a "if" it will fail but "when". I shucked one in my Ram Air III at 93k when I locked up the brakes (stick shift) when a car blew a stop sign in front of me. 

 

One other thing. Dealership repair procedure was to drop the oil pan and remove all the nylon debris in the bottom. If not the oil pickup screen would usually plug up with nylon debris. Most aftermarket shops would shortcut the job. When the oil light would come on at idle or the oil pressure gauge would indicate low pressure and a lifter noise at idle, that was the tipoff. Then it was replace the rod bearings and oil pump.

[GMPARTSMAN]

Em Tee, They were covered at the time by a drivetrain 5 year/50,000 mile warranty. The "tiny time capsule" we used to joke about worked correctly that time.

Edited April 26, 2016 by GMPARTSMAN (see edit history)

[Guest]

8 hours ago, GMPARTSMAN said:

The dreaded Pontiac cam sprocket.

Replacement parts (steel gear) 483047 cam sprocket, 532993 timing chain, 9772517 timing cover gasket,9794125 oil pan gasket. Still remember those part numbers from 1971. About 1965 or 66 they started using the nylon and aluminum cam sprockets IIRC. Pontiac finally quit using those in production about 1972. It was not a "if" it will fail but "when". I shucked one in my Ram Air III at 93k when I locked up the brakes (stick shift) when a car blew a stop sign in front of me. 

 

One other thing. Dealership repair procedure was to drop the oil pan and remove all the nylon debris in the bottom. If not the oil pickup screen would usually plug up with nylon debris. Most aftermarket shops would shortcut the job. When the oil light would come on at idle or the oil pressure gauge would indicate low pressure and a lifter noise at idle, that was the tipoff. Then it was replace the rod bearings and oil pump.

You mean the dreaded nylon coated aluminum timing gear sprocket. It's not a Pontiac thing. Everybody used them in the GM family starting in 1964. Cadillac used them all through the 425" engine ( 1977-1979 and the 368" 1980 ).

First one I changed was a 330" 64 Cutlass.  Plus ford products.

Edited April 27, 2016 by helfen (see edit history)

[GMPARTSMAN]

1970 I worked in a Chevy dealership, went to a Pontiac dealership in 71-72 then back to Chevrolet middle of 72. We did not seem to have the problem with Chevys that Pontiacs did. Those part numbers literally were burned into my mind, we did so many of those back then.

[EmTee]

Thanks, GMPARTSMAN -- I'm both impressed and at the same time sorry that you remember those part numbers 40 years later!  ;-)  I think the reason the Chevys didn't have that problem may be because around the same time there was a bunch of them that were 're-grinding' their own cam lobes as they were driven.  That tends to take some of the stress off the cam sprocket!  (Remember the alleged 'Quaker State cam failure conspiracy...?)  I want to agree with you that Pontiac didn't start using them until at least '65 -- but I don't know that for a fact.  There's another old Pontiac nut (like me) a few miles down the road from me, so I'll stop-in and talk to him about this the next time I see him out in his garage.

[GMPARTSMAN]

Yes, Chevrolet and the amazing disappearing camshaft lobes. How I would like to forget that fiasco. Lost one of them in my 77 El Camino with 36k on it and two years almost to the date in service. Factory rep did everything to try and avoid paying for it even though I worked in a Chevy store at the time. Best thing was the alleged "abuse" of the car PER OUR DEALERSHIP REP. I ordered a El Camino Classic and within a year had changed the factory steering column for a tilt column, added factory cruise control, added a factory tonneau cover and replaced the crap factory steel belt radials for BFG Radial T/A's along with a set of Corvette YJ8 option aluminum wheels that the 'Vette guys were almost trading their first born child for. 

 

I vowed to never buy another Chevrolet product which is true to this day.

[Guest]

 I have a open question on Ames performance Engineering forum regarding the question. I have one respondent saying his 1964 GTO had a nylon cam sprocket that failed at 55,000 miles.

[EmTee]

Crap. I didn't really want to hear that!  My GP currently has 49,77X miles on it...

[Guest]

2 hours ago, EmTee said:

Crap. I didn't really want to hear that!  My GP currently has 49,77X miles on it...

I'm certain it does, but it would take you less than 15 minutes to tell for sure if you have one or not.

Edited April 29, 2016 by helfen (see edit history)

[EmTee]

The car runs well now (I know that doesn't mean much in this case) and the weather is just beginning to break here in NY, so I would rather wait and do this over the winter.  You're right, though, that without A/C the front of my engine is really pretty accessible.  I guess it would be a good rainy-day job.  I think I'm going to start gathering the pieces...  Does anyone have strong feelings about going with a Cloyes roller chain vs. a stock-style link belt with a steel cam sprocket?

[Guest]

2 hours ago, EmTee said:

The car runs well now (I know that doesn't mean much in this case) and the weather is just beginning to break here in NY, so I would rather wait and do this over the winter.  You're right, though, that without A/C the front of my engine is really pretty accessible.  I guess it would be a good rainy-day job.  I think I'm going to start gathering the pieces...  Does anyone have strong feelings about going with a Cloyes roller chain vs. a stock-style link belt with a steel cam sprocket?

 Just to inspect to see if you have one just remove the fuel pump. You can see the gear from there with a flashlight and a dentist mirror....say open wide say ahh big 389 ! 

[EmTee]

Genius!  Yes, I shall do that and report back what i find...

[EmTee]

OK -- I finally got the chance to remove the fuel pump and peek into the timing case.  And the verdict is...

 

Steel/Iron cam sprocket - not aluminum/nylon.  I could clearly see shiny silver witness marks on the cam sprocket teeth.  It has a stock style link-belt chain (rather than an aftermarket roller chain).  So, I'm relieved that I don't need to worry about the timing set for awhile (the car has just shy of 50K original miles), but I don't know whether the previous owner replaced it, or if it is original to the engine.

 

Thanks again Helfin for the neat inspection tip.  Using my dental mirror and a drop light I was able to peer inside and clearly see the bottom of the cam sprocket and the fuel pump eccentric.  It worked so well that I'm going to try the same trick on the 430 in my '67 Riviera.

[Guest]

Glad I could help you out, and thanks for saying thanks.