Cam gear replacement. Who says?

["Cadillac Kid" Greg Surfas 15364]

I bought a 300,000 mile 75 motor for the crank.  I started to pull it apart and I was amazed. Look at the timing cover. Absolutely no wear of corrosion under the water pump.
Look at the cylinders. a ridge and lots of oil on top of the pistons.  That came from bad valve seals.  The valves were good. I resealed the heads and they are on one of my other cars with no oil consumption.
Look how little play there is in the timing chain.
Look at the condition of the cam gear. Worn?Yes, but no where near failure.  Look at the oil intake screen.  Clean with no debris or sludge.  Remember with the exception of the last photo of the cam gear, ALL these shots are just as the parts were on the motor and not cleaned up[.
This is a high mileage motor that was looked after well.  It would suggest constant oil changes and maintenance of the cooling system.
The oil pump was absolutely pristine.
I know there has been a constant cry about IMMEDIATELY changing the timing set when you get a new vehicle, but let this episode show you that is not always necessary. Without fail, pulling the distributor and the fuel pump will give you adequate visual inspection of the timing set, especially with a bore scope device. Perhaps save you quite a bit of time and money.
Greg Surfas

[bcroe]

I look and I see parts of the plastic teeth gone, apparently cracks
in places.  That whole mess could fall off, plug your oil pickup, mess
up your lifters, and ruin your engine at any time.  If you want to
play Russian Roulette with your engine, its your choice.  I however
prefer to avoid unnecessary risks if practical. 

I suppose there are even some old cam sprockets with no damage
in evidence, that just means the risk is somewhat less FOR NOW. 

When I bought my little driven 77 at its 30 years of age, had to drive
it in 3 states to get home.  I kept that police engine to the right lane
and PRAYED it wouldn't blow a tire or the timing chain till I could get
it in my shop. 
Bruce (I HATE FAILURES) Roe

["Cadillac Kid" Greg Surfas 15364]

Bruce
That’s with over 300,000 miles

[bcroe]

Bruce    That’s with over 300,000 miles   

Certainly results will vary, I have seen the chain completely off
on junk yard engines.  Even low miles fail, due to age, and how the
engine is operated (temp cycles) no doubt has an effect.  Plenty of
people have told of their failure, other cars still run, for now.  Had
my own problems with a 100,000 mile car.  I am not a gambler. 
Bruce Roe

["Cadillac Kid" Greg Surfas 15364]

Never suggested a gamble Bruce. Only that before carte blanche replacement a thorough visual inspection would be in order.  Again, there is virtually no wear at any of the normally anticipated locations (oil pump, cam bearings, front cover seal) which indicates this motor was very well cared for for it's entire 300K lifetime.
Greg Surfas

[bcroe]

Well it wouldn't be any fun if we all agreed on everything.  Bruce

[fishnjim]

Motors is 43 years old and how to verify it's never been worked on?   It should show 300K wear, if it's all original with that mileage.   
In this case, it's better so it's a benefit to you, so you did good.   I'd expect at least slop in the timing chain.   When removed, does it droop/deflect when on it's side?   or stiff like new
Mic the crank journals and see if it's at spec or below - evidence of repair.   -10 > -40 thou.

[cadillacmike68]

These timing gear teeth do not look line they were nylon capped. That's the reason why everyone is recommending timing gear replacement, because the teeth would be all worn off.

Was Cadillac still capping the teeth with nylon in 1975? If so, then this engine has had its timing gears replaced before.

["Cadillac Kid" Greg Surfas 15364]

Bruce: Of course
Jim: You can see in two shots that there is absolutely minmal chaoin slop. When removed there is no side play.
        Yes there is about 3/1000 cylinder wear, just what Cadillac Engineers said there would be with this high   
        Nickle Block. The cylinders show 0.003"taper (from standard).  If the motor had been rebuilt it would have
been bored out.

Mike: look at the pictures of the cam gear again. As Bruce pointed out you can see very minor cracks in the Nylon
         THAT IS THE REASON FOR THIS POST.  I WAS AMAZED AT THE CONDITION.  LOOK AT THE TIMING COVER.
          I do not believe that Nylon gears were never available as replacement parts

I'm not selling this. For what earthly purpose would I make this up? I believe the seller as to the mileage. (why on earth would he lye about the excessive mileage when he wanted to sell the motor?) This segment of the forum is for technical information and that is just what I intended to present.

Greg Surfas

[cadillacmike68]

I've never seen an original gear set, only the chunks on the bottom of the pan.

So that entire outer gear was covered in a nylon coating, not just the teeth?? That would explain it. And yes, amazingly little wear.

["Cadillac Kid" Greg Surfas 15364]

Yes Mike.  It is an exceptional example of what happens when a motor is "treated right",
Greg Surfas

[Jason Edge]

Most of the Teflon coating on the 1963/64 390/429's I have parted out have some degree of disintegration.  The last parts car showed 33K on the clock, but looked like a 133K car, and had a really pristine cam timing gear as seen below.  I love to find them like this as I believe it is a good indicator of the overall health of the engine block otherwise.

["Cadillac Kid" Greg Surfas 15364]

Here is the gear just lightly cleaned up with solvent and a rag. No brushing or other abrasives.
Greg Surfas

[bcroe]

All the above show signs of possible imminent failure.  And plenty of
wear on the teeth, resulting in sloppy timing.  My own experience is
that high compression engines are pretty fussy about timing, at least
if you pushed them the way I did. 

More recently even the Honda dealer has argued with me "we never
replace those parts (until the car has been towed in)".  But they
finally admitted maybe I wasn't all wrong after the CRV rolled over
400,000 miles with never a breakdown.  No tolerance for failures
here.  Bruce Roe

[Jeff Rosansky CLC #28373]

400,000 miles with never a breakdown.

I'd be impressed Bruce but it says you need maintenance----Just kidding. Wow!
Jeff

[TJ Hopland]

I used to have a new in the box sprocket that was plastic.  Based on the delco logo I would guess it was from the early 80's.  It was just the sprocket in a cardboard box not much bigger than the sprocket and it was wrapped in brown waxed paper kinda like you used to get bearings in.  I think I got it in the trunk of a car I bought in the 90's.   In the late 90's I ran across it and had it laying on the workbench, accidentally knocked it on the floor and the plastic shattered.   Not just the teeth where it first hit but a lot of it came off most of the way around.

I bought a 75 that I think had 40K on it and inspected the sprocket from the distributor hole and it looked good.   A year and 10k later it was pretty much naked.   Maybe having 300k on an engine means it got regular use its whole life and the constant heating and lubrication helps keep the plastic from becoming brittle?  Sitting is maybe what is really hard on em?   

["Cadillac Kid" Greg Surfas 15364]

I think you’ve got it TJ.
Greg Surfas

[bcroe]

I'd be impressed Bruce but it says you need maintenance----Just kidding. Wow!
Jeff   

Coming home with camera at the ready, had to drive around the block
a couple times till it rolled over.  Should have turned off the key for the pic. 

The first argument with the Honda dealer was over the alternator (there is a
regular alt preventative maintenance prog for my own cars).  We knew from
the previous car that these fail (brushes) at about 250,000 miles, and the
dealer would require another day just to order one in.  I don't change these
myself since it requires removing an axle. 

At 200,000 miles I told the Honda dealer to install a new alternator. 
"We never change those (till they fail)" he says.  What he didn't understand
was that it WOULD fail, and the options were:

A. Change the alternator at our convenience and min cost; or

B. Wait till the alternator failed on the road, possibly 800 miles from home
     (as it was yesterday), incur towing charges, waste a day getting it repaired
     after another day ordering the part, and finally ruin the cars perfect service
     record. 

The dealer was really out in left field if he thought we might buy another car. 

The alternator was replaced.  Today alternator #3 is in a box in the back, to
be installed at the same time as the next timing belt change.  I see the cam
sprocket in a similar light, but I do these myself.  Bruce Roe