checking to see if I have the plastic timing chain gears - 1973 472

[Mike Baillargeon #15848]

Is there an easy way to see if I have the original plastic timing gears without ripping everything apart.

I found a 1973 472 motor and now would be the time to change them if need be.

thanks,  Mike

[The Tassie Devil(le)]

The best way is to carefully mark the distributor, both where the rotor is, and the distributor in the block, and pull it out.

With a simple torch, as in flashlight, or trouble lamp, look down the hole, and observe.   With a long thin screw driver, reach down and "rattle" around the chain.   If it is loose, it is in need of replacement.

Then reassemble the distributor, and decide your next move.

Bruce.

[Scot Minesinger]

Bruce is right, easiest way

[m-mman]

Another method to quantify the total number of degrees of slop in a timing set (chain & gear) is to crank the engine to TDC using the timing mark on the pulley. Then remove the distributor cap  and use a socket to turn the engine backwards (may be easier if the plugs are out) while watching the rotor.
As soon as you detect the slightest movement in the rotor then stop and look at the timing marks. It will tell you exactly how many degrees of slop you have.

Ideally it should be zero (1-2 because you could not stop the wrench fast enough) but anything over 5 degrees you should worry and anything over 10 should be replaced.

If you remove the fuel pump you can also put a finger in the hole and touch the chain to feel for some play BUT if you have turned the engine you might be feeling the tight side of the chain.

[Mike Baillargeon #15848]

Thanks guys these are a big help!

So, If I don't have any noticeable slack, I should leave the plastic alone?

Mike

[The Tassie Devil(le)]

Well, if you don't have any noticeable slack, and the gear is okay, when you start driving the car with that engine, it will soon disintegrate.

One thing I have found is that the nylon will harden with age, and it doesn't take much to cause it to crack, and once warmed up, after long periods of non-use, as in heat cycling, nothing good happens.

If the engine is out of the car, that is the ideal time to drop the sump, waterpump and timing cover, and change it.

Bruce.

[TJ Hopland]

Ya if the engine is out of the car I would for sure take all the sheet metal covers for a good look at things.  Even if the timing set does not need to be changed I would still want to look in the pan to make sure it got cleaned out.     With the oil pan off there are a few places you can see the cam to get an idea of its condition.  You can check the rod bearings for wiggle.  You can get an idea what the cylinder bores look like.  You can't actually see the critical part of the bore but if what you can see is a mess its likely the important part is bad too.

When you have the timing cover off weld a couple nuts on the inside where the 1/4-20 water pump bolts go through.   If they are not stripped now save yourself the trouble of having it happen in the future and do it now.    It really stinks to have a fresh engine almost fully assembled and get to those bolts only to find that they were barely hanging on and have to take it apart again.  Been there done that.   There is no clearance issues in there and you can't see em from the outside so no one will ever know they are there unless they take the timing cover off. 

[35-709]

Agree 100%.  If the plastic coated gear isn't a problem now, it almost certainly will be soon.  Since the engine is out and everything accessible take that cover off and put an eyeball on that chain and what's in the oil pan.  A waste of time and money not to do it now because if that plastic coated gear is still in there you WILL be changing it out sooner or later, and maybe doing your engine harm when the plastic pieces plug up the oil pump screen before you get around to doing it "later".

And TJ is right on about the 1/4-20 water pump bolts, been there, had to do that too and it is no fun having to do the job twice.

[Mike Baillargeon #15848]

Thanks guys!! 

Mike

[Rdtreur]

I did the "slack check",  I got 8 degree slack at the distributor. This is what 8 degree slack looks like on the cam sprocket:

[The Tassie Devil(le)]

Boy, that IS sprocket wear.

I would be looking at the condition of the filter, and the oil pump gears and housing as there has been a lot of aluminium travelling through that pump.

Worth checking the engine bearings as well.

Bruce.

[Scot Minesinger]

I have changed sprockets with 100k plus miles on them and they looked pristine compared to that sprocket, never seen that bad before even in photos on this site.  Definitely all other engine components (oil pump, bearings, oil pick up screen, and etc.) are suspect as suggested.  You are on the way with engine out and all.

[TJ Hopland]

I have seen em worse than that but don't have any pictures.    I had one in a Buick that there was barely a nub left on the sprocket.   Car seemed to be running alright.  Hit the gas at a green light and it just stalled.  Tried to restart and by the way it was cranking could tell something went wrong.    I think I had a buddy push me home with is Eldo.  Tore it down in my dad's driveway and found it was the timing set.   Didn't have the $20 for a new one so I was riding my bicycle to work till payday.

That Buick I think had 113K on it at the time.   I remember thinking that was a lot of miles.  Now 300 seems to be a lot.  People get angry if they have a few drips of oil leaking off a 100K motor. 

[savemy67]

All,

With all the discussion about replacing the nylon sheathed sprocket, and the photos showing a great deal of sprocket wear, how may of you are spending the extra money for roller timing sets?  Many manufacturers of newer cars use roller lifters and or rockers in the valve train to minimize friction and maximize mileage.  Do some of you think a roller timing set provides less friction, and possibly quieter operation?  I am curious as to your thoughts.

Christopher Winter

[Scot Minesinger]

Chris,

MTS in CA offers the roller rockers and all just like a modern engine for the 472/500/425 block.  They make a custom head with large valves.  If you were going to build a modified Cadillac with improved cam this would be quite something.  The valve covers are much larger so it does not look stock, or I might have them on my car.  If someone had a non-matching numbers engine and some extra cash, it would be the way to go.  I think this makes the engine more durable, reliable, powerful, and economical.  MTS will also take stock heads and improve them with larger valves.

[m-mman]

Personally I dont get that excited about that sort of stuff.
1. These are not race cars, they are generally driven in a respectful manner and if it all increased performance by only a 'tiny bit' who would notice? You would not have run sheets to compare against.

2. Lasts longer? If you are JUST replacing the chain/gears in a 100k mile engine you will likely be pulling it apart again for something else long before the replacement timing parts are worn.

3. If you are doing a total rebuild on what is to be a collector car and not a daily driver, how long before it hits 100k miles again? I have collector cars that dont get driven 1000 2000 miles a year. What ever you put in will last for decades.

As an FYI my 1929 Cadillac 341B flathead V-8 with 4.5:1 compression has factory roller lifters(!)

As for plastic vs metal?
Many years ago I was given a 69 Pontiac Le Mans convertible. Nice car but it didnt run, it needed a timing set. (common on those cars) I went to the parts house and reflexively asked for metal parts but then I thought "NO! just give me what ever is cheaper". Turns out the plastic was almost twice the price of the metal gear. I installed them and the car was sold 2 weeks later. They lasted as long as they needed to.

[TJ Hopland]

Roller lifters are available but a low volume custom item so they are very expensive.   You could easily have $3K invested in just the cam and rocker components and machine work needed.  As part of a $10K race motor no problem but for a 'street' engine that is a lot of money for a tiny gain.   

The roller chain timing set is not that big of a deal.   A roller chain is the one that looks more like a bicycle chain.  The stock ones were usually called link belt, think of the tracks on a bulldozer.   I got a roller set for my engine when I rebuilt it.  One reason was they have the multiple key slots so you can dial in the cam timing.  I had the engine completely apart and a new cam with the cam card so I was able to 'degree' the cam.   Degree means you actually set the relationship between the crank and cam by measuring the cam lift and the piston height. 

I had a defective oil pump that tore up the motor after about 1000 miles and the timing set was one of the things damaged in the process.  I accidentally ordered the standard link belt chain with the rest of my new new parts.  Thought about exchanging it for another roller but figure by the time I wear that out it will be a fairly minor issue compared to the rest of the stuff that has worn on the car.

This is a degree wheel.  You install this on the crank and then find the actual TDC using a dial indicator on a piston.  This eliminates the possible tolerances in the keyway, crank hub, ballancer / pulley, and timing indicator.   

 

This is the dial indicator that fits in a lifter bore to measure the cam lift.   You then refer to the 'cam card' that came with the cam to know where it should be timed.



This is the Cloyes roller sprocket and its multiple slots.  Different orientations give you different offsets so you can either get it timed stock 'straight up' or advance it if you think you need that for performance.

[bill06447]

Is there an easy way to see if I have the original plastic timing gears without ripping everything apart.

I found a 1973 472 motor and now would be the time to change them if need be.

thanks,  Mike

Someone else may have mentioned it already, but easiest way is to remove the distributor and use a hooked tool to pull on the timing chain. If it moves an appreciable amount, time to replace. I've also cleaned debris from oil pans without removing them with a combination of shop vac, duct tape and small hose guided through the oil drain plug. The big pieces don't always get sucked in the tube, but it holds them to be fished out.

Bill

[35-709]

This was the question ---
"... how may of you are spending the extra money for roller timing sets?"   
Does not look to be about about roller rockers.

There are three timing chain sets offered by MTS, the roller chain is an upgrade from the standard.  The standard set (no plastic tipped gear of course) works fine for stock applications.  The roller chain is better and mostly for higher performance engines.  The full-on SUPER HP Race roller chain is for all-out performance engines.

http://www.500cid.com/#!product/prd1/3509967021/timing-set%2C-3-piece-heavy-duty-all-steel

[Scot Minesinger]

m-mman,

Keep forgetting that they are not race cars and that they do not drive great distances.  My car is all stock engine components except for the MTS improved intake manifold, had to remove the original to do a valve job.  Yes I agree you would have to invest a ton of money in a 1970 era Cadillac to beat my Mother in law's 2008 Camery V-6 in a race.  I guess this impulse just surges because you want the best for your baby.  I did qualify the statement with non-original engine and extra cash.

My Mother in law could not invest enough money in her Camery to beat the coolness of the 1970 era Cadillacs, which is why I drive one.

Have replaced the chains on all three of my 1970 Cadillacs with standard all metal, $60 set from MTS.  It is unlikely in my life that they will ever be driven more than the original lasted.