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346 Bronze Idler Gear

Started by jackworstell, May 19, 2020, 08:05:48 PM

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jackworstell

Over the years I have heard stories about failures of the idler gear.

I've never had problems myself with the idler gear.
But......I have two curiosity questions.

First question........to replace the gear I guess:
     - Remove the air filter
     - Then remove the intake ( with the carb ) manifold and the
           the exhaust manifold
     - Then remove the cover ( the rear one of the two )
            covering  hydraulic lifters and the camshaft
So what have I left out ?

Second question
      -Supposedly some time back there were reproduction gears and these
            didn't work out ( because of metallurgy  or because of dimensions  ? )
        More recently there's another source or reproduction gears that
              work quite well.
  Do I have these two points correct re:  reproduction gears ?

I know I don't have the complete story on either point
........but I know that  several of you know more and can fill in the gaps.

Thanks     Jack Worstell

LaSalle5019

#1
I recently rebuilt my engine and the bronze gear was really worn (to knife edges on the teeth).  I went to Headquarters Machine https://hq-ma.com/cadillac-and-lasalle-bronze-gears/) for a solution.  I have no interest in this company but have been happy with their product and service - quality equipment.

You can read the story about how they got into this side business here:
https://hq-ma.com/wp-content/uploads/2016/09/Gear-Story-2016.pdf

The replacement gear they are now producing is a high strength polymer vs bronze as they found the material to be superior to bronze. Additionally, the long oil pump drive shaft is made in two sections with a coupler to remove any side loading due to misalignment.
Scott

jackworstell

Scott....can the new polymer  idler gear be bought separately ( separate from the
$995     " package " )  ?

Jack Worstell

LaSalle5019

Jack,
I don’t know if it can be bought separately as I bought the kit. You could call Headquarters Machine and ask.
Scott

Brad Ipsen CLC #737

On your instructions on removing the gear you need a couple of more steps if you want to remove the gear.  Your steps will allow inspection.  To remove the gear remove the distributor and  tower.  Then the lifter group assembly of 4 closest to the gear needs to be removed.  Then the bolt and washer that holds the gear on.

My opinion on the brass gear story was formed after many years of hearing stories about it and having no problems but then I had the luck to observe a used military engine.  This engine had been installed in a car and run an unknown amount.  The engine and some other parts were then stored in a house in the early 50's.  It stayed in the house for many years until the early 2000's when the house was sold.  Saw the ad on CL and bought it.  The one hope I had was that it would have low miles and a really good brass gear.  On taking the engine apart it indeed was a low mileage engine but I was really disappointed when I saw the brass gear had knife edges on it.  So what caused this.  A fresh Cadillac made gear, low miles and almost a gone gear.  If this had been the case when these cars were new Cadillac would have found a solution.  After investigating here is the story.  When putting a military engine in a car the distributor and tower from the old engine is put in the new military engine.  The bushing in the distributor tower is shot in the old engine because the oil passage for the tower bushing gets plugged and no oil gets to it.  One local member in the process of evaluating this brass gear problem measured the hardness of each gear, cam, brass and distributor.  The small distributor gear is the hardest and if not held in line by the bushing acts as a cutter of the brass gear.  Even during a rebuild if the engine is not taken down clean of every single piece it is possible not to get this oil passage cleared.  The stub shaft for the brass gear must be removed to get it clean.  The clearance on the bushing is 0.002 inches.  I had the occasion to inspect one of my cars at 20,000 miles after rebuild and the gear is worn very little and most likely the same as when I put it in since it was not new.  If this is the cause which I believe it is you can see how it would be possible for new repo gears to fail since Cadillac gears did also if the distributor gear was moving around cutting it. So in summary the solution is inspect the tower bushing and if excessive clearance make new one.  Get a brass gear that is still in reasonably good shape.   If you want an engine with a long life tear down your engine completely to clean the oil passages.   


Brad Ipsen
1940 Cadillac 60S
1938 Cadillac 9039
1940 Cadillac 6267
1940 LaSalle 5227
1949 Cadillac 6237X
1940 Cadillac 60S Limo

jackworstell


OK  Scott I'll give them a call.  It would be good to have a spare gear stashed away in the trunk of our 1937 series 60.

Brad.....thanks.  Interesting and useful information.  QUESTION:    we removed the distributor cap
and tried to wiggle the distributor shaft by pushing the distributor rotor  from side to side.
The rotor didn't bulge....no play.   So does this mean that the bushing you talk about
probably has very little play  ?

Jack Worstell



Brad Ipsen CLC #737

Not sure.  I don't think you can feel the slop from the top end.  Just take the tower off and check the shaft coming out.  Easy job.  Just two bolts and with the Cadillac design you don't upset the timing as long as you just take the one bolt out holding the distributor in.  After looking at a spare engine you can inspect the brass gear very well also just be taking the tower off.
Brad Ipsen
1940 Cadillac 60S
1938 Cadillac 9039
1940 Cadillac 6267
1940 LaSalle 5227
1949 Cadillac 6237X
1940 Cadillac 60S Limo

LaSalle5019

#7
It's the play at the base of the distributor support tower that you want to check so you need to remove that support to check it. That is where the distributor driven gear gets it's support and leads to bronze gear wear when bushings are worn.

There is a bit of a trick to reinstalling that to keep your timing correct - below is an excerpt from Walt Brewer's instructions along with a comment from me. I suggest you get the timing set to TDC before removing it and noting preciously where the rotor is pointed and just leaving the distributor assembly tightly bolted to the tower. Then get it installed in the same rotor orientation.

Two key points to note - the rotor turns slightly once the driven gear engages the bronze gear due to the helical gears so when dropping the tower back in you will want to position the rotor a few degrees one way (I can't recall exactly which way it turns so maybe just look at which way the helix is cut on the driven gear).  Secondly, the alignment of the oil pump drive shaft to the slot in the shaft coming below the driven gear will not align if you have it off a tooth. So once everything is aligned correctly it should fall into place with the flange flush to the engine block.
Scott

Now is the time to put in the distributor shaft, so start by setting the timing mark on the pulley to the “I” on the IGN, with the No. 1 piston coming near the top of the compression stroke. Make sure you are not 180 degrees off by watching the piston come up with both valves closed. (Note: Use this mark due to the difference in modern fuels and altitude. You can fine tune more precisely at a later time.)

Install the distributor onto the distributor shaft as well as the rotor and cap. Position the distributor assembly in the position it should sit on the block, and mark the cap and side of the distributor with a crayon where the No. 1 spark plug will be. This will be three holes clockwise from the notch in the cap. Take the cap off and set the rotor near the crayon mark. Note the position of the slot on the top of the oil pump.
Using your long screwdriver (or rod), turn the oil pump to as close as you can to the same direction as the shaft on the bottom of the distributor shaft. Set the distributor assembly on the block so the mounting holes line up. Rotate the rotor until the shaft slips down into place. If you are lucky, the tip of the rotor will be right in the middle of your crayon mark on the side of the distributor.

If you get it just right the first time, you have just made history. However, it will give you an idea of how much you have to turn the oil pump to make it fit right. This may take several tries to get it exact. As you put the shaft down into the cavity, you will notice that the rotor turns slightly as it slips into the idler gear. Keep moving the slot on the oil pump until it comes into place with the rotor pointing near the center of your crayon mark. If you are one tooth off on the gear, you will have a hard time later getting your ignition timing just right. (Scott â€" this tower has no gasket underneath so, when reassembling, only use sealant, like Permatex “The Right Stuff”.  A gasket will change the geometry of gear contact. I got the drive and rotor orientation just right, gently removed it, applied sealant to the engine block, to avoid touching the drive housing gear. Then installed and torqued.)

Daniel Szydel

When I rebuild my flathead, I found the idler gear worn almost to a knife edge.  Exactly what Brad said happened.  The distributor housing was completely plugged as was the the shaft that holds the gear.  As a result the shaft that holds the gear was worn out of round and the distributor shaft along with the bushings were worn.  I ended up finding a better idler gear shaft and had to machine a new distributor shaft and bushings.

Dan
1946 Cadillac Convertible
1931 Ford Model A Coupe

jackworstell

#9
Scott...I called the company and they will in fact sell the gear separately
About $200 plus shipping.
How wise this would be...vs buying the entire kit...I have
know way of knowing .ahead of time.  It would depend on the circumstances of
a given engine

Again ....we don't have any problem ( that we know of ) at this time
with the gear.  We will pull the distributor tower and check visually

My inquiry was more of a "what if" sort of thing.

Thanks everyone for the advice.
There sure is a lot of expertise in the CLC

Jack Worstell