JMcc

1928 Pontiac rotor doesn't turn

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I have a 1928 Pontiac that I got from a friend. It had been sitting for at least 10 years. Got the fuel tank and carb rebuilt and got about 100 miles for fun on it.  As I was putting it away for the winter it was idling away and just stopped running. After a few minutes of investigation I found the rotor was not turning in the distributor. I have pulled the distributor and was surprised that there wasn't a gear on the shaft, nor was there a place for a gear. The shaft appears to run off of a spade at the end of the shaft.  The manual says the distributor shaft runs off the camshaft via a gear and down to run oil pump. Any help wound be appreciated!

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Pull the pan first,not sure if we still have it ,but will check the length of the dis.Sounds like something locked up,oil pump,broke the shaft.At this point,you committed on pullng the pan

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Most likely causes.

1). Check and see if the distributor has  come out. the pinch bolt that secures it to the base plate holding it to the motor may have worked loose.

2). The most likely cause is a stripped fibre cam gear or broken timing chain. A lot of the old cars had a fibre gear on the camshaft, these were meant to be changed about every 50000 miles. Ask Model A Ford owners, it is quite common for the gear to suddenly lose a few teeth and the motor stops as the cam stops turning.

3). It is possible the oilpump has come loose in the block and dropped down, so it wont drive the distributor.

 My money would be on 2). as your most likely culprit.

Viv.

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He has no gear,correct me if I am wrong,As far as a fiber gear.i doubt that,,Not arguing but I thought the fiber gears started in the 60s

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Thanks for all the Ideas. I think I'll pull the pan and the oil pump. If the timing chain and or gears are bad I'll need to pull the pan anyway to get the broken pieces out. I agree with Old Car Fan that the fiber gears were {as far as I know} were started in the 60s. I'll continue to update the findings.

 

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Fiber gears were around LONG before the 60s. I think you just lost one.

 

The trouble is, a camshaft is constantly rocking back and forth with relation to the crankshaft, with a lot of torque, due to the action of the valvesprings against the cam followers and lobes. It really is a violent motion, and there has to be some backlash so the gears do not tear themselves up. The large gear rocks back and forth against the little one and makes a knocking noise. With minor wear, it gets really loud.

 

FIber is a "dead" sounding material, and is used because it makes less noise. It has been around since at least the 20s and probably longer. Anywhere there is a gear driven cam in a passenger car, you will probably find fiber. They still have to deal with all that banging around, even though they do not "ring" like a metal gear. The life of a fiber gear is rather short, and the failure sudden.

 

Later Pontiac flathead engines use a chain and sprockets. I am guessing yours uses gears. @Tinindian will probably know what is in there.

Edited by Bloo (see edit history)

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we have a 28 Knight that has fiber gears .on the generater,The cam is not rocking back and  forth,it is a shaft in cam bearings,the cam is as strait as an arrow It is not violent ,peace of art

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The distributor drive gear is on the shaft just below the housing.  It is pinned to the shaft.  The "spade" at the end of the shaft is below the gear and it drives an intermediate gear that drives the oil pump.  I hope you removed the retainer before pulling the distributor?  (the bolt and lock nut between cylinders 3 and 4 just under the water jacket on the left side.)

019.JPG

020.JPG

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The Chrysler 4 cyl cars of 1927/8 had fibre cam gears, so did Ford model A in 1927. It would be interesting to know who was first to use a fibre gear.

Viv.

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Why do people keep talking about "Fiber Gears".  Pontiac "split head" engines 1926-1932 and their successor 6 and 8 cylinder engines up to 1954  DID NOT HAVE FIBER GEARS.  They used two steel gears with a roller chain.

Edited by Tinindian (see edit history)

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If this is a Delco distributor, there are some that you change the timing by tightening a screw in the center with the rotor removed.  If this screw is loose, the rotor would just sit there and do nothing. 

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There is nothing like that on these distributors.  If he has pulled the distributor from the block and it doesn't look like the picture I posted he has broken something. Most likely the gear sheared off (thankfully that stops the engine so lack of oil doesn't do any damage)  this allowed him to pull the distributor housing and the shaft leaving the lower housing (which olds the unit in place and provides a bushing for the lower end of the distributor shaft and the upper end of the intermediate shaft.  I believe the pan must come off.  Then you need a tubing wrench to remove the oil tube assembly from the main beatings, the oil pump and the block.  When you undo the oil pump the intermediate shaft will come down with it and if the gear has sheared off it should fall down as well.  You probably will need to pull the lower bushing up and out the top.

This would be a good time to clean the sediment out of the oil pan (from under the screen). Good time to open the pump anc check for wear. Make sure you use a pinch and mark the oil pump cover so you get it on the right way (otherwise it will not pump).  There is no priming needed when you reassemble as the pump sits submerged in the oil.

You might also consider moving this thread down below under "Pontiac Oakland".  Some Pontiac specialists might not see it under this "Wanted" heading.     http://forums.aaca.org/forum/47-pontiac-oakland/

Edited by Tinindian (see edit history)

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