Distributer gear retaining pin broken

[shuckett]

Hey Folks, I am stumped and hope that one of you may have an answer/solution for this peculiar problem. I am resurrecting a 1968 Buick 225 with a 430 V-8 for my uncle. It sat (but started regularly) in storage for nearly 20 years before I started work on it. At first it started and ran fine, but over time the engine ran rougher and rougher, with backfiring, until one day it would not start. Upon thorough inspection, I found that there was no spark and that the rotor was not spinning with the engine. Digging deeper I found that the roll pin which secures the distributer timing gear to the distributer shaft had sheared off, leaving the gear to float on the dist shaft. The distributer gears are a bit worn but are not broken. The timing chain/gears are spinning when the starter is engaged, but I have not gotten a good look at them. Also, the oil pump moves freely when turned with an screwdriver through the distributer port. So, I replaced the roll pin, reset the timing, and it started/ran. However, after less than an hour run time, the same thing has happened; roll pin has sheared. All else remains the same.

Before proceeding, I would like to know what could cause this pin to shear? Second, Solutions?

Thanks in advance,

 

[Dr. Frankenbuick]

There are a few ways this can happen. A high volume oil pump and high viscosity oil can shear pins with RPM before the oil warms up. These pumps need the oil to warm up at idle before experiencing any RPM. These pumps are found on race engines or as a band-aid on very worn engines that had oil pressure issues. These pumps have longer gears and can be identified by a a spacer plate around the gears in the pump. A worn pump housing or improper clearance will let the gears gall the housing while running and can cause pin shear. Junk from the oil pan can get caught between the pump gears if the oil bypass is compromised. The teeth from the nylon upper timing gear disintegrate over time and small parts can get into the pump.

I think your next step is to identify the pump and pull it apart for inspection. Check the by-pass spring and by-pass for proper operation. Make sure the pump shaft is not extremely loose or wobbly where it fits through the timing cover. Check the gear housing and bottom plate for galling. Check that the gear to housing clearance is not too tight. It might also be time for an oil change to see if anything looks suspicious in the oil.

 

[shuckett]

Dr. F., Thanks for your reply and insights. Being a bone stock engine/car, and having sat for so long, my first chore was to change the oil and spin up the pump before starting the car [twice!]. I did not drop the oil pan though. What drained out was more than bad. Plus, there is a lot of sludge/debris built-up under the valve covers, so the probability of debris/sludge in the system causing pump/pressure relief valve issues, or oil pick-up by-pass blockage, is sound.

Once changed and freshened up, I had not thought to look at the pump because all seemed OK until just recently. My next step is to investigate the oil pump for any issues, drop/clean the oil pan, correct anything necessary, and then do an engine oil flush before trying to run the thing again. Plus, I did not know about the nylon timing gears. What were they thinking!? I'll keep you all posted. Thanks again!

 

[LARRY70GS]

Nylon tipped gears were quieter. I believe that was their thinking. You can also easily check the relief valve and spring. Just remove the large nut on the oil pump cover. Make sure the valve moves freely and isn't binding.

IMO, any Buick engine needs a real oil pressure gauge. It will show you the actual pressures, cold and hot.

 

[Dr. Frankenbuick]

Take a look at your pick up tube while you have the pan down. The screen could be damaged or partially plugged up with the same stuff that came out of your pan.


Sent from my iPhone using Tapatalk

 

[Brushwolf]

Had something similar happen. Got a used 1971 455 with unknown history that was missing distributor. Took a distributor off another 455 and eventually got spark working. Put new oil and filter in and cranked it on the engine stand and did a compression test. 140 low and 155 high. Oil pressure showed about 50 lbs on gauge. Seemed ok to me. Decided to start it just manually fueling the carb, so only expected it would run a second or two.

So started it several times momentarily, but then it would not fire any more. Rotor was no longer turning. Pulled distributor and saw cam and distributor gears both had broken teeth. Oil pump had seized inside housing, which broke aforementioned gears and twisted distributor shaft end to boot. Upon cover disassembly the oil pump gear tips had obviously been gouging the housing and it seized. I assume that timing cover is scrap metal.

Almost got it all back together now with different timing cover, better oil pan, new cam, timing set, yet another distributor from a stuck 455, new lifters, oil pump kit, a much better pickup tube (3/4 of screenface of original pickup was plugged with black grit. IDK what it was, but not metal). Discarded that... Probably disintegrated valve stem seals cuz several were missing, so replaced all those while I was at it and cleaned the lifter galleys out. Not much crud in there...

Oil pan had nothing too gruesome inside it, except broken gear teeth laying in pan directly below where they broke off. Decided to replace it just cuz of rust pitting on the exterior (Minnesota...) Under thevalve covers and lifter valley were pretty clean. Motor apparently had at least valve work done on it previously too. Pushrods and rockers all appeared fine, just cleaned them and blew out the oiling holes in them.

So, kinda the same experience. Engine was stored for years and fired up initially but then broke from what was probably wrong in the first place. Worn out oil pump housing and missing distributor probably had been damaged and that is why it had been removed. Except this time it broke even more stuff...

I am building a different more expensive 455 anyway and this one is just for practice and to drop in a driver chassis that is lacking a motor. But, is the packing of the oil pump with Vaseline something that should be done on any new oil pump on these motors. I have a new drill-driven oil pump primer from TA and so I can just run that in a drill, or can do the Vaseline on top of that if it makes a difference..

 

[LARRY70GS]

I am building a different more expensive 455 anyway and this one is just for practice and to drop in a driver chassis that is lacking a motor. But, is the packing of the oil pump with Vaseline something that should be done on any new oil pump on these motors. I have a new drill-driven oil pump primer from TA and so I can just run that in a drill, or can do the Vaseline on top of that if it makes a difference..

Packing the pump with Vaseline is something that was done on the assembly line because you absolutely needed oil pressure to build upon initial start up. In the chassis manual, they advise the same because anytime you disturb the timing cover to block seal, there is the potential to lose oil pump prime. Some guys balk at putting Vaseline into their oil because they don't want something of that consistency in their oil, but in reality, it readily dissolves in oil. You can probably skip the Vaseline if when assembling the pump, you coat the gears and pocket with oil, and then run the pump with a drill to verify priming/pressure BEFORE you start the engine. If you have trouble, it can help to run the pump backwards then forward, and/or squirt some oil in through the block sender hole.

I recently had to replace my timing cover gasket for a coolant leak. I did not disassemble the pump or pack it. The pump primed right up when I spun it with a drill.

What is WAY more important is to check and adjust if necessary, the end clearance inside the pump. That is explained in a thread on V8buick that I authored some time ago.

Oil Pump clearances and oil pressure

A lot FAQs here have to do with oil pressure. Buick engines, other than the Nailheads have a front mounted oil pump. The pump is actually housed...

www.v8buick.com