When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
So I finally decided to do the timing chain and gears on my red '76 98 Regency. The car has just shy of 150K on the original motor and the chain has never been done. I couldn't not believe my eyes when I pulled the cover off! The chain had an incredible amount of play and I could just about pull the chain right off. Take a look at the teeth on the cam gear. That's the old gear on top of the new one and they are lined up on center. The teeth are so pointy that I could have easily cut myself on them. The chain is also pretty worn and the links are more pointy than curved. The crank gear was actually in pretty good shape but I still decided to change it for the sake of all components being brand new and with no wear at all.
I'll be dropping the pan and changing the oil pump next over the next few nights. I'm almost afraid to see what's hiding in there but either way, I am SO glad I decided to do this when I did. I wouldn't doubt that this chain would have been jumping the gear within only a short time if I had not. WHEW! Cannot wait to get her back together and see how much better she runs!
Very true! It has had some hesitation upon acceleration from idle. I wonder how much of that was due to the amount of slack in the chain?? I'm also changing the harmonic balancer as it's starting to separate. I'm hoping for an even smoother running engine after all of this.
Hate to break it to you, but that original timing gear is broken. There used to be a nylon set of teeth cast around those aluminum ones in your picture, and your oil pump is probably clogged from all of the plastic pieces.
That engine is a bomb ready to blow.
remove oil pan
remove oil pump
replace it or tap all the plastic pcs out of the pickup
Clean and re-assemble.
front cover install will be super easy w/o oil pan in the way.
May have to jack motor up a little and rotate crank to favorable position to get oil pan out easily. 1/4 drive universal socket 3/8" size is handy for the oil pan bolts near/ under the motor mounts.
You should get all of these plastic pieces out of the system before it starves itself and locks up.
Hey, yeah I know about the nylon teeth. Why did they do this anyway? Was it to keep it smoother and/or quieter?
I'm dropping the pan and changing the oil pump over the course of this week. I'd like to think I'll find remanents of the plastic bits in the screen and even in the pan. I've put quite a few miles on this car in the 16 years I have her, including some awesome road trips between Connecticut and North Carolina with NO issues EVER. The chain was always in the back of my mind to change but just never go to until now. Boy am I glad I didn't wait any longer!
remove oil pan
remove oil pump
replace it or tap all the plastic pcs out of the pickup
Clean and re-assemble.
front cover install will be super easy w/o oil pan in the way.
May have to jack motor up a little and rotate crank to favorable position to get oil pan out easily. 1/4 drive universal socket 3/8" size is handy for the oil pan bolts near/ under the motor mounts.
Absolutely! I just did this same job on my black 98 and you couldn't be more right about putting the front cover back on without the pan in place. Although I'm told you CAN put the cover on with the pan still in, I tried it and I wouldn't do it that way. You almost have to force it in and I don't think you're going to get a good seal trying it like that. The book even says to drop the pan so that's what I do now.
I will raise the motor a few inches using a home-made lift / cradle that I made recently. Using this, I can easily get enough clearance to drop the pan, clean the bottom of the block, replace the pump and get it back together. I made this rig while doing this job on my black 98 because I don't have a hydraulic hoist and honestly, I feel safer using this than a hoist because it rests solid as a rock on jack stands instead of swinging from a chain. Check out these pics.
In case the link doesn't work for anybody, I attached the pic here. It took me a little while to design and build it but it's simple and works perfectly. I should be bolting it up and raising the motor tonight.
In case the link doesn't work for anybody, I attached the pic here. It took me a little while to design and build it but it's simple and works perfectly. I should be bolting it up and raising the motor tonight.
Wow, that's nice! I would have just raised mine with my picker and blocked it. My HEI cover probably would also have to be removed as mine is tight. Nice set up.
We had the same surprise when we did our motor last winter. And I agree about no motor of today could run with that kind of wear. These Oldsmobile motors seem bullet proof at times.
You should get all of these plastic pieces out of the system before it starves itself and locks up.
why does your sprocket have 3 bolt holes in it??? trader... my delta has 0 oil pressure at hot idol caus all the teeth are in the pickup. 20 hot, been that way for about a year now, dam thing wont blow
Last edited by Lars; December 11th, 2013 at 11:51 AM.
my delta has 0 oil pressure at hot idol caus all the teeth are in the pickup. 20 hot, been that way for about a year now, dam thing wont blow
I dropped the pan last night and at least at first glance, I didn't see anything in the screen. I'd imagine that the plastic bits have come and gone with the oil and filter changes over the years. I'm pulling the pump tonight and will blow out the screen to make sure it's clear. I've never had any issues with oil pressure or overheating with this car so I'm pretty confident it will continue to be trouble free after this job is done. It should only run better with the new chain, gears, pump and balancer.
I'm glad your motor won't blow, even with no oil pressure!
Do what Octania said
There will be a LOT of pcs in the pickup
PS the screen has a failsafe feature I believe such that if it becomes too clogged, the screen can move and allow unscreened oil [and plastic bits] into the oil pump.
Let's hope that has not happened. The next step is indeed the oil filter. Pieces small enough to go thru the pump could conceivably interfere with relief valve operation also.
Do what Octania said
There will be a LOT of pcs in the pickup
PS the screen has a failsafe feature I believe such that if it becomes too clogged, the screen can move and allow unscreened oil [and plastic bits] into the oil pump.
Let's hope that has not happened. The next step is indeed the oil filter. Pieces small enough to go thru the pump could conceivably interfere with relief valve operation also.
He's right, the 350 in my car now had a chain that looked like that and all the plastic chunks where inside the covered part of the screen, it sounded like a baby rattle, couldn't believe how many chunks came out of it.
I hate to say it, my chain and sprocket looked like that too...
I didn't opt to pull the pan, I went with the "pray" option. 20,000 miles later, it's still giving me sold, steady oil pressure, hot and cold. Not that I recommend this method. I have another car and plans to replace/rebuild this motor anyway.
Thanks for all the input guys. I didn't get to pull the pump tonight but I will for sure over the neztcouple of days and I'll report back. Hoping to find some chunks in the covered section of the screen. This engine runs awesome so I'm pretty confident she'll be fine after all this.
Well, here's what came out of the screen. I could not believe my eyes once again. Better in there than the engine but just think of how restricted the oil was before. Probably a no-brainer to just replace the screen and not risk any little particles being stuck in the old one.
Just wanted to give an update on my engine project. I wrapped everything up over the weekend and she came back to life yesterday. I still have a little tuning to do but holy cow she is running WAY better than before!
Here a quick rundown of what I did:
NEW: Oil pump (cleaned all of the plastic cam gear bits out of the very choked screen!), water pump, timing chain and gears, harmonic balancer, pan gasket, positive battery cable, a little bit of detailing and I replaced the diaphragm on the cruise servo.
The car is now running much smoother and with more pick-up and properly working cruise. Such a great feeling to finish up a project and come out with a big improvement. Thanks for the advice guys! It's very much appreciated!
Not to hijack, but to hijack...I am in the process of getting a car with a 73K mile 403 in it. Would now be a good time to swap the chain as a precaution?
I assume they got the same nylon teeth timing gears.
Not to hijack, but to hijack...I am in the process of getting a car with a 73K mile 403 in it. Would now be a good time to swap the chain as a precaution?
I assume they got the same nylon teeth timing gears.
Hi Ron,
Even with the fairly low mileage on the car you're buying, it's still old so I would do it sooner than later so you don't have any surprises like I did!
Originally Posted by MDchanic
Great to hear, John!
- Eric
Thanks Eric! So glad this project is done and led to such an improvement. I now have a leaking power steering pump to replace but that will have to wait until some projects on the black 98 are done first.
Bringing this old thread back up to ask if the '79 403's still had these nylon teeth and can I expect to find a similar situation in my 79 Buick wagons 403 when I change out the timing gear set. Seeing this suggests that the pan needs to be dropped not only for ease of reinstalling the timing chain cover but also to allow the oil pan and pump to be cleaned. Correct?
Thanks
Edit) oops, seeing now this isn't a 403 engine thread. I've been searching for info re swapping timing chains and this one came up. May still be applicable though???
Last edited by MrEarl; March 27th, 2020 at 07:11 AM.
Bringing this old thread back up to ask if the '79 403's still had these nylon teeth and can I expect to find a similar situation in my 79 Buick wagons 403 when I change out the timing gear set. Seeing this suggests that the pan needs to be dropped not only for ease of reinstalling the timing chain cover but also to allow the oil pan and pump to be cleaned. Correct?
Thanks
Edit) oops, seeing now this isn't a 403 engine thread. I've been searching for info re swapping timing chains and this one came up. May still be applicable though???
Ever Olds V8 from 1964-1990 came with the plastic teeth on the cam gear. If there's an all-metal gear in there, it didn't come from the factory. Yeah, the pan wants to be dropped, but you pretty much have to pull the motor to do that. Trying to pull the pan with the engine in the car is painful and you're only six bellhousing bolts away from pulling the motor anyway. I've done a lot of these without pulling the pan. Change the gear before 80K miles and the amount of plastic fragments in the pan is usually pretty small.
The performance difference should be noticable, think about how much out of spec/late the valve timing was. This should actually be part of every major freshen up to protect the motor from oil starvation and to regain performance. A motor with incorrect/late valve timing will never come close to optimal performance.
Last edited by Sugar Bear; March 27th, 2020 at 02:59 PM.
Here's what a new one looks like before it falls apart. I have an NOS set with crank gear (#382880), chain (#401584), cam gear (#381263) with nylon teeth and all. They're going to be used as conversation starters. Not recommended on any Olds V8.
Definitely clean out the pan. I had an engine with a timing gear worn like that and one of the pieces of nylon from the gear blocked the bypass on the pump open. I only had about 4 psi oil pressure at idle and 20 psi at speed.
Since this thread has been resurected and has current, relevant comments I thought I would add some comments. When the annual Olds convention came to Albuquerque a couple years ago, I went and listened to the guest speaker. He had some great stories about past issues and repairs he had encountered over the years. He also mentioned a vehicle he had encountered with over 250K miles on it with the factory timing set still intact. The owner said it was because he changed the oil every 2K miles. While I can appreciate his dedication and affection for his engine, he has paid more money for oil changes than he would have for a timing set change-out at the 80K mile interval that Joe mentioned. Even when they don't come apart, they still develop cracks and become delicate over time so that would be like driving with a grenade under the hood with the pin already pulled. I have changed my share of timing sets on Fords and Chevys and it can be a pain but it sure puts the mind at rest knowing the engine won't eat itself because the cam sprocket failed. The pic below is a cam sprocket out of a 60K + mile engine. It was extremely well preserved inside with a few minor exceptions. The sprocket is still in one piece, but it is definitely ready to fail because of all the cracking.
I wouldn't rule out the possibility that perhaps it's not the original nylon gear? Recall any GM service work would have replaced a cam gear with another freaking nylon gear! As far as I know, GM never changed the part number or used another cam gear. Not saying it isn't the original gear, but that's about one rotation away from falling apart in any case. Honestly, I've never seen an original cam gear without at LEAST a couple of teeth missing.
Originally Posted by cjsdad
Since this thread has been resurected and has current, relevant comments I thought I would add some comments. When the annual Olds convention came to Albuquerque a couple years ago, I went and listened to the guest speaker. He had some great stories about past issues and repairs he had encountered over the years. He also mentioned a vehicle he had encountered with over 250K miles on it with the factory timing set still intact. The owner said it was because he changed the oil every 2K miles. While I can appreciate his dedication and affection for his engine, he has paid more money for oil changes than he would have for a timing set change-out at the 80K mile interval that Joe mentioned. Even when they don't come apart, they still develop cracks and become delicate over time so that would be like driving with a grenade under the hood with the pin already pulled. I have changed my share of timing sets on Fords and Chevys and it can be a pain but it sure puts the mind at rest knowing the engine won't eat itself because the cam sprocket failed. The pic below is a cam sprocket out of a 60K + mile engine. It was extremely well preserved inside with a few minor exceptions. The sprocket is still in one piece, but it is definitely ready to fail because of all the cracking.
I wouldn't rule out the possibility that perhaps it's not the original nylon gear? Recall any GM service work would have replaced a cam gear with another freaking nylon gear! As far as I know, GM never changed the part number or used another cam gear. Not saying it isn't the original gear, but that's about one rotation away from falling apart in any case. Honestly, I've never seen an original cam gear without at LEAST a couple of teeth missing.
That is the first and only one I've ever seen that didn't have a tooth or more missing. Maybe it's good that the valve popped off and sent that engine to the yard. Otherwise no telling what would happen to the engine if later the timing chain teeth went away. Because eventually, they would.
Back in 1982 when I rebuilt the engine in my 1970 Supreme there was no nylon at all on the cam gear, just very pointed aluminum teeth. The reason for the rebuild was a detonated piston due to a stupid young kid running cheap gas and revving to 5500 RPM. At that time I did not know about the nylon and just assumed the gear teeth had worn from use. As said, the engine had been running well even with all that wear.
December 9th, 2013, 07:30 AM
... my delta has 0 oil pressure at hot idol caus all the teeth are in the pickup. 20 hot, been that way for about a year now, dam thing wont blow
