What caused this cam Gear damage?

[svwilbur]

I was going to try to adjust my valves today for the first time since I purchased my 2000 4 years ago. I got the valve cover off and started looking around.

I was interested in if the timing chain was slack, if I had and Evil-L, and if there were shims in the upper tensioner.

Yup (chain was slack), yup (Evil-L bracket is in place) and yup (shims are on the tensioner). The first yup was alarming. The timing chain was tight against the tensioner but was very slack on the opposite side. It was so slack it could touch or almost touch the edge of the Evil-L bracket.

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This shows that the slack was so great that I could push the chain into the Evil-L bracket. At this pioint I have not moved the crankshaft at all to try to see if it goes away when the motor turns in the correct direction.

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This picture shows that at some time the chain had started to rub the Evil-L bracket and notched it a little.
Also note that some of the teeth have some strange wear on them. Chips and marks? What causes that?
At one time was something bouncing around in there?

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I removed the oil pan last month before Solvang and did not find anything in there. maybe this was from a while back, before I owned it?
I have never had any strange noises but I do have some valve noise I think which is why I wanted to check the valve adjustment. That and I have not had it done during the 5,000 or so miles that I have put on it. So it is over due.

The car has been turned off for weeks and may have been rolled backwards accidently while I was positioning it in the garage. Maybe that push that did not move the car slackened the chain? It was slack without doing anything else other than shutting off the motor a couple weeks ago. Since then I have pretty much just rolled it around a bit in neutral other than the one attempt to roll it backwards while it was still in gear.

Any ways I took the spark plugs out and got a 27MM socket and tried to turn the Crankshaft nut. I then realized there is not enough clearance with the fan shroud in place to fit a socket wrench on top of the socket and get it in there. So I purchased a flat serpentine wrench to fit on the socket and that worked but it is slow going as you only can move it about 1/8 th a turn and have to take the socket off and re position it on the wrench and then back on the crankshaft.

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But I got it to move and the slack magically all went away. I guess the tensioner picked it up??? It is all tight.



Now the other alarming thing......The cam gear seems to have worn funny. There seems to be some scratches and small chips or dents on some teeth.

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What could cause all that damage or wear?

Some look like something was dragged on it.
Some look like something gouged it or chipped it.
Some are from a slack chain at some point and it rubbed on the Evil-L

Assuming that whatever caused these dents and scratches is not in the engine anymore, as I did not see anything when I removed the oil pan earlier and I have never heard any strange sounds, is it OK to continue to run with this cam gear??

Is it OK to continue to run with this cam gear??

If Not is it just because of the marks, dents, chips?

Or is it that the cam gear is worn too much?

Looking at the end of the gear through the chain it appears that there is still flat spots on the spokes, it is not worn to pointy ends:

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How do you tell if the chain is worn out?

I also looked down to see if I could see the gear on the jack shaft from the top. Here is a pic:

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From what I can tell maybe those are OK?



I don't want to change any of this out if it is still safe to use. I have more pictures if you need more detail.
I think some of the nicks look worse than they really are as it is blown up.


What is the verdict?
Is it safe to run with this cam gear or should it be replaced?
What about the chain?

[svwilbur]

More pics

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[AidanDawn2000]

Wow Stacy this is a very detailed post and I hope we can get a lot of helpful discussion going on this issue. The tensioner is operated by oil pressure so it is not really working when the engine is off though it does have a spring in it.

[AidanDawn2000]

Looks like you're missing the little Philips head screw that goes in the cam sprocket. Was that bouncing around down there maybe?

[svwilbur]

Looks like you're missing the little Philips head screw that goes in the cam sprocket. Was that bouncing around down there maybe?

I suppose it may have at one point but I do not see anything down in there and there was nothing in the oil pan when I took that off before Solvang.
Is that the screw that you use to hold the cam gear to the Evil-L when you pull the head?

It may have been left off last time someone did something to this.

There were/are marks someone wrote on the gear/sprocket with a sharpie. I suppose someone messed with something and was trying to repair stuff or adjust timing or replaced the gear or something. No info from the previous owner on that. There was suppose tpo have been an engine rebuild about 20-30,000 miles ago. maybe something they did and left that screw out.

[svwilbur]

looking at some other sample gears that JT68 posted a while back I would guess that this cam timing gear sprocket is toast.

his post is here Re: U20 Cam Timing Gear Wear http://www.311s.org/phpBB3/viewtopic.ph ... in#p216058

but I am no expert.

please give me opinions.

also if it needs rplacing can I just replace it?
do I need upper chains?
is there a way to do that without much trouble?
or does the motor need to be pulled?
or just rhe radiator to get access to the front?

comments please.

[bakerjf]

The upper gear isn't very difficult to change out. JT, as well as Rallye sells them. I think Paul Wells and Rallye sell the little cam screw. It comes in handy and I'd look into getting one. I would personally do a chain swap too, but that could really lead you down the rabbit hole in additional parts and would require a lot more work as the head has to be removed if the PO didn't swap out the small forward studs for bolts permitting the timing cover to be more easily removed.
Sounds like the car is running ok though. Maybe just address the obvious and keep driving it...

[AidanDawn2000]

I recently had the timing cover off and it defiantly takes some time.

[svwilbur]

The upper gear isn't very difficult to change out. JT, as well as Rallye sells them. I think Paul Wells and Rallye sell the little cam screw. It comes in handy and I'd look into getting one. I would personally do a chain swap too, but that could really lead you down the rabbit hole in additional parts and would require a lot more work as the head has to be removed if the PO didn't swap out the small forward studs for bolts permitting the timing cover to be more easily removed.
Sounds like the car is running ok though. Maybe just address the obvious and keep driving it...

What are these: " small forward studs for bolts permitting the timing cover to be more easily removed." Where are they located and is there a way to tell if they were changed out already?

What type of additional parts? Related to pulling the head or other stuff for the timing cover like this?:
From Dean's site
2751 Datsun Roadster U20 Timing Cover Servicing Kit
2- - timing cover gaskets, 1 - timing cover seal, 2 - water pump gaskets inner & outer $54.00

What else?

I was not aware of Paul Wells, I just looked him up and found reference to his site and these parts:
http://www.datsun-roadster-parts.com/index.php?id=879 This is for the screw
http://www.datsun-roadster-parts.com/index.php?id=878 this is for timing gear set but does not seem to sell just the upper gear.
http://www.datsun-roadster-parts.com/index.php?id=257 for the upper timing chain
http://www.datsun-roadster-parts.com/index.php?id=883 for timing cover set

What else would I need if I decided to replace the chain too?


If I were to just replace only the upper cam gear/sprocket, what parts would I need other than the sprocket and the U20 cam timing gear dowel / alignment pin and washer?

[JT68]

I do have the gear separately. Changing the chain is a MUCH bigger job/ dropping oil pan/ and carefully avoiding breaking the front cover if you leave the head on. Lower sprockets have to come off as well. PIA in the car.

(if you are a good mechanic, it is do-able, but tough for the average guy.)

Suggest you just change the gear unless you are very capable with engine work.

Jt

[nismou20]

I ditto JT68 advice. Sprocket alone is easy but chains get more involved. With a new gear you will end up tightening the slop a bit too. If no unwanted noises, you're good for awhile.

[svwilbur]

I do have the gear separately. Changing the chain is a MUCH bigger job/ dropping oil pan/ and carefully avoiding breaking the front cover if you leave the head on. Lower sprockets have to come off as well. PIA in the car.

(if you are a good mechanic, it is do-able, but tough for the average guy.)

Suggest you just change the gear unless you are very capable with engine work.

Jt

thanks JT, I sent you an email for a quote as it is sounding like maybe I should at least replace that cam gear. is that your suggestion?

I was just looking at the front of the engine and reminding myself all the stuff that has to come off for a chain replacement. probaby radiator, fan, pully, water pump, hoses ..... looks like a real pain your right.

and it is all running fine now. the top sprocket just looks bad and may fail so swapping that out now seems to make sense if everyone agrees it needs to be replaced.

[fj20spl311]

That gear has the "Christmas Tree" look, so its past time to replace it.
I agree that you can get time by replacing the upper gear. I would start saving for a complete chains, guides and gears soon. I have heard of new chains going bad in 10,000 miles because it was run on a bad gear.
That could be years of driving or ????

[svwilbur]

I was looking back at my cars historical documentation to see if I could find anything concerning the timing chains and gears.

It shows that it had a full engine rebuild at 88,375 miles, which is just under 20,000 miles ago, that was back in 1981 (35 years ago). it ran another 8K to 96,000 and then was not used after 1984. until 2005. 21 years it had sat. It had 101,842 miles in 2006 and 103,570 in 2012 when I bought it. now it has 108,077 now. so just shy of 20,000 miles since the rebuild in 1981.

In the machine shop listing for the 1981 rebuild it shows the following for the chains and gears:
"new cam gear and cam chain where replaced, 2 new timing chain guide rails, and new upper and lower tensioners".
it does NOT show the jackshaft sprocket or the crankshaft sprocket as ever being replaced. So I assume they are still original.

So I guess that 3 years later in 1984 there must have been some issue that it was no longer used. Maybe the cam gear crunched something that made those marks? Like the cam guide screw?

I assume the guy in 2005 did something to fix it and get it running. Or maybe there was no known issue and it had just sat, but either way that cam gear has some odd wear on it. Especially if it has only been in there for about 15K as I know what I have done with it for my 5k of the 20k.

Kind of weird. I know the person I bought it from did lots of cosmetic stuff to it and had some mechanical stuff done. Maybe the tensioner shims and cam gear were messed with at that time? Some one use a sharpie on the cam gear and made notes on it, visible in my pictures. Maybe that was a result of installing the electronic distributor and having to recurve and tune stuff?????

Who knows?


But I guess the consensus is that I at least need a new cam gear/sprocket????

Looks like at least 4 forum members are hinting that way.

[Gregs672000]

Definitely need a cam gear, and I am very happy with JT68's adjustable one. However unless you want or need to mess with cam timing id just go with the stock set up gear thats offered as well. Other venders have gears as well. Gear you have appears modified to me, with additional holes, and would not be new or old stock. If it was a manufactured one it looks like it was not hardened correctly?
Change the gear and run it.