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cam gears

 
Old 08-30-2012, 08:25 PM
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Dads928
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Default cam gears

I just started in to my TB job after finishing the MM and gasket and cleaning gunk from everywhere. I have had the car 4 years, postponed the work because I was having way too much fun. No history when I bought it but runs perfectly and has 110,000 miles on it now. Thought I should get at it before my luck runs out.
Looking at the belt it clearly has been changed at least once, belt is perfect, no signs of wear, no rubber powder residue or evidence of wear anywhere. Belt tracked very straight, tensioner system is in good shape and working fine. I am replacing it with the porkensioner however.

My cam gears are showing wear however and are a bit shiny in the track line. The belt however shows no sign of distress from the gears. I am having trouble uploading the pictures but I will keep trying.

Are the cam gears still hard to get and expensive if I decide to replace them or can they be re-coated...
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Old 08-30-2012, 08:28 PM
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ammonman
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New aren't hard to get, just bloody expensive. Some have re-coated successfully. A search should turn up the specifics.

Mike
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Old 08-30-2012, 10:28 PM
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The belt one my '86.5 looked like brand new also except the part that spun off the crank. I saw a set of new old stock (not the new version) on ebay awhile ago for $300 or so.
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Old 08-31-2012, 03:48 AM
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New cam gears are $400 a gear. You need two.

I need to change mine too.
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Old 08-31-2012, 07:12 AM
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If you upload I pic, or email me one, I can see if they are able to be recoated.
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Old 08-31-2012, 08:52 AM
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Dads928
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Default pics I hope??

Thanks, I am still trying to upload pics. I have a damaged connector near the left side cam gear, I am wondering what it is. Looks like it rubbed something.

no pictures arghhhh.

Last edited by Dads928; 08-31-2012 at 08:53 AM. Reason: no pictures again
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Old 08-31-2012, 09:05 AM
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I think you need to be a member to upload to this site, but if you can upload them somewhere else you can link to them or embed them here...
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Old 08-31-2012, 09:05 AM
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Default pics I hope??

i hope I have a picture. I need to know what the connector to the left does, it is damaged.
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Old 08-31-2012, 09:13 AM
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Default that worked - try for another pic

maybe a better look

Do I need a new oil pump gear as well??
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Old 08-31-2012, 10:30 AM
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New gears are in your future unless Colin thinks they can be recoated.
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Old 08-31-2012, 10:31 AM
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The connector is to one of the Knock sensors and they are toast as well I am sure.
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Old 08-31-2012, 10:53 AM
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Roger, how do I know if the knock sensors need replacing and do I do that when I do the intake stuff. I was planning to do fuel lines and intake stuff next spring..

How much is the oil pump gear, and do I need a new one and a crank gear???
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Old 08-31-2012, 11:17 AM
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OK, I found this in another thread:

Originally Posted by Dads928 View Post
Thanks Guys i keep forgetting to post year and miles
89S4 106,000 miles

Ian
Ian, it is hard to tell from the pic's how worn the gears are-- it is hard to photograph shiny surfaces.

The cam sprockets/gears are aluminum, coated with a relatively hard coating. They wear primarily at the top of the teeth, where it contacts the flat part of the belt. Once the coating wears through then the aluminum starts wearing pretty quickly.

Wear on the top of the teeth does three things, all bad: It reduces the diameter & circumference of the sprocket, which changes the pitch of the teeth and the belt no longer fits properly, which wears the teeth; More of the load is taken by the teeth rather than the flat part of the belt, which accelerates wear; and, as the teeth wear, the edges get sharp which helps the teeth chew up the belt.

The definitive test is to lay a straightedge (e.g. a steel ruler) along the teeth and look for daylight between the sprocket tooth and the straightedge. (It helps to back-light it with a flashlight). The teeth wear in the middle where the belt contacts them, and not at the ends. If the gear is worn then you will see light in the middle, and not at the edges.

From the pic's, and from your description of a belt in good condition, I suspect that you haven't gotten to that point, yet. And if they are not yet worn (except for the coating), then they are candidates for recoating. Once the aluminum starts to wear then they are junk.

But if you are seeing shiny areas now then they will not make another 60K miles. So you either need to replace (or recoat) them now, or commit to checking on them every year or so.

If the oil-pump sprocket is coated aluminum then it should be changed also. I thought '89's were steel but that my be wrong-- check it. Steel sprockets (cam and later oil-pumps) last longer and should be fine at 110K miles, but do check them.
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Old 08-31-2012, 11:26 AM
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Default oil pump gear

It looks aluminum, same as the cam gears and is shiny on the tooth surface as well. I will check it when I go back out to the garage but I am pretty sure its aluminum. Thanks for your input, I think the general consensus is that I am in need of replacements.

Roger will know if the gear is aluminum..
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Old 08-31-2012, 12:00 PM
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Ian, here's some pic's for reference. (EDIT: These are not Dads928's gears-- they are from my junkbox, for illustration purposes. They are from a '87 motor).

First, a cam gear, clearly "toast" :

Name:  IMG_4445.jpg
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And here is the straightedge check, same gear:

Name:  IMG_4446.jpg
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Here's an aluminum oil-pump gear, from an '87. No shiny bits, just polished coating:

Name:  IMG_4444.jpg
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Here's the straightedge check, no light visible:

Name:  IMG_4451.jpg
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And here is a steel crankshaft gear, which is making a liar out of me-- it is clearly worn and should be replaced:

Name:  IMG_4448.jpg
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And a failed straightedge check:

Name:  IMG_4450.jpg
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These are all off of an '87 engine, unknown history but stated to be 57K miles. If that is correct then the belt spent its life severely over-tightened.

Last edited by jcorenman; 08-31-2012 at 01:07 PM. Reason: Clarification
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