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Originally Posted by faapgar View Post
Hi,maybe my wife made me the wrong batch of brownies this morning and I am FUBAR here on the beach in C.R.but the previous post said chain sprockets and wear looked good on the right side which is 4-6 cylinder.Right side chain sprocket is installed backwards and the small chain sprocket does not look so good to me.I would question everything from the previous build.I just finished a 3.0 Carerra engine for Nathambs in September that had the left side & right side reversed and it ate the aluminum intermediate shaft gear.Fred
There is an inside and outside to the chain sprockets? Never noticed or knew that... Now will have to look at them...
Old 11-07-2017, 01:35 PM
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Fred picked up on the right gear, no way the chains can be parallel, or even checked for parallel
I like the use of nyloc nuts inside the motor on the Tensioner surely the heat would help dissolve or melt the nylon inside the motor for better plugging of cam oiling, if not mains and rods.
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Old 11-07-2017, 02:42 PM
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Originally Posted by faapgar View Post
Hi,maybe my wife made me the wrong batch of brownies this morning and I am FUBAR here on the beach in C.R.but the previous post said chain sprockets and wear looked good on the right side which is 4-6 cylinder.Right side chain sprocket is installed backwards and the small chain sprocket does not look so good to me.I would question everything from the previous build.I just finished a 3.0 Carerra engine for Nathambs in September that had the left side & right side reversed and it ate the aluminum intermediate shaft gear.Fred

Unbelievable.
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Old 11-07-2017, 03:17 PM
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It amazes me the stuff you learn on here...

You guys have some sharp eyes...
Old 11-07-2017, 04:06 PM
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I do not know about you but sometimes I spell a word and look at it about 5 times and still think it is misspelled.That is how I look a the right chain gear picture.I have repaired or rebuilt a few thousand 911 motors and thought maybe the dementia is catching up to me because no one else picked up on it.I think I need the good brownies tomorrow just to make sure.I am still sane.Thanks Fred
Old 11-07-2017, 06:51 PM
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. . . I am still sane.Thanks Fred
That is open for debate, FaaptabulousFred!
Old 11-07-2017, 07:23 PM
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It definitely looks like it is on backwards to me. I can't imagine it ran that way without destroying itself.
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Old 11-07-2017, 09:25 PM
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It definitely looks like it is on backwards to me. I can't imagine it ran that way without destroying itself.
I assume if its on backwards then the chain alignment is way off, correct? Wouldn't that be picked up when shimming the sprockets?
Old 11-08-2017, 05:15 AM
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Really good catch by Fred. And I too sometimes find myself staring at a word i've spelled a bazillion time and think, I know that's right but that word looks goofy for some reason.......

Totally admit I missed that the right side sprocket is backwards. I'll preface my next statements by saying it's not always the worst thing in the world. And I don't say that just to cover my arse for the oversight. I say that because i've seen this before (actually recognized it on an engine I was working on) and the engine didn't tear itself apart in terms of showing bad wear at the time of servicing it, along with it behaving fine several thousand miles later via use of the preexisting sprockets and chains.

When doing a cylinder head service on a 3.2 (valve guides at high 60-something thousand miles) in late 2006, I found the same sprocket backwards on the right side. The chain + sprocket wear was not something that struck me as a major issue. Flipping the sprocket around to the proper "flat" orientation, and setting/shimming the parallelism via the typical procedure to arrive at the proper measurements, as they should be has engine still operating just fine at 90-something thousand miles 10 years later.

I know this because it was my personal car of 14 years from 2000-2014 and I sold the car to someone who ended up becoming a close friend. Unfortunately I didn't check the parallelism prior to disassembly because I recognized it after the fact during reassembly. Although in hindsight I could have assembled it the way I found it, since I know I kept track of how many shims were on that side by keeping parts in separate plastic bags, just to determine how far out of parallel it really was. Maybe Trackrat can jump ahead to that procedure, just to give us an actual measurement of how close to parallel that backwards sprocket really is?

Don't get me wrong. I'm not endorsing this backwards sprocket and thereby saying the orientation isn't that big of a deal. Just saying my one instance of encountering this situation apparently was a lucky one that didn't do damage to the engine. Fred's experience is so much greater than mine and he's worked on way more engines than i'll ever see. So i'd tend to think that more often than not, a grossly misaligned sprocket is a significant problem. Trackrat's situation may be another one of those lucky ones? Also agree with Fred that the idler sprocket does show some noticeable wear on the side of the teeth, as evidenced by the bright area below the root of the teeth.
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Old 11-08-2017, 07:19 AM
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Really good catch by Fred. And I too sometimes find myself staring at a word i've spelled a bazillion time and think, I know that's right but that word looks goofy for some reason.......

Totally admit I missed that the right side sprocket is backwards. I'll preface my next statements by saying it's not always the worst thing in the world. And I don't say that just to cover my arse for the oversight. I say that because i've seen this before (actually recognized it on an engine I was working on) and the engine didn't tear itself apart in terms of showing bad wear at the time of servicing it, along with it behaving fine several thousand miles later via use of the preexisting sprockets and chains.

When doing a cylinder head service on a 3.2 (valve guides at high 60-something thousand miles) in late 2006, I found the same sprocket backwards on the right side. The chain + sprocket wear was not something that struck me as a major issue. Flipping the sprocket around to the proper "flat" orientation, and setting/shimming the parallelism via the typical procedure to arrive at the proper measurements, as they should be has engine still operating just fine at 90-something thousand miles 10 years later.

I know this because it was my personal car of 14 years from 2000-2014 and I sold the car to someone who ended up becoming a close friend. Unfortunately I didn't check the parallelism prior to disassembly because I recognized it after the fact during reassembly. Although in hindsight I could have assembled it the way I found it, since I know I kept track of how many shims were on that side by keeping parts in separate plastic bags, just to determine how far out of parallel it really was. Maybe Trackrat can jump ahead to that procedure, just to give us an actual measurement of how close to parallel that backwards sprocket really is?

Don't get me wrong. I'm not endorsing this backwards sprocket and thereby saying the orientation isn't that big of a deal. Just saying my one instance of encountering this situation apparently was a lucky one that didn't do damage to the engine. Fred's experience is so much greater than mine and he's worked on way more engines than i'll ever see. So i'd tend to think that more often than not, a grossly misaligned sprocket is a significant problem. Trackrat's situation may be another one of those lucky ones? Also agree with Fred that the idler sprocket does show some noticeable wear on the side of the teeth, as evidenced by the bright area below the root of the teeth.
Perhaps a silly question...

Why is there not a simpler way to check chain alignment? There are several threads on here about case alignment not being perfectly flush at the IMS flange. This in turn makes measurements "iffy" by checking for parallelism. A .001 difference at the joint line is probably a large difference at the sprocket using a straight ruler.

For example, Put some white paint on the sprocket sides. Put it all together, spin the crank a couple times by hand and see if the paint is rubbed off. If it is, its too tight. If it isn't, or its barely touched, its just fine.

Or, if the paint idea is too crude, just use a .001 feeler gauge and see if it slips between the side of the chain and the side of the sprocket...


Or, why not align the sprocket to the idler gear? The idler gear/tensioner are in a fixed plane, correct?

Just trying to figure why Porsche did it the way that they did...
Old 11-08-2017, 07:44 AM
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The reality is that you just want to get the alignment of the sprockets as close to even as possible. If you have done this you know that changing out one shim will sometimes move the sprocket to far. So unless you make some special shims, you get it as close as possible. Which is usually good enough. .005" + or - is no big deal IMO.

Trackrat: read the section in Wayne's book on aligning the sprockets during assembly. Then measure what you have now. Then take off the right sprocket and see what is going on. Maybe there is an issue there that caused a need to have the sprocket reversed. I would want to know exactly what is going on with that sprocket and chain before proceeding.
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Old 11-08-2017, 09:52 AM
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The idle gear floats.
The math and measurement isn’t rocket science
The factory spec books tell that the suggested amount of shims for each cam.
It’s just up to the builder to measure and check spec. +/- .25
Bruce
Old 11-08-2017, 09:59 AM
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Bruce is right that the idler gear has some float. On its own shaft it has a little bit of float, yes. But not that much. However, the idler arm/body also has some float on the big shaft. The tensioner eyelet that slips over the large shaft contains the idler from falling off the shaft and there's enough gap between the eyelet and the idler body that it can move side-to-side. But when the tensioner pushes on the idler arm, it loads the arm pretty good and doesn't move sideways all that easy. I suppose the strong forces of the chain have no problem guiding that idler arm & sprocket into some kind of happy place?

Regarding the parallelism, the face of the engine case is not necessarily your reference point. We're measuring from the intermediate shaft itself. But yes the straightedge is mounted on the face of the case and it needs to be square with the case. This is where the straightedge support comes into play. If you hold your straightedge across the case face, and the case halves are staggered a tiny bit, yes it's of course hard to hold the straightedge against the case because it has a little bit of rocking. I would shim the case face with some feeler gauge material to close that gap. Or, borrow someone's Stomski tool that uses a support block to square the straightedge on the proud part of the case. Bo, I have this tool if you'd like to borrow it.

https://www.stomskiracing.com/products/911-sprocket-alignment-tool watch the video and it tells you all you need to know about checking the parallelism

Here's the spec book pages that give some background on where the numbers come from (they're based upon the blueprint numbers used to design the engine) and also included is the chain ramp arrangement








BTW I did some searching and actually found how my incorrectly installed sprocket was shimmed. Installed wrong it had one shim and and properly oriented it used four shims

Quick cam sprocket question...
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Old 11-08-2017, 01:46 PM
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Kevin, thanks for the info. May take you up on the offer to borrow the tool when I get to that point...

Still working on figuring out my case alignment. Because the IMS pulley faces are a fraction off on the pulley end, the IMS thrust bearing is also slightly staggered, and rubbing on the IMS shaft face. Took a look at the bearings last night, and the original dated 1988 thrust bearing have the thrust faces on opposing sides worn a lot, down to copper.


So, best I can tell, this misalignment has been there since new... will play with it more this weekend. Clearly didn't effect the motor one way or the other. Will also recheck the same alignment with the crankshaft in. I wonder if the crankshaft applies some pressure against its thrust bearing, also aligning the case longitudinally.

FUN, fun, Fun...

Learning a lot...

Hope to see you at some PCA events next year. I will be there with either this car... or a Spec Miata if this takes too long...
Old 11-08-2017, 02:02 PM
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Trackrat: read the section in Wayne's book on aligning the sprockets during assembly. Then measure what you have now. Then take off the right sprocket and see what is going on. Maybe there is an issue there that caused a need to have the sprocket reversed. I would want to know exactly what is going on with that sprocket and chain before proceeding.
I've already torn down the chain housing and have already taken the timing chain covers off.

Right now I'm struggling at getting these 10mm cylinder head nuts off. These things are TIGHT!!!! sprayed it with PB Blaster and will try again later.
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Old 11-08-2017, 03:11 PM
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I've already torn down the chain housing and have already taken the timing chain covers off.

Right now I'm struggling at getting these 10mm cylinder head nuts off. These things are TIGHT!!!! sprayed it with PB Blaster and will try again later.
Do you have any dewalt tools and chargers already? Any other manufacturers battery or chargers handy?

If so, go on ebay and get yourself an impact wrench. About $110 refurbed ($300 new)...

You will find a million uses for it...

Have you gotten to the exhaust nuts yet?

Bo
Old 11-08-2017, 03:15 PM
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Chain timing gear all removed...




I noticed this small nick on the top of the left side timing chain cover. The gasket material covered it up.

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Old 11-08-2017, 03:22 PM
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Do you have any dewalt tools and chargers already? Any other manufacturers battery or chargers handy?

If so, go on ebay and get yourself an impact wrench. About $110 refurbed ($300 new)...

You will find a million uses for it...

Have you gotten to the exhaust nuts yet?

Bo
I have an impact wrench I will have to charge up and try.
Exhaust nuts were easy... just had a couple of studs come out with the exhaust.
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Old 11-08-2017, 03:24 PM
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Now removing the camshaft casing....
Note... took the rockers out... put the parts back together in the rocker and labeled the rockers with their location in a plastic bag.



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Old 11-08-2017, 03:29 PM
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and... the most difficult part on getting this off was those darn oil tubes. They were holding on tight. Took a flathead screwdriver and pried them off at the case to loosen the tightness.

Then I had to take rubber mallet and whack the corners (BE CAREFUL NOT TO HIT THE FINS on the cylinder heads)... to get the camshaft case to start moving off the studs.
As I mentioned, the oil tubes were difficult to let loose.


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Old 11-08-2017, 03:33 PM
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