85 928S Valve/Cam timing?
04-06-2012, 08:06 PM
#1
Burning Brakes
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85 928S Valve/Cam timing?
Hello -
I'm using John Pirtle's most excellent article on replacing the timing belt on my '85 S. I've gotten to the step where I hand crank the engine to 0 TDC and check the timing marks on the cam drive wheels, and mine don't line up. John doesn't mention what a person should do in this circumstance, I guess he assumed the marks would line up (who wouldn't?)
Because the article is written for an S4 there are differences in the cam markings. The photos in his article show what look like a molded in divot in the toothed wheel that drives the cam, which should line up with a molded in arrow on a plate behind the drive wheel. On my car, there's an arrow, but no divot in the wheel, just what looks like a black permanent ink mark on the wheel. On the left cam (driver) the mark is about 2.5 teeth clockwise of the arrow, on the right cam it's about the same.
What's the best way to deal with this? Should I remove the belt and reset the cams with the crank at 0?
Thanks for any advice,
Scott.
I'm using John Pirtle's most excellent article on replacing the timing belt on my '85 S. I've gotten to the step where I hand crank the engine to 0 TDC and check the timing marks on the cam drive wheels, and mine don't line up. John doesn't mention what a person should do in this circumstance, I guess he assumed the marks would line up (who wouldn't?)
Because the article is written for an S4 there are differences in the cam markings. The photos in his article show what look like a molded in divot in the toothed wheel that drives the cam, which should line up with a molded in arrow on a plate behind the drive wheel. On my car, there's an arrow, but no divot in the wheel, just what looks like a black permanent ink mark on the wheel. On the left cam (driver) the mark is about 2.5 teeth clockwise of the arrow, on the right cam it's about the same.
What's the best way to deal with this? Should I remove the belt and reset the cams with the crank at 0?
Thanks for any advice,
Scott.
04-06-2012, 08:26 PM
#2
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Hey Scott,
Well I bought Porken's timing setup kit and his bump stick which makes this job easy. I believe the way to go is to set the mark on the drivers side spot on, and turn the mark on the pass side one notch inside to the right. Then after things settle down, you will find it pretty close to 0 on both sides. You can really see this with Ken's gauge on the gear. That mark on the pass side is just off. I found that mine was one tooth off before I could even think of setting the detailed timing. I highly recommend Ken's setup which I think you can get from Roger. Not too much $$$ for the time and peice of mind it will bring.
Best of luck,
Well I bought Porken's timing setup kit and his bump stick which makes this job easy. I believe the way to go is to set the mark on the drivers side spot on, and turn the mark on the pass side one notch inside to the right. Then after things settle down, you will find it pretty close to 0 on both sides. You can really see this with Ken's gauge on the gear. That mark on the pass side is just off. I found that mine was one tooth off before I could even think of setting the detailed timing. I highly recommend Ken's setup which I think you can get from Roger. Not too much $$$ for the time and peice of mind it will bring.
Best of luck,
04-06-2012, 08:32 PM
#3
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If you have an early '85 with original 00 cam gears you will only have a small notch on the back of the gears. The front indent starts in '86.
The small rear notch should normally be close, within ±1/2 tooth, of the Λ on the rear cover.
If the gears have been loosened at some point, then it may not be a true indicator, however.
Check that the distributor rotor bolt holes are roughly centered in the cam gear slots. And/or use a PK32V'r to verify.
Note that late '85 have 01 gears, but only the driver's side revised cover.
The small rear notch should normally be close, within ±1/2 tooth, of the Λ on the rear cover.
If the gears have been loosened at some point, then it may not be a true indicator, however.
Check that the distributor rotor bolt holes are roughly centered in the cam gear slots. And/or use a PK32V'r to verify.
Note that late '85 have 01 gears, but only the driver's side revised cover.
04-06-2012, 08:46 PM
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Ken, I think that loosening the gears will only move the camshafts....not the gears in relationship to the timing marks on the aluminum housing pieces.
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greg brown
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Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
Free consultations will no longer be available.
Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
greg brown
714 879 9072
GregBBRD@aol.com
Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
Free consultations will no longer be available.
Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
04-06-2012, 11:14 PM
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Burning Brakes
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Hey Scott,
Well I bought Porken's timing setup kit and his bump stick which makes this job easy. I believe the way to go is to set the mark on the drivers side spot on, and turn the mark on the pass side one notch inside to the right. Then after things settle down, you will find it pretty close to 0 on both sides. You can really see this with Ken's gauge on the gear. That mark on the pass side is just off. I found that mine was one tooth off before I could even think of setting the detailed timing. I highly recommend Ken's setup which I think you can get from Roger. Not too much $$$ for the time and peice of mind it will bring.
Best of luck,
Well I bought Porken's timing setup kit and his bump stick which makes this job easy. I believe the way to go is to set the mark on the drivers side spot on, and turn the mark on the pass side one notch inside to the right. Then after things settle down, you will find it pretty close to 0 on both sides. You can really see this with Ken's gauge on the gear. That mark on the pass side is just off. I found that mine was one tooth off before I could even think of setting the detailed timing. I highly recommend Ken's setup which I think you can get from Roger. Not too much $$$ for the time and peice of mind it will bring.
Best of luck,
Regards,
Scott.
04-06-2012, 11:18 PM
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Burning Brakes
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Hello Ken -
Thanks for the reply, I looked at the marks and the rear notches on both gears are about 1 tooth off to the counterclockwise.
Frank mentioned a "kit" you sell to deal with this? What does it do and how might I order one?
Regards,
Scott.
Thanks for the reply, I looked at the marks and the rear notches on both gears are about 1 tooth off to the counterclockwise.
Frank mentioned a "kit" you sell to deal with this? What does it do and how might I order one?
Regards,
Scott.
04-06-2012, 11:49 PM
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"If the gears have been loosened at some point, then {the cam gear notch position, vis-à-vis the Λ} may not be a true indicator {of the camshaft position/valve timing}, however."
More info, and manuals here - http://liftbars.com
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04-07-2012, 01:03 AM
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It is odd that the front marks are not on the 85 motors. I have several 85 motors and they all have the front marks.
On setting the belt I find it is easy to be one tooth off the first time around especially on the right cam pulley. It is also common for them not to be exact. Cam timing will move the marks closer. Of course I do the dial indicator method.
On setting the belt I find it is easy to be one tooth off the first time around especially on the right cam pulley. It is also common for them not to be exact. Cam timing will move the marks closer. Of course I do the dial indicator method.
04-07-2012, 01:05 AM
#9
It's never a good idea to deal with the front marks, there is a 8-10 degree spread over those front spaces.
04-07-2012, 02:27 AM
#10
Burning Brakes
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My guess is the front felt tip marks are from an earlier belt replacement.
04-07-2012, 03:29 AM
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Afforementioned statement revised for enhanced clarity, Greg.
"If the gears have been loosened at some point, then {the cam gear notch position, vis-à-vis the Λ} may not be a true indicator {of the camshaft position/valve timing}, however."
Scott, Roger at 928sRUs.com, or Carl at 928Motorsports.com, sell the PK32V'r cam timing tool 'kit'.
More info, and manuals here - http://liftbars.com
"If the gears have been loosened at some point, then {the cam gear notch position, vis-à-vis the Λ} may not be a true indicator {of the camshaft position/valve timing}, however."
Scott, Roger at 928sRUs.com, or Carl at 928Motorsports.com, sell the PK32V'r cam timing tool 'kit'.
More info, and manuals here - http://liftbars.com
After reading the liftbars ref and the manuals for both the PK32VR's and the PKBumpStick I'm convinced these tools will do the job I need done. Now my question is, where to get them? The two sources at liftbars show 928's R Us supplying both, but visiting their website I only find the PK32V'r, no BumpStick.
Is the BumpStick included with the PK32V'r now (web site doesn't say). It seems like it would make sense.
Thanks,
Scott.
04-07-2012, 10:06 AM
#12
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Hey Scott,
Call Roger, he doesn't have his new website up yet. He can get you just about anything you will need for a 928 but it doesn't show on his website. Spoke with them yesterday and they have a new one on the way. He got my bump stick and timing tool to me in just a couple of days.
Good luck and you are right to listen to Ken, he is da man when it comes to this stuff.
Call Roger, he doesn't have his new website up yet. He can get you just about anything you will need for a 928 but it doesn't show on his website. Spoke with them yesterday and they have a new one on the way. He got my bump stick and timing tool to me in just a couple of days.
Good luck and you are right to listen to Ken, he is da man when it comes to this stuff.
04-07-2012, 08:24 PM
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Hey Frank -
I called Roger and left a message. The more I look at this the more confused I get. The manual says to turn the Crank to 45 TDC before trying to turn the cams, but since my cams aren't marked at 45 I have no clue as to how I'd time them right with the crank at that position. I'm terrified of crashing my heads if I try moving the cams even a little with the Crank at 0. PorKen's manual doesn't seem to address this question, looks like the tool assume everything is done at 0.
On a similar note, does anyone have any idea how to get the timing belt off a 32 valve engine without pulling the vibration damper off the crank? I can't see any other way to get the belt off. I assume I'd need a big gear puller to get the vibration damper off if that's what needs to happen, but then there's the problem of getting it back on in exactly the same position to keep from screwing up the cylinder indicators etched into it.
Am I missing something really obvious? The manual doesn't say a word about this problem, just "Remove toothed-belt from right-hand side over cylinder 1 - 4 camshaft sprocket, water-pump sprocket, cylinder 5 - 8 cam- shaft sprocket, oil-pump sprocket and crankshaft sprocket." Like it was clear as crystal and so obvious it requires no further explanation. I hate Porsche factory manuals.
I called Roger and left a message. The more I look at this the more confused I get. The manual says to turn the Crank to 45 TDC before trying to turn the cams, but since my cams aren't marked at 45 I have no clue as to how I'd time them right with the crank at that position. I'm terrified of crashing my heads if I try moving the cams even a little with the Crank at 0. PorKen's manual doesn't seem to address this question, looks like the tool assume everything is done at 0.
On a similar note, does anyone have any idea how to get the timing belt off a 32 valve engine without pulling the vibration damper off the crank? I can't see any other way to get the belt off. I assume I'd need a big gear puller to get the vibration damper off if that's what needs to happen, but then there's the problem of getting it back on in exactly the same position to keep from screwing up the cylinder indicators etched into it.
Am I missing something really obvious? The manual doesn't say a word about this problem, just "Remove toothed-belt from right-hand side over cylinder 1 - 4 camshaft sprocket, water-pump sprocket, cylinder 5 - 8 cam- shaft sprocket, oil-pump sprocket and crankshaft sprocket." Like it was clear as crystal and so obvious it requires no further explanation. I hate Porsche factory manuals.
04-07-2012, 08:36 PM
#14
Burning Brakes
Mark your cams with a marker when the crank is at 45 degrees. Based on what you have done so far you should know how much each cam needs to be moved as you reinstall the belt.
If I understand correctly you have the belt on just the cams are about 1 tooth off. If that is the case you can back off the tensioner, remove the belt from the right hand sprocket, then the left cam sprocket. Move the left cam 1 tooth and install the belt making sure that the entire time you keep the belt tight on the leading side, keep all the slack you can out of the belt and rethread onto the right cam sprocket, again with the cam indexed 1 tooth from you mark. Then retension the belt. Crank the engine over by hand at least two revolutions and check your TDC cam timing marks.
I know it can be a pain to keep tension on the belt and keep the cams from snapping out of place but with some patience it is not all that hard.
If you are cranking by hand and are within 1 tooth of correct cam timing you will not damage any valves.
Good luck.
If I understand correctly you have the belt on just the cams are about 1 tooth off. If that is the case you can back off the tensioner, remove the belt from the right hand sprocket, then the left cam sprocket. Move the left cam 1 tooth and install the belt making sure that the entire time you keep the belt tight on the leading side, keep all the slack you can out of the belt and rethread onto the right cam sprocket, again with the cam indexed 1 tooth from you mark. Then retension the belt. Crank the engine over by hand at least two revolutions and check your TDC cam timing marks.
I know it can be a pain to keep tension on the belt and keep the cams from snapping out of place but with some patience it is not all that hard.
If you are cranking by hand and are within 1 tooth of correct cam timing you will not damage any valves.
Good luck.
04-07-2012, 09:07 PM
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Roger, thanks for clearing that up, I was starting to think that's the way it had to work. I can't really mark the cams with the crank at 45 because they aren't timed right at 0, which is what I'm trying to correct.
Look at it this way: with the Crank at 0 TDC, the marks on the cam gears don't line up with the arrow on the back cam belt cover. The DS cam is only off by a tooth or two, the PS is off by about 5 teeth.
It sounds like my best bet would be to lock the crank at 45, take off the belt, move the cams as close as I can to 0, unlock the crank, move it to 0, put the belt back on while going through the pre-load procedure you describe to get the cams as close to dead on 0 as I can.
After that, I expect I use PorKens precision cam timing tool to get it absolutely right.
All this assumes I can figure out how to get the belt off. I'm still stumped on that one. I can't figure out how to get it of without taking the vibration damper off the crank and there's no procedure for that I can find in the manual.
Look at it this way: with the Crank at 0 TDC, the marks on the cam gears don't line up with the arrow on the back cam belt cover. The DS cam is only off by a tooth or two, the PS is off by about 5 teeth.
It sounds like my best bet would be to lock the crank at 45, take off the belt, move the cams as close as I can to 0, unlock the crank, move it to 0, put the belt back on while going through the pre-load procedure you describe to get the cams as close to dead on 0 as I can.
After that, I expect I use PorKens precision cam timing tool to get it absolutely right.
All this assumes I can figure out how to get the belt off. I'm still stumped on that one. I can't figure out how to get it of without taking the vibration damper off the crank and there's no procedure for that I can find in the manual.