Cam Timing Question - tensioning timing belt
Thread Starter
Three Wheelin'
Joined: Dec 2001
Posts: 1,424
Likes: 3
From: Florida
Cam Timing Question - tensioning timing belt
I am tensioning my timing belt. The light cam on twice in the last month in spirited driving, and I don't want to take a chance.
Bottom line is that belt alignment is good, no marks on the belt, it looks and feels like new even though it is about 4 years old. According to the tool, it is on spec, but just barely. It is on the limit of the loose side of the adjustment window. I will tighten it slightly, but before I do I need some info on the following.
My question is relating to finding TDC on the compresion stroke. When I have perfect alignment between the notch in the passenger side cam sprocket and the pointer on the cam housing, the 0 BTDC mark on the harmonic balancer is about 1/4 to 3/8 inch 'past' the pointer. When I say 'past', I mean going clockwise, like engine rotation. Does this mean that my cam timing is slightly retarded? What is spec regarding how precise these alignments should be? Am I losing power due to this?
Your advice is appreciated.
Thanks
Bottom line is that belt alignment is good, no marks on the belt, it looks and feels like new even though it is about 4 years old. According to the tool, it is on spec, but just barely. It is on the limit of the loose side of the adjustment window. I will tighten it slightly, but before I do I need some info on the following.
My question is relating to finding TDC on the compresion stroke. When I have perfect alignment between the notch in the passenger side cam sprocket and the pointer on the cam housing, the 0 BTDC mark on the harmonic balancer is about 1/4 to 3/8 inch 'past' the pointer. When I say 'past', I mean going clockwise, like engine rotation. Does this mean that my cam timing is slightly retarded? What is spec regarding how precise these alignments should be? Am I losing power due to this?
Your advice is appreciated.
Thanks
Three Wheelin'
Joined: Sep 2006
Posts: 1,269
Likes: 107
From: Arvada, CO
My question is relating to finding TDC on the compresion stroke. When I have perfect alignment between the notch in the passenger side cam sprocket and the pointer on the cam housing, the 0 BTDC mark on the harmonic balancer is about 1/4 to 3/8 inch 'past' the pointer. When I say 'past', I mean going clockwise, like engine rotation. Does this mean that my cam timing is slightly retarded? What is spec regarding how precise these alignments should be? Am I losing power due to this?
Matt
Three Wheelin'
Joined: Jan 2007
Posts: 1,466
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From: not where you think I am
from reading your signature (read: BLOWER), and your time statement of "it's been four years", I personally would not bother with trying to straighten up the timing issues at this point.
I would go ahead on do a timing belt/water pump replacement NOW, if not sooner.
As for your balancer not lining up perfectly, you may also have a "tired" balancer that has slipped the donut on the main part of the balancer. A new balancer is not necessarily mandated (or you can use timing balancer tape, available at any "speed shop"), but you should at the very least find top dead center on #1 and see where it lines up on the timing indicator. If it doesn't line up perfectly, you've got a bad balancer. That spells trouble.....
---Russ
I would go ahead on do a timing belt/water pump replacement NOW, if not sooner.
As for your balancer not lining up perfectly, you may also have a "tired" balancer that has slipped the donut on the main part of the balancer. A new balancer is not necessarily mandated (or you can use timing balancer tape, available at any "speed shop"), but you should at the very least find top dead center on #1 and see where it lines up on the timing indicator. If it doesn't line up perfectly, you've got a bad balancer. That spells trouble.....
---Russ
Rennlist Member
Joined: Oct 2003
Posts: 7,210
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From: Nova Scotia
Probably best to pull both cam covers ... and #1 plug: now you can read the full story as the crank is rotated to index ( all) the marks.
A wood or plastic dowel inserted into #1 plug is a crude but effective indicator of correlating piston TDC to the crank index mark: if that checks out, odds are that the left cam will index correctly .... and the right cam will be off a tooth; however, I digress
, for the outcome should not be anticipated until you do the check.
Anyway, the little digression had a purpose: if it turns out that the indexing is off, it is not a huge amount of extra work to pull the harmonic balancer and check the gears, idlers & rollers .... and string on a fresh belt.
Cheers, Garth
A wood or plastic dowel inserted into #1 plug is a crude but effective indicator of correlating piston TDC to the crank index mark: if that checks out, odds are that the left cam will index correctly .... and the right cam will be off a tooth; however, I digress
, for the outcome should not be anticipated until you do the check.Anyway, the little digression had a purpose: if it turns out that the indexing is off, it is not a huge amount of extra work to pull the harmonic balancer and check the gears, idlers & rollers .... and string on a fresh belt.
Cheers, Garth
Thread Starter
Three Wheelin'
Joined: Dec 2001
Posts: 1,424
Likes: 3
From: Florida
I appreciate the advice, but not the extra work. I wanted this to be a quick job to be out driving agian. I guess I will have to check the passenger side cam as well and report back.
Another Q - what would the symptoms of a bad balancer be?
Another Q - what would the symptoms of a bad balancer be?
Addict
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From: Helsinki, Finland
Based on several measurements alarm will come on at 4ish while correct window is 5.0-5.3 on factory special tool 9201.
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Michael S. Palmer
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From: Nova Scotia
I can't tell squat from pic #3 - but the pointer should be smack on the "/" of O/T. To my eyes, it appears that the small dimple notched on the backside valley of each cam wheel lies smack on the center of a radial line joining the cam center to the backplate index: if that is the case, you are dead on time .... and need only to retension the belt.
If using the Kempf version of tool 9131, set the tension to the higher side of the window when @TDC ... rotate two full turns, and reconfirm.
.... and need only to retension the belt.If using the Kempf version of tool 9131, set the tension to the higher side of the window when @TDC ... rotate two full turns, and reconfirm.
Drifting
Joined: Nov 2001
Posts: 2,233
Likes: 1
From: zürich, switzerland
Looks like both the cam gears are on time to me too - but it maybe that they look different if the foto were taken either from directly above or lower down & level with the cam gear periphery.
Myself I check the cam gear timing by sliding a thin screw driver between the 2 teeth nearest to the mark on the gear & then checking where the screwdriver touches the motor.
Marton
Myself I check the cam gear timing by sliding a thin screw driver between the 2 teeth nearest to the mark on the gear & then checking where the screwdriver touches the motor.
Marton
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From: Florida
I would turn it over again to be right on TDC. Then check the cam marks again and tension, turn again... check again...
I remember, mine looked the same. It was not perfectly aligned...
I remember, mine looked the same. It was not perfectly aligned...
Addict
Rest In Peace
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Rest In Peace
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Joined: Jul 2002
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From: Glen Mills, PA
All of the previous advise is excellent. But, you said "According to the tool, it is on spec, but just barely. It is on the limit of the loose side of the adjustment
window".
If you are using the Kemph tool, then you are way loose. That tool was designed for the early 16valve engines. On 32 valve engines, the tool has to be all the way on the tight side of the window to get even close to the proper tension. That is why Porsche released the 9201 tool.
window".
If you are using the Kemph tool, then you are way loose. That tool was designed for the early 16valve engines. On 32 valve engines, the tool has to be all the way on the tight side of the window to get even close to the proper tension. That is why Porsche released the 9201 tool.
Thread Starter
Three Wheelin'
Joined: Dec 2001
Posts: 1,424
Likes: 3
From: Florida
OK, I am feeling better.
I went at the problem differently. Rather than aligning the notch on the passenger side cam sprocket, and the checking status of drivers side cam and crank position, I aligned the crank first.
So with the crank at precisely the line between the O and T, I checked the location of the cam sprockets against the notches. The driver's side is almost exact and the passenger's side is off by less than 1/2 a sprocket. It is closest to the sprocket that holds the notch. In other words, the belt is not off by one tooth. It is off by less than 1/2 of one tooth, and it is on the correct side ( the closest side to being in perfect alignment).
I hope this makes sense.
I have retensioned just slightly to the tighter side of middle of spec and I am going to butten her up.
thanks for all of the help.
I went at the problem differently. Rather than aligning the notch on the passenger side cam sprocket, and the checking status of drivers side cam and crank position, I aligned the crank first.
So with the crank at precisely the line between the O and T, I checked the location of the cam sprockets against the notches. The driver's side is almost exact and the passenger's side is off by less than 1/2 a sprocket. It is closest to the sprocket that holds the notch. In other words, the belt is not off by one tooth. It is off by less than 1/2 of one tooth, and it is on the correct side ( the closest side to being in perfect alignment).
I hope this makes sense.
I have retensioned just slightly to the tighter side of middle of spec and I am going to butten her up.
thanks for all of the help.
Burning Brakes
Joined: May 2006
Posts: 809
Likes: 0
From: Portland, Oregon
I don't remember ever hearing or reading this. Excellent info.
Jim
Jim
All of the previous advise is excellent. But, you said "According to the tool, it is on spec, but just barely. It is on the limit of the loose side of the adjustment
window".
If you are using the Kemph tool, then you are way loose. That tool was designed for the early 16valve engines. On 32 valve engines, the tool has to be all the way on the tight side of the window to get even close to the proper tension. That is why Porsche released the 9201 tool.
window".
If you are using the Kemph tool, then you are way loose. That tool was designed for the early 16valve engines. On 32 valve engines, the tool has to be all the way on the tight side of the window to get even close to the proper tension. That is why Porsche released the 9201 tool.