Cameron

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

leperboy

My understanding is that the tension light is designed to go on while the belt is still in the tension window, but on the loose end, so it sounds right.


That sounds like it's off by a tooth, which I think is something like 7-8 degrees and that is enough to affect performance. You can line it up at BTDC and see where the notch lines up. If you can, check the other cam gear too and see if it lines up or if it is off by the same amount. If it is a full tooth on the passenger side, I think it would be good to do a timing belt job a little earlier than planned.

Matt

largecar379

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

Garth S

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

Cameron

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?

Vilhuer

Based on several measurements alarm will come on at 4ish while correct window is 5.0-5.3 on factory special tool 9201.

Cameron

Here are the pics. I hope they turn out.

In order of Passerngers side cam marking, driver's side cam marking and the TDC marking.

the flyin' scotsman

Both cams are out what looks like 1 notch.......retarded.

Re-string the tbelt or replace with new and any other rollers, w/p required.

Garth S

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.

Cameron

At the crank (pic three), the pointer is between the O/T marking and the 1/T marking when the passenger cam is dead on notch.

marton

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

Sab

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...

Earl Gillstrom

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.

Cameron

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.

pmotts

I don't remember ever hearing or reading this. Excellent info.
Jim