Intro and TDC verification (sanity check)
02-20-2012, 12:57 PM
#1
Instructor
Thread Starter
Intro and TDC verification (sanity check)
Hi,
First time poster (premium member as of today) six month lurker. I bought an 87 951 from my friend at work after he bumped a girl in the rear (cough). I repaired the cosemetic damage and although it needs paint for the most part it is in pretty darn good mechanical condition. The first thing I did was change the steering bushings and broke a couple of bolts in the process but- eventually it came together. I have decided I am going to spiff it all up and clean/inspect and replace a lot of items with performance stuff although I am not going to take the car too far out of stock (I call it "no diameter increase" rule). A little background on myself... I am mostly a computer/electronic tech although I have spent time in the navy and in powerplants and have broken down some pretty badass machines, but I have never done a whole lot with a car but do understand the mechanical concepts etc involved. I have gone down the rabbit hole of "while I'm there I might as well _____" to significant degree and doing a lot of cleaning at the same time... Mostly because I had to change the brake booster. I've got that back on but I also took the heat shield out and got the manifold and fuel rail off. I have sent the injectors off to be cleaned/refirbished by witchhunter and I ordered Lindey's fuel rail with remote regulator. I also have a mirror finished maniflod and pipes waiting for the reassembly... replaced all the coolant hoses... I got new brake lines and found 4 stock rotors that measured to brand new thickeness which I've had machined and they're also going on soon (140 bucks final cost, can't beat it)...
So... what I want to do is pull the cam box off so I can (attempt to) polish it with a kit that I bought. I did some preliminary steps but thought that I screwed up (I moved it a few degrees by accident but set it back to some marks I made on the belt) and was wanting to check for TDC again. I performed all the checks and have the car at TDC now according to both the flywheel indications - the one under the car and also the one on top. Now my cam looks like this:
It's a little off but I've seen that this is ok.. still for my own sanity- is this OK? The red is the machined indication; the green and black are just some belt makers I put on there also. I think doing th timing belt is a bit advanced for me right now but do I need to lock the crank to remove the cam tower? It doesn' tmove without some pretty deliberate effort. as long as I don't spin the cam while it's off the car, I should be ok.... >.> <.<
This is the car:
First time poster (premium member as of today) six month lurker. I bought an 87 951 from my friend at work after he bumped a girl in the rear (cough). I repaired the cosemetic damage and although it needs paint for the most part it is in pretty darn good mechanical condition. The first thing I did was change the steering bushings and broke a couple of bolts in the process but- eventually it came together. I have decided I am going to spiff it all up and clean/inspect and replace a lot of items with performance stuff although I am not going to take the car too far out of stock (I call it "no diameter increase" rule). A little background on myself... I am mostly a computer/electronic tech although I have spent time in the navy and in powerplants and have broken down some pretty badass machines, but I have never done a whole lot with a car but do understand the mechanical concepts etc involved. I have gone down the rabbit hole of "while I'm there I might as well _____" to significant degree and doing a lot of cleaning at the same time... Mostly because I had to change the brake booster. I've got that back on but I also took the heat shield out and got the manifold and fuel rail off. I have sent the injectors off to be cleaned/refirbished by witchhunter and I ordered Lindey's fuel rail with remote regulator. I also have a mirror finished maniflod and pipes waiting for the reassembly... replaced all the coolant hoses... I got new brake lines and found 4 stock rotors that measured to brand new thickeness which I've had machined and they're also going on soon (140 bucks final cost, can't beat it)...
So... what I want to do is pull the cam box off so I can (attempt to) polish it with a kit that I bought. I did some preliminary steps but thought that I screwed up (I moved it a few degrees by accident but set it back to some marks I made on the belt) and was wanting to check for TDC again. I performed all the checks and have the car at TDC now according to both the flywheel indications - the one under the car and also the one on top. Now my cam looks like this:
It's a little off but I've seen that this is ok.. still for my own sanity- is this OK? The red is the machined indication; the green and black are just some belt makers I put on there also. I think doing th timing belt is a bit advanced for me right now but do I need to lock the crank to remove the cam tower? It doesn' tmove without some pretty deliberate effort. as long as I don't spin the cam while it's off the car, I should be ok.... >.> <.<
This is the car:
Last edited by miragezero; 02-20-2012 at 01:43 PM.
02-20-2012, 01:08 PM
#2
Rennlist Member
The marking under the rear should only be an estimate (set it in the center), the true marking you should following is on top of the bellhousing by the speed/ref sensors.
http://clarks-garage.com/shop-manual/eng-13.htm
http://clarks-garage.com/shop-manual/eng-13.htm
02-20-2012, 02:23 PM
#4
Rennlist Member
Welcome to rennlist!
Let's see, if the top TDC mark (shown in the picture above) is lined up perfectly, then I'd say your cam wheel is one tooth off. If you did not remove or loosen the belt, then chances are the last guy to change the belt missed by a tooth. Being one tooth off will change your cam timing but is close enough to avoid valve-piston contact. I'd fix that for sure. To fix it, you will need to have a way to tension the belt properly. Porsche sells a $400 gauge for setting the tension to their specs. There are also a few aftermarket tensioner tools for this car, along with endless debate about whether they are good enough. In order to fix the timing, or remove the cam tower, the belt needs to be loosened and re-tensioned. Might as well put on a new belt at that point. No need to lock the flywheel to remove the cam tower. One great resource is www.clarks-garage.com -- it has complete details on retensioning the belts and removing the tower, etc.
Let's see, if the top TDC mark (shown in the picture above) is lined up perfectly, then I'd say your cam wheel is one tooth off. If you did not remove or loosen the belt, then chances are the last guy to change the belt missed by a tooth. Being one tooth off will change your cam timing but is close enough to avoid valve-piston contact. I'd fix that for sure. To fix it, you will need to have a way to tension the belt properly. Porsche sells a $400 gauge for setting the tension to their specs. There are also a few aftermarket tensioner tools for this car, along with endless debate about whether they are good enough. In order to fix the timing, or remove the cam tower, the belt needs to be loosened and re-tensioned. Might as well put on a new belt at that point. No need to lock the flywheel to remove the cam tower. One great resource is www.clarks-garage.com -- it has complete details on retensioning the belts and removing the tower, etc.
02-20-2012, 02:43 PM
#5
^ +1 Tom is right on the money.
FWIW, I've used about every tension measuring/adjustment tool out there including the [very spendy] factory tool. The Arnworx tool is by far the most reliable and repeatable IMHO.
http://www.arnnworx.com/catalog/inde...dbff2dc8b93e03
Depending on your location [update your profile??] there's a decent chance that you'll find a Rennlister locally who may even have one you can use.
FWIW, I've used about every tension measuring/adjustment tool out there including the [very spendy] factory tool. The Arnworx tool is by far the most reliable and repeatable IMHO.
http://www.arnnworx.com/catalog/inde...dbff2dc8b93e03
Depending on your location [update your profile??] there's a decent chance that you'll find a Rennlister locally who may even have one you can use.
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02-20-2012, 05:12 PM
#9
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Well, I have a flywheel lock, if you feel you need it. I would use it, for CERTAIN, if you are going to do the T-belt. I'm about to do my early spring work, so I'll need it back in the next 2 weeks.