Valvetrain Inspection
#61
Three Wheelin'
Join Date: Jul 2001
Location: San Francisco, CA Porsche: '92 968 Blk/Cashmere
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If you shave the head or use a different thickness head gasket or do anything to alter the distance between the crank center and cam gear center you need a bit of adjustability in the cam gear to get the cam timing set back to stock settings.
#62
RL Community Team
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Thanks Chris, that totally makes sense.
So older cars like 944s where the cam sprocket only goes on one way, they are just lacking this adjustability?
So older cars like 944s where the cam sprocket only goes on one way, they are just lacking this adjustability?
#63
Addict
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You're right about the cam cover bolts being fragile and expensive to replace. Knowing this, I "woke up" each bolt by putting the tool snugly inside each bolt head and tapping it lightly with a hammer. Also, I put a little spray lube around each head bolt thinking that every foot pound might make a difference. They came out without problem but they didn't come easily. I was lucky than none broke.
When replacing 968 bolts, you should (!) use a good torque wrench that works for low foot pounds (not one designed for lug nuts) and torque to spec. In fact, given the aluminum you're dealing with, all bolts should be carefully tightened using a torque wrench. If you're used to working on a steel block engine and tightening by "feel" I predict you'll break or strip a few bolts. It's too easy to over-torque. Extracting a steel bolt from an aluminum block is not a piece of cake.
At the time I changed out the cam belt, rollers, tensioner, etc. (pre-emptive work as I didn't have proof positive of when this work was done....at any rate the shop receipt said 25,000 miles so I just changed them out to be safe).
At the same time, I pulled the cam cover to replace the cam chain and tensioner pads, etc. In fact, I bought the parts to do this before pulling the cover. This was after reading the cam chain/tensioner "war stories" (some pics of worn cam gears are scary). However, when I opened it up, the tensioner pads and chain looked virtually new (no sign of wear) and the cam gear teeth were pristine, so I closed it back up.
Good luck.
H2
When replacing 968 bolts, you should (!) use a good torque wrench that works for low foot pounds (not one designed for lug nuts) and torque to spec. In fact, given the aluminum you're dealing with, all bolts should be carefully tightened using a torque wrench. If you're used to working on a steel block engine and tightening by "feel" I predict you'll break or strip a few bolts. It's too easy to over-torque. Extracting a steel bolt from an aluminum block is not a piece of cake.
At the time I changed out the cam belt, rollers, tensioner, etc. (pre-emptive work as I didn't have proof positive of when this work was done....at any rate the shop receipt said 25,000 miles so I just changed them out to be safe).
At the same time, I pulled the cam cover to replace the cam chain and tensioner pads, etc. In fact, I bought the parts to do this before pulling the cover. This was after reading the cam chain/tensioner "war stories" (some pics of worn cam gears are scary). However, when I opened it up, the tensioner pads and chain looked virtually new (no sign of wear) and the cam gear teeth were pristine, so I closed it back up.
Good luck.
H2
#64
RL Community Team
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Good points, H.
Everyone who is going to do the VarioCam R&R should have a good inch-pound torque wrench. Normal 3/8" torque wrenches have a minimum setting of 15 ftlbs, and many bolts you will work with need to be set to 7 ftlbs. Inch pound torque wrenches typically go from like 40 inlbs (3.33 lbfts)to 200 inlbs (16.67 ftlbs).
EDIT: I meant "Normal 1/2 in torque wrenches" not 3/8 in
Everyone who is going to do the VarioCam R&R should have a good inch-pound torque wrench. Normal 3/8" torque wrenches have a minimum setting of 15 ftlbs, and many bolts you will work with need to be set to 7 ftlbs. Inch pound torque wrenches typically go from like 40 inlbs (3.33 lbfts)to 200 inlbs (16.67 ftlbs).
EDIT: I meant "Normal 1/2 in torque wrenches" not 3/8 in
Last edited by FRporscheman; 01-31-2008 at 03:14 PM.
#65
Burning Brakes
Join Date: Mar 2007
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Sheesh. This sounds like brain surgery. Or surgery near your ding-dong.
While fixing the head gasket on my Neon 2years ago I learned about being delicate with head bolts. I broke 2 bolts (which the local "pick n pull" had) and striped two others. It seems no matter what car you work on you have to be very careful with head work.
While fixing the head gasket on my Neon 2years ago I learned about being delicate with head bolts. I broke 2 bolts (which the local "pick n pull" had) and striped two others. It seems no matter what car you work on you have to be very careful with head work.
#66
RL Community Team
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Care and caution are always good. This job is tedious but straightforward; you need to be careful, but it's very doable.
Remember that Porsche is better than the competition because they are robust and they are comparatively easy to work on. If a camshaft removal gets you flustered just be glad you're not wrenching on an f-car.
Remember that Porsche is better than the competition because they are robust and they are comparatively easy to work on. If a camshaft removal gets you flustered just be glad you're not wrenching on an f-car.
#67
Rennlist Member
Good points, H.
Everyone who is going to do the VarioCam R&R should have a good inch-pound torque wrench. Normal 3/8" torque wrenches have a minimum setting of 15 ftlbs, and many bolts you will work with need to be set to 7 ftlbs. Inch pound torque wrenches typically go from like 40 inlbs (3.33 lbfts)to 200 inlbs (16.67 ftlbs).
Everyone who is going to do the VarioCam R&R should have a good inch-pound torque wrench. Normal 3/8" torque wrenches have a minimum setting of 15 ftlbs, and many bolts you will work with need to be set to 7 ftlbs. Inch pound torque wrenches typically go from like 40 inlbs (3.33 lbfts)to 200 inlbs (16.67 ftlbs).
3/8 5ftlbs to 75ftlbs
1/2 50ftlbs to 250ftlbs
They cover most Porsche jobs except the rear hub nut. I think that is the only part that uses over 250 ftlbs of torque. Most Porsche nuts/bolts are very high quality. You can get the exhaust nuts/bolts out after 15 yrs of heat cycles without breaking them. It all depends on how good a contact you make and how much rust/corrosion they have endeared.
Raj
#68
Three Wheelin'
Join Date: Jul 2001
Location: San Francisco, CA Porsche: '92 968 Blk/Cashmere
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#71
RL Community Team
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I have one snap on tool. Just one. And it happens to be a 3/8 torque wrench, but it only goes down to 16 lb*ft. Strange!
For the rear axle nut I just calculate how long of a lever would produce 350 lbft with my body weight of 200lbs. Then I stand on the wrench+pipe until it stops turning. I think this works?
For the rear axle nut I just calculate how long of a lever would produce 350 lbft with my body weight of 200lbs. Then I stand on the wrench+pipe until it stops turning. I think this works?
#73
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#74
Racer
All right guys, what's the trick on getting the cam gear off the cam. Seemed to hit a brick wall. I do have the cam gear rebolted to the zinc plate and scribed. And of course the cam gear bolt is removed(almost stripped it). Do I need a puller? Should I unbolt it from the zinc plate and try it that way?
Kevin
Kevin
#75
Rennlist Member
Kevin, try some PB blaster. The water/moisture gets in there and makes it a little tight. All you need is to soak it with a penetrant and it should slide off in a few minutes. Don't try to force it, it should slide off once you spray something. You also might want to give some love taps in the area to break the pulley loose. I always try to turn it clockwise and anticlockwise to break the jam.
Raj
Raj