| Author |
Message |
Trent Carter (Tcarte04)
New member
Username: Tcarte04
Post Number: 27
Registered: 2-2001
| | Posted on Thursday, August 22, 2002 - 3:09 pm: | |
On my 81 308GTBi I went to TDC, and used nothing to hold cams. It went smoothly.
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Edward Gault (Irfgt)
Intermediate Member
Username: Irfgt
Post Number: 1854
Registered: 2-2001
| | Posted on Thursday, August 22, 2002 - 2:24 pm: | |
You can also take two pairs of vise grip locking pliers and clamp onto the cams with the ends of the pliers touching and tie the plier ends together. Works perfectly and no need to remove the valve covers. |
Verell Boaen (Verell)
Member
Username: Verell
Post Number: 262
Registered: 5-2001
| | Posted on Thursday, August 22, 2002 - 1:10 pm: | |
Interesting, I go the other way, lock the cams down & use the crank to get enough slack to get the belts into place.
I made a metal pointer that fits on the alternator bracket.
With the flywheel on the PM1-4 mark, I marked my damper with a small dot of white paint at the end of the pointer. This made it easy to get back to PM1-4. My paint dot/pointer usually gets me to within ~1/8" of lining the flywheel up on PM1-4.
Then I use the following procedure:
1) lock the cams on the marks with cardboard & 2)lock the tensioner in the retracted position.
3)slip the belt over the 3 pulleys.
4)lock the belt in place on the drive pulley w/a pair of 1-1/2" binder clips.
5)Work all the slack out of the non-tensioner belt section and lock the belt in place on the cam pulley w/a pair of 2" binder clips. It's usually necessary to back the crank up about 4-8 degrees (1/3 to 3/4 belt tooth width) to get the belt to slip into place. DO NOT back the crank up until you've got the belts clipped down to the drive pulleys.
6)Repeat for the other belt. (If the crank is backed up for the 1st pulley, leave it backed up until you've got the 2nd belt on.)
7)Rotate the crank forward to align the PM1-4 mark with the pointer. This usually takes the rest of the slack out of the non-tensioned belt section. (Stop turning the crank if you run out of slack before you're back on the mark. You DO NOT want to force the cam to turn against the cardboard brake. If you run out of slack early, then you're going to have to adjust the pulley on the cam using the pin.
8)pull all the slack out of the belt section between the two pulleys, & release the tensioner.
9)Repeat for the other bank.
10)Remove the binder clips & cardboard locks from both banks.
11)Rotate the engine forward 4 turns to PM1-4 & check the cam marks to see if fine adjustments using the pulley pins are needed.
NOTE: Once you've removed the binder clips, If you rotate the engine backwards while the tensioners are floating, a belt will skip grooves on a cam pulley, or even come completely off. Now you've got an engine that isn't on PM1-4, and one or more cams that are in a unknown orientation relative to the crank (Don't ask-DUH).
11)When everything's aligned to your satisfaction, rotate the engine forward noting where the tensioner moves in & out slightly. When a tensioner is in it's most extended position, lock it into place.
This should also work with just marking everything the way Robert suggests. You won't have the cardboard brakes & cam mark alignment steps of course.
BTW, you can do most of this with the tranny in gear & the park brake engaged.
A POSSIBLE TRICK TO EASILY & PRECISELY RE-ESTABLISH PM1-4:
I keep forgetting to try the following before I pull the belts off, It takes 2 people:
1. With the tranny in 5th gear & the parking brake set, rotate the engine forward until all the slack is taken out of the drive train.
2. Have someone depress the clutch & hold it while ou rotate the engine forward to align it on the PM1-4 mark.
3. Once the PM1-4 mark is aligned, the clutch is released.
At this point, the gear train slack will allow the engine to be backed up as described above. When the engine is rotated forward, the gear train should run out of slack just as the engine reaches the PM1-4 mark. This should be verified before pulling the cam belts of course.
It'd be handy to know for sure if this works as it would make it easy to know when you're exactly back on PM1-4. It might take a couple of tries to get the clutch released at exactly the right point.
If anyone tries this & it works, please let us know.
BTW, there's a surprising amount of slack in the drive train. Maybe 15 degrees or so of engine rotation. Probably more or less depending on gear tolerences & wear. |
Robert W. Garven Jr. (Robertgarven)
Junior Member
Username: Robertgarven
Post Number: 69
Registered: 2-2002
| | Posted on Wednesday, August 21, 2002 - 1:01 am: | |
I found that it is easier not to use anything on the gt4 as you need to move the camshafts a little to get the new belts on. I tried the card thing first but have done it several times without it and would suggest using nothing. i marked the cam belts, pulleys, cam seals and shafts with a silver marker. |
jeff ryerson (Atheyg)
New member
Username: Atheyg
Post Number: 2
Registered: 8-2002
| | Posted on Tuesday, August 20, 2002 - 10:44 pm: | |
Thanks for the replies
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Verell Boaen (Verell)
Member
Username: Verell
Post Number: 260
Registered: 5-2001
| | Posted on Tuesday, August 20, 2002 - 9:37 pm: | |
James,
Very interesting. Sounds like a business card would be very close to the right thickness.
I have to admit I've been using a couple of L shapd pieces of cardboard I cut out of a cam belt box. I've only tightened the cam cap down enough so that the valve won't flip the cam out of place. The cardboard ends up moulded to the shape of the cam and cam cap. It's squeezed thinner at the ends of the cap & is still almost full thickness in the middle. I can see how torqueing the cam cap down might break it.
I came up with the L shape because I wanted to make darned sure that I wouldn't put a cam cover on with the cardboard under a cap. The L has a ~1.5" short leg that fits under the cap, and about a 5" long leg that sticks out over the cam cover flange. No way could you miss it when installing the cover... Each leg is about 1" wide.
I guess I'll keep using it, but will be real careful about how much torque I use. |
James Selevan (Jselevan)
Junior Member
Username: Jselevan
Post Number: 71
Registered: 6-2002
| | Posted on Tuesday, August 20, 2002 - 1:42 pm: | |
Terry - a match book cover is a bit thick. You run the risk of cracking the cam cap when you tighten it down on the match book cover. I have used, and it has been taught to me by experienced Ferrari mechanics, a simple piece of paper folded once. Cut the paper approximately 1 inch wide by 6 inches long. Fold it, and place it under the cam cap. Tighten gently until snug. You do not have to go to torque specification. This is merely to hold the cam while you take the belts off. For safety, you might do this on two caps to insure the necessary friction. I have seen a mechanic use a card from a deck of cards, cut to the same width. With two caps thus secured, I have seen the bolt removed from the end of a Dino cam, attesting to the friction thus created.
Jim Selevan |
Terry Springer (Tspringer)
Junior Member
Username: Tspringer
Post Number: 231
Registered: 4-2002
| | Posted on Tuesday, August 20, 2002 - 12:50 pm: | |
Hmmmmmmmmmmm is this not where the suggestion has been made to remove one cam retaining cap and place a matchbook cover in place before re-tightenting in order to prevent the cam from moving. This of coarse after the cam marks have been lined up? |
Verell Boaen (Verell)
Member
Username: Verell
Post Number: 254
Registered: 5-2001
| | Posted on Tuesday, August 20, 2002 - 10:29 am: | |
Baum tools makes such a tool the'B4500 - MULTILOCK II UNIVERSAL CAM SPROCKET/TIMING LOCK' It fits in between the cam pulleys & keeps them from turning. You'd need 2 of them. They cost $149 each!
www.baumtools.com
I haven't heard any reports as to how well they work.
Several people have reported success by rotating the crank to TDC (the PM1-4 mark on the flywheel), carefully marked the cam belts & pulleys. Removed the old belts, transferred the marks to the new belts & re-installed the new belts. This is the mfg's recommended technique for many cars. The risk is that the cams weren't quite properly aligned to begin with.
Everyone else has pulled the cam covers & aligned the cam marks. There are a lot of posts about this, just search the archives.
BTW, the rear bank cams will just tend to stay in place as the pistons are either at TDC or BDC.
The forward bank cams tend to rotate as the pistons are in mid-stroke. The front bank intake cam in particular is a PITA. It has 1 valve fully open & another partially open. It'll jump on you every time you look cross-eyed at it! Luckily there's no risk of valve-piston interference with the front bank. |
jeff ryerson (Atheyg)
New member
Username: Atheyg
Post Number: 1
Registered: 8-2002
| | Posted on Tuesday, August 20, 2002 - 8:36 am: | |
I just purchased a Racing Red 86 328 and am contemplating changing the belts my self as my experience with repair shops is very mixed with my previous 911
Does Snap on or another mfr make a tool to hold the crank/cams in place to change the belts?
Would this work anyway?
Thanks in advance |