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Timing Belts - Cam Locks

Discussion in 'Technical Q&A' started by Owens84QV, Dec 11, 2005.

  1. Owens84QV

    Owens84QV F1 Rookie

    Oct 2, 2001
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    I have a 1984 308QV. I'll be doing my 30K over the Christmas holiday. Does anyone have a set of the delrin/plastic cam locks that I could borrow for my 30K service? These are the cam locks that have a bolt running through the center and the curved surfaces 'lock' against the cams.

    I'll pay for the post to and from my house. Anyone?
     
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  3. Owens84QV

    Owens84QV F1 Rookie

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    #2 Owens84QV, Dec 11, 2005
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  4. peajay

    peajay Formula Junior

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    You can easily make what you need. Just cut out some thin card that fits between the two belt pulleys and use this as a template to make two wooden wedges. Drill through the centre of them and put a bolt though. You have just made the tool. It took me about 1 1/2 hous to make and saved me at least 8 hours work compared to the last time when I took the cam covers off. You also avoid sealing problems removing the covers. But if you haven't checked your valve timing before or are not certain of the cam timing, then I recommend taking off the cam covers anyway.
     
  5. Owens84QV

    Owens84QV F1 Rookie

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    Paul,

    Appreciate the help. Do you happen to know (A) the distance between the two cams in the center and (B) the diameter of each cam? From there, I'll be able to make the tool.

    I've got a friend coming into town to help me with the 30K service and so I have a very short window to get a lot of stuff done. I was hoping someone would either have the tool I could use or have the measurements.

    Thanks!
     
  6. robertgarven

    robertgarven F1 Veteran
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    #5 robertgarven, Dec 11, 2005
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    I am not sure about the QV's but I have changed my belts 3 times and found it was easier not locking them. I am a novice though and the first time did it with the valve covers off the next two times (because of a timing gear bearing failure) with the valve covers on.Once at TDC or PM 1-4 I marked the shafts, seals and belts with a fine silver paint marker (see photo). I am not sure if real mechanics ever do this but it worked well for me. The belts slipped on easier if the pulleys copuld be rotated a little. The only shaft that seemed to want to pop off move off was the front bank exhaust. It slipped off a couple of times and must not be that bad as the engine has run fine ever since, and I still am sporting the sodium valves. I used a card board match cover the first time and could not get the belt on until I took it out!!
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  8. peajay

    peajay Formula Junior

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    Greg, no sorry I didn't keep the numbers, but I honestly think the best way to make these is using some paper or card templates by cutting them to fit the pulleys on the car . You know they fit well and then you can cut the wood or plastic ones quite easily, the ones I made are surprisingly small but did a great job, locked very securely and made the job tons easier. I used the cards wedged under the cam bearings the first time but I don't like doing that, it means a lot more work, morr risk of leaks, plus cost, plus risk of cracking cam caps.

    Robert, I heard that 2 valve engines have less risk of the front bank cams overcentering, I know on my 328 the cam did slip on my first belt chage, but not at all with the locks in place.
     
  9. carguy

    carguy F1 Rookie

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    #7 carguy, Dec 12, 2005
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    Owens84QV.....I thought your camlock wedges looked familiar. Here is what I use on Testarossas. Very simple and easy to make....
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  10. Verell

    Verell F1 Veteran
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    Umm,
    Those aren't Owens locks, they're the rough protos I hacked out when we were doing JWise's timing drive project. Have now used them for 2 other cam belt jobs.

    BTW, I surfaced those locks with strips of hard rubber attached with trim cement. Best to give the cement a couple of days to firmly cure up before using it.

    On the QV, the rear intake cam really won't stay in position. It 's extremely unstable, the slightest jiggle & it snaps +/- a couple of teeth.

    On the job I"m currently helping with, the rear intake cam slipped on us a couple of times while we were just trying to get the cam lock in place.
    The front & rear exhaust cams are a bit more stable, but will jump out of position given a bit of a nudge.

    The trick with using cam locks is to:
    - Set the crank on PM1-4, & the cams on their marks.

    - Verify that the cam gears are lined up with each other. I use a strip of belt glued to a strip of 1" wide, 1/8" thick steel plate that's long enough to span both cam gears. I've done it with just a strip of belt, but it isn't as accurate.
    Once they're lined up, clip the test strip in place with a binder clips or some other kind of small clamps until the cam locks are on.

    - use the cam lock(s) to ensure the cams stay on their marks.

    - Put a mark on the damper just where the rear bank drive pulley's flange goes behind it. This gives you a TDC reference from the front of the engine. (Alternatively make a sheet metal pointer & mount it on an alternator bracket stud., then use it's tip to mark the damper.)

    - lock the belt stretcher (aka tensioner) in the outwards (maximum belt slack) position.

    - Route the new belt over the cam drive bearing, & attach it to the bearing with a small binder clip.

    - Loop the belt up around the belt stretcher & over the cam gear closest to the belt stretcher. (This is the gear with the flange towards you.)

    -Hold the belt up against the edge of the other cam gear, & slowly back the engine up until the belt slips into place.

    You don't need to back it up much, just so the drive gear moves about a belt tooth.

    Backing up the engine does 2 things:

    1) Takes all the slack out of the belt section routed around the belt stretcher.

    2) Transfers the belt slack to the long section going up to the gear you're trying to slip the belt onto.

    The belt should slip into place easily when the crank is in the correct position.

    If it doesn't slip into place, then rotate the crank back to TDC. Verify that the cam gears are lined up with each other, that the tensioner really is fully extended, & that the belt going around the tensioner has it's teeth down in both the drive gear & the cam gear.
     
  11. Owens84QV

    Owens84QV F1 Rookie

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    Verell...you are awesome. If anyone on this site deserves the "best spirit" or "most helpful" award, you should get it by a long shot! I've got a friend coming down for the weekend to help me. I was going to try to have as much prep work done before he gets here. I'll make my first priority task to get the cam covers off so I can make the cam-locks. I'll use your notes along with some other things I've printed off. Prep work is everything!

    Thanks!!!
     
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  13. fatbillybob

    fatbillybob F1 World Champ
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    I can't tell by the picture. Are you guys locking the cams by the cogs or actually by the cam shafts themselves? Either way I totally disagree with doing it by this method. It does work this way but you duplicate the previous mechanic's error and unless you are locking on the actual cam shaft this is a questionable way to lock the shafts so that you can torque the cam shaft cogs. But...that is just my opinion. You don't need anything fancy not even all the nail polish. I got my flame suit on...let me have it...yikes.
     
  14. jwise

    jwise Formula Junior

    Apr 2, 2003
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    Portland Maine
    It locks on the cogs.

    In this case- any mechanical error duplicated would have been my own! Verell and I had had the cam covers off, cams out, degree wheeled and dial indicated to verify timing a few weeks before this photo was taken. This photo was round two- so we knew exactly how dialed in the cams were.
    We had to take the belts off (and replace 20 mile belts) again for another problem and this was the quick way to do it. If the cam covers have not been off for a few years- than I think they need to come off to do it right and verify all four cam marks for timing.


    I agree- I'm a little heavy handed with the cam markings....:)

    jwise
     
  15. Verell

    Verell F1 Veteran
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    fatbillybob,
    Let's take your objections point by point & discuss them. In particular, I'd like to understand the technical reasoning behind some of your statements.

    I think you're assuming that using cam locks implies trusting the existing cam alignment. That isn't the case. In many previous posts, I have made this clear: YOU SHOULD ONLY TRUST THE PREVIOUS ALIGNMENT IF YOU KNOW FOR SURE THE PREV. ALIGNMENT IS CORRECT

    If there's any doubt whatsoever, pull the cam covers & verify that the marks line up.

    USUALLY YOU'LL FIND A MARK OR 2 IS OFF!
    I've done quite a few belt jobs, including several where the previous major service was done by Ferrari dealers & reputable shops. In every case, I pulled the cam covers & checked the marks. There have been only 2 exceptions where I didn't pull the covers:
    1) The 2nd time we installed belts in JWise car we knew we had the cams right the 1st time.
    2) The owner insisted on only changing the belts w/o pulling the covers against my recommendations.

    MY EXPERIENCE:
    ONLY 1 OF ALL THOSE CARS HAD ALL 4 OF THE CAMS SPOT ON THE MARKS. (That car's owner & I are currently in the process of finishing the job. I told him I was amazed when we put the engine on PM1-4 and found the marks really were dead on!!!)

    All the other engines had at least 1 cam whose cam's mark was either on the very edge of the cap mark, or else was slightly past the cap's mark. Did not seem to affect running, & the owner was amazed to discover that he had a cam or 2 slightly off.

    However, once you've got the cam marks aligned spot on, the cam locks make it a lot easier to finish the belt change.

    Please explain why you consider locking the cam gears questionable.

    BTW, How do you directly clamp the cams for torqueing?

    Due to their relatively small diameter, It takes tremendous force directly on the cams to hold them while torqueing the cam gear bolts.

    That's why I'm reluctant to recommend using the paper under cam caps for this application. It's too easy to damage the cam caps if you aren't really careful or use a piece of paper that's too thick(like a match book cover, or piece of belt box like I once suggested(duh) early on).

    I do remember Ed Gault once recommended clamping a vice grip on each cam & taping their handles together.
     
  16. fatbillybob

    fatbillybob F1 World Champ
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    <<Let's take your objections point by point & discuss them. In particular, I'd like to understand the technical reasoning behind some of your statements.



    I think you're assuming that using cam locks implies trusting the existing cam alignment. That isn't the case. In many previous posts, I have made this clear: YOU SHOULD ONLY TRUST THE PREVIOUS ALIGNMENT IF YOU KNOW FOR SURE THE PREV. ALIGNMENT IS CORRECT>>

    O.K. I agree with this and I did assume you are accepting the previous cam marks. My bad. However, once a belt is tightened you can never trust that the marks are dead on especially after you have run the car and especially if you are not pinning the cogs on the cams when the cams are spot on. This last sentence is a fundamental error in reparing these cars. It accounts for more bad running than just about any other problem. The short cut works fine on a Honda but not so good on a Ferrari because these cars are quite highly tuned for their era. The 355 in its day for example was one of the early cars to hit the magic 100hp/liter and still uses the same basic timing system of the 308.


    <<if there's any doubt whatsoever, pull the cam covers & verify that the marks line up.>>

    There is always doubt by definition of how engines work. This is not such a big deal with 308/328 but once you get to the 348 you have to pull the engine to do the belts. "If you do not have time to do the job right when will you have time to do the job again?" This is not an slight on your person but your technique. FNA slobs can get away with this because they are FNA. We DIY'ers' are always looked down upon as scum of the earth bottom feeder cheap ba$tard$ so we have to function at the highest level.

    <<USUALLY YOU'LL FIND A MARK OR 2 IS OFF!>>

    Yup that's why you always have to start with the basics and that means cams off and cam cogs off.


    <<I've done quite a few belt jobs>>

    Yup me too.

    <<Please explain why you consider locking the cam gears questionable.>>

    Because when you lock the gears you can make the cam spot on BUT you cannot "ensure" that the indexing of the belt teeth relax and spead out with equalized force over the entire belt when you release the tensioner. This can allow your marks to be off when the belts run. So you have these perfect marks in a static postion. You tension the belts and release the cogs and where the tesion is uneven the belts will seak equalibrium and your marks will now be off. This is a fundamental problem that I see all the time real pro mechanics make either because the do not understand how the timing system and tension system work or are too lazy to do it right. The proper way is to pull the pins in the cogs. Lock the cam shafts. Tension the belts and allow the cogs to turn and lay where "they" want. This equalizes the tension over the entire belt. Now replace the pins to whatever pin hole lines up with the cam holes. You have now passively placed the belt in tension and the cams are spot on and will stay that way.

    <<BTW, How do you directly clamp the cams for torqueing?

    Due to their relatively small diameter, It takes tremendous force directly on the cams to hold them while torqueing the cam gear bolts.

    That's why I'm reluctant to recommend using the paper under cam caps for this application. It's too easy to damage the cam caps if you aren't really careful or use a piece of paper that's too thick(like a match book cover>>

    First use a air gun set to proper torque not a wrench. You actually apply less force despite the torque being the same as the air gun can apply instant force and you just beat on things with a wrench.
    Second you DO NOT need lots of force to lock cams and a match book cover is entirely appropriote. It takes no force other than the multiplcation of many small forces. The trick is not to use one cover and lock from one cam journal torqueed until you rip the stud out of the head. What you do is put a 1/2" or so slip of match book under 4 or 5 cam caps with no more than hand tighness. Even if you did more can't hurt anything unless someone is truely uncoordinated. Cam caps are very strong they take 8000 rpm beating all day long. Just grab the sock wrench by the head and tighten the cam bolts snug then 1/4 turn like spark plugs. The shear volume of match book covers multiplys the force needed to turn the cam shaft. This method has never failed me and was taught to me by 2 FNA mechanics and one Formula race mechanic who later became an independent Ferrari mechanic for Lyle Tanner. Personally, I always have razor blades around for this and than. I peel off the razor blade cover and use that. They are the perfect size. When I learned how to work on Ferraris I sought out FNA mechanics then paid them to come to my house and show me how to do things. That's how I got my early knowledge. I guess it is obvious that you have to take the matchbook covers out of the cams before you put it all back together. I put my money where my mouth is I race my car. I'm not fast but I probably run my car harder than any of you and I have had zero mechanic failures on the track other than the occasional electrical gremlin.

    I also do like to rely on Ferrari tensioner bearings to be the right tension out of the box. No one I know has the proper non-porshce stegar tensiometer. I have never seen one at an FNA dealership. I do not think anyone uses one. Anyway I like to add a bit more tension on the belts than Ferrari says (i.e. just release the new tensioner and the spring will do it right). There is a way to reliably do this but that is for another story.
     
  17. speedmoore

    speedmoore Formula 3
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    I use some univeral OHC locks that I picked up for $25 and then slighlty modified in my Bridgeport to fit all Ferrari cogs.

    This delrin setup looks pretty simple and sweet and cheap and personally I think it beats the hell out of the pair of Vise Grips Factory Ferrari mechanics are taught to do "even pictures in the workshop manuals clamping them together"

    Fatbillybob? I don't understand.......I lock the pulleys, untorque cambolts if degreeing in but leave pins in, take off the belts, put the new belts on, tension bolts enough to keep the pin tight, remove locks, degree them in and if you have to move cam in relation to crank, (same goes if lining up marks vs degreeing in with dial indicator). Once I'm happy with the timing, put the locks back on, torque cambolts and tensioners, everything, remove again, roll motor again, verify timing....and of course it doesn't happen on first try every time especially if you are degreeing in....

    Verell tool seems it could be used exactly the same way. If all the marks line up and you don't want to be so anal that you have to degree the cams in, then you block em, swap belts, retension belts, verify by rolling over a few full cycles 720 degrees twice and wala...done

    Oh, I've done quite a few belt jobs too..........;-) Lots of ways to skin a cat as long as you skin it with the correct end results........be my guest.
     
  18. speedmoore

    speedmoore Formula 3
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    I just don't understand the matchbook thing. How can you move the cam to degree it if it's locked from rotating. I have to admit it's another way that would lock the cam, but right on the alumimum cap to cam journal? I got those babies lubed up with assembly lube to move like butter.

    I just can't imagine the extra amount of time it would take to do it the way you describe. I mean, don't you move the cam in the journal to properly time/degree a camshaft to the crank? Yes you hold the cam, move the crank and repin, but you can also move the cam a bit for finite adjustments and you still need to rotate motor right after to check. So then you are unbolting a cap each time to remove and then put back your piece of sandpaper? This is especially true when playing with cam timing other than "stamped" marks. Sometimes it takes half a dozen attempts to get it exacly right. If you want to be super anal, degree them in by lobe centers like all race engine builders do. That's the way I was taught.....it's the only true way to get a cam timed perfect. I was taught by a former F1 engine builder myself and still have the very magnetic base and dial indicator he gave me.
     
  19. spider348

    spider348 Formula 3
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    I have only done a couple of “belt” changes on Ferraris but I believe I understand Fatbillybob’s procedure. When I did my 348 recently I indexed the cams to precisely align to the cap timing marks, locked the cams in place with multiple matchbook slivers, hand-tight as he indicated. My crank is at TDC, confirmed with a degree wheel. Cam pulleys are not pinned in place at this time. Install the belt, release the tensioner, allow the belt take a set, unpinned pulleys self align. Confirm all is still aligned, pin the cam pulleys and tighten bolts. Remove matchbook “locks”. Crank engine by hand several rotations and confirm timing correct. Crank at TDC, cam marks align with cap marks. I am interested in Fatbillybobs revised belt tension procedure!
     
  20. Verell

    Verell F1 Veteran
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    Let's keep this discussion focused on setting up basic standard cam timing as degreeing cams for custom timing brings in more complexity & it's own challenges.

    Let's focus on the belt tension equilization point:

    OK, I follow your reasoning. Your key point is:
    "The belt tension must be equalized at all points, when the cam gears are pinned. Thus you contend that having the cam gears locked doesn't allow that equilization."

    However,
    I'm not convinced that this fully equalized condition best matches conditions while the engine is running.

    I left an important step out of my description:

    Once the belts are on, but the belt stretchers have not yet been tightened, The engine is rotated 2 full turns (720 degrees) by hand. On the last rotation it's brought up to PM1-4, held there, the cam marks are verified. If they're still on, the belt stretcher is torqued down. (I've often had to repeat this rotation, & sometimes had to re-pin the cam gears at this point.)

    It's then rotated 2 more times & the marks are checked.
    (Usually they haven't moved, but believe I've had to repin once & go back.

    If they still look good, it's rotated a final 2 turns & the check is repeated. (Don't think I've ever had to go back at this point.)

    Finally a twist check of the long belt section to verify that it can be twisted ~45 degrees.

    My experience has been that if the marks are still aligned at the end of the 3 double rotations, they're not going to move after then engine has been run.

    This is the procedure that I originally learned, and has been confirmed by conversations with technicians at some independent shops, who had been FNA trained. It also matches my interpretation of the WSM instructions.

    I've encountered one varient to the above, and have sometimes used it:

    While the engine is being initially rotated, the motion of the belt stretcher is observed. The points in engine rotation that each stretcher is at maximum inward extension is noted. The engine is brought around to that position again, & that's the point that the stretcher is locked down. I've observed that the point of maximum inward extension is also the point where the long belt section is overcoming maximum resistance from the cams.

    Note that at the end of each double rotation, the belt tension is not equalized. As during engine operation, the long belt section is being driven by the crank & is driving the cams.

    Before it's locked down, the belt stretcher is floating on it's springs taking slack out of the belt. The stretcher section is under the tension supplied by the stretcher's spring. The stretcher belt section's tension will be less than the tension on the long section by the amount of force being applied to turn the valves.

    I think the most significant difference between our approaches comes down to the belt tension condition when the decision to lock the belt stretchers down & final verification that the marks line up is made.

    ie: EITHER:
    1) Equalized Tension Condition: the belt tension should be fully equalized at all points.
    OR
    2) Unequal Tension: The long section should be under tension due to the crank driving the valves.

    IMHO, the 2nd condition most closely approximates belt tension during engine operation.
     
  21. speedmoore

    speedmoore Formula 3
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    Good stuff Verell
     
  22. speedmoore

    speedmoore Formula 3
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    #19 speedmoore, Dec 14, 2005
    Last edited by a moderator: Sep 7, 2017
    Fatbillybob's method is very similar to Porsche Motorsports cam timing of the GT3R,RS,RSR,CUP/962/956/959. ....They have a stainless steel tool that has the exact cutout of the cam lobes for both cams for each bank. That is this tool is a flat piece of metal with the cam profile cutout and you slide this tool and position the cam lobes to fit while the flat piece of medal is flush on the cam deck. It lines the cams up for what's called TDC overlap in Porsche terminology. Attached is a picture with the tool kind of laying over at mid deck. Their cams are not marked like Ferrari cams, just a prelim mark for degreeing in with a dial indicator.

    Verell, you might be able to make such a tool to lock 308 cams to make them fixed in the stock location if this is how they prefer to do it to get the matchbook/cap thing out of the equation. You'd have to have one for each bank each engine model.
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  23. fatbillybob

    fatbillybob F1 World Champ
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    Spider348 understandsme completely.

    Verell: I think you are doing what I do. You are over thinking the problem.

    <<OK, I follow your reasoning. Your key point is:
    "The belt tension must be equalized at all points, when the cam gears are pinned. Thus you contend that having the cam gears locked doesn't allow that equilization." >>

    Yes this is my contention. We cannot assemble belts dynamically so the engines must be engineered to be sone statically and easily by manufacturers.

    <<I left an important step out of my description:>>

    Yes this is critical but many extra steps that are fine and do not hurt anything . If you try it my way you will find that you will be spot on the first time after you test crank your motor and you will not need to rotate things 4 more times. Also, you will find that by design belts have less overall stretch than chains. Therein lay the reasons for their near universal use as timing control is directly related to smog control. Belts may stretch as little as 3% over their life. You will find that if you try it my way and 15000 miles later check the timing before you change the belts you will still be spot on. I do this all the time. In my personal 348 which is a race car I change the belts every year in the off season which is excessive maintenance. I am always spot on before disassembly and assemble by the method I posted above. Sometimes it is potato or po ta to but the basics for having good starting points is critical to good engine function. The fact that sometimes using your method and checking with your method and sometimes finding timing off In my mind means that your theory of setting belts with unequalized force is faulty. I have never had to repin or change positions after a timing check because I have always assumed that equalized belts are the best way to go. There is no way to know how much tension each belt segment should have and there is no way I know to compute belt tensioner tension to achieve any specific amount. I do know that Ferrari has a tensioner spec and it makes the most sence to employ that spec in the laziest of Italian tradition and I think I have done so.

    <<the belt tension is not equalized. As during engine operation, the long belt section is being driven by the crank & is driving the cams.>>

    Agreed but belts cannot and FNA does not recommend belts be tensioned dynamically nor is there a way to predictably do it. Your method may be a simulation of dynamic but the engine really is not moving. Have you introduced another problem we don't know about? When I tension my belts I can feel uniform tension everywhere in the belt. When I tension my belts they are spot on from the first time and everytime there after. We may be just spliting hairs. What I really have a problem with is that your method does not allow the cam cogs to be where there is a path of least resistence. Your method builds in an unpredictable amount of small error. My method starts with the most basic (where the cam in in the head) and then once that basic is firmly established soemthing else happens next but not upseting the first basic...and so on until the belts are tensioned and tested.

    <<I think the most significant difference between our approaches comes down to the belt tension condition when the decision to lock the belt stretchers down & final verification that the marks line up is made. >>

    No I think the most significant difference is that I place the most emphasis on the most basic parameter where is the cam in the head and I make everything else fit around that and nothing I do can ever disturb that position.

    <<ie: EITHER:
    1) Equalized Tension Condition: the belt tension should be fully equalized at all points.
    OR
    2) Unequal Tension: The long section should be under tension due to the crank driving the valves.>>

    I understand you point here and we do disagree on this tension specific. However, these two points are really a symptom of the primary basic "where the cam is in the head." How we get there is not important as long as we maintain that postion. I believe my way is easier and more reliably attained with proper tension on the belts.

    <<IMHO, the 2nd condition most closely approximates belt tension during engine operation.>>

    Perhaps I have no way to dispute you. However, have you ever thought that your long side under tension leaves the short side untensioned? untensioning aids in belt dumping and belt wear which leads to eventual belt dumping. Yes there will always be more tension on the driven side but youmust maintain tension on the non0driven side to aid in belt retension. I propose to you that it is that exact belt tension on the driven side that I want to avoid. I want tension all over the entire system and belt tension is going to naturally increase on the long side when the engine is running. I don't want that. I want equal tension over all points on the cogs for superior retention of the belt. Dynamics of the engine will defeat that. I don't need to tension the belts in such a way to make that dynamic worse.

    Verell, I enjoy this discussion. It is nice to chat with someone who thinks.
     
  24. Verell

    Verell F1 Veteran
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    I must quibble with this. The belt stretcher is tightened down with the long side under tension against the valves. This ensures that all the slack in the belt is on the belt stretcher side where the stretcher spring will have taken it out.

    I think both approaches start with the cams in exact position & doesn't disturb their setting.

    Maybe it's time to agree to disagree as I think we both now have an in-depth understanding where the other's coming from.

    If I have time, I'm going to set the belts up using one of the procedures. Mark things very carefully, then do the other procedure to see if I can measure any differences. If the cam gears have to be pinned differently, then there's a significant difference that needs to be analyzed. It's also possible that in practice both procedures produce identical results.

    Speedmoore
    That's a very unique cam lock alternative. Would require a CNC mill to produce them. Any idea what that P* tool costs?

    Hmm, let's see, how many cam profile & timing variations are we talking about?

    - Early Carb'd cars:
    .. Euro
    .. US

    - Late Carb'd cars:
    .. Euro
    .. US

    Injected 2V cars:
    .. Euro
    .. US

    QVs:
    .. Euro
    .. US

    328s:
    .. Euro
    .. US

    Ouch! We haven't even got to the P6 cams...

    Also, any chance you could fax or mail me a copy of the belt tensioning procedure from one of the P* manualls?

    Will email you my FAX # @ my 8-6 job.
     
  25. fatbillybob

    fatbillybob F1 World Champ
    Consultant Owner

    Aug 10, 2002
    19,970
    socal
    <<Maybe it's time to agree to disagree as I think we both now have an in-depth understanding where the other's coming from.>>

    Agreed

    <<If I have time, I'm going to set the belts up using one of the procedures. Mark things very carefully, then do the other procedure to see if I can measure any differences. If the cam gears have to be pinned differently, then there's a significant difference that needs to be analyzed. It's also possible that in practice both procedures produce identical results.>>

    Perhaps and that is all that really matters. Pro's at shops have used nail polish and scrib marks. We are practicing to a higher standard but hey the car belongs to us so we can take 2 hours to dial in a cam.
     
  26. speedmoore

    speedmoore Formula 3
    Professional Ferrari Technician BANNED

    Apr 15, 2003
    1,541
    Austin, Texas
    Full Name:
    D Moore
    I know that's a lot of profiles, but do you know how many different camshaft profiles have been just in the GT3R series???

    I've been fixing Ferrari's all day. If I get a chance I'll fax you procedure for timing Pcars......but as Ferrari, there are a number of variants that are evolution of the base original procedure....i.e. different tensioners, and tensioner tools, etc.

    d
     
  27. Verell

    Verell F1 Veteran
    Consultant Owner

    May 5, 2001
    7,000
    Groton, MA
    Full Name:
    Verell Boaen
    OK, we've tabled the belt tensioning discussion,

    Can we discuss the 'match book' cover cam locking method?

    I stand by the intent of my previous comment:
    Here's where I'm coming from:

    Dave Helmes, a FNA trained mechanic had some very strong comments about, & graphic descriptions of the cam cap damage risks in using something as thick as a matchbook cover. They really got me thinking about the forces involved.

    See his posts #81, #82, & #83 in this Old FerrariChat thread:

    http://70.85.40.84/~ferrari/discus/messages/256120/281134.html

    Dave stated that the clearance between the cam cap & cam is 0.003" to 0.004" for an engine in good condition.

    I agree with using a piece of paper that's somewhat thicker than the cam-cam cap gap, say writing paper which is ~0.1mm(0.004") , maybe even doubled over if the engine is well worn ie: 0.2mm(0.008") & the cam cap screws finger tightend to hold cams in place while pinning the cam gears. Paper under 1 cap should be sufficient for holding the caps.

    However,
    tightening the caps more than that in order to torque the cam gear bolts, or even worse break the cam gear bolts loose by hand is totally different.
    Here's a rough analysis behind it:
    The cam radius is roughly 1/2", or ~0.05 foot. The torque spec for thecam gear is 40 ft-lb. The tangential force that must be generated by the paper to withstand that torque is 40ft-lb*12 in/foot/(1/2) inch = 960 lb-force! Even if it's spread over 4 cam caps, that's 240 lb-force/cam cap!

    The breakaway force is probably at least 2x, possibly 3x the tightening torque, so multiply the tangential force by the same multiplier.

    I couldn't find the static coefficient of friction for paper on clean, dry steel, but it should be close to that of wood on steel which is: 0.2.

    So the pressure that must be generated by the cam cap on the paper to generate 240 lb-ft of tangential force is:
    240/0.2 = 1200 lb-force!

    or 2400 lb-force if you're only using 2 cam caps.

    I consider those forces to be 'tremendous' considering the relatively small size of each cam cap.
     
  28. marankie

    marankie Formula Junior

    Aug 30, 2004
    252
    Agoura Hills, Calif
    Full Name:
    Martin
    Just chaged belts on my '75 gt4. First Cam covers off. First checked each cam's timing. Very good. With 1-4 at TDC, match paint marked both the belts and pulleys, just like shown in Rob Garven's earlier post. Then laid old belt and new belt next to each other and transvered paint marks to new belts. Installed new belts. No cam locks used. Went very easy. Two turns on crank, tensioned tensioners, four more turns back to TDC on 1-4. All cams line up perfectly. Very straightfoward. Acually removed the cams to change out the cam seals. Much easier and less risky than trying to remove the cam (toothed belt) sprockets. As per the previuos post, trying to have a match box unber a cam bearing(s) stop the torque required to break the cam pulley nuts is likely to deform the cam bearing caps. As crude as it may sound, vice grips as back ups sounds much safer.
    BTW, being used to Porsche 911 cams, the 308 Gt4 cams looked to be a very mild grind both in duration and lift. And this is comparing to a 911S street cam not even a 911 racing cam. As such, I doubt very much if the 308 cam timing is that critical. With a 911 you can vary cam timing 3-4 degrees, advance for more low end torque, retard for more upper end power. Back to the 308, unless the valves start interfering with the pistons, and considering the mild cam profile, I suspect that cam timing variations within 3-4 degrees would not be noticeable.
    As such IMHO some of the elaborate cam timing procedures previuosly described may be OK form a perfectionist's point of view, but as a practicle matter for normal street cars they are way over the top, and threaten to intimidate those that otherwise would undertake this relatively staightfoward task themselves.

    Martin Jansen
    Agoura Hills.
    Calif.
     

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