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Timing belt change question

Discussion in 'Technical Q&A' started by PeterS, Apr 11, 2004.

  1. PeterS

    PeterS Three Time F1 World Champ
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    Can one simply take the timing belts off and replace them with new ones without doing anything else (valve adjust, etc?). Since the top bearings have segmented slots for the belt, my pea-brain thinking is that this should take a half an hour and the engine should run well (if the position is not moved). Please explain why this is a 3-6 hour job.
     
  2. Steve Magnusson

    Steve Magnusson F1 World Champ
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    Are you talking about the 308/328 layout?

    While I appreciate your frustration, it takes "half an hour" just to get the rear wheel off and the fenderliner out ;). And what about the front bank -- doesn't the A/C compressor need to be moved to get the timing belt cover off? 6 might be a little fat, but 2~3 isn't unreasonable IMO (although a belt change sans tensioner bearings doesn't make sense to me).
     
  3. PeterS

    PeterS Three Time F1 World Champ
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    OK, then my core question is when you get to the F&R banks, the new belts are simply put into place with no need to make sure of any cam alignment....Correct?
     
  4. Steve Magnusson

    Steve Magnusson F1 World Champ
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    Yes, that's basically the correct idea, but it's not "with no need to make sure of any cam alignment" -- it would rather be that instead of using the marks inside the camcovers, you would make another set of (temporary) marks on the outside of all the rotating components before disassembly so that after reassembly you can confirm they are in the same places (or at least within a degree or two due to slight belt length differences -- I put a couple of belt sets on my ex-308 and just based on the factory marks never felt the need to tweak the cam pulleys).
     
  5. Meister

    Meister F1 Veteran
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    I think there are some very important reasons for taking the time to algining the cam marks and the TDC marks while changing the belts. One would be that if something were to ever happen like a cam move/spin while you were changing belts you would be hoplessly lost in term of cam alginment. The time you would spend to fix that is far outweighed by the time it takes to line up everything IMHO. Also you'd want to know that things were done right the last time belts were changed. If the last time it was done they were a few degrees off and then you do it and another few degrees of then your getting further away each time. It's just not worth the risk.
    I did my belts last year, linned up the flywheel, took the rear cam cover off, made sure the cam marks were right, took a shortcut and did not remove the front cam cover as the indicator marks from the previous change were spot on, changed the belts and the bearings and it was half a days job.
    For me I really wanted to know that everything was linned up and it was'nt worth the risk for the little time saved to just try to swap them without checking.
     
  6. Mark 328

    Mark 328 Formula Junior

    Nov 6, 2003
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    There is always a risk that the gear( pulley) will move when you take the belt-off. On my 328, one of the front ones did move. Although I would not recommend doing the job this way, It seems that about the only way you "could" do this job and ensure returning to the previous alignment would be to hold a utility knife on the existing belt while the car is running and split the whole belt. Then remove the outside half of the old, split belt and slide the new belt on half of the pulleys. After you have tooth engagment on each pulley, cut the last half of the belt-off and slide the new belt all the way on and you should be good to go. Again, I would not recommend this at all, but theoretically it could be done. It is much better to get in there and verify the timing, replace all the seals, and adjust the valves.
    Mark
     
  7. Joe G.

    Joe G. Formula 3
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    1/2 hour !

    LMAO !

    yeah right.
     
  8. Diablo

    Diablo Formula Junior

    If you could do that job in a half hour, you would be the highest paid Ferrari tech in the world!!

    If the cam is just one tooth off, the car will run like sh*t...
     
  9. ham308

    ham308 Formula Junior

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    In the past someone marked each cam like this on my 308. When the flywheel is at TDC 1-4, also painted, then it all lines up and there is no need to take off the cam covers to check.

    Whoever it was, I take my hat off to him......
     
  10. wolftalk

    wolftalk Formula Junior

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    if you mark the toothed pulleys and the original belts, transfer the marks from the old belts to the new ones (by counting the teeth on the belt), and put the new belts on with all the marks lined up, doesn't that guarantee you've at least put it back exactly like it was?

    I'd be inclined to not remove the cam covers if they aren't leaking. plus, I think you can see the timing mark on the rear bank through the oil fill hole with a little mirror, so you can a least verify you'll have a well running 4 cylinder car :)

    Since I pulled the cam covers to fix leaks and checked alignment then, I'm not planning on removing the covers on the next belt change. if you run over bits of a 328 engine on the backroads around san francisco, you can conclude that was a bad idea...
     
  11. Verell

    Verell F1 Veteran
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    RobertGarven has successfully used the marking technique (See the old fchat tech Q&A archives) once he new he'd gotten his cams aligned.

    For my next service I'm planning on making a pair of tools that will fit in between the cam gears & keep them from rotating while removing /reinstalling the belt. (There are several threads that discuss various such tools in the old Fchat archives.)

    A tool will take most of the risk out of the marking approach, even for QV & 328 engines. I've used such tools with japanese twin-cam v6s & they make all the differences.

    MARKING METHOD IS FEASABLE ON A 2V:
    BTW, ham308's picture below is for a 2V engine. The 2V engines have that nice big gap between the cam seals/end of the head & the cam gears.

    4V ENGINES MAKE MARKING VERY DIFFICULT...
    On the 4-valve engines (QV & 328) the cam gears are only about 1/4" away from the cam gears, so there's no room to get in & put marks on the camshafts & seals the way you see them in the pix. Any marks you put on the cam gears are going to be vy hard to precisely align with a corresponding mark on the head. It's also very hard to see markings on the gears while inserting a belt (been there...). The flanges on the cam gears & cam drive gears don't help either. I wou'dn't attempt to use the marking method on a 4V engine w/o a tool that locks the cams into place.
     
  12. robertgarven

    robertgarven F1 Veteran
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    I did it with the marks and also took off both covers. I tried the cardboard under the cam caps but found it was next to impossible to get the new belts on unless the cam pulleys can move a little back and forth to accept the new belt. I am pretty sure that the only cam that wants to pop off is the front exhaust. Steve or Ric will know this one , and I am pretty sure if it does it will not hit anything. I have cahnged mine 3 times now. I took me 8 hours just to get in there and the gt4 is allot easier than a regular 308 as far as space is. My suggestion, dont rush. I also marked everything, then took the belts off and marked the new belts then put them back on, after you rotate the engine around to tension the assembly all the marks are off so make sure they are right. You can also see the rear exhast cam mark when you take the oil filler cap off, here is a picture and it was the only mark that was not spot on. I talked to several well know F-mechanics, they all told me that sometime they have set the engines up with degree wheels and even though they are really close sometimes even the cam marks are not perfect. I would have tried to align the one a tad off but my early car doesn't have the flats on the cams so I was not real excited about trying to remove the bolts. You also need to change the tensioner bearings, make sure the cam seals are not leaking etc. I was lucky, my early gt4 had steel pulleys!!!!!!
     
  13. Verell

    Verell F1 Veteran
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    On the QVs the intake cam is keeping 4 valves wide open (ie; balancing on the lobe) & insists on slipping out of place. However, it is safe if it does slip. I'm reasonably sure the same applies to the 2V engines except that only 2 valves are involved so the cam isn't so recalcitrant.

    Robert,
    If the engine is on PM1-4, That rear bank intake cam is way miss-timed, looks like almost 12-18 degrees!
     
  14. Mark 328

    Mark 328 Formula Junior

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    I agree with Verell, the cam mark in the picture looks like it is one tooth off. The distance-off is about half a tooth which is what you would expect because the Dia. of the cam, by the marks, is about half the Dia. of the pulley.
    Also, when I did mine my cam slipped one tooth and that is what it looked like.

    Mark
     
  15. ham308

    ham308 Formula Junior

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    The following is hard to describe, but I found it helped since there is very little room to move the new belts around to fit the pulleys.

    Once everything is aligned, you obviously have to fit the belts loose onto the pulleys, with the tensioners tightened in the backed off (no tension) position. The tensioners tend to rotate the cams clockwise when they are sprung on to tension the belts. So if you turn each cam a few degrees anti-clockwise before trying to fit the new belts they go on a lot easier. Then when you free off the tensioner bolts to tension the belts they snap back into the correct position.

    My 2V cams were also happy to stay where they were positioned.
     
  16. stevew

    stevew Formula 3

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    I am going to carry out the cambelt change on my QV in the next few days.I have searched the archives for related threads,but can't seem to find any.Any pointers to relevant threads or advice would be welcomed.

    Thanks

    Steve
     
  17. Mark 328

    Mark 328 Formula Junior

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    Ric Rainbolt wrote a great procedure for changing the belts for a 308. I think it was uploaded somewhere on this site, but I can't recall where. It was used for my car and I even started to modify it for the 328. If you can't find it send a PM and I'll email you Ric's and my draft.

    Mark
     
  18. Verell

    Verell F1 Veteran
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    Here's the link to Ric's procedure.

    Most of the cam belt write-ups are in the Old FerrariChat Tech Q&A archives:

    http://www.ferrarichat.com/discus/messages/112/112.html?1067658613

    Try searching them. BTW, RobertGarven & My timing drive bearing threads have a fair amount of photos, etc on cam belt replacement. Also look for some threads about installing cam seals & sealing cam covers that were written about the same time.

    There was another round of threads about cam timing & belt replacement about this time last year. I think it's in the old Fchat.
     
  19. gabriel

    gabriel Formula 3

    Wow!
    Provided the knife didn't grab or stick and cut you to pieces, or ending up with the belting flying right off and saying goodbye to your engine, it might be worth a try. :)
     
  20. Verell

    Verell F1 Veteran
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    And providing that you didn't nick one of the the plastic pulleys bad enough for it to split as well...

    Go ahead & try it... If it goes well you're a hero, if not, then we'll have a real example as to why it's a bad idea(& you'll have an expensive chunk of scrap aluminum...).
     
  21. Verell

    Verell F1 Veteran
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    Baum Tool & Snap-On both sell cam locking tools to prevent this. Also, there have been a couple of home-made cam lock tools described in previous posts, including one I proposed. There were even photos of one of them. I believe the discussions were long enough ago to be in the old Fchat archives.

    I've used cam lock tools to do major services on other twin cam engines by using the belt marking method. Some of the japanese cars make locking the cams real easy. They have cam gears with nice large holes in them and a couple of threaded bosses immediately behind each gear. A couple of bolts with large fender washers/cam gear and those suckers aren't going anywhere.
     
  22. Mark 328

    Mark 328 Formula Junior

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    Gabriel:
    I'm glad you got a kick out of the utility knife method.
    When I first thought of this (never did it though) a friend initially told me I was nuts, but after we discuused it further it made more sense to him. Later on, somebody else discussed a similar procedure used on another car. The Ferrari pulleys really are not very difficult to line-up; on some engines where there are three pulleys to line-up without an adjustable pulley, it can be quite challenging to get all three pulleys lined-up. Everytime you tighten the tensioner the pulleys move-off the mark.
    If somebody really wanted to use this method, they could devise a simple weld-together, bolt-on mechanical device that would take the risk out of it.
    Mark
     
  23. chrismorse

    chrismorse Formula 3

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    Gotta have big brass ones to try the knife.
    I would almost pay money to watch it being tried, (on someone else's car).

    Very creative thinking. One of the things that make the chat so interesting.

    good luck,
    chris

    ps post a note to let everyone how it went.
     
  24. Mark 328

    Mark 328 Formula Junior

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    How much money!!!
     

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