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348 Tricks for placing the belt ?

Discussion in '348/355' started by 348steve, Jun 26, 2019.

  1. 348steve

    348steve Karting

    Jul 18, 2018
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    Stephen G
    Hey all you weekend warriors and pros. Do you have any tips for the simple placement of the belt once you have everything lined up and ready to go? Besides brute force and pinched fingers? Some formula of specific moves to get the darn thing on nice and easy?

    The new Hill tensioner is tied back all the way!
    The cams are locked in place!
    The crack is at TDC!

    The belt is looking at me and saying, "come on give me a go!".
     
  2. steved033

    steved033 Formula 3
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    I started at the waterpump, then up over the cams (clamp the belt lightly to the cam pulleys), then around the fixed idler, the drive, then around the tensioner. voom!

    sjd
     
  3. 348steve

    348steve Karting

    Jul 18, 2018
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    Stephen G
    I'll give it a go. Thanks
     
  4. steved033

    steved033 Formula 3
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    I used those home depot small plastic pinchy clamps. they're strong enough to hold the belt, and weak enough not to damage it.

    sjd
     
  5. steved033

    steved033 Formula 3
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    #5 steved033, Jun 26, 2019
    Last edited: Jun 26, 2019
    as I think more:

    Pull it as tight as you can as you go.

    follow ernie's procedure to tension the belt.

    IMO, you want to degree the cams.

    sjd
     
  6. 348steve

    348steve Karting

    Jul 18, 2018
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    Stephen G

    I will degree the cams if they are out. I am planning on measuring their setting for sure!

    Where can I find Ernie's Belt Tensioning Thread? Sorry, I have not fully figured out where sticky items are kept?
     
  7. fatbillybob

    fatbillybob F1 World Champ
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    3/4 cogs on loose with no pins, Camshafts all pinned, tensioner fully retracted, belt over all pullys and 3/4 cogs, take last cog on belt and move it into position it goes on over snout of camshaft easy as butter then put camshaft bolt in. release tensioenr it all springs and all cogs move where they want. place cog pins that is your point of referrence , "assembly". Now do cam timing
     
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  8. 348steve

    348steve Karting

    Jul 18, 2018
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    Stephen G
    I love succinct answers! Thanks!

    What's your favorite way to loosen the cog bolts? What do you hold onto? Right now my cams are pinned via the "paper" method. Do I need to take the cams out to safely loosen the cog bolts?
     
  9. fatbillybob

    fatbillybob F1 World Champ
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    it depends on how good you paper method is. I remove cam bolts with camshafts out of car. But since you are papered and all lined up us the old T belt wrap onto cog teeth pinch good with big visegrips like using old T belt as a strap wrench then blast off cam bolt with impact gun. Those bolts are like 70ftlbs so not big. then check marks make sure shaft not move.
     
  10. 348steve

    348steve Karting

    Jul 18, 2018
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    Stephen G
    Ya, just like a strap wrench, I get it. I'll try one while the cams are on, if it moves too much I'll take them all off and start again. NP.

    I must say, speaking with you guys "live", like right now, while at the same time reading all your posts from many years ago, is like a time warp. I get to communicate with someone in the present and the past at the same time. :)
     
  11. Rupp3r

    Rupp3r Karting

    Aug 26, 2016
    127
    France
    Hello

    I should also put back my belt this week end and I am also interested in this question!

    Thank you fatbillybob, however I have a few further questions on this procedure since I am not sure to have all well understood..!

    Could you confirm me I have well understood?

    -Do we have to block the cams using some cardboard or so on the caps?
    -So we put only 3 cam pulleys at first and then put the last pulley when the belt is on all the others pulleys?
    -Then we release the tensioner, the pulleys will move with the camshaft stuck: we put the pins and block the pulleys.

    Then when it is done, we should be ready to do two engine rotations but should we expect to adjust the camshaft timing before blocking the tensioner?

    Regarding the tensioner, I have seen that the correct way to do it is to block it when it is most expanded and not when engine is at TDC, is it correct?

    Thanks and good luck 348steve!
     
  12. 348steve

    348steve Karting

    Jul 18, 2018
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    Stephen G

    I will help FBB out by answering these questions for you Rupp3r:

    #1) Locking the cams in position can be done using various methods. One method many people use is to place a small piece of thin cardboard under one of the cam bearing caps. Line up the cam reference mark and torque down the cap just enough to lock the cam effectively! Easy.

    #2) Yes, three of the cogs are on the cams to start the process. They are loose with the pins out, but the bolt and washers are in place, finger tight. The final cog is first mated to the belt then pushed up and into place on the end of the cam. Install the washer and bolt finger tight.

    #3)Then, while all the cogs are still loose and without pins, you release the tensioner and allow everything to tighten up. Then you install the pins and tighten the bolts.

    Once all this is done you can start the next step of cam timing.
     
  13. steved033

    steved033 Formula 3
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    #13 steved033, Jun 27, 2019
    Last edited: Jun 27, 2019
    it's quite possible to run out of matching holes, then you have to take everything apart and rotate the one gear (but not the cam) to better match.

    ...and without the pin in place, it doesn't hurt to finger tighten the bolt and washer back on the cam gears as a little insurance to keep the gear from slipping off.

    sjd
     
  14. 348steve

    348steve Karting

    Jul 18, 2018
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    Stephen G
    You are very correct, sometimes the index holes just don't line up. When that happens I found that by moving the gear one belt tooth, everything changes. The trick to is "check" if you are in a reasonable position as you are laying the belt over each gear, its easy to see if it will work in the end. Thanks for the warning!
     
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  15. steved033

    steved033 Formula 3
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    Maybe FBB or ernie can confirm that with all 4 cams locked down and the gears free, to "align" to the center of the hole on the cam side with whichever hole on the gear matches up with it and has even +/- distribution on each side. (i.e. the gradation of misalignment from center will be symmetrical.)
     
  16. 348steve

    348steve Karting

    Jul 18, 2018
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    Stephen G
    Like I said the instructions on how to place the belt were excellent! Thanks FBB!

    But I learned something that is interesting and I am wondering if anyone else has noticed this...

    You start with the 4 cams locked down perfectly aligned, and of course the crank at TDC. Then you install the belt, pin the gears, release the cams, release the tensioner and start rotating everything for a few minutes to get everything settled. Easy stuff!

    In my case I noted that changes can be detected in the final resting place of the cams. What appears to happen seems to me to be a function of the stretch of the belt or the "settling" of the belt, or both, let me explain...

    After releasing the cams and tensioner the cam marks remain perfect. But after you rotate for a few minutes the cam marks move a slight amount which differs increasingly with the distance of each cam from the drive gear. I noticed that the first cam (left exhaust) remained just about perfect, and that the next three are off by increasing amounts starting with only a slight difference on the 2nd cam (left intake). The difference I note is in the direction of what you would expect from a stretching/settling phenomena. The last cam gear (right exhaust) has the largest error, about three "mark widths", if you know what I mean.

    My next step will be to measure the cam action with the dial gauge, using either or both of the methods FBB described in his infamous thread.

    I am expecting that the measurements will be off in relation to the visible offsets on the cam marks and then I will have to re-set the cams again.

    My question to everyone now is .... what are the best tricks for re-setting the cams as you iterate through this process?
     
  17. steved033

    steved033 Formula 3
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    ...by going through the timing procedure.

    sjd
     
  18. fatbillybob

    fatbillybob F1 World Champ
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    YOU are thinking and you understand! I have been trying to describe what you are seeing many many times but 99% just don't get it. Based on what you have found I'm sure you understand why I unpin the cogs and why you can't just belt swap even if you previously cam timed that old belt. The 99% will quote the guys who tell you belts can't stretch yada yada. But as you understand it is not really belt stretch it is belt relax like straightening a fly fishing tippet out of the coiled package. It is all the slack between the parts even if you tension by allowing the unpinned cogs to spin free...there is still stichion there. So to remedy you either do as you propose because you are going to cam time anyway or you max your precision on every step by cheating and putting a bit of extra pressure on the tensioner spring to relax the belt more and get the cogs to move freely and hand tweek the different belt run lengths to try and equalize the pressures over all the componants. If you do this well you can pin the cogs turn the crank as many times as you want and the marks and TDC will always line up. Play with it you will see what I mean.


    As to reset of cam during cam timing you should be very very close on assembly marks...maybe dead on if using lobe centerline and just a couple of cog holes off if doing it the Ferrari way which for some models like the 550 take a close read to figure out what they are doing in the WSM. So lets say you are using the degree wheel and you need to move the cam just a bit. You unpin the cog it isstill really is being held by the camshaft land. Then you use a rubber mallet or in my case the official 1980's Ferrari F1 USAG delrin hammer to tap the nose of a cam shaft lobe noting the hole that you pull the pin from. tap the nose until the pin falls into the next hole. Rarely have I found the need to go past a few holes from the assembly marks to dial in the timing. When all 4 shafts are in time you spin the crank a few revolutions and recheck the timing. You should be dialed in then pin the cam shafts and torque the cam cog bolts. Use new O-rings and NO sealant.
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  19. 348steve

    348steve Karting

    Jul 18, 2018
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    Excellent description! I am a mechanical engineer with experience in a number of disciplines including some of the most pretentious (space based equipment) and one of my very favorite words is stiction, it describes so many situations with just a simple word!

    Hit a cam lobe with a rubber hammer ... yikes I did not think it was going to come to this, but I can see how that would work well to finesse the pins. I'll give that a go.

    Thanks again for the dialog!

    Steve
     
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  20. fatbillybob

    fatbillybob F1 World Champ
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    The camshaft moves at 9,000rpm held by aluminum caps torqued to barely double digit torque. . it can take a lot of abuse and matchbooking shafts and knocking judiciously with a delrin hammer face isn't going to damage anything. Some OHC engines have nice hexes built into the shaft then you can put a wrench there and hold it or move it. Ferrari chose not to do that since the Italians have been using matchbook covers and an abundance of hammers since the invention of cigarettes.
     
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  21. INTMD8

    INTMD8 F1 Veteran
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    Which cam moves at 9k rpm? F1?
     
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  22. 348steve

    348steve Karting

    Jul 18, 2018
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    Quick question for you .... what are the best options for preventing rotation while torquing cam cog bolts and the crank shaft bolt for that matter?
     
  23. 348steve

    348steve Karting

    Jul 18, 2018
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    I see from reading FBB's post from way back (setting up cams), that he uses 3-4 paper inserts in 3-4 cam journal caps to hold it down enough to torque the cam bolts.
     
  24. fatbillybob

    fatbillybob F1 World Champ
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    Yes. and you can hold crank at the flywheel with just a prybar on ring gear teeth. You can also be lazy if you have good feel and just use an impact gun...I've been doing this stuff for 40+ years
     
  25. ernie

    ernie Two Time F1 World Champ
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    I like to cuss at it. And if that doesn't work then I'll talk dirty to it. :D
     

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