360 T-Belt change - 1.9-2.3mm vs Frequency? | FerrariChat

360 T-Belt change - 1.9-2.3mm vs Frequency?

Discussion in '360/430' started by Trackspec_360, Jun 9, 2023.

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  1. Trackspec_360

    Trackspec_360 Rookie

    Dec 10, 2022
    10
    I m just about finished with my belt change and all has gone smooth on my new to me Challenge 360. Car has sat for about 8-10 years so a full major with hill tensioner pulleys going in. I spent a lot of time getting the 1.9-2.3mm tensioner gap just perfect. I then noticed that the next step was to check frequency of the belts. My belts came in a touch low at 180-182. I then tensioned up the belts a touch to achieve the recommended freq of 190-220 getting my belts to about 195-205. I went to recheck my tensioner gap and it shrank to the following (after rotation and rest).

    Driver side: 197 freq/ 1.42mm Gap, Pin pulls out tight
    Pass Side: 191 freq/ 1.75mm Gap, pin pulls out smooth

    I sat and thought about it for a while then said screw it, the freq seems more important to me as thats the real tension of the belt, right? I started buttoning everything back up and stopped for a moment and thought, well if the tensioners are weak, maybe that's why I'm losing gap with lower tension. So I stopped. Now I'm thinking of ordering new tensioners and leaving the car sit in the shop for another week.

    At this point, I've convinced myself that getting new hydraulic tensioners will resolve the issue. What I am asking is, has anyone come across this Gap vs Freq and just go with one or the other and seems fine? Just looking for someone to say "nah your good man, get the freq right and if the tensioners arent collapse, you should be good as that's what you should go by..." or "Set the gap and get the freq close and your good..." or "if your hydraulic tensioners were good you'd be able to hit both marks.."

    Thanks in advance. I searched all of the pages for answers but they all seem to ask the question, but never come to an answer as to what is correct or what has worked one way or another. And yes, I know, when in doubt, replace the tensioners. Im fine with ordering them. 1000$ isn't worth wrecking the motor over. I just figure Id see what peoples thoughts were as I head home and make other plans for this weekend other than firing this thing up. I kinda wanna just justify my thought process too.

    Thanks again.
     
  2. MT360.PK

    MT360.PK Rookie

    Mar 16, 2022
    16
    Pakistan
    Full Name:
    Sameer Malik
    I had the same dilemma, got new bearings but did not get tensioners (originals were still on the car) and wasn’t getting the right balance even after hours of trying… I ordered the tensioners and the balance between gap and frequency came up much better without much back and forth. Def worth it and now have peace of mind too
     
  3. 24000rpm

    24000rpm F1 Rookie

    things like 180hz vs 190hz vs 200 vs 210, vs 220 are, in my personal opinion, within tolerance. I bet you 10 thousand US dollars that even if it is 250hz it won't give you a problem in the next 5 years.
    Nothing to worry, I cut corners (read: not changing that tensioner) on my own 360s, all the time, for the last 10 years at least.
    hell, last time I did my belt changes at intervals that'll startle you: 8 years,about 25000km,on one of my 360s.
    granted my mileages per year are low so this may not be representative of the 360s at large.
    so YMMV.

    One of the reasons why people don't want to cut corners and engage "while at it" philosophy is the fact that labor is expensive.
    In my personal case where all labor are done by myself and hence free, those philosophy will no longer apply. I mean, if the engine blew , so what?
     
    Trackspec_360 likes this.
  4. Trackspec_360

    Trackspec_360 Rookie

    Dec 10, 2022
    10
    I m with ya on that. As I performed the freq test I went back and forth about it. Then finally said screw it, close enough. Then went back and said, I m already here and the car is sitting in my shop anyways, 10 more minutes to sway out the new tensioners after getting them here, I can wait. We will be racing this car so I erred on the side of caution since itll see 8500 pretty frequently. But yes, I m with you. Thanks for the reply, that was very helpful.

    John

     
  5. fotostars

    fotostars Formula Junior

    Feb 6, 2015
    343
    Bay Area
    I’ll put new tensioners if it’s going to see the track. I changed mine at 17y. I didn’t try to get it right with the original ones so can’t comment on the difference but I figured it was the way to go. You’re in there. Everything is open. What’s a little bit for $$ for piece of mind.


    Sent from my iPhone using FerrariChat
     
  6. TCrane

    TCrane Rookie

    Sep 27, 2020
    29
    MassHole
    Full Name:
    Timothy Crane
    Just curious, what tool did you use to measure the frequency. I'm due for belts soon and was debating trying the app's available for the tension, wasnt sure what you used. Cheers
     
  7. EastMemphis

    EastMemphis Formula 3
    Owner Silver Subscribed

    May 25, 2019
    1,773
    Memphis, TN
    Full Name:
    John
    A cautionary tale... A local guy with a very nice 360 farmed his belt job out to a local tech who's supposed to know how to do the belt change. Three months later, the cam belt slips a few notches and two years later, his car is still sitting in the shop getting the engine rebuilt. So while the frequency may not be critical, it is critical to do it right. I think new tensioners in a 20 year old car isn't extravagant and probably called for. The cost between a proper belt service with the tensioners changed out is nothing compared to an engine teardown and rebuild. Not counting the time sitting in a garage waiting to be worked on.
     
  8. Jjohnman

    Jjohnman Rookie

    Sunday
    3
    Full Name:
    Kar G
    Hi,

    We have a family workshop and a friend asked us to do timing job to his F360 Modena. I read the manual and he ordered the parts from the famous eurospar* store. Last timing job was done by the local dealer.
    So, we found some timing marks (propably made by the last time technician) and assuming they were marks at TDC, we removed the old parts (including tensioners) and installed all new. Trying to tense the belts, we couldn't get both tensioner gap and belt frequency.
    So, we removed the camshaft covers to check the marks and marks weren't there and engine wasn't at TDC. We turned the engine to TDC and again the same. We couldn't get gap 1.9-2.3mm and frequency 190-220hz. We removed the new tensioners and installed the old ones in case the new were faulty or not genuine. After that, we succeed the get left bank (passenger side for LHD) belt at 205-210hz and tensioner gap around 1,9mm (pin slides tight). However, the right bank is at 170hz and I can't even slide pin to the tensioner.

    Any idea guys? FYI, Camshafts are not totaly aligned with the marks on caps but this deviation is tiny. Could this be the cause?
     
  9. EastMemphis

    EastMemphis Formula 3
    Owner Silver Subscribed

    May 25, 2019
    1,773
    Memphis, TN
    Full Name:
    John
    Are you turning over the crank two revolutions between attempts at getting the frequency right? I had no trouble at all and got it nailed in the first two attempts on both sides.
     
  10. RedNeck

    RedNeck F1 World Champ
    Silver Subscribed

    Jul 8, 2016
    10,431
    The CSA
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    You don’t know what you don’t know, and you should have never started that job without proper research or experience. I hope you have the WSM and are following it to the letter. Weirdness can still happen and it may take a couple tries, but if the pin slides freely and the gap is correct, the frequency should be within spec after a couple rotations. Removing the pins should be the last step
     
  11. Jjohnman

    Jjohnman Rookie

    Sunday
    3
    Full Name:
    Kar G
    Yes, done that. I will do everything from scratch again.
     
  12. Fcar tech

    Fcar tech Karting

    Oct 22, 2021
    105
    Always nearby
    Full Name:
    XXXX
    "Lock and swaps" NEVER recommended.. Marks on the cam gear don't mean anything.. People, PLEASE learn to use a degree wheel.
     
    jjtjr likes this.
  13. RedNeck

    RedNeck F1 World Champ
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    Jul 8, 2016
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    Except by Ferrari and most dealers...nothing inherently "wrong" with a lock n' swap and I'd venture to guess that the VAST majority of timing belt jobs are done this way with no negative effects other than the motors maybe not reaching 100% of their potential output.
     
  14. RedNeck

    RedNeck F1 World Champ
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    Jul 8, 2016
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    Don't get too hung up on setting the belt frequency with the tensioner first off...I've made this mistake even after having done the job before, you can forget a lot in a few years so follow the WSM every time. Your first goal is to rotate the tensioner bearing so the pins in the tensioners slide FREELY and the tensioner gap is correct. Rotate the motor a few times, THEN the belt frequency should be within spec.
     
    EastMemphis likes this.
  15. THINKFAST

    THINKFAST Karting

    Jan 13, 2011
    194
    Earth, mostly ...
    Riiiight..Who wants 100% out of the engine anyway..
     
  16. RedNeck

    RedNeck F1 World Champ
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    Jul 8, 2016
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    Not the point of the post and you know it. Let's not act like children.
     
  17. THINKFAST

    THINKFAST Karting

    Jan 13, 2011
    194
    Earth, mostly ...
    YOU brought it up. NOT me.
     
  18. Jjohnman

    Jjohnman Rookie

    Sunday
    3
    Full Name:
    Kar G
    Thank you for the help. This part of installation procedure is not clear at the WSM. WSM doesn't clarify when to remove the tensioner pin. Also, it doesn't clarify if the pins should slide freely when you finally get the proper frequency.

    For those who say that you shouldn't "lock and swap", that is what the manual says if No1 piston is TDC and camshafts marks (on rear) are aligned. Also, main dealer is the one who used marks on the sprockets to replace the belt last time. Not to refer to some missing bolts...
     
  19. Fcar tech

    Fcar tech Karting

    Oct 22, 2021
    105
    Always nearby
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    XXXX
    Cam marks mean NOTHING, If I didn't put the marks on them. I NEVER assume they are right. Do it your way you're right..
     
  20. RedNeck

    RedNeck F1 World Champ
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    Jul 8, 2016
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    Yes it does. It's in the last part of section A3.03
    Image Unavailable, Please Login

    I will agree that you should always use a DTI in the Cylinder #1 to determine the most accurate TDC, and of course that it outlined in the WSM also...but most folks that don't do the "lock n swap" method are actually still using that method, just they are degreeing the cams to factory spec afterward, which is going to give you the best performance since it's a poorly kept secret that many left the factory slightly out of spec....IF the cams have been degree'd in the past then that's where you will run into issues where all timing marks not aligning 100% perfectly. I would venture to guess that 90% of 360's out there are running the same timing that they left the factory with so I would say that your marks are most likely correct. Here's a recent picture of my car, I had just put all new tensioners, tensioner bearings, belts, tensioner brackets, variators (after pulling the cams to do so), so I had to use a degree wheel, but my intake cams were perfectly aligned just lining up the scribe marks and making marks on the old belts. I did have to make new marks on my exhaust cams but prior to removing them everything lined up perfectly.

    Image Unavailable, Please Login
     
  21. 066/8

    066/8 Karting

    Sep 29, 2023
    112
    #21 066/8, Jul 10, 2024 at 4:18 PM
    Last edited: Jul 10, 2024 at 4:38 PM
    I want 100% out of the engine, but I can't think of any reasonable way to determine engine output with the required degree of acurracy and certainty:

    Methods that I have ruled out:
    • engine out + put it on a test stand ... seems excessive to me and I assume not too many people here have access to suitable test benches
    • chassis dyno ... too many uncontrolled factors; results lack certainty and/or accuracy
    • measuring spark plugs ... kinda expensive and still not optimal results
    • drilling the cylinder heads and proper ICPs ... yeah, I'm not doing that ...
    But perhaps I am just missing something obvious here.
    Otherwise I reckon, that worrying about half a degree timing is mostly pointless, since we have no way to detect the effects anyways.
     
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  22. THINKFAST

    THINKFAST Karting

    Jan 13, 2011
    194
    Earth, mostly ...
    I was referring to 100% on the cam timing.{ this is a cam timing thread} For the last 15+ years of being a member here Techs here have ALWAYS stressed the importance cam timing being 100% dead on spec.
    You lost me at engine out on a dyno..
     
  23. 066/8

    066/8 Karting

    Sep 29, 2023
    112
    You want 100% cam timing out of your engine? When the post you quoted reads "[...] the motors maybe not reaching 100% of their potential output."?
    I guess I missread your comment then - apologies for that.

    There is no such thing as 100% dead-on timing, no matter what some techs might claim. The question is how much deviation from the theoretical ideal position are you willing to accept. I would opine that +/- 0.5 deg is acceptable, but I'm happy to learn if someone knows a reason why this would not be sufficient.

    Once again, not meant as criticism but as a good natured contribution to the discussion from an technical perspective.
     
  24. RedNeck

    RedNeck F1 World Champ
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    Jul 8, 2016
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    He's just making sarcastic and condescending comments without offering any help. I do remember this quote from a career Ferrari mechanic. Is it debatable?. Infinitely. Is it most likely accurate? Definitely.

    Let's be honest, most people that do their belt service here find the engine to be timed the way it left that factory, which means it had most likely never been degree'd on a belt service or the factory timing was correct.
     

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