Embarassing question: which cylinder is at TDC? | FerrariChat

Embarassing question: which cylinder is at TDC?

Discussion in '365 GT4 2+2/400/412' started by raemin, Jan 26, 2021.

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  1. raemin

    raemin Formula 3

    Jan 16, 2007
    1,825
    Lyon (FR)
    Full Name:
    R. Emin
    My mechanic had forgotten that 4 years ago the machinist had rotated the flywheel by 180° and the car is now back in the engine with the timing marks all other the place...

    Before removing the camshafts and pulling back the rear axle in order to redo the timing while the engine is in the car, I'd rather try a more subtle approach!

    1. Are there any other timing marks than the one on the flywheel ?
    2. For a lack of a better solution, is there any other cylinder (6 or 9?) that is at TDC when the crankshaft has performed half a revolution?
     
  2. Tojo

    Tojo Formula Junior

    Apr 12, 2002
    481
    Sydney
    Full Name:
    Tim
    Can you pull No.1 sparkplug set the piston to TDC, and remark the flywheel accordingly?

    I've just finished stripping my engine down, haven't had a close look at my flywheel yet. I'll try to remember to have a look at it tomorrow and see if there's any her timing marks on it that might be helpful
     
  3. raemin

    raemin Formula 3

    Jan 16, 2007
    1,825
    Lyon (FR)
    Full Name:
    R. Emin
    This is actually what I am contemplating, but in order to turn the crankshaft I must first setup the camshafts more or less properly otherwise the valves will hit the piston and I will never manage to make this half turn! Obviously, without camshafts valves would rest on top of the dome, which would allow for a much easier half turn, but removing the exhaust camshaft is an absolute pain.
     
  4. 57Wayne

    57Wayne Karting

    Mar 29, 2015
    127
    Wilbraham MA
    Full Name:
    Wayne Thresher
    If the firing order is 1-7-5-11-3-9-6-12-2-8-4-10 it makes sense that #6 would be at TDC
     
  5. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    25,040
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    #5 Steve Magnusson, Jan 26, 2021
    Last edited: Jan 26, 2021
    You misread his question -- (for that firing order) cylinders #1 and #6 would be at TDC at the same time, but cylinder #11 would be at TDC and ready to fire "when the crankshaft has performed half a revolution" after the cylinder #1 TDC firing position. If that is the correct firing order (and the flywheel is mounted 180 deg out), by connecting the timing light to cyl #11 (or cyl #8), the flywheel timing marks for cylinder #1 should be visible.
     
  6. raemin

    raemin Formula 3

    Jan 16, 2007
    1,825
    Lyon (FR)
    Full Name:
    R. Emin
    Thanks Steve, If I get it right two turns to perform 12 ignitions, so half a turn would mean the 4rth cylinder in the firing sequence is at TDC (i.e #11). Image Unavailable, Please Login

    Will try to fix that mess this week-end...
     
  7. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    25,040
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    Correct. Now, please explain how your flywheel was put on 180 deg out ;) Seriously, manufacturers usually have some provision (pins, asymmetric bolt pattern, etc.) so that the flywheel can only go on to the crankshaft in one orientation - if the F 400i has a design such that it can be mis-assembled in that way, they deserve as much blame as the Mechanic IMO.
     
  8. raemin

    raemin Formula 3

    Jan 16, 2007
    1,825
    Lyon (FR)
    Full Name:
    R. Emin
    I've said it was embarrassing...

    Actually the starter sometimes made an annoying "clong". When the engine was disassembled, the machinist spotted that one of the teeth was worn-out, so he fixed it, but said the engine was probably stopping very often in this position (hence the excessive wear), so best way was to drill another pin and rotate the flywheel 180°. I asked for the flywheel to be balanced but we forgot to ask for the marks to be engraved.

    From then on then engine was properly timed and reassembled months ago. Engine put back in the car. Second mechanic decided to adjust the chain tension, and thought it could be a good idea to check again timing. My first reaction was "hey you've just ruined the 4° offset we took so long implement", then came the second question "you remember the flywheel was rotated 180°?".

    The whole of us do deserve a giant blame.
    Image Unavailable, Please Login
     
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  9. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    25,040
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    OK, the F designers are absolved of any wrongdoing ;).

    Shame that you didn't make a new PM1-6 mark (and relabel/erase the old PM1-6 mark). For the ignition, you can get by using cyl #11 (or #8) for the timing light as we discussed, but I hope that you leave some very good notes with the car for the next Owner -- these cars have a nasty habit of out-living us...
     
  10. NeuroBeaker

    NeuroBeaker Advising Moderator
    Moderator

    Oct 1, 2008
    38,744
    Huntsville, AL., USA
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    Andrew
    Embarrassing question #2:

    If the original marks are still there and the flywheel was rotated exactly 180°, what's to stop you from creating the new marks by putting a straight edge from one side of the flywheel across the diameter, to mark up the opposite side accordingly?

    All the best,
    Andrew.
     
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  11. samsaprunoff

    samsaprunoff F1 Rookie
    Silver Subscribed

    Jun 8, 2004
    4,160
    Edmonton, AB Canada
    Full Name:
    Sam Saprunoff
    Good day Raemin,

    It is truly unfortunate that this happened, but... and I hate to say it... but if it were me I would bit the bullet and remove the flywheel and mark it appropriately. If not then the next owner/shop will have an absolute nightmare trying to understand what is going on if the documentation gets lost or damaged. Certainly no one will enjoy all the effort to correct this, but in the end it is the correct and professional thing to do.

    Cheers,

    Sam
     
  12. raemin

    raemin Formula 3

    Jan 16, 2007
    1,825
    Lyon (FR)
    Full Name:
    R. Emin
    @NeuroBeaker : I can't make the new marks because the gearbox is in the way with the flexplate and converter bolted on the flywheel...

    For now the plan is to roughly adjust the timing based on cylinder 11 (this will prevent the valves from blocking the pistons), then rotate the crancksaft by 180°, find cylinder #1 TDC put the damn mark and redo the timing.

    If it fails, I will just have to remove the camshafts so as to free the crankshaft and slide the gearbox a few inches back (which is a pain) so as properly access the flywheel. While I am there I'll probably bit the bullet and put a NEW flywheel.

    With a bit of luck the machinist has left a mark on the other side, which is why I'd rather try to properly rotate the flywheel first.
     
  13. Tojo

    Tojo Formula Junior

    Apr 12, 2002
    481
    Sydney
    Full Name:
    Tim
    To answer your question about marks in the flywheel, mine has, about 14 in total. If you want full details of which mark is where, and how many teeth between them let me know and I'll check it out and get back to you Image Unavailable, Please Login Image Unavailable, Please Login

    Sent from my SM-G935F using FerrariChat.com mobile app
     
  14. mike32

    mike32 F1 Veteran

    May 13, 2016
    5,828
    Isle of man- uk
    I have seen similar flywheel damage on a diesel generator, but ours was caused by the starter motor spinning up before it had fully engaged. ie it was spinning as it was going in. Might be an idea to run it on the bench to see if it is doing the same. Our flywheel was about one metre diameter and we had to dress the teeth with a Dremel and grinding wheels through the hole where the starter was fitted. About 24 hours work and 150 grinding wheels.
     
  15. raemin

    raemin Formula 3

    Jan 16, 2007
    1,825
    Lyon (FR)
    Full Name:
    R. Emin
    #15 raemin, Feb 20, 2021
    Last edited: Feb 20, 2021
    I've bought a new starter as part of the usual "while you are SPENDING there".

    Follow-up... My mechanic made me an offer I could not refuse: I pay for the damaged parts and he rebuilds again the engine during the week-end (for free). Could have been worse as the part count is quite reasonable: 4 exhaust valves, cam-cover gaskets, 4 O-rings, plus the head-gaskets. Parts due to arrive on Monday...

    Flywheel, now, has the proper markings!
     
  16. mike32

    mike32 F1 Veteran

    May 13, 2016
    5,828
    Isle of man- uk
    Different engines have different setups regarding the hardness of the flywheel and the starter pinion. Your flywheel is softer, hence the damage. There should be some adjustment so that the pinion is fully engaged before the power is connected to the starter motor.
     
  17. raemin

    raemin Formula 3

    Jan 16, 2007
    1,825
    Lyon (FR)
    Full Name:
    R. Emin
    #17 raemin, Feb 20, 2021
    Last edited: Feb 20, 2021
    Actually I had changed the starter before dis-assembling the engine, with the new geared starter I did not experience the "clong" any-more which was good enough for me. When we dropped the engine we spotted the damage on the flywheel. No idea if this damage was caused by the old starter or the new one so we decided to fix the flywheel.

    The mesh of the starter pinion is different, and the solenoids is probably stronger. I've noticed a higher amp-draw on the ammeter during startup, which is probably due to the solenoid (which passes through the ammeter), not the starter motor itself (directly connected to battery posts). All in all with this new starter the engine would crank no matter what. Maybe the new starter is pushing hard on the flywheel? It could also well be that the old starter had started to damage the flywheel as the infamous "clong" appeared while the old starter was still on the engine.

    On my brother's 365 we saw on the maintenance records that Pozzi had replaced the flywheel while the car was quite recent. Maybe there is a weakness on these flywheels?
     

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