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Thread: 355 cam timing.....

  1. #1
    ferrari-spider Guest

    Default 355 cam timing.....

    I just have to post this new artical regarding the timing of the 355.
    This was wrote by FERRARIFIXER and i have copyed and pasted it here.
    I have always asked on all forums how much the average 355 is out regarding its timing degrees. But no one has answerd the question but only say that the factory camshaft marks are usualy out. Well there not The factory cam marks are more or less spot on. So all this BS about always putting a dial gauge on a 355 to set the timing becourse the factory timing marks are so far out, is BS as i have always said So it must be concluded that the only reason that a 355 would be out of time by a large degree is becourse its been tamperd with after it left the factory so it will need to be re-timed back to factory standards which was more or less perfect.
    Heres the copy and paste....

    #89 Today, 04:52 AM
    ferrarifixer
    F1 Veteran
    Consultant Join Date: Jul 2003
    Location: Melbourne
    Full Name: Phil Hughes
    Posts: 7,288

    OK, here goes.

    Firstly, I'm of the school of thought that the reference marks put on the cams are pretty good usually... certainly, in my experience, I've never found any to be wildly out... always within the rough tolerance of the line width, which is easy to see by eye. I only dial cams in by request or for investigation purposes.. NOT as part of std service schedule. If I happen to know or even feel (nearly 20 years experience) that cam timing is correct, I'll happily just replace belts to save expense if it's enomically viable or requested.

    Recently, I've done belts and cam timing on a 355 that I suspected of having bad cam timing since PPI... due to poor power/throttle response initially, lack of the full on WAAAAA noise (despite bypass working correctly), but subsequently and more recently (18 months into new ownership) the C/E light came on for cat failure.

    Now, and here's the crux... I reckon there's many areas for human error in dialling in the cams. I've dialled perhaps 10% of the belt changes I've ever done, and I always triple check my work in this regard.

    Upon dismantly, the recent job was found to have significant mis-timing DESPITE perfect belt wear/tension conditions.

    To check... firstly we have to establish a true TDC mark... 348/355/360 dont have crank markings, so we need to find the centre of the TDC dwell and mark it... I have a simple tool I drop in the clutch vent hole, and put a mark on the flywheel edge as the front pulley radius is too small for accuracy. This has to be done for both 1-4 and 5-8 banks.

    The flywheel is on a spline, so the tiny amount of slack has to be considered... But it's not much and easy to set.

    Then, we use the dial gauge to measure valve lift at TDC... on the inlet we must use the lateral (side) valve and not a central one of the 3. On the exhaust, either is ok. (In fact, it's interesting to compare valves... some discrepancy in the cam grind is quite common). I DON'T measure the point of max opening on the 5 valve cars because it's all too restrictive to get the tooling in the hole with any real accuracy, but I DO prefer this method wherever possible).

    Now, it is ESSENTIAL that we measure lift in a perfect line with the valve... if we measure on an angle, the lift is effectively reduced, so I've made a specially bent pointer to wrap a round the cam to achieve perfect alignment.

    To measure the timing, the CRANK PULLEY MUST BE TIGHT... as the helical gear otherwise allows the timing gears to retard a little.

    Arrange the dial gauge perfectly in alignment, and turn the engine to TDC as marked... the lift should match the spec values. bear in mind the cam sprocket only allows 1.5 degree increments of adjustment, which is 3 degrees of crank rotation, so perfection is sometimes impossible to achieve.. in which case set the timing with new belts to be a little advanced, as it will retard with stretch.

    On my recent job, the 1-4 bank was found to be just about perfect, but the 5-8 bank was considerably out...

    I've included a few pics...

    You can see my crank TDC tool which positively locates in the vent hole, the tape just stops it falling out and acts as visual reminder to take it out!!

    You can see the marks that look really accurate, and you can see the ones that are clearly out as deliberately set previously by error... you can see also the amount of crank misalignment the incorrectly timed cams had.. about 12 degrees on one and 9 on the other... 4 holes and 3 holes on the cam sprockets...

    When they were all adjusted... guess what happened with the reference marks.... they were all VERY close to perfect.
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  2. #2
    Join Date
    Jul 2006
    Location
    Essex
    Name
    Ken
    Posts
    479

    Default

    Excellent. Mods should this be in Tech QA

    Ken

  3. #3
    ferrari-spider Guest

    Default

    I put it here knowing the mods will put it in he tec section anyways. But i ask that it is left here for the non tec visitors to read first and hen move it tomorrow I have told Ferrarifixer that i have posted it here We once had a big discusion on here when i was only one of two who knew that the timing marks at the factory was correct straight out the factory. A few guys claimed to have used a dial gauge and pratractor to time a 355. But i knew the posters never even did a 355

  4. #4
    ferrari-spider Guest

    Default

    I asked for it to be moved here tomorrow ya ****in ******.

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