Check Timing with degree wheel | Page 2 | FerrariChat

Check Timing with degree wheel

Discussion in 'Boxers/TR/M' started by Nick G48, Mar 11, 2021.

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  1. vincenzo

    vincenzo F1 Rookie

    Nov 2, 2003
    3,373
    When I first bought my car, I had the belts done by a ‘pro’. He got it 4 degrees out and burnt up a cat. These cams do NOT tolerate ‘close enough’ approaches.
     
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  2. Ferrari Tech

    Ferrari Tech Formula 3

    Mar 5, 2010
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    Wade Williams
    Zero clearance is achieved by installing a shim thicker than the clearance. If the valve is open some, it makes no difference. I just want to see complete followed action of the cam lobe. Even getting it perfectly 0.50mm is all but impossible. But if I have zero clearance and see the bucket move 0.50mm on my dial indicator then I KNOW I have 0.50mm on the cam lobe. I have even put the cam at 0.50mm lift and moved the crank to my desired number and then found the pin hole that works. Tighten it up and make a few turns to see if it hit it right. I use that method if I have to change pulleys (like going from plastic to all metal). I have as well measure the cam lash, say 0.26mm and then moved the bucket 0.24mm on the gauge and that is again 0.50mm lobe lift. I have tested this and it gets the same result as zero lash.
     
  3. vincenzo

    vincenzo F1 Rookie

    Nov 2, 2003
    3,373
    “Zero clearance is achieved by installing a shim thicker than the clearance.”

    Does that not introduce an unknown, additive amount of lift on top of your measured 0.5mm?
    Note that “zero clearance” is a very different number from “zero lift”.
    Cam duration and timing is only based on lift.

    I always take it to an extreme number to test a theory. Say for example, you inserted a 50mm shim (silly idea, but stay with me). Essentially holding the valve open all the time. Obviously it is impossible to measure timing. Ponder this.... how much can you open the valve by way of a thick shim before you introduce an unacceptable amount of lift and error?
     
  4. Ferrari Tech

    Ferrari Tech Formula 3

    Mar 5, 2010
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    Wade Williams
    I think you are missing the point. The point of the action is to set the cam timing with a specific crank position. The cam lift and duration are ground into the cam. WHERE the duration and lift starts is all that is adjustable. The actual position of the valve on the seat is irrelevant. In this action, the valve is used only to keep the cam bucket in full contatct with the cam so any movement is read exactly on the dial indicator. If the cam timing is set at 0.05mm of cam lift (and it is) then accurately measuring the 0.50mm will end with the best results.

    If a 328 calls for the intake to open @ 16 degrees BTDC with a lift of 0.50mm, then zero lash and turning the crank until the valve bucket moves 0.50mm should have the crank degree wheel at 16 degrees. You want to read what the cam lobe is doing not the valve. After it is timed, install a shim that gives the proper clearance and go drive it.

    I have degreed hundreds of cams in different engines. Always at zero clearance. It is just how I was taught.
     
  5. vincenzo

    vincenzo F1 Rookie

    Nov 2, 2003
    3,373
    If I understand you correctly:

    1) start at zero clearance (or less) with a thick shim as shown in light blue
    2) rotate engine until the valve moves an additional 0.5mm as shown in purple
    3) adjust the cam’s rotation to move the purple dot to 13 deg btdc.

    As I understand it, you are using an incorrect place on the lobe.... the factory calls for the red dot to be at 13 deg, not the point shown in purple. Perhaps try the methodology that I advocate and see how the results change. I’d suggest that your method will always result in a retarded cam by ‘who knows’ how much.

    Not trying to be a smart a$$ here... but I think the guy that taught you was incorrect. If I misinterpreted your method, please correct me!

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  6. Ferrari Tech

    Ferrari Tech Formula 3

    Mar 5, 2010
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    Wade Williams
    So let me understand. You want the cam timing spec to be at 0.50mm of cam lift. Is that correct?
    You set your clearance at 0.50mm and when the cam makes contact, you are there. Is that correct?
    I set my clearance at zero and when the cam move the valve 0.50mm I am there.
    The only difference I see it that I have zero clearance, thus I have a true reading at all times. No air gab to take up.
    If we are both reading the cam lobe, then I am doing it with the ability to see every bit of cam action. You however will not see anything until the cam takes up the 0.50mm and then moves the valve. We will end up with the timing very close. I just don't have to take up clearance before I arrive at my desired point. Your way is not wrong, just different and has more room for error. In my opinion.
    It is always nice to see different ways of doing things. Looking forward to your reply.
     
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  7. vincenzo

    vincenzo F1 Rookie

    Nov 2, 2003
    3,373
    #32 vincenzo, Apr 17, 2021
    Last edited: Apr 17, 2021
    After some thought and a different style sketch.... I think(?) your methodology would work. Yes, even if the valve is slightly open from too large a shim. You can see where I marked “0.5mm?” away from the cam’s base circle. Point”B”.

    Unfortunately I do not have an engine open to try your method out. If your instrumentation is well laid out and secure, it may be easier to judge that 0.5mm movement rather than ‘1st contact’ with a gap. It is VERY difficult to get your plunge indicator exactly in line with the valve. If it is canted over a bit, it will affect your measurement.

    Good discussion. I think I may have learned a new methodology and am eager to try it out and compare results.. Thanks for sharing!

    PS: As I was measuring first contact, I could actually see how the shim was being rocked within the bucket while riding on the oil film during rotation. It makes interpretation of movement more difficult. The nice thing about your method is that you have solid, zero clearance contact from the get-go with less ‘interpretation’. I am eager to try it out. Thanks again!


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  8. turbo-joe

    turbo-joe F1 Veteran

    Apr 6, 2008
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    your system makes sense ! ! !
    never tried it this way

    as I have written already I do it a 3rd way:
    put on new belt with the original markings. then check the opening and the closing with the normal working valve play. has to be for example exhaust opens 54 ° BDC and closes 10° after TDC. because the cams of the camshaft are symmetrical the readings has to be then also same difference to the 54 ° and the 10°. nevertheless what valve play you have. the valve play only tells you the duration.
    so when my readings are for example 44° before BDC opening and closing at TDC then I know the timing is correct.
    if the readings are 50° before BDC and 6° after TDC it is also right.
    but when the readings are 44° before BDC and 10 ° after TDC then I know that the camshaft is wrong adjusted by 5° ( because of the symmetrical cam the difference for BDC is 10°, TDC is ok. so have to turn then the camshaft 5 ° to have both sides the same "offset" ( right word? )

    but here also it is not as correct as wade williams describe because I only see after touching the shim. so to have all without play or better with minus play ( so valve still open a little ) it is much more correct. will try this next time
     
  9. Ferrari Tech

    Ferrari Tech Formula 3

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    You can also try my method with the correct valve clearance in the head.
    Say the intake valve being tested checks exactly at 0.26 on a 0.25-0.30 spec.
    If the spec is 54° @ 0.50 then you can rotate the crank until the cam moves the valve 0.24 and combined with the clearance of 0.26, that is 0.50 of cam movement.
    I have tried back to back with zero and added clearance method and had the same results.
    This one is kind of the best of both worlds, no need to take out the shim and you see the bucket move.
    Hybrid if you will.
    What a great discussion, so glad to be able to work through ideas.
     
  10. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    That's good because we'd have to burn you as a witch if you didn't ;).

    The three methods are identical as they are just three different ways to find the exact SAME point on the cam lobe profile.
     
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  11. vincenzo

    vincenzo F1 Rookie

    Nov 2, 2003
    3,373
    Wade,
    Rough guess please....
    about how many crank degrees do you need to get 0.5mm?

    Is it a super low number that is difficult to control and hit exactly... or a pretty high value that is easy to reach with full control?
     
  12. Ferrari Tech

    Ferrari Tech Formula 3

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    It depends on the cam, but I find it very easy to hit 0.5mm. I also recommend the largest degree wheel you can fit. In chassis limits that but on the bench/engine out, I have an 18 inch degree wheel that I just love.
     
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  13. turbo-joe

    turbo-joe F1 Veteran

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    wow, around 45 cm diameter that is great
    my degree wheel ( self made ) is only 25 cm. so with yours you can work much more exactly :)
     
  14. vincenzo

    vincenzo F1 Rookie

    Nov 2, 2003
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  15. Nick G48

    Nick G48 Karting

    Aug 18, 2016
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    Thanks so much for all the help. We will be ordering the belt kit from Ricambi soon. Once we start the replacement, we will be posting videos and I am sure we will have questions. We will start a new thread for TR Timing Belt replacement. Thanks again
     
  16. Veedub00

    Veedub00 F1 Rookie
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  17. Veedub00

    Veedub00 F1 Rookie
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    It was a pain to adjust the increments I needed. Had to rotate the cam holes around to get the smaller degrees I needed.
     
  18. Rifledriver

    Rifledriver Three Time F1 World Champ

    Apr 29, 2004
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    The head of the department at Ferrari agreed with me that doing it that was was faster, easier and more accurate but it required special tools to do. Ferraris method was developed so it could be done with nothing but very simple standard tools. No dial gauges required their way.
     

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  19. vincenzo

    vincenzo F1 Rookie

    Nov 2, 2003
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    “…faster, easier and more accurate…”

    music to my ears.
     
  20. Rifledriver

    Rifledriver Three Time F1 World Champ

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    I throw in any shim that closes the clearance. Having the valve a little open is of no consequence.


    Doing it Ferraris way on most of the cars did not require a degree wheel as the flywheels were marked with In. Open and Ex. Close times and it was anticipated a small screwdriver in the notch in the side of the cam follower was used to detect valve open or valve close events so no dial indicator needed.

    Then hydraulic valves came along. .

    You have a nice long handle on your degree wheel.
     
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  21. Rifledriver

    Rifledriver Three Time F1 World Champ

    Apr 29, 2004
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    Had the same problem at a dealer I was brought in as a shop foreman. Retaught everyone how to time cams. My 1st week I hopped in a 348 with a fresh service to move it and could not believe how bad it ran. Good fortune it never got delivered.
     
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  22. Rifledriver

    Rifledriver Three Time F1 World Champ

    Apr 29, 2004
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    I have done it all 3 ways and all are very accurate if you are very consistent. What I was looking for was a way where it was harder to make a mistake.
     
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  23. turbo-joe

    turbo-joe F1 Veteran

    Apr 6, 2008
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    that is right and for sure a big help and absolute correct. but with degree wheel it is easier to look at ;)
     
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