cylinder head removal | FerrariChat

cylinder head removal

Discussion in '206/246' started by daviekj, Jan 17, 2009.

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  1. daviekj

    daviekj Formula Junior
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    #1 daviekj, Jan 17, 2009
    Last edited by a moderator: Sep 7, 2017
    Removing the cylinder heads to investigate another thread "valve shims and cam wear" as well as address suspected cylinder gasket.

    Can anyone tell me what the manual is refering to on page 20

    ........,with, tool 622-AS-5422 extract the centering and drag pins..............

    Do I need to do this. I plan the slacken off the timing chain tensioners and gently withdraw the cam sprockets with a hub puller. Is that correct?

    Kevin
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  2. jselevan

    jselevan Formula 3

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    #2 jselevan, Jan 17, 2009
    Last edited: Jan 17, 2009
    Kevin -

    1) None of your pictures provide a visual of your chain tensioners. I assume that your car is late enough (production date) to have the modification to the chuck-cap that includes the 8mm hex threaded bolt acting as a stop for the tensioner piston. If not, then you must perform the modication. Make sure that you seal the locking nut with a soft copper washer, else oil on your alternator is not in doubt.

    2) You will NOT need a gear puller to remove the cam sprockets. You will need to remove the two pins aligning the holes in the sprocket with the cam end. It is easy to remove these pins with the proper size drift. You will have to rotate the engine to bring each pin towards the top of the gear, thereby allowing the drift to approach from the engine side to drive the pin away from the engine and out. Once the pins are removed the gear will be easily separated from the cam. TAKE CARE to not allow the pins to drop into the chain front cover. I suggest placing a large towel tucked under the cam sprocket as you do this work just in case.

    3) Prior to driving the pins out, use some paint or other method to mark which holes the pins cam out of ON BOTH THE CAM AND THE SPROCKET. Do not simply use two marks, one on each pin, as this will allow you to reassemble 180 degrees incorrectly. Make three marks (each pin hole and a third arbitrary point on the circle) so that you can put it together as it came apart.

    Item #3 is necessary because you will have to turn the engine away from TDC #3 to extract the pins for each came. Hence, you will lose your reference.

    Once reassembled, do not tighten your cam-end bolts until you have inserted the pins and checked for 4-cam alignment at TDC. After loosening the chain and rotating everything, you may have to adjust cam timing a bit by moving the holes in the "Vernier" sprocket-cam system.

    Jim S.
     
  3. jselevan

    jselevan Formula 3

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    Kevin - referring to my previous post, allow me a few additional comments of explanation. First, I should have used the expression tensioner rod, not piston. It is a better description. The modification acts as a stop preventing this rod from slipping in the chuck-like clamp. The threaded 10 mm hex head screw should be finger-tightened against the tensioner rod....no more. Then hold the screw as you tighten the lock nut against the copper washer. Not too tight...these are easy to strip.

    Second, When you remove the cam sprockets, the cams will immediately snap to their low-energy state. Hence, it is really not important to mark the sprockets and the cams for reassembly as you will have to reset the cams anyway. It won't hurt, and may make the process easier, but the cams are going to move.

    Finally, there is a trick that you can perform if you want to keep the cams from turning. Before loosening the chain and before taking off the sprockets, take off two caps from each cam. Use a piece of notebook paper and fold it over once, perhaps 1 inch wide and several inches long. Now place the paper under the cap, between the cam journal and the cap bearing surface, and tighten the 10 mm nuts barely snug. (Too tight and you can crack the cap - really easy to feel when to stop). The friction of the two pieces of paper under two caps on each cam will keep them from rotating.

    This really is not necessary as it is easy to rotate the cams to align them when ready.

    Jim S.
     
  4. jselevan

    jselevan Formula 3

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    Kevin - funny how the brain works. I awoke at 3:00 am with a picture of the sprockets in my mind's eye. Please refer to the sequence of posts that I have authored in the past day or so.

    There is an alternative to my prior comments vis-a-vis driving the pins out with drift. As mentioned earlier, this will require rotating the engine to provide access for the drift to drive the pin. As I recall, the pins are internally threaded. A 3 or 4 mm fine-thread (1.75 mm?) machine screw can be threaded into the pin to act as an aid in extracting them. This also helps when reinstalling. You can get purchase on the pin by use of the screw, and pull the pin out.

    HOWEVER, if I recall correctly, you are removing the heads to accomplish some valve seat and valve stem length issues. If this is the case, then it is easiest to loosen the chain tensioner, remove all of the cam caps, and simply lift the cams off of the engine. Why worry about taking the sprockets off? You will have to loosen the chains all of the way, else you cannot tilt the cam sufficiently to remove the chain. Take the tensioner locking cap off and this will not be a problem. Use a piece of safety wire or similar item to hang the chain from a stud to prevent it from falling down into the timing cover. If it should, no big deal, you can fish it out later.

    When removing the cam caps, take care to loosen the 10 mm nuts in a sequence such that the cam comes up parallel to the head. Do not take off the cap from one end and then work down the line. This will place a great amount of force on the edge of each journal. The valve springs will push up on what ever is free to rise.

    Jim S.
     
  5. John Corbani

    John Corbani Formula 3
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    #5 John Corbani, Jan 18, 2009
    Last edited: Jan 18, 2009
    Kevin and Jim,
    Jim is right on most everything. I have had the cams out twice and it is faily simple. First, lock down the tensioners! You don't want the spring loaded piston to move now. Loosen the two tensioner assemblies so there is lots of play in the chains. Slowly remove cam caps as Jim describes. Cams and sprockets lift rght out. Remove floating sprocket and remove tensioner assembly. Put assembly in a large vise so spring force is captured and the vise can open a couple more inches. Loosen tensioner lock and slowly open vise. This is the only safe way to get the spring out and back in. Check that the tensioner lock has the modification Jim notes. Good pictures on omgjon's web site. You can take sprockets off of cams any time you wish. Or leave them on, just loose. Don't loose the timing you have during clean-up.
    John
     
  6. daviekj

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    #6 daviekj, Jan 18, 2009
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  7. daviekj

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    #7 daviekj, Jan 18, 2009
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  8. daviekj

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    Just read your comments Jim/John, retrospectively. Ironically, I ended up making a tool pretty much as you describd Jim. Must be telepathic, 3am your time, 11am mine. Thats was when i was working on the sprockets. Spookey.
    Kevin
     
  9. jselevan

    jselevan Formula 3

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    Just think of the casting imperfections as oil feeds. Won't hurt the cam or the bearing cap. Standard operating procedure for Ferrari. Nothing you can do about it anyway.

    Jim S.
     
  10. daviekj

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    #10 daviekj, Jan 19, 2009
    Last edited by a moderator: Sep 7, 2017
    The heades are off.
    First glance on valve and seats from cyliner 1 is that there are no major issues. More detailed analysis to come.
    Has anyone come across deep pitting on the head. I think this must have worsened through corrosion, but the origin in curious. All I can think of is an inperfection in the casting. What are the views on this. Should I have it welded up and skimed, or leave alone? Does not look like it will effect function, just looks ugly.
    Kevin
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  11. daviekj

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    #11 daviekj, Jan 25, 2009
    Last edited by a moderator: Sep 7, 2017
    Started to strip the cylinder head for cleaning.

    There were two types of valve oil seal. Out of curiosity, anyone know which is the original, and if there good/bad alternatives.
    The black ones were quite difficult to get off. Took me about an hour to do the 6. Even now I am not entirely sure i have got all the rubber off the valve guide. Very difficult to get hands and eyes close enough.

    Timing chain tensioner parts came apart easily and look easy enough to re-assemble.

    Can anyone tell me what the exterieor steel slipper plate is plated with. Its a sort of grey/green matt finish. Does not look like dull zinc plating.

    Kevin
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  12. John Corbani

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    #12 John Corbani, Jan 25, 2009
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    The white Teflon oil seal is too good. Not enough oil on the valve stem. Attached picture shows the right type. Viton is the prefered material but other plastics work. Manual shows this type but pictures are too small to show details. Readily available. Should come off fairly easily if oil was on guide when installed. Everything should be a little juicy as things go back together.
    John
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  13. fastradio

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    The original valve stem seals were the white nylon ones (Perfect Circle PN: T9010). As John pointed out, these seals work too well and literally wipe the valve stem clean of all oil (not good)..and as the guide wears, these particular seals will then wear quickly.

    The best replacement seal is one of the "Viton variety" as used on most BMW's and VW's with an 8mm valve stem diameter. The BMW PN for a set of six (as I recall) seals is 11-34-9-059-172. They may be green, or red in color. This is a far superior seal, although they can be a bit tougher to install.

    David
     
  14. daviekj

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    #14 daviekj, Jan 27, 2009
    Last edited by a moderator: Sep 7, 2017
    John / David thank you for the information on oil seals. I will follow this one up.

    I had another look at the corrosion on the face of the #1,2,3 cylinder head on the downward side between #1 and #2. This was worrying me, and was considering having the corrosion welded up. However, I am less concerned now as well as intrigued. As you can see from the pictures, the corrison lines up with the much larger water opening in the block. It is not surprising that corrsion can occur. Why did Ferrari/Fiat design the water ports to be of such different size?

    Kevin
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  15. John Corbani

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    Kevin,
    Take a look at the head gasket. Water holes are truely small. Looks like Ferrari made casting holes plenty big and let gasket determine how much and where water goes between block and heads. Just use plenty of anti-freeze and no problem. A couple more pictures will show it.
    John
     
  16. daviekj

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    #16 daviekj, Jan 29, 2009
    Last edited by a moderator: Sep 7, 2017
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  17. jselevan

    jselevan Formula 3

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    Kevin and John,

    I believe that you are giving too much credit to the gasket maker. I suspect that they made the gasket holes much larger to allow for poor fit, that is, not lining up correctly with the studs. It would seem to me, if I were a gasket maker, that I would err on the side of making the gasket hole larger to allow for misalignment. At least the water passage is not compromised.

    Furthermore, this gasket may have been used on a similar head by FIAT, one with slightly different passage geometry.

    Jim S.
     
  18. daviekj

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    #18 daviekj, Apr 16, 2009
    Last edited by a moderator: Sep 7, 2017
    Decided to get the corrosion in the cylinder heads welded rather than leave it. Glad I did. Chesmanengineering.co.uk in Coventry England did a very good and reasonably priced job. I visited their workshops prior to the job. Highly recommended, with experienced in Dino's, Ferraris, Jaguars and other exotica.
    Kevin
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  19. daviekj

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  20. daviekj

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    #20 daviekj, Apr 16, 2009
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  21. daviekj

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    #21 daviekj, Apr 16, 2009
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    Worth making effort to replace the seaks and make sure everything clean. Several posts before have decribed how important it is to seal the adjuster above the alternator. I have covered 60 miles since the rebuild and happy to report so far no oil leak from the adjuster.
    Kevin
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  22. daviekj

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    #22 daviekj, Apr 16, 2009
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    Unfortunately I did not take any photos when re-installing the valves and springs. The excitement got to me. All fairly straight forward. Chesmanengineering.co.uk re-faced the valve seats using the three angles described in the workshop manual. I did not replace the original bronze valve seats as they were in very good condition. I had been running on unleaded 97 octane for approximatey 10K miles and with no signs of wear. Total milage with these seats is close to 50K. Exhaust valves were replaced with unleaded ones (superformance.co.uk) as they were warn. In the end I re-used the inlet valves. Apparently these are classy race type valves. Nothing wrong with them other than the stem was approx 0.5mm too long and lacked clearance for suitable valve shim thickness (hence the reason for the re-build, see early in the thread). Chesman simply ground the top of the valve stems to give suitable clearance. All carefully measured and now within good shim range. Case hardening is apparently not an issue with these particular valves. Chesman ground matched the valves to the seats.

    I ran a check on the valve seat sealing as per photo.

    Kevin
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  23. daviekj

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    #23 daviekj, Apr 16, 2009
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  24. daviekj

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  25. daviekj

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