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How to Adjust Intake/Exhaust Valve Clearances on a 308

Discussion in '308/328' started by Brian A, Mar 23, 2014.

  1. Brian A

    Brian A Formula 3

    Dec 21, 2012
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    1983 US 308 GTS QV
    Please post here general instructions and tips regarding adjusting intake/exhaust valve clearances (shims) on a 308. Indicate if your advice is for 2v or 4v engines. At the time of creating this thread, there is no such article posted in http://www.ferrarichat.com/forum/308-328/281516-interesting-3x8-technical-diy-threads.html. If there are other good threads, please post links to them here as well.

    In other treads, the following points were made about the importance of adjusting valve clearances and valve timing (correct me where I am wrong in my understanding):

    1. The Owner’s Manual advises checking valve clearances at 15,000 mi / 24,000 km intervals.

    2.The valve clearances can drift materially from the factory specified clearance by this interval.

    3. The consequence can be a loss of clearance between the cam lobe and the shim. If this clearance reduces to zero, the affected valves will no longer fully close, hot combustion gases will blow-by the valve and this will result in a burnt valve requiring an engine rebuild to repair.

    4. A compression or leak-down test can reveal damaged valves, but is of no value in indicating valve clearance adjustment.

    5. Often cam shaft seals are replaced at the same time as the valve adjustment on a “while you’re in there” basis.

    6. The valve clearances can be adjusted independent of a timing belt replacement, although they are usually done together as part of the famous “Major Service”.

    7. Adjusting the valve timing requires the cam belt covers removed, so the most logical time to check and adjust valve timing is the same time the timing belts are being replaced.

    8. Having valve timing off-spec is less serious than having valve clearance off-spec. To a limit, the only consequence of having valve timing off-spec is a small loss of performance (power).

    ... I, of course, have a selfish interest in this thread: I need to check/adjust the valve clearances on my 1983 308 GTS QV within the next few months.
     
  2. Ehamilton

    Ehamilton Formula 3
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    More:
    - The valve clearances are checked with the camshafts in place (of course). The clearances can be adjusted either with the cam in place by using an appropriate tool to depress the bucket; or by removing the camshafts to get at all the shims at once.
    - The 2V shims are the same as the shims used on the Fiat SOHC and DOHC motors of that era. I have been told, but not verified with my own eyes, that these shims are also used in the Volvo motors of that era.
    - Always mike the shims, even brand new shims with the thickness printed on them.
     
  3. VIZSLA

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    I've got to dig out my 71 Fiat 124 shop manual.
     
  4. Ehamilton

    Ehamilton Formula 3
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    One of the differences between the Fiat and the Ferrari here is that the Fiat camshaft housing is a single line-bored aluminum casting (the "cam tower") bolted to the head, and the buckets ride in the cam tower, not the head. Thus, with the Fiat you can't remove the cam to get at all the shims at once - you have to do the shims with the cams in place and using the special tool.

    (You can also change the clearance of all the valves at once by using a different gasket between the cam tower and the head. This is NOT an advantage, especially when you go to retorque the cam tower bolts after a few hundred miles and a few heat cycles, and all your clearances tighten up by .003" or so).

    There's also no provision for fine-tuning the valve timing: The cam sprockets have timing marks on them, there's a single precisely dimensioned locating dowel between sprocket and camshaft, and I've never found that a belt tooth won't line up perfectly when the cam sprocket is on its timing mark. I've conjectured that the 308 motor needs more adjustability because there's more chance to lose a degree or so in the more complex lower belt drive mechanism.
     
  5. andyww

    andyww F1 Rookie

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    #5 andyww, Mar 23, 2014
    Last edited by a moderator: Sep 7, 2017
    Checking and adjusting the clearances is the easy part.
    Getting the cam covers back on in a way which doesnt leak is the tricky part.
    Some pointers:

    Only use gaskets made from the rigid green material as supplied by Ferrari (ferrariparts.co.uk or other genuine supplier).

    Cut the ends which abut the seals or seal carriers very carefully just short of the seals.

    Clean the whole of the mating surfaces with acetone.

    Use a blob of gap-filling sealant such as Permatex Ultra Grey between the ends of the gasket and the O-ring (4 valve) or oil seal (2 valve). Note RTV and engines dont mix. ensure none will squeeze into the engine!

    Fit the gaskets dry except at the ends which sit behind the belt sprockets which need to be secured to the head to prevent them moving and causing leaks. There is nothing to hold this part of the gasket other than friction and its very narrow. I used Loctite 518 to glue the thin ends of the gaskets to the head. I would bet that 90% of the oil leaks in this area are not from the actual seals but are from gaps developing between the seal/O ring and the end of the gasket.

    I used X rings on the cam seal carriers instead of O rings. They fit very snugly into the square slots. The size is BS330 and they need to be Viton (see picture).

    File a very small rounded corner on the ends of the O-ring slots in the head and covers. On mine there was a huge burr on the front one which had cut into the O-ring. Rounding the corners slightly prevents the O-ring from being pinched when the cover is put back on. I would think X-rings are less likely to get pinched.

    Probably just me being anal but I always fit new belleville washers on the cam caps and the covers rather than re-using. make sure the washers are the right way up!
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  6. VIZSLA

    VIZSLA Four Time F1 World Champ
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    Just as well,
    Most likely couldn't find it in any case.
    ;)
     
  7. GordonC

    GordonC F1 Rookie
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    Great idea for a thread, thanks!

    It would be extremely helpful if people could post where we can buy the shims, for 2V and especially 4V. I believe the 2V shims are common with a few other cars, including Volvo, but the 4V shims seems to be harder to locate. I also need to check my 4V valve clearances in the next month.
     
  8. Bell Bloke

    Bell Bloke Formula 3

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    #8 Bell Bloke, Mar 24, 2014
    Last edited: Mar 24, 2014
    Hi Folks here is the first part of the valve clearance measuring and adjustment video
    All the best, Bell.

    https://www.youtube.com/watch?v=BT3qW16BCqw&feature=youtu.be

    Oh by the way: According to my service history it was done by a reputable London dealer recently....very recently.......and on measuring all my clearances it had indeed been done very diligently and accurately.....BUT TO A MONDIAL 8 SPECIFICATION!!
    Bloody hell it's a good job I checked!! I only took my cam covers off because I wanted to paint them and make a video. If I'd have left it I could have been facing an engine rebuild due to burt valves which is an engine out, not something I relly have time for right now.

    Anyway, rant over...I'm calm now ;-)
     
  9. andyww

    andyww F1 Rookie

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    #9 andyww, Mar 24, 2014
    Last edited: Mar 24, 2014
    My exhaust clearances were all around 0.30, same as yours (328). Mine have never been done before and they must have set them to 0.30 in the factory. The 308QV-328 WSM specifies 0.30-0.35. Yours are likely correct. Some other sources quote 0.35 - 0.4 but I am certain mine were originally set to 0.3.

    I left them at 0.30 except for a couple which were tight.

    Thats very generous to do this to make the video as the cost of the gaskets is pretty high! I noticed you had the crappy grey ones on there, did they leak?

    I really do think the cam covers should be torqued with a torque wrench of the correct range though, not by feel. The same range is needed anyway (definitely!) for the cam caps.

    I dont think its possible to do this on a 3x8 with the engine cover still on. Anyone done this?
     
  10. Bell Bloke

    Bell Bloke Formula 3

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    #10 Bell Bloke, Mar 24, 2014
    Last edited: Mar 24, 2014
    Hi Andy, my book says 0.35-0.40 for a QV Exhaust valve clearance, I will try and find out why that is but thankyou for the reasurance. My gaskets were perfect but I will track down some better ones if you think these are not good, I was going to use Superformance ones...
    Yes torquing those little cam cover nuts can be a problem. I've seen quite a few people pull at least 2 studs out by over doing it with a torque wrench. To befair though that was 15 years ago and I expect torque wrenches are way better in the low ranges now. Know ye of any good ones out there?
    Cheers for the response Andy, all the best Bell :)
    ps, feeling slightly better about the clearances on the exhaust now, but a little confused.
     
  11. Bell Bloke

    Bell Bloke Formula 3

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    #11 Bell Bloke, Mar 24, 2014
    Last edited by a moderator: Sep 7, 2017
  12. smg2

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    They are all the same, the clearances for the 3x8 engine series is;
    Intake: 0.20mm~0.25mm
    Exhaust: 0.30mm~0.35mm

    308, 308QV, 328, Mondial 8, Mondial 3.2. From Carb to CIS injected it's all the same running clearance. Now cam timing is a different matter, but that's dependent on the cams not the body of the vehicle.

    The Mondial QV WSM notes a bit different for the Exhaust: 0.35mm~0.40mm.
    I'm not sure as to why as the engines are identical between all QV's even the camshafts are the same including the 288GTO. Conflicting information is not a first here though.
     
  13. andyww

    andyww F1 Rookie

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  14. Bell Bloke

    Bell Bloke Formula 3

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    Hi SMG, thanks for posting. So what are your thoughts here, do you think that there is a risk to burning the valves on the tighter 0.30-0.35 as opposed to the specified 0.35-0.40 clearance? Logic would say that are engines are all the same except maybe cam profiles, but heat expansion of the valves and clearances should be a constant surely.
    Also how much I wonder do the gaps close up to at working temperature, maybe some extreme tuners out there would know. Facters being head expansion and valve stem expansion, off the top of my head.
    All the best, Bell
     
  15. smg2

    smg2 F1 World Champ
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    I run them all at the 0.3~0.35 spec, even for the monster 400+Hp builds. The QV engines have SS valves as OE. The cam profiles are the same across all the QV engines including the 288.

    I've got the numbers in a pile of papers in the shop on expansion rates etc. I can dig them up later today/tonight, top 'o the head it's not enough to cause issues. I'm more bothered by the tiny face area of the shim to the cam lobe, it's runs so close to the edge it may as well run off the face! surprised it doesn't spit shims, but they are deep pocket. I now replace the buckets and shims with a lash cap setup, drops the valve train weight to 1/3 the original and gets rid of high rpm float.

    As soon as I can get more time free I'll get the schematic dwgs done tonight (PST) on the cams and timing marks, it should make a nice clean sheet reference that would go well in any binder. Busy with a couple race engines and my Post doc work in theoretical physics. I don't sleep much :(
     
  16. andyww

    andyww F1 Rookie

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    The Superformance gaskets are notorious for leaking unless they have upgraded the material they use, following complaints.
    They are really expensive though as Ferrari original parts. If I were about to do this again I think I would be tempted to get on the blower to Colin at Superformance and see if he can get some made in decent material. I meant to make a note of the manufacturer of the green stuff but forgot.

    If someone has stripped a thread using a torque wrench it either needs to be recalibrated or thrown in the scrap bin!
    I use a little 1/4in drive Sealey Premier torque wrench for these. Personally I dont see any point in skimping on tools. The cost pales into insignificance when you think of the saving you are making on service costs. Also oil filter strap wrenches are cheap (hint) :)
     
  17. Bell Bloke

    Bell Bloke Formula 3

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    Hey Gents, thanks for your responses, SMG can't wait until you post that info, cheers ;-)
    Hey Andy, Ok time to confess, I do actually have a filter strap but I like to put little things in my videos for those who don't have the correct tools to hand, ha ha, also adds a little entertainment value I hope. However thatsaid I am still looking for a low poundage torque wrench that I can trust with those little delicate cam caver bolts, I'll see what I can find but a UK search didn't bring up anything. I even considered a wrench made for mountain bikers but no luck so far.
    All the best, Bell
     
  18. Steve Magnusson

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    #18 Steve Magnusson, Mar 24, 2014
    Last edited: Mar 24, 2014
    No - some US versions have continuous air injection at the exhaust port that raises the average exhaust valve temperature (and, therefore, the valve stem length). The earliest reference that I've seen for the change to the .35-.40 mm spec on the exhaust side is in the 1982 US 308i OM (like it was something that they "learned", or got more nervous about, since 1980, 1981, and 1982 US versions 308i-2V engines are identical). In 1984, when they went to the pulse air injection on the US models (that only operates during cold-running), they probably could've gone back to .30-.35 mm spec with less worry (but didn't, even thru the US 328 series).

    Since you have a euro version Mondial QV shouldn't be an issue for you.

    (The 308QV/328 WSM only covers the euro engines 105A and 105C, not the US engines 105A040 and 105C040.)
     
  19. andyww

    andyww F1 Rookie

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    Good spot!
    That seems to be evidence that this change was originally intended for US engines only but "scope creep" got into the other manuals.
     
  20. andyww

    andyww F1 Rookie

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    STW101 Torque Wrench Micrometer Style 1/4"Sq Drive 5-25Nm/44-221lb.in: Amazon.co.uk: DIY & Tools
     
  21. Iain

    Iain F1 Rookie

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    This 30-35 or 35-40 thing is an old argument. Ferrari published different numbers in different places. Most of the US techs seem to work with 35-40. The last time mine were done by someone else they clearly used 30-35 because they were ALL in that range when I checked them a few thousand miles later..

    At that point I had a few at around 30 & I set them all up towards 34/35. Plenty of reports of people having them at around the 30 mark without issues though.

    The whole purpose of the valve clearance (obviously!) is to cater of the expansion under heat to make sure the valve still closes properly but it would seem that anything above 30 is certainly OK judging by the number of people who report clearances in that range & sometimes a little tighter when they check them.

    Anecdotally, they really don't change much over time either.
     
  22. Bell Bloke

    Bell Bloke Formula 3

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    So just to clarify Steve, are you saying that on the 4 valve heads they brought air injection in and that raised the valve temperature so they increased the valve clearance to 0.35-0.40 and that this spec crept into all the other models from then on?
     
  23. andyww

    andyww F1 Rookie

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    Mine were definitely set to 0.30 from factory. The scope creep only seems to have affected the manuals which cover US cars and Euro, not the actual engines.
     
  24. Steve Magnusson

    Steve Magnusson F1 World Champ
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    No -- as I wrote, the .35-.40 mm exhaust spec appeared towards the end of the US 2Vi engine (and the 1983 US 308QV also had the same continuous air injection so makes sense to use it there too). It has seemed to creep into everything else documentation-wise (as other than that 308QV/328 WSM) even the later 3.2 euro models are spec'd that way.
     
  25. Bell Bloke

    Bell Bloke Formula 3

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    Ok cheers Steve sorry. :)
     

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