News

What is the average valve replacement mileage for a 308

Discussion in 'Technical Q&A' started by rob58, Apr 6, 2021.

  1. rob58

    rob58 Rookie

    May 30, 2020
    12
    Full Name:
    Robert Orris
    What is the average valve replacement mileage for a 308 euro model with 55,000 miles. I read that the 308 valves should be replaced at 40,000 miles. Is this a concern , or true?
     
  2. To remove this ad click here.

  3. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    20,142
    Texas
    Full Name:
    Steve Magnusson
    40K miles is super, super conservative IMO -- and the vast majority of 308 go way beyond that (barring some sort of other cam drive problem causing a valve-to-piston collision). Can you give the reference where you "read" that? My data point for a US carb 2-valve for valve wear out is that at about 90K miles things got bad enough to start to notice some symptoms, and at 99K miles two of the exhaust valves got bad enough to give a leakdown of ~15% (so refreshed the top end then).
     
  4. raemin

    raemin Formula Junior

    Jan 16, 2007
    766
    Lyon (FR)
    Full Name:
    R. Emin
    The sodium exhaust valves should be replaced as when they fail they brake unlike regular valves that bend. I had such a valve failure. Not fun.

    This being said, I had a few damaged valve stem seals, and while you are there, replacing the valves makes sense as they are cheap. So we even trash some inlet valves that are still in reasonably good condition.

    All in all these are replaced early either as part of a while you are there job or as a way to avoid catastrophic sodium valve failure.
     
  5. Ferrari Tech

    Ferrari Tech Formula Junior

    Mar 5, 2010
    661
    Georgia
    Full Name:
    Wade Williams
    I have been working on Ferraris since 1995 and I have yet to see one sodium valve fail without influence. I am sure it happens, but it is not common and I don't recommend new valves to my clients because they are sodium filled. I have had valve seat sealing issues from poor maintenance and will never put an old valve back in when the head are off. Modern technology in material and manufacturing just makes is an easy decision to install new valves. Also, the valve seat work on old Ferrari heads are poor at best. A multi angle valve job can do a great deal to help with not only sealing but low lift flow as well. Again modern technology comes through.
    If a valve job and new valves are within your budget and you want peace of mind, then find an outstanding shop that has done this before and let them make your engine better.
    The next one I do I am planning to run before and after on my flow bench to see what the gain actually is.
     
  6. raemin

    raemin Formula Junior

    Jan 16, 2007
    766
    Lyon (FR)
    Full Name:
    R. Emin
    "Influence" is not necessarily what one would presume. My own head (400i, same valves as the 308) had a crack on the exhaust port, so we decided to perform a full rebuild: thinner valve seats, new guides, etc. As the 98.000km valves were within specifications we decided to keep them. One broke shortly after.

    That's pure speculation on my side, but I presume that the new guides induced stress on a section of the valve head that was interacting differently with the previous guides. In any case that's an unfortunate way to destroy a newly rebuilt engine.

    So based on my own experience, as long as you work on the head it's better to replace the $40 valves. The 308 is a revy engine, so it would make even more sense to play it safe.
     
  7. To remove this ad click here.

  8. Ferrari Tech

    Ferrari Tech Formula Junior

    Mar 5, 2010
    661
    Georgia
    Full Name:
    Wade Williams
    That is a good example of outside influence. New seats & guides would definitely fall under outside influence. Raemin is correct. Valves are cheaper than pistons, sleeve and cylinder head welding.

    Funny side note: I had someone call (2001) and ask when the scheduled engine rebuild is on a '77 308. I said right after the rod comes out or the valve breaks or it starts smoking.
    He was under the impression that all 308s would need a rebuild very early in there life. I don't know where this comes from but it is out there.
    I have had a number of 308s that are 100,000 plus miles and are still going strong. They are well maintained and driven often. I think that makes a huge difference.
     
    f355spider likes this.
  9. Foxie

    Foxie Rookie

    Oct 9, 2011
    30
    Wexford, Ireland
    Full Name:
    Sean Murray
    At 50K miles my '78 308 dropped both valves in No. 8 due to faulty cam timing on front exhaust after a belt change. ( Didn't lift the valve cover using lock the cams method )

    I asked them to check the wear in both heads and valves. (5 - 8 exhausts and 8 inlet were getting new valves )

    All the valves were very good. The guides were slightly worn, and were serviced with inserts, and new seats cut and ground.

    Will be getting the cam with the new distributer drive plug fitted back this week, then it's ll go !
    Image Unavailable, Please Login
     
  10. rob58

    rob58 Rookie

    May 30, 2020
    12
    Full Name:
    Robert Orris
    Thank you all for your insight, much appreciated. What are the years that had Sodium filled valves in 308's. Looking at a 1985 Euro qv. 55,000mi
     
  11. GordonC

    GordonC F1 Rookie
    Rossa Subscribed Owner

    Aug 28, 2005
    3,853
    Calgary, AB, Canada
    Full Name:
    Gordon
    Only the 2 valve per cylinder 308s - 1974 through 1982. All the 4 valve per cylinder 308s have non-sodium exhaust valves, and don't have an inherent breakage concern.
     
    Ferrari Tech likes this.
  12. To remove this ad click here.

  13. rob58

    rob58 Rookie

    May 30, 2020
    12
    Full Name:
    Robert Orris
    Thank you Gordon, much appreciated

    Regards
     
    GordonC likes this.

Share This Page