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308 piston - valve contact

Discussion in 'Technical Q&A' started by jtoce, Apr 26, 2004.

  1. jtoce

    jtoce Rookie

    Apr 14, 2004
    18
    Connecticut
    Full Name:
    Joe Toce
    Hello Everyone,

    I have enjoyed reading the many posts written on 308's and appreciate all of the information I have gathered.

    Here is my problem. I have a 1983 308 QV that overheated more than once, so I am now doing head gaskets among other things. My pistons had heavy carbon build-up and after cleaning them I found small indentations where the valves had come into contact with the pistons. On the front bank there are marks made by the exhaust valves on all four pistons. On the rear bank it's the intake valves with only slight marks from the exhaust valves. My heads are out getting surfaced, valves lapped etc., so I called them to make sure they check the valves for straightness. I think I should be able to check for connecting rod damage by matching the height of TDC on each. What is confusing me is what caused this; why exhaust on one bank and intake on the other; and why is there carbon build-up in these dented areas. I have to assume whatever the problem was has been repaired or the dents would be clean. The car has 39k miles, about 900 of which has been put on by me in the past 7 years.
    Any help or suggestions would be greatly appreciated.

    Joe
     
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  3. MRFOTOS

    MRFOTOS Karting

    May 26, 2003
    232
    Maui, Hi
    Possibly at one time the timing belts were out of adjustment, this could cause the pistons to hit the valves, or when a cam belt was change, the crank was turned without the belts on causing a slight collision between the two ?
    just a simple thought
     
  4. 308GTS

    308GTS Formula 3

    Dec 27, 2001
    2,220
    TN
    The pistons have small indentions in them for the valves. Are you sure you are not seeing this on every piston?
     
  5. jtoce

    jtoce Rookie

    Apr 14, 2004
    18
    Connecticut
    Full Name:
    Joe Toce
    The marks are not consistent from one piston to the next. As a matter of fact the pistons on the front bank actually look like they took a double hit. There's one mark then another above it. I'll try to post some pictures tomorrow.
     
  6. Mitch Alsup

    Mitch Alsup F1 Veteran

    Nov 4, 2003
    7,398
    Cam timing is what prevents valves from hitting the pistons--it may have been out of time sometime in the distant or not so distant past.

    You can check rod damage by magnaflux and checking the center-to-center distances. Any rod more than a couple of 0.001"s out should be replaced.

    Why are you NOT replacing the valves and guides as long as the engine is apart?
    If you have any high performance intents, you should consider replacing the pistons as long as the engine is apart. A valve indent my not look like much, but if a piston fractures at high RPM, you can/will write off the whole block.
     
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  8. jtoce

    jtoce Rookie

    Apr 14, 2004
    18
    Connecticut
    Full Name:
    Joe Toce
    $4800 (Italian Car Parts .Com) to replace all valves and guides is unfortunately not in my budget. I was really hoping to avoid pulling the bottom end apart. Not to mention new pistons, rings etc.. The car seemed to run well prior to overheating, and turns over very freely now. I am battling with the "how far do you go" syndrome. I don't want to take the risk of grenading the motor, but at the same time I was hoping to drive the car this year, and I still have a lot of other work to do. Also, I'm fairly comfortable with my abilities up to this point but a little overwhelmed by a complete rebuild.
     
  9. 1975gt4don

    1975gt4don Formula Junior

    Nov 5, 2003
    662
    Peoples Rep of CA
    Full Name:
    Smog Exempt
    what in the F are you doing getting your parts from that place? They charge at least double for all ferrari parts, if not more. Intake valves usually are not replaced as long as they are within spec. Exhaust valves are ALWAYS replaced due to heat fatigue. My heavens, call GT Carparts in Arizona (623-780-2200) for petes sake and save your bank account. You will need new rings and all new main bearings irregardless of engine condition otherwise if you reassemble the engine the way it is, the parts will not reseat properly and you will have a loss of power from blowby it won't be funny. superformance is another fabulous and very reasonable place to get parts for 308's, don't let the shipping costs scare you off. http://www.superformance.co.uk/


     
  10. atlantaman

    atlantaman Formula 3

    Mar 31, 2002
    1,726
    Roswell, Georgia
    Full Name:
    Charles
    jtoce--TRutlands is the place to call--italiancar parts is about the highest you will find--they want 90.00 for an f-50 key when the dealers sell them for 52



    also--if is not necessary to go with Ferrari parts on the valves--any good racing motor shop will just order the appropriate sized valves and guides from Manley or DelWest--etc.
     
  11. atlantaman

    atlantaman Formula 3

    Mar 31, 2002
    1,726
    Roswell, Georgia
    Full Name:
    Charles
    btw--i had all 16 exhaust valve guides on my car replaced for under 600
     
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  13. Dale

    Dale F1 Veteran

    Oct 7, 2003
    5,211
    uk
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    Dale Juan
    As mentioned valve timing,pick on any cylinder on each of the banks and make note's of the figures you have before you pull it down,if they are standard cams then just double check yourself,if they are a different grind from factory resarch them and find out who cut them and set to there spec's,
    make sure when the heads are removed to get the deck hight's checked,
    just to see if anyones been milling away at them like a madman,it realy is worth pulling the crank and measuring it up,new shells and rings if the budget wont streatch to piston's,washing the components off is not nice and time consuming,but the most important bit,the guy's have posted up some good parts site's so enjoy and take your time,and please post some pic's,

    cheers
    Dale.
     
  14. tbakowsky

    tbakowsky F1 World Champ
    Professional Ferrari Technician Consultant

    Sep 18, 2002
    15,388
    The Cold North
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    Tom
    Got to http://www.SIvalves.com. I ordered all my valves and guides from them. They are stainless steel and they can do any kind of angle job you want. The valves are very well made and my machine shop is now dealing with them also. Don't forget to order seals as well. $4800 is way over the top. I think everything for my engine came to about $400. But my car is a 2 valve engine so your going to be in the $800 range.

    As far as the marks in the tops of the pistons, it sounds to me like at one time in it's life a timing belt swap was done, and the engine was not timed right. They probably started the car..heard the wracket as shut her down and redid the timing on the cams. I would most defeinatly have ALL valves checked and ALL guides checked. I would also pull the pistons out and have a close look at the ring lands, and have the pistons magnafluxed to check for any cracking. More then likely you'll be alright but when dealing with expensive stuff like Ferrari engines your better safe then sorry!

    Tom
     
  15. jtoce

    jtoce Rookie

    Apr 14, 2004
    18
    Connecticut
    Full Name:
    Joe Toce
    #12 jtoce, Apr 27, 2004
    Last edited by a moderator: Sep 7, 2017
  16. tf308

    tf308 Formula 3
    Silver Subscribed

    Dec 14, 2003
    1,122
    Virginia Beach
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    Tim
    "You will need new rings and all new main bearings irregardless of engine condition otherwise if you reassemble the engine the way it is, the parts will not reseat properly and you will have a loss of power from blowby it won't be funny."

    Why the hell would you have to replace rings and bearings just because he pulled the heads off? Am I missing something?
     
  17. tf308

    tf308 Formula 3
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    Dec 14, 2003
    1,122
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    Tim
    regarding pricing.....CALL AROUND!!!

    No one person is the cheapest. I have had dealers charge less for things than Trutlands! I even call 3 different dealers and get 3 different prices. Most recently Foreign Cars Italia in NC had the best pricing.

    and you do not always need oem parts. Ferrari will charge you an arm and a leg for valves. The si valves are a cheaper and better alternative.
     
  18. 1975gt4don

    1975gt4don Formula Junior

    Nov 5, 2003
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    Smog Exempt
    Because he was asking if those were necessary IF he rebuilt the engine. Obviously, to check the condition of the ring lands, the pistons have to come out, which means the rods must come out. Automatic new rod bearings and pin fit the rod bearings. Might as well check the crank and that means an automatic check of the mains as well as checking the line bore of the block.


     
  19. tbakowsky

    tbakowsky F1 World Champ
    Professional Ferrari Technician Consultant

    Sep 18, 2002
    15,388
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    Tom
    For some reason to me anyways...That does not look like piston to valve contact. The marks appear to be much to close to the outer edges of the pistons. Would it be possiable to have a shot of the valves in the heads and a shot of the block showing all 4 cylinders on the one side that was hit? For somereason it just does not look right to me to be valve contact..I could be wrong though.

    Tom
     
  20. Dale

    Dale F1 Veteran

    Oct 7, 2003
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    Dale Juan
    Im in agrement with Tbakowsky,that doesnt look like valve contact to me either,

    Dale.
     
  21. Verell

    Verell F1 Veteran
    Consultant Owner

    May 5, 2001
    7,000
    Groton, MA
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    Verell Boaen
    Could you get some pix showing the entire piston tops?
    Also a couple of photos showing the valve positions in the combustion chamber in the head.

    Those look more like sloppy handling dings than valve taps, but I'd have to see their location on the pistons vs the valves in the head to be sure.

    Sure don't look at all new. If they are valve taps, I"m wondering if the heads w/cams miss-aligned were dropped into place & the valves tapped. This could go all the way back to original factory ass'y. If it were a Detroit factory product i'd guess the heads went on about 4:45 Friday night...
     
  22. jtoce

    jtoce Rookie

    Apr 14, 2004
    18
    Connecticut
    Full Name:
    Joe Toce
    I'll post more pics tomorrow. The heads are at the machine shop so I can't get those.
     
  23. BigTex

    BigTex Seven Time F1 World Champ
    Rossa Subscribed Owner

    Dec 6, 2002
    74,113
    Houston, Texas
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    Bubba
    You know what those are???

    I suspect a carb nut, or stud sleeve was dropped down the intake, rattled around, possibly thru more than one chamber, and then left!

    Put your new heads back on and boogie!

    I concur a valve would not leave that kind of dent IMO.
     
  24. chrismorse

    chrismorse Formula 3

    Feb 16, 2004
    2,149
    way north california
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    chris morse
    What happens when the engine "sees" a ~10,000 rpm missed shift???
    Are the valves going to hang open waaay too long or do the hip hop on the cam ramp??

    curious
    chris
     
  25. tbakowsky

    tbakowsky F1 World Champ
    Professional Ferrari Technician Consultant

    Sep 18, 2002
    15,388
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    Tom
    You would float the valves and have a heck of alot more damgae then what is being showen on the tops of the pistons in the pictures. You would more then likely have very large marks and bent valves and an engine that would barely run if at all. Floating the valves is not a good thing to do!!
     
  26. Mitch Alsup

    Mitch Alsup F1 Veteran

    Nov 4, 2003
    7,398
    Lets just say you could cause valve to piston interaction for one or two cycles at 10,000 RPMs and then majically the valves never hit again. You would not get the squished look of metal protruding from the area of high force that we see in the picture. This, to me, indicates a slower RPM interaction (like starter/starting speeds).

    Also note the piston with two marks is indicative of piston to valve interaction on one stroke resulting in a bent valve which was rotated in the valve guide before hitting the piston for the second time from a bent angle.
     
  27. theunissenguido

    theunissenguido Formula 3
    Silver Subscribed Owner

    Jan 21, 2004
    1,673
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    Guido
    Lookes to me factory marques. Some neglegant labourman at F mist his tool with a hammer to put the marques USA> in to the piston. Working for less then 1.500 $ a month on exotic cars....
    Guido
     
  28. jtoce

    jtoce Rookie

    Apr 14, 2004
    18
    Connecticut
    Full Name:
    Joe Toce
    #25 jtoce, Apr 28, 2004
    Last edited by a moderator: Sep 7, 2017

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