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308-v4 "hot pistons"

Discussion in 'Technical Q&A' started by atlantaman, Nov 16, 2003.

  1. atlantaman

    atlantaman Formula 3
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    Somehow I have lost compression of 3 cyls and have to take the motor out for repairs. No oil smoke--no mixing of fluids--a mystery--may have burned a valve or bent one..

    Anyway--since it is coming apart- I am going to look for some better pistons. Any history here? any suggestions?
     
  2. thecarreaper

    thecarreaper F1 World Champ
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    with all the bazzillion cars i have had / worked on it seems you should be able to get bore over size, dome or flat top pistons any way you want as long as you have the $$$$$$ . i would try TRW or federal mogul ect . do a search on google as a start or try some or the guys that race ferraris as there has to be a reasonably priced source for pistons. seems odd that you lost comp. on 3 cyl. on one bank and have no oil/ water mixing ( head gasket) geeze i hope its not a crack in the head. maybe one of the cams jumped and as you suspect, several valves were bent. seems a leakdown test would confirm this before you take it apart. with my luck when i do get a 308 its going to have everything go wrong with it...... i am in savannah if you need anything please feel free to ask. i am not an owner yet but i have the passion! good luck to you.
     
  3. Sean F.

    Sean F. F1 Rookie

    Feb 4, 2003
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    Go to www.norwoodperformance.com, download the Forza article and read it.

    Also, go to the archives off the old board and do a search for "High Compression Rebuild". Their is a LONG thread about it somewhere in there.
     
  4. mk e

    mk e F1 World Champ

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    I think Norwood uses JE which are excellent pistons. They can make them to any spec you want. Also, I remember Bret (the missing) had wisco make a set and was happy with them.
     
  5. Peter

    Peter F1 Veteran
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    We haven't heard from Bret in a long time here, but he got a set of hi-comp pistons for his QV from Wiseco and was really impressed with them. He went with them based on the recommendation of another FChat member who installed them in his car (can't remember who it was).

    Apparently, they were reasonable in price and very easy to work with.
     
  6. pma1010

    pma1010 F1 Rookie
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    You might check with Bill Badurski (FCATech). He's had quite a bit of experience with hi-comp pistons in Daytonas and would have an informed view.
     
  7. Verell

    Verell F1 Veteran
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    May 5, 2001
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    There's good & bad news.
    As people have already mentioned, there are multiple sources of 3x8 pistions.

    Bad news is don't plan on an over-bore. The 308 QV & 328 cylinder sleeve walls are plasma gun deposited Nikasil over a much softer silicone/aluminum alloy. The WSM says no-way can they be bored, or even honed. Once they're scored, you either live with it or replace the
    sleeve.
     
  8. mk e

    mk e F1 World Champ

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    If scored, they can be recoated. I had mine redone and they turned out great. I had them refinished to stock bore, but they could be done to a larger bore if thinner cylinder walls don't scare you. Stock cylinders are taper bored which they could not do, but it is only a couple tenths, so I went ahead and had them redone with a straight bore and they work fine. Porsche cylinders are the same materials with a straight bore. I think it was $80 per cylinder. I'd have to look to find the name of the company, but I found them in a dirt bike magazine, all the 2-stroke dirt bikes (and some of the 4 stroke roadrace bikes) use the same coating these days.
     
  9. Verell

    Verell F1 Veteran
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    VERY INTERESTING,
    We had a long discussion on reboring feasibility about 6-months ago and consensus was that they couldn't be re-bored because of the coating.

    THANKS! You learn something every day!
     
  10. atlantaman

    atlantaman Formula 3
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    thanks for the info
    from my reading it would appear that my 4v motor likely has mahle pistons in it. I may contact Mahle (luckly i know someone there) and see if they can send me a set of 9.8 pistons just like the originals.

    I am wondering if anyone has gone with any kind of domed pistons and who designed them for you ?

    I suspect that the stock style "dish" pistons are not the best if going above 10:1
     
  11. Sloan83qv

    Sloan83qv F1 Rookie
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    I bought a nice set for my QV from Nick at Forza ferrari (Sponsor) he can have them made for any compression ratio you wish.
     
  12. mk e

    mk e F1 World Champ

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    Dished vs. dome is about the CR. To get a low CR you need to dish the piston to increase the combustion chamber volume. To get a high CR you need the dome to decrease the volume. Pick a CR and the piston maker will design the correct piston to achieve it.
     
  13. atlantaman

    atlantaman Formula 3
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    the question still remains on the pistons--I am curious to see how much of a dome has been applied to various pistons and what kind of valve reliefs were necessary.

    I am not going to buy any from a car shop but will order from Mahle or JE. Last set of 330 pistons I got( from JE) for my v-12 I paid 60.00 per hole including rings and wrist pins. When I looked at Norwoods site he wants more than 200 per hole
     
  14. mk e

    mk e F1 World Champ

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    I think the last set of JE pistons I bought were $100 with pins when I bought 8 and no rings. The rings were about $220 for total seal. I think it's a run cost, 4, 6,8,12, still costs about $800. That may have changed though.
     
  15. atlantaman

    atlantaman Formula 3
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    Piston Compression???

    I am seeing numbers ranging from 8.6:1 to 9.2:1 listed for 308 v4 motors in factory literature and various websites... anyone know why there is a discrepency???
     
  16. Steve Magnusson

    Steve Magnusson F1 World Champ
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    version differences? (which then get further confused by mis-application during literature translation for different markets;))
     
  17. mk e

    mk e F1 World Champ

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    US is 8.6 (I checked mine), euro 9.2 (I think)
     
  18. atlantaman

    atlantaman Formula 3
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    good point--then it would be interesting to look for a set of euro pistons if indeed that is the difference.
     
  19. billb

    billb Formula Junior
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    JE is a good source for pistons. I've had them make sets for me, usually about 10:1 which works fine with pump gas. The order form is very thorough, and you will end up with some dome and generous valve reliefs. Order them with JE supplied ring sets as the originals are wider than those readily available from domestic manufacturers.
     
  20. atlantaman

    atlantaman Formula 3
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    thanks for the help but I decided to take the easy way out---
    went over to Trutlands and swapped my 308v4motor out for a freshly rebuilt 3.2 and prepping it to drop into my 308 now.

    since I have EFI it will work with out modifications
     
  21. bert308

    bert308 Formula 3
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    Correct me if I'm wrong, but that'll be the 4th engine in this car? :)
     
  22. mk e

    mk e F1 World Champ

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  23. atlantaman

    atlantaman Formula 3
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    well, actually it is the 6th--but who's counting?

    1-factory oil burner
    2-another factory oil burner
    3-good 2-v motor--no power
    4- v12 being rebuilt currently to put back in car
    5- recent 4-valve 308 motor--loss of compression at 3000 miles--suspect a broken piston ring and 2 valves apparently not seating.
    6-nice fresh rebuilt 3.2 motor about to go into the car. Only to use unitl v-12 is completed then back to the big motor.

    considering that this car sat in my garage for 15 yrs and never ran---that cones to about 1 motor every 8k miles. AND the first 2 were with the original owner--not me. This is likely the most worked on 308 in existance.

    Thank God I have no wife or kids--this baby is enough!
     
  24. Matt Morgan, "Kermit"

    Matt Morgan, "Kermit" Formula Junior

    Nov 12, 2003
    405
    Ferndale, WA
    As I recall, 4 valve pistons with 11:1 will be flat topped, with valve reliefs.
    The formula for compression ratio calculation is:

    C=D+Vd+Vs+Vc
    _______________
    Vd+Vs+Vc
    Wherein:
    C=Compression ratio
    D=Displacement of one cylinder
    Vd=Volume of dish (+) or dome(-) on piston
    Vs= Volume of squish clearance
    Vc= Volume of combustion chamber.
    One side note: not all motors will have a zero deck height, or the piston being even with the block surface, so watch for that in calculating.
    Hope this helps
     
  25. Matt Morgan, "Kermit"

    Matt Morgan, "Kermit" Formula Junior

    Nov 12, 2003
    405
    Ferndale, WA
    As I recall, 4 valve pistons with 11:1 will be flat topped, with valve reliefs.
    The formula for compression ratio calculation is:

    C=D+Vd+Vs+Vc
    _______________
    Vd+Vs+Vc
    Wherein:
    C=Compression ratio
    D=Displacement of one cylinder
    Vd=Volume of dish (+) or dome(-) on piston
    Vs= Volume of squish clearance
    Vc= Volume of combustion chamber.
    One side note: not all motors will have a zero deck height, or the piston being even with the block surface, so watch for that in calculating.
    Hope this helps
     

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