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1975 308 GT4 Engine/Trans Rebuild

Discussion in '308/328' started by jlonmark, Jul 21, 2021.

  1. jlonmark

    jlonmark F1 Rookie

    Mar 29, 2005
    2,994
    Beverly Hills, CA
    Full Name:
    Jay
    So after all this time I've decided to pull the engine and trans from my 75 gt4. Total breakdown, machined the heads, new lines, new synchros in the trans. Anything else I should check or redo at the current time?

    Thanks!
     
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  3. miketuason

    miketuason F1 World Champ
    Silver Subscribed Owner

    Feb 24, 2006
    14,471
    Cerritos, CA.
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    Mike
    How about a new set of high compression pistons?
     
  4. absostone

    absostone F1 Veteran
    Silver Subscribed

    Jul 28, 2008
    6,113
    SS valves.
     
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  5. jlonmark

    jlonmark F1 Rookie

    Mar 29, 2005
    2,994
    Beverly Hills, CA
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    Jay
    Keep em coming guys! I like all of the ideas thus far


    Sent from my iPhone using Tapatalk
     
  6. smg2

    smg2 F1 World Champ
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    Apr 1, 2004
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    Dumpster Fire #31
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    Mileage, condition, goals?
     
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  8. kiwiokie

    kiwiokie Formula 3

    Aug 19, 2013
    1,110
    Tulsa, OK
    Upgrade main +ve cable from battery to starter. Replace heater and brake vacuum hoses that run through drivers side rocker panel. Clean all electrical connectors. Rebuild starter (or go lightweight) and alternator. Thoroughly clean engine bay and address any corrosion. Clean and rebush shifter and new seals.


    Sent from my iPhone using FerrariChat
     
  9. absostone

    absostone F1 Veteran
    Silver Subscribed

    Jul 28, 2008
    6,113
    I replaced the starter to alt cable with some really cool looking silver copper or something from a custom shop.
     
  10. marklintott

    marklintott Formula Junior

    Jul 13, 2005
    548
    Taipei / Somerset UK
    Full Name:
    Mark Lintott
    Lightweight hi torque starter
    Repair/replace headers + ceramic coating
    Switch out ignition system to Pertronix or Black stallion or similar
    Change all your valves to solid SS - lose the sodium filled originals
    JE pistons from California
    Clean up the engine bay of course
    Possibly change the radiator to a modern aluminium item
    Shift shaft seals
    Service/rebuild your carbs

    etc etc.....good luck!
     
  11. dave80gtsi

    dave80gtsi Formula 3
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    Nov 3, 2003
    1,527
    Ohio
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    Dave Meredith
    Since you will likely be using new pistons anyway, see if you can find a used 328 crankshaft. The "Poor Man's Stroker Kit"
     
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  13. jlonmark

    jlonmark F1 Rookie

    Mar 29, 2005
    2,994
    Beverly Hills, CA
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    Jay
    An old timer mechanic friend said you can put 365 cylinders on and make the car 4.0 liter! That coupled with the 328 crank would really be something. The car is a driver that goes out on the Ferrari club runs, first sat of every month. We go hard for 6-9 hours and cover 300-500 miles. So more power and reliability are in mind. This is the first time the motor has been opened. I really appreciate the help!


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  14. steven_ew

    steven_ew Karting

    Apr 3, 2009
    104
    I would also replace the long aluminium water pipes to/from the radiator with stainless steel. Can only be done with engine out or jacked up and a sitting duck for corrosion
     
  15. miked

    miked Formula Junior

    Feb 7, 2001
    681
    Cincinnati, Ohio
    Full Name:
    Mike Dawson
    The 308 and the 365 share the same bore and stroke (81mm x 71mm), there would be no change in displacement. Using a 328 crankshaft (73.6 mm stroke) does increase displacement but not by much. Some people on this forum have used a 348 crankshaft (75mm) to increase displacement. Maybe your mechanic friend was thinking of replacing the V8 engine with a 330 (4.0 liter) V12 engine, it has been done.
     
  16. smg2

    smg2 F1 World Champ
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    Apr 1, 2004
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    Crankshafts all the way up to the 360 will fit. Requires changes to connecting rod lengths and/or piston gudgeon pin to deck distance.

    I've built everything from 3.5L to 4L 308's. It's just a matter of how many wheelbarrows of cash one wants to spend.
     
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  17. derekw

    derekw Formula 3

    Sep 7, 2010
    1,353
    London, UK
    Full Name:
    Derek W
    The chances are your piston/wall clearances are beyond the limit. If so, hone the liners and order higher compression pistons to suit. If you can find a 348-360 crank and want to spend the extra $, then the pistons can be made to suit the longer stroke. I think the early GT4 cams are ok but for a little more power you could get higher lift CAT cams for $1500. You will need to tune the carbs for the new internals and change the advance curve to suit. Minimal gains from porting the head but make sure the machine shop didn’t fit new guides and cut the now eccentric seats to suit (sinking the valves into the seats.) It’s a common problem with these engines. Just check and fix if the inlet manifolds don’t match the ports (they were very close on my two engines.)

    As others have said, get solid stainless exhaust valves. I have some 21-4N valves left at £10 each but in the US several places sell them. Fit viton or Teflon stem seals as the nitrile seals don’t last as long on the hot exhaust valves. You can lighten the valve train with titanium valve spring caps (£160/set).

    Drill the exhaust cam seal drain hole and blind shifter vent hole in the intermediate plate (both discussed in this forum.)
     
  18. Pizzaman Chris

    Pizzaman Chris F1 Rookie
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    Mar 13, 2005
    3,918
    New Hampshire
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    Pizzaman Chris
    Wise quote from a wise man.
     
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  19. eskamobob1

    eskamobob1 Karting

    May 9, 2020
    105
    SoCal
    Seconded. We need info. Without you giving a budget ima recomend a 3.6 qv conversion. They should start at like 40k if you dont do your own head work ;)
     
  20. jlonmark

    jlonmark F1 Rookie

    Mar 29, 2005
    2,994
    Beverly Hills, CA
    Full Name:
    Jay
    Well to be "Feng shui," less is more. Our initial budget was $20,000 and I hope to not go over much. Just figure now is the time to do it. A stroker motor or turbo setup (like the 288 gto), would be awesome! But unrealistic
     

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