What is the recommended Valve to Piston Clearance on a 2 Valve Ferrari 308 Engine? | FerrariChat

What is the recommended Valve to Piston Clearance on a 2 Valve Ferrari 308 Engine?

Discussion in '308/328' started by ItalianProjects101, Jun 22, 2024.

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  1. ItalianProjects101

    Feb 5, 2023
    215
    Full Name:
    D
    Hi everyone,

    We are making good progress. We are seeking some advice regarding the valve to piston clearance on my 2 Valve Carburetted Ferrari 308 Engine. I am using Wossner 81.5mm High Compression (10.5) Pistons along with Catcams sport camshafts.
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    After measuring the clearances, I found the minimum on the exhaust side to be 2.8mm and the minimum on the intake to be 2.9mm. These measurements were calculated by first each piston at TDC using a dial gauge. Then we timed each valve by rotating the camshaft correctly and continued rotating it until it touched with the top of the piston and calculated this using a dial gauge. This was done on every valve.

    Now taking the minimum into consideration, the values resulted in 6.55mm on the intake and 5.9mm on the exhaust. By subtracting the valve lift @tdc for both intake (3.65mm) and exhaust (3.1mm) as per the diagram, I ended up with the mentioned figures of 2.8mm on the exhaust side and 2.9mm on the intake side.

    Are these clearances acceptable, or should I consider recutting the valve seats (if there is still meat left) to achieve better valve clearance and this way have the clearance even throughout or also possibly cut the valve pockets on the pistons?

    Any insights or suggestions would be greatly appreciated.

    Thanks in advance!
     
  2. Rifledriver

    Rifledriver Three Time F1 World Champ

    Apr 29, 2004
    37,274
    Cowboy Capitol of the World
    Full Name:
    Brian Crall
    Trial assemble one piston and 2 valves, with clay on the pistons and see what the real clearance is.
    I have used Wossners before. Good pistons and had big valve pockets.
     
  3. ItalianProjects101

    Feb 5, 2023
    215
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    D
    We've done that already however we'd like to also check the accepted clerance via a dial guage.
     
  4. mk e

    mk e F1 World Champ

    Oct 31, 2003
    13,767
    The twilight zone
    Full Name:
    Help me get this thing finished! https://gofund.me/39def36c
    The standard automotive answer is 0.080" intake, 0.100" exhaust but the standard US stuff tends to run pretty high lift. Motorcycles run closer to our lift numbers are 0.050" Intake and 0.080" exhaust which is where I set my 4V engine with cams similar duration but a touch more lift than what you have.
     
  5. ItalianProjects101

    Feb 5, 2023
    215
    Full Name:
    D
    From a quick search I also got those standard automotive answers but I was hoping there is a specific to this engine I should be running.

    So I assume I am just about okay?
     

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