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Returning 1961 Vignale spyder 1341 to the road

Discussion in 'Maserati' started by thecarnut, Jan 21, 2024.

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  1. thecarnut

    thecarnut F1 Rookie
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    #26 thecarnut, Jan 27, 2024
    The oil leak is coming from the back of the cylinder head gasket therefore it will not be simple. The compression is a bit higher than I normally see on an inline 6 engine with most cylinders around 175 psi. My guess is that the head has been shaved and is now again not true, thus the leak. Shaving the head again would increase the compression even more unless the cylinder chambers are made a bit larger. More will be known once the head is off and measured.

    Ivan
     
  2. Froggie

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    #27 Froggie, Jan 28, 2024
    That looks challenging: you would need to enlarge the bores or to put thinner liners (plus wider pistons)?
     
  3. thecarnut

    thecarnut F1 Rookie
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    #28 thecarnut, Jan 28, 2024
    I do not believe the bottom end of the engine needs to be touched. To lower compression the area between the top of the pistons and the valves needs to increase. This can be done by removing some metal from the head's combustion chamber, or adding metal to the bottom of the head or using a thicker head gasket. The current compression is not horrendous and should not cause any problems,. I am just thinking ahead in case the head will need to be trued again which could be a problem. At this point I am just speculating.

    Ivan
     
  4. ronfrohock

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    #29 ronfrohock, Jan 29, 2024
  5. 71Satisfaction

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    #30 71Satisfaction, Jan 29, 2024
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  6. thecarnut

    thecarnut F1 Rookie
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    #31 thecarnut, Jan 30, 2024
    I need one stub axle carrier. It is part #144 table 13 on the 3500GT parts manual. Both sides have the same part number. The same carrier was used on the 3500GT thru the early Ghibli. Anyone has one laying around?

    Ivan

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  7. Ferraripilot

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    #32 Ferraripilot, Jan 30, 2024
    It's questions like this that make us all miss Kyle Fleming. He may not only having 3 laying around but he'd have 2 hours of stories about them.
     
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  8. eogorman

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    #33 eogorman, Feb 2, 2024
    The oil leaks on the 6 cylinder engines is usually caused by the old style head gasket, which is still the best in my opinion. It is very important to be sure the head has the groves and the small BB are installed. Many people do not put the groves back in the head when they are surfaced
     
  9. thecarnut

    thecarnut F1 Rookie
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    #34 thecarnut, Feb 3, 2024
    This engine appears to have the one piece head gasket. I am in the process of removing the head. Hopefully it wants to cooperate when it comes to separating it from the block.
    Ivan
     
  10. Nembo1777

    Nembo1777 F1 World Champ

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    #35 Nembo1777, Feb 3, 2024
    Leo Peschl in Cologne, Germany has restored lots of 3500's and made bespoke head gaskets after a lot of study. You can read about him in the Classiche Masters book. His staff speaks English.
     
  11. staatsof

    staatsof Nine Time F1 World Champ
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    #36 staatsof, Feb 4, 2024
    The traces of green paint is rather curious.
     
  12. thecarnut

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    #37 thecarnut, Feb 4, 2024
    I think it was some sort of primer. Very difficult to remove.
    Ivan
     
  13. thecarnut

    thecarnut F1 Rookie
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    #38 thecarnut, Feb 4, 2024
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  14. Ferraripilot

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    #39 Ferraripilot, Feb 5, 2024
    Moving quick on this! Alfieri really liked that shape of dome didn't he. We see it consistently in his engines of varying sizes
     
  15. thecarnut

    thecarnut F1 Rookie
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    #40 thecarnut, Feb 5, 2024
    The engine builder, who has a ton of experience with race engines, believes the head is good and that the oil leak was a head gasket failure. He is going to clean things up, make sure the head is true and set valve clearances.

    What is the proper valve clearances for this engine? The Mistral owner's manual list the clearances as .15 mm intake and .25 mm exhaust. A video that Frank Mandarano posted on Youtube has them listed as .1mm intake and .2 mm exhaust. The engine builder finds both of these figures rather small (tight) compared to the Ghibli engine he recently did. I am inclined to go with the Mistral numbers but would like to get some feedback from people with real world experiences.

    Ivan
     
  16. DWR46

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    #41 DWR46, Feb 5, 2024
    Ivan: The Factory Build Sheets for 3500 GT #2200 list 0.10 mm for Intake and 0.20 mm for Exhaust.
     
  17. thecarnut

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    #42 thecarnut, Feb 5, 2024
    Thanks. The build sheet of my engine only has signatures in those fields, no numbers. I wonder why the Mistral would be different. Did they find out later that a larger clearance was better?
    Ivan
     
  18. DWR46

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    #43 DWR46, Feb 5, 2024
    Ivan: I do not know. However, I can tell you from experience with Birdcages, 300S and 450S motors, their Build sheets are all over the place when it comes to valve clearances within the same engine type. Possibly, they were opening up the clearance (less duration) for slow circuits and closing them down (more duration) for faster circuits.
     
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  19. GIOTTO

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    #44 GIOTTO, Feb 6, 2024
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  20. thecarnut

    thecarnut F1 Rookie
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    #45 thecarnut, Feb 9, 2024
    What is the combustion chamber volume of a new (unshaved) 3500GT cylinder head? This is usually measured in CCs.
    Ivan
     
  21. Ferraripilot

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    #46 Ferraripilot, Feb 9, 2024
    I have not confirmed this myself but I have heard it is somewhere between 85-90cc. I indeed have all the appropriate burette equipment to measure yours if you'd like, I'm happy to stop over as you're not at all far from me.
     
  22. thecarnut

    thecarnut F1 Rookie
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    #47 thecarnut, Feb 9, 2024
    Thank you for the offer for the test equipment. The head is with the engine builder and I am pretty sure he has a way of measuring the chambers. He is also able to enlarge them if needed.

    The build sheet of this engine indicates what appears to be a combustion chamber of 430cm (square), except volume is normally measured as a cube (not square). Any thoughts?

    Ivan

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  23. Ferraripilot

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    #48 Ferraripilot, Feb 9, 2024

    I have seen that before, which translates to explosion chamber volume. I have no idea how the noted 430cm fits into the equation but there's no way the chamber is 430cc or even 43.0cc for that matter. The closest similar example I can think of is a 4 cyl Alfa Romeo 2L engine, same bore of 86mm and very similar hemispherical chamber which when pristine condition measures out to 90-91cc. I think I'd have yours measured to be certain. Do you know the CC of the dome on the pistons?
     
  24. eogorman

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    #49 eogorman, Feb 10, 2024
    The reason for the various cam to valve clearance numbers on the six cylinder engines is related to which set of cams are installed. Most of the 3500 engines had the cam#48377 for both the intake and exhaust and the clearance for those cams are intake .10 to .12mm and exhaust at .20 to .22mm. I have found these work very well. another set of cams found in some of the 3500 engines were intake # 50024 and exhaust # 50022. These cams were stated to have clearances of .30 to .32mm on the intake and .25 to .27 mm exhaust. Your build sheets may tell you the cam numbers you have. THe Mistral info i have shows intake .12 to .15mm and exhaust .22 to .25mm. A little more but in the same range, and these would not be a problem for your engine. Different books have different infomation. The V8 also have different clearances for different cams. And in most instances the clearance is much greater for the V8 like .28 intake and .50mm exhaust. Bottom line is the clearance is related to the cam design.
     
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  25. thecarnut

    thecarnut F1 Rookie
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    #50 thecarnut, Feb 10, 2024
    Thanks Gene!
    Do you know the proper combustion chamber volume for a standard 3500GT engine?
    Ivan
     
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