308 Piston Removal | FerrariChat

308 Piston Removal

Discussion in '308/328' started by JimBow, Feb 7, 2024.

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  1. JimBow

    JimBow Rookie

    Aug 15, 2006
    17
    Maine
    I have a 1977 GTB and have a possible issue with the rings on cylinders #3 and #4 (the rear bank) and would like to remove pistons while the engine is in the car. Has anybody done this before? I have already have the head removed. Before I drop the pan I want to make sure there will be access to the connecting rod nuts. I rebuilt the engine myself a few years ago and when I installed the pistons, con rods and tightened nut, the engine block was removed from the tranny. The tranny casting also the forms the crankcase sump so while it is attached I want to make sure there still access to the con rod nuts. The tranny part of the casting partially extends under the rear of the engine block leaving some space towards the front of the engine. (front/rear I mean orientation of the car) I think the con rod nuts for cyl #3 and #4 would be toward front and accessible from this space. Before I start removing the pan, I just wanted to see if anyone else has done it. I would like to avoid pulling the engine

    Why do I want to remove just 2 pistons, you ask? I rebuilt the engine myself a few years ago and did new valves, valve guides and seal and JE pistons etc. I have a few hundred miles on the engine but cyl #3 and #4 have never been right. I get blue smoke out the exhaust after doing a vacuum pull and when I pull the plugs on #3 and #4 they have been wet with oil. I pulled the head and there were a lot of carbon deposits on the exhaust valves and exhaust passages on #3 and #4. I cleaned the head and valves and see not problem with the head - no sign of wear on valve stems and guides, they fit perfectly with no play and the stem seals seem fine. I took the head to a couple of machine shop friends who build competition engines and they also found the head to mechanically fine. But since there was build up on the exhaust track plus the fact that the piston crowns on #3 and #4 were very clear compared to other cylinders, it was clear there was oil washing going on (instead of rich carburation or poor ignition or other problems). Since oil is not coming from the head, it must be coming through the rings. I am am not a professional car person but am careful when I do my work but can't be certain that I didn't damage the oil control rings or installed the oil scraper ring upside down or sometime like when I installed them. I would like pull the pistons and check.

    Sorry for the long post. Thanks in advance for any help.
    Jim
     
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  2. Ferraripilot

    Ferraripilot F1 World Champ
    Owner Project Master

    May 10, 2006
    17,849
    Atlanta
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    John!
    sorry for your troubles there!

    Can't remove pistons with engine in place nor would I recommend it as new rings (if the cylinders are ok) would require honing and I wouldn't personally do that with the rest of the bottom end together.

    Installing an oil scraper ring upside down would still control oil albeit it may not be optimal. The other 2 rings in the oil scraper package do not have a specific orientation.

    Leakdown and compression results? I know you think it may be something else but it's an awful lot of work on a hunch. That carburetor feeding #3 and #4 may be dumping excess fuel, float related, bad needle valve etc. As you stated excess carbon on the exhaust valve may just be way too much fuel getting in there. Did you set it up with a wideband O2 sensor post rebuild to make certain jetting was correct? If you bumped the compression with JE pistons the jetting was probably not optimal.

    How did it run? Constantly fouling plugs? Burning oil? What heat range are you running? Type of ignition?
     
  3. JimBow

    JimBow Rookie

    Aug 15, 2006
    17
    Maine
    Thanks for the reply. I did a compression check at it was strong across all cylinders include #3 and #4 - about 165 PSI. Leak down was good and consistent across the board also.

    I did put 10.5 compression JE pistons in the engine. I rejetted since I have high compression pistons and also a competition Tubi exhaust and think I got jetting mostly correct. The same jets in all the carbs and about the same idle mixture turn-out. Six cylinders seem happy, but #3 and #4 are not. I did not tune with an O2 sensor. Still running original points ignition and NGK BP5ES plugs.

    As I said: I am running everything the same across the cylinders and six of them look are happy with clean valves and plugs but #3 and #4 have exhaust valve deposits and oily plugs.

    Jim
     
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  4. Ferraripilot

    Ferraripilot F1 World Champ
    Owner Project Master

    May 10, 2006
    17,849
    Atlanta
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    John!
    Thanks. I am thinking it’s more likely air/fuel or ignition related.

    Do those two cylinders just die/foul when idling for too long? How is the float level and needle valve in that carb? And distributor cap and wires ok? Air cleaner ok?

    Do you recall what size main jet, air correct, idle and which emulsion tube?

    Stock ignition on these is quite awful. These engines love a couple of MSD boxes with a tach adapter all hidden in the trunk just behind the left rear wheel. Works wonders and the points last a ton longer. Note stock ignition wires cannot be used as they are solid core, needs spiral core.
     
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  5. Rifledriver

    Rifledriver Three Time F1 World Champ

    Apr 29, 2004
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    #5 Rifledriver, Feb 7, 2024
    Last edited: Feb 7, 2024
    I strongly suspect his JE rings had up and down orientation. While not the best around they are not Victorian age parts like the originals were.

    Id also suggest if it really needs BP5's it has issues possibly extending beyond #3+4. Its just too hot a plug.

    If rings are the culprit or the suspected culprit put a bore gauge in it and look for the crown of the piston being washed down. Taking a motor apart is not a proper diagnostic procedure.
     
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  6. Ferraripilot

    Ferraripilot F1 World Champ
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    John!
    I believe the JE scraper ring is just a Hastings sourced 3 piece ring. Works well and should be oriented as per the instructions. I am almost certain I have pulled a motor apart and saw more than one was installed upside down. I have also seen the oil scraper rails come out of their groove above or below the expander likely due to incorrect installation when installing the piston. As far as the expander is concerned it’s the same profile up or down, just the opening needs to be pointed down as per the below pic.

    But note having a scraper rail all jacked up like that in the bore is both easy to feel and easy to see on the cylinder walls as it screws up the cylinder wall and shows lower compression than the others pretty quick. It’s easy to feel in that when initially shoving the piston in it creates a heck of a lot more drag just pushing it down the bore. You know something is wrong just getting it in there, that is if you can get it in there as the clearance is already tight.



    Image Unavailable, Please Login
     
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  7. JimBow

    JimBow Rookie

    Aug 15, 2006
    17
    Maine
    Thanks for all the great advice! I am not currently suspecting rich carburetion since jetting and idle mixture screw turn-out of the carb feeding #3 and #4 is similar to the other carbs. I double checked that the float was not cracked and the needle valve was working correctly. Also, I am getting oily spark plugs. I am not suspecting ignition system fault since the other cylinders on that distrib are fine.

    I believe the second compression ring is a tapered ring to help scrap oil so putting it in upside down could allow oil passage. If I was careful about orientation when installing but not absolutely sure I didn't make a mistake.

    The cylinder walls on all cylinders are nice a smooth with bit of the cross-hatching still there. All the pistons slid freely when I installed them.

    Jim
     
  8. Rifledriver

    Rifledriver Three Time F1 World Champ

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    Who cares about the oil ring? Its the scraper that keeps oil out of the chamber.
     
  9. Rifledriver

    Rifledriver Three Time F1 World Champ

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    No such thing as a 2nd compression ring. That ring is there to keep oil out of the combustion chamber.

    Unless possibly you are using pistons from the 40's.
    The bores were fresh right? Or did you put new pistons in old bores?
     
  10. JimBow

    JimBow Rookie

    Aug 15, 2006
    17
    Maine
    Excuse my mis-terminology about the second compression ring.

    I had the cylinder liners bored 40 mils over and the pistons were matched to the liners with the JE specified piston to cylinder wall clearance. Ring gaps set to specs.

    I am going to call JE today for some tech advice.

    Jim
     
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  11. Rifledriver

    Rifledriver Three Time F1 World Champ

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    #11 Rifledriver, Feb 8, 2024
    Last edited: Feb 8, 2024
    By the way, thats not the scraper. Thats the oil control ring.


    https://www.wiseco.com/auto/wiseco-auto-blog/what-does-the-2nd-piston-ring-do-purpose-and-function-explained/#:~:text=Combustion%20sealing%20is%20100%20percent,to%20quickly%20escape%20to%20the
     
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  12. JimBow

    JimBow Rookie

    Aug 15, 2006
    17
    Maine
    Rifledriver,
    Thanks for the advice and the article was very informative.

    I called JE and the ringset I installed has a tapered style second ring. They said if I installed that ring upside down then the ring would be scraping oil up instead of down and would be causing the problems I am experiencing. I knew of ring orientation when I installed them and I am generally very careful when doing work, but I can be certain that is didn't make a mistake. I will look at it some more, but I am thinking I may end up removing the two pistons.

    Curious that if a made a mistake on ring installation, I did it on just two adjoining pistons. But anything can happen.

    Jim
     
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  13. Ferraripilot

    Ferraripilot F1 World Champ
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    John!
    Man I hope that's not the case! Rough. Good luck with that and keep us posted
     
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  14. Rifledriver

    Rifledriver Three Time F1 World Champ

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    It can and we have all screwed up, damaged rings etc. I would still peek down the cylinders with a bore scope. If that is where all the oil is coming from the circumference of the piston will be wet and clean.
     
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  15. Newman

    Newman F1 World Champ
    Consultant Owner Professional Ferrari Technician

    Dec 26, 2001
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    Newman
    Regarding removing the pistons in the car, I dont see why you cant but I've never done it. On my car I had to pull the oil pickup off and I refused to remove the engine to do that, although I didn't enjoy doing it in place it was possible and I'd do it again. With that out of the way I would think the windage tray would come down? It depends if you can access the M8 nuts on the rear side of the tray.
     
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  16. Rifledriver

    Rifledriver Three Time F1 World Champ

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    Tray too big to come out.
     
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  17. JimBow

    JimBow Rookie

    Aug 15, 2006
    17
    Maine
    Thanks for the replies. A couple of photos might be helpful. I already have the head on that bank removed. In picture below cyl #3 and #4 are the top two and their piston crowns are very clean compared to the other two. (The little drops of liquid on the pistons are a few drops of coolant remaining in the head when I removed it. I took this pic right after I pulled the head). I borescoped the other bank and the piston crowns had deposits similar to #1 and #2 in the photo below.

    Image Unavailable, Please Login

    Also, the exhaust valves and exhaust passages in the head of #3 and #4 have deposits on them compared to #1 and #2. As I said before, the spark plugs on #3 and #4 would get oily wet when the engine is running and the others remain dry. I checked the head and a couple of other people checked the head and the valves stems and guides show no wear and the valve temp seals are good. All this make me suspect the rings.

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  18. Rifledriver

    Rifledriver Three Time F1 World Champ

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    Sorry for all the work. **** happens. Given enough chances we all get it wrong once in a while.
     
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  19. Newman

    Newman F1 World Champ
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    Something else to double check is if the oil is leaking between the guide and the head because the guides were replaced. I've seen it before. Just rule it out before going further.
     
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  20. JimBow

    JimBow Rookie

    Aug 15, 2006
    17
    Maine
    I dropped the oil pan and answered the question if a piston could be removed with the engine in the car. No, It cannot. As pointed out be other posters: the windage tray cannot be removed which needs to be removed to access the con rods. The tray is held in by 4 nuts and the forward ones are accessible but the rear ones are blocked by the part of the tranny that comes under crankshaft. Even if I could get all the nuts out, the tray is too big to remove though the pan hole. So this would require an engine out, remove the bell housing and separate the engine block from the tranny/sump casting.

    This is a lot of work and I got a lot of other projects I want to finish this winter. So, I am thinking I will put the oil pan and head back on and running it for another summer and just keep the spark plugs clean. Next winter I will budget the time and mental energy to do an engine out.

    Thanks for all your help.

    Jim
     
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  21. Ferraripilot

    Ferraripilot F1 World Champ
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    John!

    As they say, once you've done this job once you can do it again in half the time. Keep us posted on this. Wish I were closer as I'd come to help. In the meantime, adding a couple MSD boxes would likely help a ton.
     
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  22. JimBow

    JimBow Rookie

    Aug 15, 2006
    17
    Maine
    Thanks for all the replies! I will be looking into adding the MSD ignition units.

    Jim
     

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