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Dino 246 service

Discussion in '206/246' started by pshoejberg, Jul 1, 2020.

  1. pshoejberg

    pshoejberg Formula 3
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    #1 pshoejberg, Jul 1, 2020
    Last edited: Jul 1, 2020
    It must be time for a little hardware thread. I pulled the engine from my early L series yesterday to perform an extended service. Ever since I completed the car project some 4 years and +-10.000 KM ago I’ve had a few issues that needed attention:

    1. I forgot to use sealing type Loctite on the piston head stud bolts and ended up with a slight cooling fluid leak around two bolts. The problem was solved by applying Loctite to the nut and the spacer washer. Not a permanent solution but it worked very well. I need to address this issue and I will at the same time install new stud bolts and nuts all the way around.

    2. From day one i had slightly lower compression in cylinder #4 and this issue did not improve over time, the opposite actually. I know both the valve seats in this cylinder had been machined more than once and the seats were on the borderline of wear spec. I performed a leak down this morning, and it revealed a clear leak past the exhaust valve. All other cylinders were fine. I will need new seats and valves for cylinder #4.

    3. From first day off I struggled with high cooling fluid temperature in the engine and I never found out why. The radiator is overhauled with a higher capacity core and the water pump and thermostat is also new. I changed to another fabricate of thermostat, but it didn't help. The problem solved itself over a couple of months. Later, I read a thread on FC about the Dino water pump and a small air drain hole above the water pump impeller that has a tendency to be blocked. I have never noticed this drain hole and it struck me that a blocked hole could explain the hot fluid issue. This morning I looked down into the water pump and found a completely plugged air bleed hole. I unplugged the hole in 5 minutes using a piece of wire.

    I cleaned the engine and thoroughly washed out all the stud bolt threads in the block in preparation for new bolts and Loctite.

    Next up is ordering spares and a time slot at my machinist for piston head work.

    Nice summer to all and stay fresh. Best, Peter

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  3. TonyL

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    Peter, that vent hole comes from the water pump upper chamber above the impeller and stops air locking and possibly pump cavitation. It is vital the hole is open to the thermostat housing so air is bled out. I hadnt noticed this untill comparing my old pump with a new unit i purchased.

    If you have used a new thermostat housing make sure the thermostat actually closes against the inlet port and doesnt leak past. There are some nasty repro therm housings out there.

    Tony
     
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  4. pshoejberg

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    Thanks for the comments Tony. There is no doubt that my cooling problems was caused by an air lock. The air will eventually escape, but in my case that took a long time and there is a potential risk of overheating the engine. All the parts are the original and I've checked the correct thermostat function back then when I changed to an alternative thermostat.

    Best, Peter
     
  5. TonyL

    TonyL F1 Rookie

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    I am sure you have already done this but check the water sender unit, my old one was out of calibration and being non adjustable i eventually bought a new one. There are no accurate resistance reading for the sender so I bench tested a few. The Veglia gauge sender is no longer available and many over here sell "Veglia matched" sender units for silly money. I did a trail of 4 senders on the market and the cheapest one was the best in terms of accuracy to the Veglia gauge.

    If you are still having what you consider as cooling issues (i hope you dont) but put a temperature probe in the flow to the rad, if its reads about 90C then you are good, regardless of what the gauge reads. A small resistor can be used to correct it if needed.

    Airlocking can cause major issues on the dino cooling system as can over dosing the system with corrosion inhibitor. The best way i found was to fill the sytstem via a temporary external elevated tank (the higher the better) connected to the car expansion tank. then vent through the heater matrix with the heater control open.

    Tony
     
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  7. pshoejberg

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    In addition to the gauge readings I could actually feel the raised temperature in the engine room and ended up buying a laser temperature gun and it verified the readings on the car gauges. I’m very optimistic that the issue is sorted now, but will keep you all updated upon completion of my service. I remember reading all your adventures in the gauge issues (and many other very inspirational threads of yours).

    best, Peter
     
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  8. TonyL

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    Laser guns are good but dont actually read water temp accurately and it depends where you spot test. I tried that as well and the most accurate way was to push a thin probe under the jubilee clip, retighten and read the actual water temp to the rad immediately after the thermostat. It also tells you if you have a lazy thermostat as well, my original was opening to late @ 88c instead of 82C, i changed it for a lower unit and now it opens at 78C.

    I dont like the after market water pumps that are currently for sale, most if not all of them have the impeller set to far from the housing, the spec is 1mm, the ones i have inspected are around 3-6mm which can lead to loss of performance from the pump (short circulating) itself, less flow means poor cooling.

    There are improved impellers on the market and willl try one when i next re-do the water pump.
    kind regards

    Tony
    Ps is that the original veglia sender unit fitted to the head?
     
  9. Skippr1999

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    FYI, the water pump I got from Dino Parts last year seems to be functioning fine.
     
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  10. pshoejberg

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    I have the original Veglia sender installed on the aft bank just as a blanking plug. I read the temperature from a new sender mounted on the forward bank (Superformance delivery). I'm using the original water pump housing with a new impeller from Dino Parts.

    Best, Peter
     
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  12. pshoejberg

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    Finally, time for a update on my engine service. I have made the following repairs with reference to the start of this thread:

    1. Changed out all studs bolts and nuts and applied thread sealer in the block to isolate against the cooling water.

    2. Found out why compression on CYL#4 was non existing. Turned out to be my own fault. I had shortened the valve stem too much during the engine rebuilt in order to obtain optimum shim size and consequently the cam follower started riding directly on the valve spring retainer cap wearing down valve collets and collets seats. Eventually after 5000 Km the wear was so extensive that the exhaust valve never closed. The issue was easy fixed by changing the exhaust valve to one with a longer stem, changing out the valve collets and spring retainer and shim it all up again. I checked all the other valves for same issue with no findings.

    3. Found out why I initially had severe problems with hot engine. It turned to be airlock caused by blocked bleed hole in water pump housing.

    4. Finally upgraded the generator to a 75 amp type with build in regulator. I'm using daylights and high amp ignition etc and are tired of problems with low charging effect especially when slow driving. I hope this issue is solved now.

    The engine is now re-assembled using Elring piston head gaskets (Bought cheaper Spesso gaskets first but binned them when I saw the lack of finish) and the engine has been lowered into the car. Hopefully starting the engine up in a day or two, can't wait for a final drive in the car before winter sets in and salt hit the roads.

    Best, Peter

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  13. daviekj

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    Looking good Peter, thanks for the update.
    Did the old block to head studs come out easily?
    Kevin
     
  14. Nuvolari

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    Fascinating problem causing the low compression. Luckily it was contained to the head and some easily replaced parts. Hopefully you can get some miles in before the salt hits the road.
     
  15. pshoejberg

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    Yes, every thing was greased up nicely upon initial assembly some +-10K KM ago so both heads and studs bolts came free with no issues. I always apply a small amount of copper grease along the studs bolts in attempt to avoid heads seizing over time.

    Best, Peter
     
  16. pshoejberg

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    Yes, I didn't see that coming. But it explains the ever so slight ringing sound I started hearing from the engine after some 5K KM of driving after restoration. The ringing increased over time and suddenly I lost power and compression. I was lucky that it didn't drop the valve. That would have been another story and would have ruined my maintenance budget. I feel lucky this time. I have added 0.5 mm to the length of the new valve stem and the new shim size is reduced to 3.65 mm witch is perfectly within optimum thickness.

    Best, Peter
     
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  17. daviekj

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    The valve stem length issue was similar to the experience I had (see thread and last post in https://www.ferrarichat.com/forum/threads/valve-shims-and-cam-wear.222622/page-2 I caught it before compression loss, but quite a puzzle to solve...

    I also used a light smear of copper ease on the head stud shanks. Not having had to remove the head since, curious as to how well it will help....you have boosted my confidence level Peter, thanks...

    Kevin
     
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  18. pshoejberg

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    #16 pshoejberg, Nov 1, 2020
    Last edited: Nov 1, 2020
    Just a small roundup on the service job. Got the car fully assembled and fixed a few additional issues such as a leaking steering rack rubber bellow And adjustment of the clutch. The car started right up and drove beautifully again with no need of any adjustment of either ignition or carburettors (Oh I just love that digital msd ignition box, thanks again to Rob). Managed to get 100 miles of driving before travelling to job (No cooling issues anymore and cooling system just bled once). Such a good feeling to have the gocart back on the road, it is such a different and charming driving experience than my recently acquired BBi. Thanks to all for participation in the thread.

    ps: The new uprated generator is working like charm and is charging happily even in idle. I’m excited to see if the integrated regulator will survive in the hot conditions just below the front header, time will show.
    best, Peter
     
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  19. Skippr1999

    Skippr1999 F1 Rookie
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    Great to hear. Enjoy and thanks for sharing the experience.
     
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  20. Mark Shannon

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    Tony

    I need a water pump rebuild kit. Please could you tell me who is selling improved impellers ?

    Mark
     
  21. TonyL

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  22. pshoejberg

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  23. Mark Shannon

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    Thank you Tony & Peter. Does look good.

    Mark
     

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