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Countach engine and engine bay refresh

Discussion in 'LamborghiniChat.com' started by sp1der, Nov 20, 2019.

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  1. sp1der

    sp1der F1 Rookie

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    #26 sp1der, Dec 17, 2019
    Has anyone used CPS pistons in their rebuilds? Looks like best route is over-bore to 86mm and new pistons as 2 liners are lightly scored and there is a bit of wear.
     
  2. MiuraP400

    MiuraP400 Formula Junior

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    #27 MiuraP400, Dec 17, 2019
    Per the owners manual the intake opens 42 deg before TDC and closes 70 deg ABDC. Duration is 292 degrees. The exhaust opens 64 deg BBDC and closes 40 deg ATDC. Duration is 284 degrees. The manual also lists 62 degrees of overlap but based on the numbers provided for intake opening and exhaust closing it should be 82 degrees. I do have the cam profile for a S1 and a 5000S FI but they are on a computer that is having issues right now so I do not have access. You can measure the lift pretty simply but using a set of calipers and measuring from the peak of nose of the cam to the base circle, then take a measurement 90 degrees to the first. Then simply subtract the second measurement form the first.

    Cheers Jim
     
  3. MiuraP400

    MiuraP400 Formula Junior

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    #28 MiuraP400, Dec 17, 2019
    I do not have any experience with these pistons, but if you are buying new pistons I highly recommend increasing the compression ratio. These cars have a fairly low compression ratio for the valve timing they run. I can provide some recommendations when I get my computer sorted out.

    Cheers Jim
     
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  4. S_AGATA

    S_AGATA Formula Junior

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    Jon/Sean Sohaei
    #29 S_AGATA, Dec 17, 2019
    In the LM we bumped compression and went to smaller (bigger bore) liners, which are a much stronger design anyways. Running 5228ccs at the moment.

    There is definitely room to push the internals of these engines. All things combined I feel that it’s made a bit of difference.
     
  5. sp1der

    sp1der F1 Rookie

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    #30 sp1der, Dec 17, 2019
    Last edited by a moderator: Nov 25, 2022
    Bit more progress, block now stripped, the timing gear was a pain to remove as the inner bearings on the roller bearings are extremely tight on the shafts but got them off in the end. Plan over Christmas is to get the sump all cleaned up an all seals sorted out then figure out how to progress with the pistons/liners. One thing of note that could have been a disaster is that one of the blanking screws had started to back out as was extremely close to the main caps. Also noted oil restrictors are in the wrong way round on the block.

    Thanks for the advice on the pistons sounds sensible, may also go for nail-head valves on the inlet to improve flow, I am currently talking with CAT cams about getting some new cams manufactured as well. Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login
     
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  6. sp1der

    sp1der F1 Rookie

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    #31 sp1der, Dec 17, 2019
    Jim thanks for the reply, was looking for the lift specs to check if there is any wear, the lobes seem ok but the exhaust cams seem to be fairly low lift compared to the inlet, it just seemed a bit odd.
     
  7. MiuraP400

    MiuraP400 Formula Junior

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    #32 MiuraP400, Dec 18, 2019
    I am not sure why they did it but Lamborghini was not big on exhaust flow. For a Euro S1 cam (which I believe you have in your 5000S) the exhaust lift was only 0.319 inches, the intakes are 0.364 inches. These numbers are as measured at the valve. It you are measuring the cam you need to add the valve lash to these numbers. FYI, I had my emissions cams redone. They were 0.325 exhaust lift and 0.338 intake lift. They are now 0.387 exhaust and 0.402 intake.

    Note the intake responds really nicely to a bigger valve, I picked up a significant flow improvement. If you do go for bigger valves you should plan on porting the exhaust side. It gets difficult to get enough exhaust flow to balance the intake flow. Note you have to be careful when changing valve sizes and cams on these engines, it is very easy to make an engine that wants to run in the 8000 to 9000 RPM range to make their max power, especially the 4 liter engines. The 5 liter engines have a little more leeway but you can still run into issues with the engine speed getting higher than most people are comfortable using.

    Cheers Jim
     
  8. sp1der

    sp1der F1 Rookie

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    #33 sp1der, Dec 18, 2019
    I think I will leave the valve sizes alone but opt for nail-head inlet valves, I will re-check cams as both seem to have higher lift, they may have been changed as mark for cam timing is etched rather than engraved and I cannot see any numbers but I have not checked the heads that much, focus was on the block to get it stripped down.
     
  9. MiuraP400

    MiuraP400 Formula Junior

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    #34 MiuraP400, Dec 18, 2019
    Last edited by a moderator: Nov 25, 2022
    Just in case you wanted to do some performance upgrades I ran my model and made some changes so you can get an idea of what the changes will do to your engine. Note the last column is pushing the limit for premium fuel. There is a risk of detonation with it. The green rows give you the predicted Hp, the RPM that it occurs at, and the vacuum at idle which is an indication of the torque just off idle. Note these vacuum numbers are fairly low but since one cylinder is always firing on a 12 cylinder it is not as critical as it is on engines with fewer cylinders. The rows highlighted in blue are the changes that need to be made to get the performance shown in the green rows.

    Cheers Jim

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  10. MiuraP400

    MiuraP400 Formula Junior

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    #35 MiuraP400, Dec 19, 2019
    Last edited by a moderator: Nov 25, 2022
    Looking at my post I see I made an error in the max CR you could consider using. A CR of 10.5 is the max you could consider running with pump premium fuel. However the airflow and combustion characteristics of the hemi head make it very risky to try, I would stick to 10 to 1. I also figured you would want to see the effects of a 0.020 inch overbore. Then for fun I ran some numbers to see what it would take to play with the DD guys. To play with the DD guys you need to be able to run up to approx 8300 RPM and you would have to look at using a 50 DCO Weber with 41mm chokes. The results are below.

    Cheers Jim


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  11. sp1der

    sp1der F1 Rookie

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    #36 sp1der, Dec 19, 2019
    Cool many thanks for running this, I think spec is likely to be 86mm bore, 10:1 compression ratio and will decide a bit later on valves. Primary first job is to get bottom end sorted.
     
  12. sp1der

    sp1der F1 Rookie

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    #37 sp1der, Dec 24, 2019
    Last edited by a moderator: Nov 25, 2022
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  13. sp1der

    sp1der F1 Rookie

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    #38 sp1der, Dec 24, 2019
    Last edited by a moderator: Nov 25, 2022
    Every ring nut socket except the right one for the drive output nut in the sump - item 20. Hard to measure as well down the tube so easier to buy a new nut and then get the right tool.

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  14. sp1der

    sp1der F1 Rookie

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    #39 sp1der, Dec 27, 2019
    Last edited by a moderator: Nov 25, 2022
    A few more pictures, pistons taken off the rods, each rod is engraved with the chassis number and location, cams taken out and a couple of valves out ready to get new ones custom made. The casting dates are also interesting all 82 but various dates for the block and heads. Pistons made by AE. Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login
     
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  15. raymondQV

    raymondQV F1 Rookie

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    #40 raymondQV, Dec 27, 2019
    590 on the rod should be the weight in gramms.
    The factory tried to use the same weight rods in one engine to have a smooth running, blueprinted engine got the lightest rods.
     
  16. sp1der

    sp1der F1 Rookie

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    #41 sp1der, Dec 27, 2019
    Cool my chassis number is 590
     
  17. Adamo

    Adamo Karting

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    #42 Adamo, Dec 27, 2019
    Do you have the camshaft spec’s of a F.I Q.v and a down draft? Would love to know and compare.
     
  18. MiuraP400

    MiuraP400 Formula Junior

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    #43 MiuraP400, Dec 27, 2019
    Unfortunately I do not.

    Cheers Jim
     
  19. sp1der

    sp1der F1 Rookie

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    #44 sp1der, Dec 29, 2019
    Hopefully will get pistons on order this week and new valves - CPS for pistons and Manley for the valves.
     
  20. raymondQV

    raymondQV F1 Rookie

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    #45 raymondQV, Jan 2, 2020
    Last edited by a moderator: Nov 25, 2022
    That's the picture I was referring to concerning the weight of the connrods, see 590 - common weight, be happy you didn't get 616gramms!
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  21. sp1der

    sp1der F1 Rookie

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    #46 sp1der, Jan 2, 2020
    Cool picture, the guy does not look over happy though!
     
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  22. sp1der

    sp1der F1 Rookie

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    #47 sp1der, Jan 2, 2020
    Will hopefully shed over 100g on the new pistons
     
  23. MiuraP400

    MiuraP400 Formula Junior

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    #48 MiuraP400, Jan 2, 2020
    Simon,

    Any chance I could get a favor? Could I get some photos of the fuel filter/pressure regulator and it's installation on the firewall?

    Thanks Jim
     
  24. raymondQV

    raymondQV F1 Rookie

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    #49 raymondQV, Jan 2, 2020
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  25. MiuraP400

    MiuraP400 Formula Junior

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    #50 MiuraP400, Jan 3, 2020
    Thanks Raymond. I see the QV uses a six screw filter king with barbs for clamp on fuel lines. In Simon's photos in the beginning of this thread I thought I saw a four screw filter king, but I suspect the photo is not clear enough to tell. I was looking to see what is correct for a 5000S. Most likely it is the same six screw filter king as your old QV.

    Cheers Jim
     
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