Compression leakdown test F355 | FerrariChat

Compression leakdown test F355

Discussion in '348/355' started by BOBAER, Jun 8, 2006.

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  1. BOBAER

    BOBAER Formula Junior

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    I just had a compression leakdown test on a 95 f355 and would like to know if someone can interpret them as I am no mechanic. Are the results within range of where they should be, and if not, what does that mean.

    1 13%
    2 6%
    3 10%
    4 7%
    5 10%
    6 3%
    7 7%
    8 3%.

    Any input is helpful. Thanks
     
  2. Harmonyautosport

    Harmonyautosport Formula Junior

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    The engine compression cycle is the air fuel mixture being compressed into a smaller volume in the engine cylinder. Most engines require 145-160 PSI to complete this operation. The test will determine if there are any leaks causing a cylinder to not have the correct amount of pressure. A compression and leakdown tests both determine this in differnt ways. Your numbers should be very close to the same values in a health running engine.
     
  3. 1Turbo

    1Turbo Formula Junior

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    Clylinder 1 is High.Post ALL the Compression Numbers.They should be in the 180-200+ Range.They should be "Close" to each other.
    What's the Mileage ?
     
  4. BOBAER

    BOBAER Formula Junior

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    The mileage is 30,500. Based on the numbers I gave, should any action be taken?
     
  5. 1Turbo

    1Turbo Formula Junior

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    Is this a PPI ? or have you already purchased the Car ?
    Did the Mechanic perform a "Leakdown" Test only (those were the results you posted. The Lower, the Better).I'd want the Compression results before i bought it.
    I see that Harmony already posted the Explanation.
     
  6. chaa

    chaa F1 Veteran

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    I dont think mileage has any thing to do with the strenth or power of a 355 engine. My engine was dynoed last month with 328 bhp at the rear wheels, which is more than a standard 355. My car has 42,000 miles on it. Apart from the Capristo it has a Hamonn chip which does not incease the bhp much but spreads the fuel better. I think the more miles on a 355 engine the looser the engine.
    It would be interesting to compression test mine, maybe my reading would not match up;) Mind you i dont think i will bother becourse they will probably not match and i will stress me self out and start a worring thread about it:D:D
    Though i wonder what the compression reading were straight from the factory.
     
  7. Llenroc

    Llenroc F1 Veteran Rossa Subscribed

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    Chaa, have to chuckle at your comment on not knowing the comp.nos. hell your building good HP who cares right? And nobody wants you stressing out. Hahaha, Regards, Vern
     
  8. Llenroc

    Llenroc F1 Veteran Rossa Subscribed

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    Just thoughts here but anyway, no. 1 cyclinder seems slightly high and since the others aren't to bad to excellant you might consider the possiblity that there could be some crud on that no. 1 valve seat(s) to make it leak slightly. If they were all 10% or 13% then I might be more concerned. As was said above it would be nice to see the compression Nos. too you need both to get a thorough picture. Regards, Vern
     
  9. BOBAER

    BOBAER Formula Junior

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    I do own the car already, and this test was done before my purchase as I am reviewing all the service records, I came across this and wanted to find out the interpretation.

    I know it was said that they should all be the same number, but I find it hard to believe that after 30k of use they would all be the same. If in fact 13% is high, what can be done to correct it. Is it something major, does it present a major problem?
     
  10. Llenroc

    Llenroc F1 Veteran Rossa Subscribed

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    Jon its not so much the leakdown nos. need to be the exactly the same its more the compression should close to the next cyclinder nos. Lets say all were 200 lbs. or they veried by 5 lbs., that would be great. To have leakdown % nos. varing from 3% to 10% isn't real bad, it would be great if they were all 3% but I think that is kind of rare things to be that perfect. hope that makes some sence. Regards, Vern
     
  11. BOBAER

    BOBAER Formula Junior

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    Thanks Vern.

    In the report, the receipt from Ferrari of Houston said that a compression leakdown test was preformed, but no lbs were described. In pen, the cylinders were listed with a % next to them. I think that after 30k miles, you will never have all of them the same.

    Just curious, do you think that the higher scale of 13% effects either the performance or the long term condition of the engine?
     
  12. Llenroc

    Llenroc F1 Veteran Rossa Subscribed

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    Jon, there are so many opinions on leakdown numbers and when they are good, bad and OK. I think if I was you I would do it again and the reason is that you only have one barely questionable cylinder and I don't think it's that bad. Also I would do it again because it could be, as I said before, maybe there is something on that particular seat that is giving that reading. Allowing it to not seat properly. I'm only saying this because of the other readings. Run it hard for a few miles and do it again. If they were all above 13% and that depends on which camp you are in then maybe you have something that needs to be looked at further. The 13% isn't perfect(but not bad) but you do have 30K on the engine I would say that is not to bad. regards, Vern
     
  13. BOBAER

    BOBAER Formula Junior

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    Overall, the car is running great and as you said the 30k was done, new rh header, both cats, both boots a clutch about 10k ago. So far so good, I am going to relax and enjoy the experience this summer.
     
  14. chaa

    chaa F1 Veteran

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    Now thats exactly what i am talkin about dude:D leave the worrying to all the ferrari hypercondriacs on this mans forum;) and god knows theres alot of them on here:D
     
  15. jabramson

    jabramson Formula Junior

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    I'm going through something like this right now. I am in the middle of a purchase and had a PPI done. The compression test showed that the #2 cylinder showed 30% whereas all the rest showed between 6% to 8%. The seller has taken extremely good care of the car so at this point this is the only issue. He is running an addative in the gas tank to see if there is some carbon build up that is preventing a good seating. Hope it works but I have my concerns it is probable something more. Fingers are crossed.
     
  16. BOBAER

    BOBAER Formula Junior

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    30% does sound high and I wonder why it effected only one cylinder as the other readings sound very strong.

    Has that car you are looking at had a Major service or is it due. If it is due, than it could be addressed at that time and I would you the cost of that fix against the purchase price.
     
  17. chaa

    chaa F1 Veteran

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    But why do ya think its broken?? Its no small job to equilize compression. the heads have to be removed and the valves reseated or replaced at best. At worse the pistons have to be removed and the rings replaced and the bores honed:( But is this any garante of having all 8 of the compression equil?
    So armed with that information......how does the car feel, how strong is the engine? Is the compression readings so bad that it effects the performance of the engine? If you was to of set the cost of the work against the cost of buying the car......then the car could only cost ya $3,000 to buy:D:D
    Like i have said further up the thread, i have never had mine checked and the engine is a strong Mo Fo;) Chances are my compression may not be equil. But i will not loose sleep over it and start stripping the engine down.
    Of course this is my opinion. Makes sense to me.
     
  18. Ade

    Ade Formula 3

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    My 355 engine decided to give up a couple years ago (started burning lots of oil = tons of smoke). When it was taken apart and rebuilt there was really only a major problem with 1 cylinder. compression was around 30-40 psi lower on the cylinder than the rest.

    ... so be suitably cautious regarding un-equal wear and cylinders that stick out like a sore thumbs..... $20,000 later....
     
  19. BOBAER

    BOBAER Formula Junior

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    In the long run, your obviously much better off paying the price and buying a car that has been completely sorted out.

    On the other hand, if your already own the car than I would be concerned if one cylinder was 30% and I would have to pay the price today to get it fixed as opposed to possibly paying a lot more if you let it go and became a problem that you had to fix.

    Just saying if you had to do a major engine out, how much more would you think it would cost to fix the valve in that cyclinder?
     
  20. Harmonyautosport

    Harmonyautosport Formula Junior

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    We charge $5,500 for a 30k miles engine out service. Doing head work and replacing valves gets expensive. Since the 95 F355 had brass valves its very common for them to fail and this was later upgraded in the following years. Shoot me over an email at [email protected] and I will get you a basic quote on valves, etc.
     
  21. Steve B

    Steve B Formula Junior

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    It should be noted that all F355s from 1995 through mid-1998 had bronze valve guides. According to mechanic Tony Palladino, the changeover to sintered steel guides came at assembly no. 27689.

    The leak-down numbers posted above appear to be high in some cylinders. I bought an 11,000 mile 1995 F355 last year and the leak-down percentages were 2% in all cylinders except one, for which it was 3%.
     
  22. mfennell70

    mfennell70 Formula Junior

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    Hi Jon, glad to hear it. I'm the guy with the Esprit that was looking at the car at the same time you were. You certainly didn't screw around - they called me barely an hour later to say the car was sold. Did they come up with the fender liner that covers the battery?
     
  23. No Doubt

    No Doubt Seven Time F1 World Champ

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    I'd phrase it a just little bit differently. The leakdown test measures valve tolerances/sealing whereas the compression test measures timing precision.

    You could have perfect valves/sealing (measured by leakdown test) and still have lousy compression (measured by compression test) if the valves are opening/closing at the wrong times...since you don't get much compression out in the open air!

    Closed spaces yield more/better compression or "overpressure." Ask Abu Musab al-Zarqawi on the last point.
     
  24. BOBAER

    BOBAER Formula Junior

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    MF

    The battery cover was actually in the bonnet.
     

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