DOHC bore service limit in real world?

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  1. #1

    Default DOHC bore service limit in real world?

    I have shop manual that shows:
    Out-of-Round Limit 0.015 mm measured max 0.05mm
    · Out-of-Round Service Limit 0.020 mm
    · Taper Service Limit 0.006 mm measured max 0.05mm

    According to values the block has to be rebuild, I doubt that no one has stress plates for it in my country, and labour is rather expensive here. Parts must be bought from US and my government needs toll and taxes about 30% above parts and freight. It's gonna cost me my sellable organs
    I'm thinking that I will assemble it as it is, and drive it until it blows? If I make another kid and sell it, I maybe can get enough money for new engine, I have two allready but I've become too attached to them.

    If it would be pushrod engine, it would be fine. But my driving habits don't suit v6 and I'm using it also on road courses and autocross, how long will it last

    Edit: measures was taken engine in stand, no stress plates, but I don't think it matters in taper readings.
    Last edited by FinnCobra; 01-10-2017 at 12:44 PM.

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  3. #2

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    Quote Originally Posted by FinnCobra View Post
    I have shop manual that shows:
    Out-of-Round Limit 0.015 mm measured max 0.05mm
    · Out-of-Round Service Limit 0.020 mm
    · Taper Service Limit 0.006 mm measured max 0.05mm

    According to values the block has to be rebuild, I doubt that no one has stress plates for it in my country, and labour is rather expensive here. Parts must be bought from US and my government needs toll and taxes about 30% above parts and freight. It's gonna cost me my sellable organs
    I'm thinking that I will assemble it as it is, and drive it until it blows? If I make another kid and sell it, I maybe can get enough money for new engine, I have two allready but I've become too attached to them.

    If it would be pushrod engine, it would be fine. But my driving habits don't suit v6 and I'm using it also on road courses and autocross, how long will it last

    Edit: measures was taken engine in stand, no stress plates, but I don't think it matters in taper readings.

    Your block will require a light honing to straighten out the bores, FinnCobra. That is the good news. The bad news is you will need new pistons and rings also. I would recommend getting the pistons before honing the block and then hone bores to specific pistons. The only folks I know that will build pistons to any size you request is Gibtec in Denver, Colorado. That is a $1200 cost, with pins rings and locks, before shipping and duty.

    Rather than blow it up why not sell it to other enthusiasts that could use the parts. You could easily sell cheaper than they can import and you can make some money for your rebuild and not waste usable parts.

    The engines generally last until they break. No expiration dates are provides with them so it is not possible to say with any certainty when they will break.

    If you measure the bores from the crankcase side with the heads torqued down using old gaskets you can get very accurate measurements of the taper and out of round.


    Ed

  4. #3

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    I'm in deep ****. I bought Mach 1 complete salvaged car for drivetrain parts. I have already sold everything 5.0 stuff, and modular engines aren't so popular here in Finland. Car turned out to be insurance fraud, and it had almost not one part that is good.

    How can piston clearance be negative in shop manual : -0.010/+0.026 mm
    What if block will be bored "020 over, is it ok.
    Last edited by FinnCobra; 01-11-2017 at 10:31 AM.

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  6. #4

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    I lightly honed bores, and they are good for me, pistons are worn out. Slightly out of round, but when I find suitable pistons, I shall see if they can be honed straight.

  7. #5

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    After some misfortunate events, I got new short block. I had good deal from freshly build iron block.
    Build sheet:

    4.6L Supercharged Short Block
    Engine Block 1 Cast Iron 4.6L Engine Block, no knock sensor posts.
    MAN-594220C-8 1 Manley 18CC Dished Pistons, 0,020"
    MAN-14042R-8 1 Manley H-Beam Connecting Rods w/ARP 2000 Bolts
    MAN-46620-8 1 Manley File Fit Piston Rings
    Sealed Power 148M 1 Speed Pro Competition Series Main Bearings
    CB-1442H 1 Clevite H Series Performance Rod Bearings
    FR-M-6303-D46 1 Ford Racing Steel Cobra Crank 8-bolt
    M-6600-D46 1 4.6L High Volumume Oil Pump and Pickup Tube
    MMR-BILLETGEARS 1 MMR Hurricane Billet Oil Pump Gears
    ARP-156-5201 1 ARP Main Cap Side Bolt Kit
    ARP-156-5401 1 ARP 4.6L Main Studs
    1 Balancing
    1 Boring/Honing with stressplates
    1 Crank polished
    1 Piston rings fitted

    I first assemble this and install. Then running in. I think I drive this summer N/A but I start to planning power adders, turbo or twin turbo.

  8. #6

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    I would recommend against the 0.020" overbore, the Manley pistons and the Manley rings. The 0.020" overbore especially on a boosted iron block is marginal strength wise. You are only asking for trouble especially in a boosted engine build.

    My recommendation would be to go the least overbore necessary to clean up the bores. That may easily be as small as 0.002". Get a set of Gibtec Pistons built to that size. The pistons come with tool steel pins, TotalSeal rings and are custom made billets built to your exact bore size and compression ratio.


    Ed

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