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4.3l sohc v6?

Discussion in 'Need for Speed!' started by 2000StreetRod, January 17, 2014.

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  1. 2000StreetRod

    2000StreetRod Staff Member Moderator Elite Explorer

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    Factory overbore

    Thank you for that very useful information! According to my workshop manual the specified oversize pistons sizes are +.5mm (.020") and +1.0mm (.040"). The stock cylinder bore is 100.4mm (3.953") and piston diameter is 100.380-100.400mm (3.952-3.9528"). If the min wall thickness is only 0.1777" with the stock bore then a +.040" overbore leaves only 0.1377". According to L.A. Sleeve's website their most popular sleeve thickness is .093" which allows for an overbore (I assume +.010"). But their sleeves are made from billets stronger than our cast iron cylinders. A 4.0" bore is a .047" overbore leaving only a minimum wall thickness of .1307". If Tom Morana's statement that the later SOHC blocks have thicker walls than the earlier ones is correct then a 4" bore might be feasible but I don't know how it would hold up on the street. I've been searching the Mustang forums for anyone who has bored their block and the largest I've found so far is +.020".
     
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  3. Bronco2

    Bronco2 Elite Explorer

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    then a 0.15 should be enough in a sohc engine block..
    as my machine sop told me

    Thx for the Pic!! btw i have installed a UK Shifter, its same than a Australien.. only thing is the front is not straight, so there is a 20mm Gap to my dashbord...
     
  4. 2000StreetRod

    2000StreetRod Staff Member Moderator Elite Explorer

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    0.15 inch wall thickness

    Bronco2, thanks for posting that 0.15" wall thickness is what your machine shop told you. Unfortunately, that only allows for .1777-.1500 = a +.0277" overbore or a diameter of 3.9807". That's not even enough for a +.040" overbore.
     
  5. jd4242

    jd4242 Explorer Addict

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    I figured this would be the outcome. I would have figured if a 4" bore would have worked, someone would have done it by now.im just praying that the 90tm ohv block can handle it like I've read/seen..makes me very nervous as my pistons are already paid for and being machined as we speak..

    In my opinion the major benefit to going to a custom piston is the strength, not size..I dont think there would be much power gains over a .040 or say a .060!!! Personally if it was me, I would be looking at how big of a valve would fit or how big of a cam could be made..WAAAYYYY more power to be gained there, then trying to fit a HUGE piston in there..;)
     
  6. jd4242

    jd4242 Explorer Addict

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    can you be more specific when you say ""front side" ??

    I would think you mean the major thrust side of the piston wall??typically if its the ""front side"" that means the wall facing the front of the engine or left side if your standing looking at the engine from the driverside. .but typically if its the left or right side then typically the middle cylinder will be thin on BOTH sides between the cylinders(where I was told its to thin to handle larger than.040 bore)

    Also where it was thin did you check the bore measurement to see if it was outa round?? ""If"" it was the major thrust side and not the ""front side"" then its very possible the thin wall is from wear...
     
  7. Carguy3J

    Carguy3J Well-Known Member

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    Actually, I think you are overlooking a big benefit of a bigger piston / bore...... It helps to un-shroud the valves. In fact, smaller valves, with less shrouding can often flow better then cramming a larger valve in and ending up with increased shrouding, both in the chamber and from the top of the bore. Same thing with a "bigger" cam. It may or may not help to lift the valve higher, depending on chamber design and bore size. Now, playing with cam timing "under the curve" is a different story. Getting them on/off the seat quicker and earlier could make big gains.
    http://www.eurospares.com/graphics/...tNews.com - All Racing News All the Time!.pdf

    Also, on the wall thickness / strength issue, has anyone considered using a partial block fill? Its been proven to help retain bore shape/size and reinforce "excessively" bored blocks in many applications, both street and race. I just don't know if the SOHC's cooling system passages/design will allow for it? http://www.hardblok.com/
     
  8. jd4242

    jd4242 Explorer Addict

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    I would have to look at the spare sohc heads again but if I remember correctly you can only go so big of valve before they touch and shrouding of the valve doesnt come into being a MAJOR factor..I know for sure on a ohv it doesnt..if the sohc valve size is anything like the ohv then they are WAYY undersized for the motor.your major power gains have come from head flow, obviously there is a fine line but its been proven on dynos again and again that most power has been gained with larger valves and cam design, not over bore
     
  9. jd4242

    jd4242 Explorer Addict

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    Just double checked the valves and its not as big of an issue as it is in ohv...

    Sohc has basically a IN 1.8 AND EX 1.5(surprisingly)..not bad for 4.0 but could still be larger especially on the exhaust side for a forced induction motor..just for comparison the ohv has IN 1.7 & EX 1.3....
     
  10. Carguy3J

    Carguy3J Well-Known Member

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    Huh.. That is pretty good for the SOHC. Chevy Vortec heads, capable of making 400hp on a mild 350, only have 1.94 in / 1.50 ex valves, and they are regarding as one of the best flowing oem iron heads GM ever made. I have a set on my currently disabled Chevy K30 pickup.

    I do think that a larger exhaust valve would be a good idea on the 4.0-OHV 1.7 on the intake seems reasonable, but only 1.3 on the exhaust seems a little small, especially with a better cam, headers, etc...
     
  11. jd4242

    jd4242 Explorer Addict

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    Yea I was pretty shocked also..of course like I said its a fine line on size and even port work.I would like to see a 1.9 &1.6 for forced on the sohc.

    Fyi I went with 1.8 &1.5 on my ohv and very nervous the 1.5 may not fit, definitely the max ;)
     
    Last edited: October 8, 2014
  12. Bronco2

    Bronco2 Elite Explorer

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    got the SOHC engine drawings, 5,0mm is the cylinder wall thickness on the paper...theoretical

    its from a 1L2E-6010 Casting

    [​IMG]
     
  13. jd4242

    jd4242 Explorer Addict

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    Where in the world did you get that? I would love to get a copy for the 90tm ohv block....
     
  14. jd4242

    jd4242 Explorer Addict

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    Even at 5 mm thick, that still not enough for a 4" bore....5mm=.196 You take the minimum wall thickness of .15 and only leaves you a .046 over bore (4"= .047 over bore) I wouldnt trust it,especially for a boosted applications. ..
     
  15. Bronco2

    Bronco2 Elite Explorer

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    as i told before....

    i know people who was involved in resizing 2,9 to 4,0 and to SOHC...
     
  16. Bronco2

    Bronco2 Elite Explorer

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    my block will also been sonic testet before i start boring the hell out..

    if its not possible.. i will stop by 4"
    still waiting for sonic..
     
  17. 2000StreetRod

    2000StreetRod Staff Member Moderator Elite Explorer

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    5l2z-6010-a?

    Nice going Bronco2! What model and year is your 1L2E-6010 for? Any chance to find out the thickness from drawings for 5L2Z-6010-A? I think that's the block that was used in the early Mustangs. I suspect there were some changes in the block casting in 2004.

    After doing a little searching I think you have a 2001 block. Is that what is in your propane powered 90 Bronco2?
     
    Last edited: October 10, 2014
  18. Sedition

    Sedition Engine Repair Guy Elite Explorer

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    Maybe Bronco got it straight out of the factory in Cologne. It looks like I'm going to have to measure my bores after I finish honing. It's taking quite a bit of honing to flatten out that upper lip too.
     
  19. Bronco2

    Bronco2 Elite Explorer

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    Yes the Block i m in is a 2001 Explorer block

    the Block in my Propane B2 is a 10/98Explorer ...
    The Casting i asked for is a spare, which i will rebuild...

    i will ask for another drawings (5L2Z-6010-A)but i think the a same..
    i m waiting for another mate who work in the engine casting factory if he has more infos to me..

    any OHV number to search for?
     
  20. Bronco2

    Bronco2 Elite Explorer

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    he did... but its under property of F...
     
  21. Sedition

    Sedition Engine Repair Guy Elite Explorer

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    I just gave my bores a quick measure after honing them. They're 0.6mm over (.024")
     

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