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  • cbremer
    replied
    what rick said i'm using a 258 crank, 242 rods, and custom pistons with a higher pin height. i haven't decked the block at all; assuming it was flat when I took it to the machine shop. if it's not, then it'll likely have .010 taken off. I'll likely shave the head (which is also getting rebuilt) a little, then use a thinner than stock head gasket to bump up the CR a bit. I'm looking at ~9.5:1 right now (actually more like 9.45:1 ) throw in a mild cam with a little more lift & duration, and viola! that's my new engine.

    also getting all new/reconditioned goodies- high volume water & oil pump, distributor, harmonic dampener, H.O. alternator, etc.

    good stuff!
    Last edited by cbremer; 03-11-04, 05:14 PM.

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  • rick
    replied
    The crank Chuck is using is a 258 crank. The 258 crank is 3.9" stroke, and the 258 rods are 5.875" long. Stock 4.0L rods are 6.125" long, which makes the piston top higher than the deck at TDC. Thus, you need a custom piston with a higher pin location. Using stock 258 5.875" rods increases the quench hieght to 0.081" (I think 0.051" is stock on a 4.0), resulting in higher emissions, not as much power, higher fuel consumption, and prone to detonation. If the block is milled to restore the quench height to closer to stock, the combustion volume is decreased even further, resulting in close to 10:1 compression, requiring high octane fuel and ECU remapping. Hence, the custom piston which allows use of the longer 4.0 rods. It is possible to increase the combustion chamber volume to help reduce the CR, but this also costs money unless you are into cc-ing heads yourself and using a die grinder very very carefully. Thus, the real cost of the custom pistons is the difference in cost between purchasing stock 4.0 pistons and 258 rods, assuming you have good 4.0 rods to mount the custom pistons on:

    Short 258 rods + stock 4.0 piston = $350

    Custom pistons + reuse 4.0 rods = $550
    Difference = $200

    The longer 4.0 rod also results in a higher, more desirable rod ratio. This is not really a major concern in an engine with a redline of ~5,000 rpm, but what works on a race engine just makes a lower rpm engine last longer. Custom JE pistons are $550 a set, possibly lower if I buy more than one set. The machine shop I use would probably not feel good about ordering you pistons though Chuck unless they look at the block. They don't like doing things twice

    rick

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  • Dukes69
    replied
    What about a stock 258 Crank and rods? I *think* thats what I was going to do. If I remember, its the same crank, just longer stroke. It might save a little.

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  • cbremer
    started a topic Stroking it!

    Stroking it!

    you sick, sick pervert :yawn:


    i got a credit card limit increase... so naturally i'm going to run it right back up

    Here's the plan so far:

    Accurate Pistons $600.00 (or maybe not... rick?)
    Accurate rings 58.75
    NAPA Crank (PRR25300) 210.00
    Summit Sealed Power Gasket kit (SLP-2601424) 74.39
    AutoZone Melling Oil Pump (M167HVS) 53.99
    Summit Cloyes Timing set (CLO-9-3127) 106.69
    Accurate Timing tensioner 9.00
    Summit Crane cam & lifters (CRN-753901 & CRN-9927812) 178.87
    Summit Crane valve springs (CRN-99833-12) 52.39
    Summit Sealed Power freeze plugs (SLP-3818084) 16.69
    Summit Mopar pushrods (DCC-4529675) 16.39
    Accurate head bolts 56.65
    Flowkooler water pump (BRA-1747) 102.39

    reusing stock 4.0L "long" con rods


    sound good? any room for improvement? i've been doing my homework on NAXJA and on the strokers yahoo list, and this seems like it's going to work pretty well with a .030" over block and mild head work. Gotta keep the smog nazis happy too

    i'll post pics as I build this puppy up over the next several weeks (still waiting for the block to come back from the machine shop )

    thanks-
    Chuck
    :hat:
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