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safe limits for piston and bearings

Discussion in 'Early CJ5 and CJ6 Tech' started by ktm25089, Aug 3, 2015.

  1. Aug 3, 2015
    ktm25089

    ktm25089 Member

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    Hello,
    after 2 years jeep sitting i was tried to start it again.As you guess the engine f-134 is stuck,tried all combinations with thin oil,mystery oil,atf fluid for 1 and half month now and nothing.today i was tried to pull it with a tractor and leave the clutch.4wd and tried all the gears the clutch slips and no engine turn.tomorrow i will remove the head to see the damage.
    I want to ask what is the safe limits for boring the cylinders?they are 30 under now.and what is for the crank and conrods?i know that the crank is solid steel.can i go 50-60 under without problems?i dont use the jeep as a tractor but trips around and little off road.

    Thanks
    George
     
  2. Aug 3, 2015
    47v6

    47v6 junk wrecker! 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    I believe you can go as far as 80 thousandths oversize on pistons and rings. You're gonna have to see whats rusted or seized or frozen together before you think about boring it or cutting the crank. this will be a lot of money relative to a swap of another running Fhead or a transplant engine. It may be a cheap easy fix like a cylinder hone, but it still means pulling the engine and a complete disassembly.

    good luck.
     
  3. Aug 3, 2015
    ktm25089

    ktm25089 Member

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    80 over???is that limit safe?i will se tomorrow what the damage is but im making a list of the parts that i need.
     
  4. Aug 3, 2015
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    This block design dates back to the 1930s, and arguably earlier. It is a heavy casting. I would not be surprised if most 134 blocks can go 120 over (not under) and select blocks more.

    If you are concerned, your machine shop can sonic test the wall thickness and advise you on the maximum overbore size.

    Really, as 47v6 advises, you want to strip the block and have the block, crank and rods tanked and magnafluxed for cracks before you decide anything. If you want to sonic test the cylinders, this will be the time to do it.
     
  5. Aug 3, 2015
    Glenn

    Glenn Kinda grumpy old man Staff Member

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    My 3B is bored .060 over and it's fine. I've heard of going .080 over, and obviously if they sell pistons for it then it's doable.
     
  6. Aug 3, 2015
    47v6

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    I have seen .080 over pistons/rings for sale. Like I said, if you get into a rebuild with boring its going to add up real fast and a repower becomes more economically feasible. If you are looking for stock, a running replacement will also be cheaper for sure. I was looking to rebuild an Lhead 10 years ago and the numbers to buy a core 225 and rebuild it was MUCH cheaper than rebuilding that Lhead, not to mention the 225 was lighter and had quite a lot more power. You can pick up running FI 4.3 v6s with harness for under 800 bucks.

    There is nothing wrong with the Fhead. It just becomes expensive quickly when compared to more modern engines. Your problem may be as simple as a re ring and a hone though. Thats pretty cheap, just a bunch of labor. You can do that yourself with a hone, a drill and some new bearings and rings.
     
  7. Aug 3, 2015
    tarry99

    tarry99 Member

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    No guessing here , take it apart...........mic the crank and rods.......use a bore gauge on the bores and see what you have. If there is rust in the cylinders between the cylinder wall & piston rings as I would suspect there is which is locking it up , it may already be on it's way to the grave...........even just turning it over by hand with the carbon/rust buildup inside can continue the damage to the cylinder walls making them un-repairable...........as far as rebuilding , over-sized pistons and undersized bearing will be determined by what you can find out there.
     
  8. Aug 3, 2015
    ktm25089

    ktm25089 Member

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    Ok for the pistons.now for the bearings??i hear horror stories about cutted cranks etc.is something like 60 under acceptable??or i need new crank??i try to guess that if im 30 on pistons now would be something 40-50 on crank.
     
  9. Aug 3, 2015
    Glenn

    Glenn Kinda grumpy old man Staff Member

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    I don't believe the crank wear is necessarily the same as cylinder walls, so you might still have plenty left on the crank. It really depends on how much money you want to put it to the engine. You can also have it sleeved which is an option to discuss with the machine shop.
     
  10. Aug 3, 2015
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    A 134 has a forged steel crank. Steel cranks are tough. Modern cars have cast iron cranks, which are softer. You may not need to grind the crank at all. Measure.

    Don't jump to conclusions. Take the engine apart, inspect and measure.
     
  11. Aug 4, 2015
    ktm25089

    ktm25089 Member

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    ok,
    removed the head today,1st cylinder was stuck.with little help for a wooden block and a hamme after second hit the piston was free.big amount of anti-seize oil and the piston oving free.cleaned the bore and it is in very good shape.a quick hone to the cylinder and will see the results.but found another big problem,i have removed the oil pan to see the bottom and remove the first conrod.i have drained oil plus about 8 liters of antifreeze!!!!!!!!!!!!!
    the first bearing is in good condition with no rust.will remove another one to see.
    found that the first cyl-head bolts from 1-2 cylinders was loose,but i cant explain so much water.only think is that when last time started the water entered the crankcase.
    will see tomorrow from cracks and will close the engine and try to start it.just some quick question,
    cyl head bolts lubed or dry at assembly??
    retorque cold or at operating temp???

    Thanks
    George
     
  12. Aug 4, 2015
    tarry99

    tarry99 Member

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    George , are you having fun yet?...............Head bolts with oil for torquing or a suitable lube...........clean the threads in the block and also on the bolt.........re-torque after it's been run cold again. Put a straight edge across the head and block...........look at the gasket closely as well as the block and head.........water will leave a trail sometimes that's easy to follow......motors that set for long periods of time may or will leak fluids , called a cold leak.
     
  13. Aug 4, 2015
    47v6

    47v6 junk wrecker! 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    Great news its not wrecked. Hone, new bearings, rings, gaskets and go?
     
  14. Aug 5, 2015
    ktm25089

    ktm25089 Member

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    cold leak???first time heard about that.thank you very much.
    the only trail that found was from a water passage to the first cylinder.front bolts from the first two cylinders was little loose,will check with a straight edge today before closing and will cross fingers to start the engine.
    will use it as is for a short time to see if there is other problems and then will change bearings,hone it and change piston rins.
    by the way...........................what is the mostreliable head gasket that you used???i mean brand name.im using some OEM asbestos that i found in a yard.
     
  15. Aug 5, 2015
    ktm25089

    ktm25089 Member

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    :p:D:D:rofl:
    jeep started!!!!!!!!!!!!!!!!it smokes a little when revving but not something bad.i have now to retorque the gasket and adjust the intake valves.then use a radiator cleaner and fill with correct antifreeze.Very happy.Pray to God to be just one bad gasket or loose bolts and not a hidden crack.we will see after the retorque and the first kilometers in the road.
     
  16. Aug 5, 2015
    tarry99

    tarry99 Member

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    Ktm Congrads............that's good news,depending on how you use it......... it may last forever...............Head Gaskets? I'm a big fan of Felpro. Not sure if they make one that fits though............the old asbestos gaskets I've heard that guys used to soak those in water before installing?
     
  17. Aug 5, 2015
    Glenn

    Glenn Kinda grumpy old man Staff Member

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    Congratulations, glad you got it running again! Like Tarry said maybe you'll not have to do anything more to it. Now, don't let it sit so long next time! ;) :)
     
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