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Thread: well, the darn thing is out

  1. #1871
    Super Moderator bmorgil's Avatar
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    You might want to make sure a valve didn't get a little tight on the lash. Can you show a picture of the plugs? Do you have a way to see if the vacuum is steady at idle?

  2. #1872
    Senior Member pelago's Avatar
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    no vacum check, just went around the block and get to 30+ in 2nd and just dont have a run long enough to run out 3rd. highest on short flat hwy 40ish but was a improvement. sounds throatier and stronger?? kinda warm not to be sticking fingers in there for another compression check....

    did another compression test.... not good
    SEEMS LIKE I GAMBLED AND LOST....
    WHEN I BOUGHT THIS THING WAS TOLD THE MOTOR RAN FINE, WELL IT DOES BUT DOES NOT HAVE ANY OOOOOMPH TO IT SUPPOSED TO GET 25 IN FIRST, 40 IN SECOND AND 60 IN 3RD
    I DONT CLOSE TO IT IN FIRST AND 35 IN SECOND BUT CAN NOT EVEN GET ABOVE 40 IN THIRD

    BUT DO HAVE A COMPLETE SPARE ENGINE THAT WAS TOLD WHEN JEEP PARKED IT RAN.
    Guess the new chapter in Magoo will be major motor overhaul with exception maybe having to get new pistons extra 150.00 al piecees and parts come to about 400 catalog prices. i have a engine stand and will start mounting the spare motor to the engine stand today. there is a excellent machine shop close by if need to be bored or what have you, and they can dip and clean both head and block then valves.

    I will keep my original plan too finish the jeep before holidays, canvas for seats, pair of seat belts (not original of course but i feel needed) windshield wipers, bumpettes. next year will only get full set of canvas, was quoted 1400.00 for all of it, bows, top, sides, doors the whole shooting match
    Last edited by pelago; 10-04-2019 at 04:32 AM.

  3. #1873
    Senior Member pelago's Avatar
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    OKAY, NOW THIS IS GOING TO RAISE AN EYBROW OR TWO.. COMPRESSION AS A RATIO
    Compression Ratio 7.4 to 1 M38A1 134F MOTOR

    HOW DO YOU EQUATE RATIO FROM A MIN OF 100 POUNDS TO MAX OF 125 POUNDS

    WHERE CAN I FIND CRANKSHAFT SPECS, MAIN AND ROD BEARING DIAMETER MIN/MAX GONNA PUT THIS IN A FILE, I KNOW THE BORE IS 3 1/8": PROBABLY NEED FOR CAM TOO

  4. #1874
    Super Moderator bmorgil's Avatar
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    Everything should be here https://cj3b.info/Hurricane.html

    Also here are the different versions of the F head 4-134 https://www.jeeptech.com/engine/hurricane134.html

    Attached files are from the Universal Service Manual
    Attached Images Attached Images

  5. #1875
    Senior Member pelago's Avatar
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    Quote Originally Posted by bmorgil View Post
    everything should be here https://cj3b.info/hurricane.html

    also here are the different versions of the f head 4-134 https://www.jeeptech.com/engine/hurricane134.html

    attached files are from the universal service manual


    but wht is the diameter for rod bearings on crank and main bearings on crank?? And still to this day do not understand compression ratio how does ratio come into ply when compression at 125 std 100 acceptable?

  6. #1876
    Super Moderator LarrBeard's Avatar
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    Compression Ratio and PSI

    Quote Originally Posted by pelago View Post
    but wht is the diameter for rod bearings on crank and main bearings on crank?? And still to this day do not understand compression ratio how does ratio come into ply when compression at 125 std 100 acceptable?
    I need a while to organize my thoughts and I'll try to tie it together.

    Ok, I gathered a bit .....

    What does compression ratio have to do with how many PSI you get on a compression check?

    To get a first quick answer, we go back to Boyle’s Law (Boyle is a dead Englishman) that says the volume of a gas is inversely proportional to its pressure – assuming constant temperature. Let’s just look at the first part of this – it means if you squeeze it, the pressure goes up.

    To make a rough connection to compression ratio, let’s take atmospheric pressure as 15 PSI (close for an example). If I compress the gas (air) in a L-134 cylinder by a factor of 7.4 (compression ratio), I should multiply 15 times 7.4 to get an idea of the pressure I would expect. When I do the numbers, I get 111 PSI – somewhat less than the 125 PSI the spec calls out. Where are the other fwe PSI?

    Well, part of the added pressure comes from the second part of Mr. Boyle’s Law – the part about constant temperature. When you squeeze that air together in the top of the cylinder, it gets hot and we can discount that “constant temperature” stuff. As the compressed air gets hotter, its pressure rises even more (think about a big Cat diesel engine just before the injector opens).

    If we had a perfectly sealed chamber, that air we just squeezed would have a lot more pressure than the 125 PSI we are talking about because it would be a lot hotter – which also raises pressure. But – we don’t have a perfectly sealed chamber in that cylinder. Good valves seal very well – no appreciable leakage there, but we do have leakage back through ring gaps. Worn cylinder walls let ring gaps open up and oval shaped cylinders don’t let rings seal well at all.

    The pressure we measure in a compression check is a function of the compression ratio, how hot the air gets when it is compressed and how much of it leaks back past rings and cylinder walls as it is being compressed. There is probably no really good way to calculate the answer any closer than we did with our Boyle Law example, so we rely on what people have measured on known good engines.

    An L-134 with good rings, good valves and good ring sealing will give you 125 PSI (plus some or minus just a little). If there is something wrong (leaky valve seats, worn rings, out of round cylinder walls or scored walls), there is enough leakage to drop the pressure down to 100 or even less. We've seen engines at 50 or 60 that still kind of run ... Experience tells us that compression much below 100 PSI indicates wear and will give hard starting (especially on a hot engine) and as we all know -blue oil smoke out the exhaust.

    Did that help any – I didn’t want to turn into a “perfesser”.
    Last edited by LarrBeard; 10-04-2019 at 05:22 PM. Reason: Gathered My Thought a Bit

  7. #1877
    Super Moderator bmorgil's Avatar
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    The rod bearing diameter on the crank (listed in the attachment as Crankpin Journal) is 1.9375" to 1.9383" . The Mains on the crank (listed in the attachment as Journal Diameter) is 2.3331" to 2.3341". .003" bearing clearance is max.

    100 psi is not acceptable "by the book". The acceptable compression for the 6.9 to 1 compression F134 is 120 to 130 psi. The high altitude option 7.4 to 1 compression is slightly higher at 125 to 135 psi. Though 100 is not considered "acceptable" in the service manual, I have known many an engine to run OK on less. My 6.4 to 1 compression L134 has a pressure range of 90 to 110 psi "by the book".
    Last edited by bmorgil; 10-04-2019 at 06:13 PM.

  8. #1878
    Senior Member pelago's Avatar
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    Quote Originally Posted by larrbeard View Post
    i need a while to organize my thoughts and i'll try to tie it together.

    Ok, i gathered a bit .....

    What does compression ratio have to do with how many psi you get on a compression check?

    To get a first quick answer, we go back to boyle’s law (boyle is a dead englishman) that says the volume of a gas is inversely proportional to its pressure – assuming constant temperature. Let’s just look at the first part of this – it means if you squeeze it, the pressure goes up.

    To make a rough connection to compression ratio, let’s take atmospheric pressure as 15 psi (close for an example). If i compress the gas (air) in a l-134 cylinder by a factor of 7.4 (compression ratio), i should multiply 15 times 7.4 to get an idea of the pressure i would expect. When i do the numbers, i get 111 psi – somewhat less than the 125 psi the spec calls out. Where are the other fwe psi?

    Well, part of the added pressure comes from the second part of mr. Boyle’s law – the part about constant temperature. When you squeeze that air together in the top of the cylinder, it gets hot and we can discount that “constant temperature” stuff. As the compressed air gets hotter, its pressure rises even more (think about a big cat diesel engine just before the injector opens).

    If we had a perfectly sealed chamber, that air we just squeezed would have a lot more pressure than the 125 psi we are talking about because it would be a lot hotter – which also raises pressure. But – we don’t have a perfectly sealed chamber in that cylinder. Good valves seal very well – no appreciable leakage there, but we do have leakage back through ring gaps. Worn cylinder walls let ring gaps open up and oval shaped cylinders don’t let rings seal well at all.

    The pressure we measure in a compression check is a function of the compression ratio, how hot the air gets when it is compressed and how much of it leaks back past rings and cylinder walls as it is being compressed. There is probably no really good way to calculate the answer any closer than we did with our boyle law example, so we rely on what people have measured on known good engines.

    An l-134 with good rings, good valves and good ring sealing will give you 125 psi (plus some or minus just a little). If there is something wrong (leaky valve seats, worn rings, out of round cylinder walls or scored walls), there is enough leakage to drop the pressure down to 100 or even less. We've seen engines at 50 or 60 that still kind of run ... Experience tells us that compression much below 100 psi indicates wear and will give hard starting (especially on a hot engine) and as we all know -blue oil smoke out the exhaust.

    Did that help any – i didn’t want to turn into a “perfesser”.
    put it in doc file and saved it

  9. #1879
    Senior Member pelago's Avatar
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    Quote Originally Posted by bmorgil View Post
    the rod bearing diameter on the crank (listed in the attachment as crankpin journal) is 1.9375" to 1.9383" . The mains on the crank (listed in the attachment as journal diameter) is 2.3331" to 2.3341". .003" bearing clearance is max.

    100 psi is not acceptable "by the book". The acceptable compression for the 6.9 to 1 compression f134 is 120 to 130 psi. The high altitude option 7.4 to 1 compression is slightly higher at 125 to 135 psi. Though 100 is not considered "acceptable" in the service manual, i have known many an engine to run ok on less. My 6.4 to 1 compression l134 has a pressure range of 90 to 110 psi "by the book".
    saved it to a doc file

  10. #1880
    Senior Member pelago's Avatar
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    I WANT A MANUAL FOR THE 134F MOTOR NOT THIS
    https://www.kaiserwillys.com/mechani...ts-52-66-m38a1
    during my years in Marines this would have been a 1st or 2nd echelon maintenance manual. does not have a "blow up" of motor although a worthwhile manual it does not do this as it so describes
    "Reprint of the original service manual. Includes complete vehicle disassembly, assembly, and blowup diagrams. If your looking to restore your vehicle - this is the first thing you should buy. A complete walk thru to help you rebuild or trouble shoot just about any mechanical or electrical problem. Don't rely on those wrong universal manuals - this is the proper one. Guaranteed. Original military issue."

    this one??
    https://www.kaiserwillys.com/master-...h-4-134-engine

    tired of spending 40-50 bucks on a manual that does not tell me what torque to put on main bearings or rod bearings

    I rebuilt a Kubota engine and they had the most incredible manual it had diagrams and pictures of each and every step in the process... i rebuilt my 4cyl diesel with this one

    RUNNING.jpg

    I WANT ONE THAT I CAN GET INSIDE THIS THING

    REBUILD3.jpg
    Last edited by pelago; 10-05-2019 at 08:25 AM.

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