F-Head Troubleshooting And Repairs

Discussion in 'Flat Fender Tech' started by william_cj3b, Jan 14, 2017.

  1. Mar 1, 2017
    william_cj3b

    william_cj3b Sponsor Sponsor

    Milton, FL
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    Funny...:rolleyes:
     
  2. Mar 2, 2017
    william_cj3b

    william_cj3b Sponsor Sponsor

    Milton, FL
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    On the stand...
    [​IMG]

    Found this
    [​IMG]

    Teardown started...
    [​IMG]

    [​IMG]

    I wanted to have the head off last night, but these 12+ hr shifts are killing me. I must be getting old :(
     
  3. Mar 3, 2017
    Rozcoking23

    Rozcoking23 RUN & GET BIT! Sponsor

    Stockton, CA
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    I hear you there.....i'm working 18's right now.
     
  4. Mar 7, 2017
    william_cj3b

    william_cj3b Sponsor Sponsor

    Milton, FL
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    Finished tearing down the F-head over the weekend.

    Measuring intake valve lift. All intake and exhaust were very close to nominal per the FSM-
    [​IMG]

    Definitely some head gasket issues-
    [​IMG]

    [​IMG]

    [​IMG]

    The ugly - evidence of rust pitting in #4. Suprisingly, this engine ran really well and had little problem maintaining highway speeds until very recently.
    [​IMG]

    Measuring exhaust valve lift-
    [​IMG]

    Removing the exhaust valves. I'll leave the intake valves in the head and let the machine shop r&r them when they grind the valves and seats-
    [​IMG]

    Mismatched pistons and broken rings. The second ring on #1 and both compression rings on #2 are broken. Pistons 1 & 2 have t-slots, 3 & 4 do not. The engine was 'rebuilt' in the 1980's according to some documentation that came with the jeep. Based on the pitting I found in #4, I believe the engine sat with #4 intake valve open and got rained on-
    [​IMG]

    Some scoring on the rod bearings. This is the worst-
    [​IMG]

    Measuring crank journals. The crank looks good with minor scuffing only on #4 rod journal (bearing pictured above), but will be a little under tolerance once polished-
    [​IMG]

    Starting with the good, there's absolutely no sludge buildup in this engine. No visible cracks or evidence of old repaired cracks. The block already has hardened exhaust valve seats and the cam and valve train are in very good condition.

    I didn't find anything that stood out as the cause of the excessive noise this engine had. No really ugly bearing shells, discolored caps or trashed journals. Oh well, I'll have the machine shop check the line bore and resize the rods as needed.

    The bores are the biggest problem in this engine. They're as much as +0.013" OOS for the current 0.040 overbore and tapered as much as 0.010". I don't think #4 will clean up at 0.060 and 0.080 seems questionable for a decent quality build. I could have #4 sleeved and bored back to 0.060. Can an F-head block stand up to sleeving all 4 pots? There's not a lot of material between the bores.
     
    Last edited: Mar 7, 2017
  5. Mar 7, 2017
    timgr

    timgr Jeepin' Nerd Sponsor

    Medford Mass USA
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    Pretty sure you are ok with 80 over with a 134. The block casting design was decades old even in 1954, and they used a lot more iron in these older engines. If you worry, you could have the block sonic checked to see whether the water passages are well registered with the bore ("core shift" within acceptable range). Walck's has your 80-over pistons - you could call them and ask for comments/advice.

    If you want to sleeve, last I checked it's about $100 per hole. I don't see any reason why a F134 would be any different wrt sleeving, as long as the sleeves are available. If you sleeve all four, you can choose your bore diameter - standard, 40-over and use your existing pistons, or even say 120 or 160 over to get a displacement boost.

    I would also spring for magnaflux of the block, head and crank, considering the age of the engine.
     
    Last edited: Mar 7, 2017
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  6. Mar 7, 2017
    william_cj3b

    william_cj3b Sponsor Sponsor

    Milton, FL
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    Thanks Tim. I'm not totally against the 80 over build. Maybe I'm just disappointed that this block is on it's last build without sleeving.

    I'll definitely magnaflux. Cheap insurance when putting several hundred dollars into a rebuild.
     
  7. Mar 7, 2017
    jpflat2a

    jpflat2a what's that noise?

    Riverside CA
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    You might consider balancing it as well......
    I did it to mine on the only rebuild I did to it.
     
  8. Mar 8, 2017
    william_cj3b

    william_cj3b Sponsor Sponsor

    Milton, FL
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    Definitely considering it. I'm going to start by weighing the rods at work tomorrow. I'm not sure they are a matched set.
     
  9. Mar 14, 2017
    spm1us

    spm1us New Member

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    If you don't have one, get yourself a factory service manual or a reprint of the fsm - they can be had on ebay for usually less than $20. They are an invaluable source of information, torque specs, etc. All the parts for the F-head can be readily had from any major engine supply house. There are two different style connecting rods on the Willys engines - #1 & 3 and #2 & 4 - they are machined differently due to their location on the crankshaft. You probably know there's a hidden head bolt under the carburetor - that one has stumped many a mechanic during dis-assembly in the past. There's also an oil nozzle, above the camshaft timing gear, that should be removed, checked for size and saved prior to sending the block to the hot tank. I would suggest using the complete gasket set from BEST GASKET as they have the only reliable and proven rear main seal out there. It is most definitely worth the little extra they cost to avoid tearing down a newly rebuilt engine to re-install a replacement rear main seal. Be sure and label each of the lifters (if re-using the original cam and lifters), when removed, so that they will be mated back to the same cam lobe as when removed. Also, be very selective in your choice and purchase of break-in oil for your new engine - we specifically use a straight 30W ZDDP enhanced labeled "Break-In Oil" by Drive Oil/Joe Gibbs. Although the stock valve springs do not generate a ton of pressure the newer oils have all but eliminated the required additives to keep from wiping a lobe on start-up. Since you can't spin the oil pump, prior to start-up, to pre-oil the engine - see if you can locate a pressure tank to temporarily plumb into the oil galley to pre-oil the motor. Vary your break-in rpm from 1200-2000 rpm for 20 minutes during break-in and NO heavy loads for the first 500 miles. Try to run a Diesel rated oil, after initial break-in, as they have more of the needed "anti-wear" additives for a flat tappet cam. Keep us posted - Good Luck with your project, Sam
     
  10. Mar 15, 2017
    PeteL

    PeteL Member Sponsor

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    Piston slap (skirt clearances)? :n:

    Open question to all - every F-head engine I've ever worked on had broken rings. Why?
     
  11. Mar 15, 2017
    timgr

    timgr Jeepin' Nerd Sponsor

    Medford Mass USA
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    Well, the main thing I would point to about the 134 is the high piston velocity for a small bore resulting from the very undersquare design. Maybe that has something to do with it. High velocity, highly curved ring.
     
  12. Mar 15, 2017
    william_cj3b

    william_cj3b Sponsor Sponsor

    Milton, FL
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    Possibly. There was a large amount of wear on the thrust side of the two older pistons.
    I can tell you that the two bores with broken rings had a lot of taper in the top 3/4" of piston travel.
     
  13. Mar 15, 2017
    timgr

    timgr Jeepin' Nerd Sponsor

    Medford Mass USA
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    Fatigue. It's what wears out new rings in crooked bores.
     
  14. Mar 15, 2017
    Glenn

    Glenn Kinda grumpy old man Staff Member Sponsor

    Apopka, Fl
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    Makes you wonder about Jasper engines.
     
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  15. Mar 15, 2017
    william_cj3b

    william_cj3b Sponsor Sponsor

    Milton, FL
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    I had that thought momentarily, but then remembered some record of the engine having been rebuilt in 1986 by a PO/amateur restorer. That Jasper rebuild tag looks very late 60's to me. I won't lay the flaws to their charge this time.

    [​IMG]
     
  16. Mar 18, 2017
    william_cj3b

    william_cj3b Sponsor Sponsor

    Milton, FL
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    Good news from the machine shop. No cracks or other unrepairable damage on the block, head or crank.

    I'll know about the overbore size by Tues or Wed.

    Question - I usually replace rod bolts during my rebuilds, but given the aftermarket sources for these engines, am I better off with the originals?
     
    Focker likes this.
  17. Mar 18, 2017
    Glenn

    Glenn Kinda grumpy old man Staff Member Sponsor

    Apopka, Fl
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    That is good news indeed. Rod bolts, good question. Are you getting your parts from the machine shop, or wherever can you get bolts there too? Walck's lists their rod bolts as being USA made, so it's maybe a pick your poison answer?
     
  18. Mar 24, 2017
    Glenn

    Glenn Kinda grumpy old man Staff Member Sponsor

    Apopka, Fl
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    Any updates on the engine?
     
  19. Mar 24, 2017
    william_cj3b

    william_cj3b Sponsor Sponsor

    Milton, FL
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    Machine shop is backed up. They were supposed to bore it and tell me the oversize today. I haven't heard anything :rolleyes:
     
  20. Mar 27, 2017
    william_cj3b

    william_cj3b Sponsor Sponsor

    Milton, FL
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    Finally got word from the machine shop this morning. The block required an 0.080 overbore with a sleeve in #4.

    The machinist said it looked like someone had gotten carried away with a ridge reamer in the past. That makes a good explanation for the amount of taper in the top of the bores and the broken rings in 1 & 2.
     
    ronnie victor likes this.

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