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Thread: 4A084 inline motor rebuild

  1. #1
    Member Bart's Avatar
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    4A084 inline motor rebuild

    I am starting to wonder if I will ever get this in the boat, or it I will be just going from one project to another with it..
    over the summer I have found out some things that might be worthwhile, for anyone out there looking for parts and pieces. for the 084 motor
    I know last summer, fall and winter Saturn Surplus was trying to sell all of his inventory, and shut the door, I am still glad he is still answering his phone though..
    but there was a big frenzy in gathering up all, or any part that you thought you might need. in case of the dreaded rebuild.
    me I picked up a few items, but I was told the motor had just been rebuilt. so why should I worry????

    so after finally finishing the EFI and ignition. The motor would idle, okay, and I was stoked, there was a lot of time and energy in getting all the parts and pieces together. But there just was something always going on with the motor. I would look at the fuel table charts and things just were not where they were supposed to be. I kept thinking it was an air leak, bad injector, I had done a compression test, had great oil pressure. and it all looked good. my #2 & 4 cylinders were the big problem children, one or the other was always going down, or running way to hot...
    Finally I had enough and delved into it, to look for what was the bigger issue.
    I knew someone had been through this motor before, a few of the bolt had been replace with grade 8, and gone where the slotted ones..
    I did a leak down test, and the pressure really didn't hold on the one cylinder that I tested. a lot was going past the rings..
    all the pistons and rings looked okay, but then I measured the ID of the cylinders. max is 2.995, and in the middle of mine 3 were measuring 3.005
    at least at the moment I am thinking this might have been the problem, at least I hope so..
    now comes the fun part looking for replacement parts, and I found a few items along the way, but now I had wished I had known about the suppliers below earlier, it would have saved me a lot of time looking for rod bearings and the correct chrome rings...

    the Pistons and cylinders both have a stamp on them, A,B, C, & D. that designates the ID of the cylinder, & OD of the piston..
    NEVER use a "D" piston with a "A" cylinder, it will work for a little, but there is not enough expansion, sooner or later it will over heat and seize to the wall...

    this and other useful information I found when I started looking at the forums that dealt with the 274 mule or the 2A042 motor and the link that started it all
    https://forums.g503.com/viewtopic.php?f=148&t=262382
    I visited with Charles Witt, a couple of times, he has been rebuilding the 2A042 motor for the past 40 years. and had some great information, on what to look for. and will always need to be replaced, and depending on what rings you use with the piston. Cast Iron rings, will wear out the cylinder wall. Chrome rings, just put a light hone on the cylinder walls and new rings, you will be good to go.
    also replace the rod bearings,, the other problem that he has seen is the camshaft bearing will spin, his fix is to loctite the outer flange to the case.
    the beauty about the 2a042 motors, you have plenty of crankshafts, and camshafts out there, and they are cheap.. not so lucking for those using a 4A084 motor, I have yet to find a spare.
    so as I was looking at this forum, a name of John Emery, kept coming up, that carried an inventory of parts. so I got in touch with him and found out that he carries, matching piston to cylinder sets, rod bearings, stock and undersized, an double chrome ring sets. (he sends the piston and cylinder to a machine shop, where they are fitted as a matching set. and are sold as a set)
    when I found out the pricing, I was wishing I had found him a week earlier, before I purchase a bunch off Ebay, now I gots lots of stuff...

    one of the things that impressed me, when I got my shipment from John was the bearings and rings where still in the manufactures sealed pouches, the dates were over 50 years ago, and when I opened them up. they didn't look over a day old.
    the rod bearings looked tired, but when I measured the crank journals they were still in factory spec. so I didn't need to send the crank out to be reground, and that helped out a lot.. and I plasti gauged the new bearings, they all were close to .002 clearance.

    the one thing I did notice is when I picked up the motor, without the plugs I could turn the motor over by using the rope pulley. I could do it with 2 of the new kits in, but once all 4 cylinders with new rings, I had to use a strap wrench to rotate the crank...but the starter has no problem...
    also with this style of ring, you will need a ring compressor to install them to the cylinder,, the old ones I could do it with just my hands,,,

    true to my nature I had to spruce something up on this motor, with this rebuild. the exhaust nuts were driving me crazy, I needed 2 different wrenches, a 7/16 & a 5/16, so I picked up some 7/16 brass hex rod and turned out some custom exhaust nuts,

    also one other thing that I am attempting on this rebuild, I notched grooves on the connecting rod to squirt oil at the base of the piston. to see if I can get the heads to run a little cooler. from all that I have read, it can reduce the head temp from 50 to 100 degrees. I will find out if that is the case, for my motor also before too long. some of my friends are worried that it might stress crack the rods, where this motor should never see anything over 4000 rpms. I am thinking why not..
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  2. #2
    Super Moderator Corky's Avatar
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    Re: 4A084 inline motor rebuild

    Bart, it'll be interesting to see how those chrome rings do for you...I know they're a little tougher to get seated compared to the cast iron rings but if the wear is as minimal as you're stating it would definitely help in the life of the parts..

    Aluminum .120 14' X 76" hull
    Teledyne 4a084-4 engine
    Circle S 1.69:1 reduction
    67" Whirlwind "Razor X" prop



  3. #3
    Member Bart's Avatar
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    Re: 4A084 inline motor rebuild

    Quote Originally Posted by Corky View Post
    Bart, it'll be interesting to see how those chrome rings do for you...I know they're a little tougher to get seated compared to the cast iron rings but if the wear is as minimal as you're stating it would definitely help in the life of the parts..
    I have been wondering about that also. with how tight the rings were to install, and being the first time rebuilding this motor, I reached out to John Emery, and Charles Witt about questions that I had. Below are a copies of a few of the Emails.

    Attached is a pic of a "gen" piston with it's original rings, note the spacer ring in groove 1 on top of the main ring, which is a chrome ring, second ring has no spacer, and is not chrome, then third groove has the expander ring and a one piece, non chrome, oil ring

    The "mule" ring set is all chrome rings, uses same spacer on top of the #1 ring (which was already in the groove so you will not need the one in the kit), but the oil ring setup is 4 pieces, the same expander ring as the gen ring set, 2 separate oil control rings and a spacer ring.

    I have had the same thought when I put these together that is all seemed tight but they all go in when using a ring compressor (with lots of oil !), or I made up a compressor tapered sleeve, same result.
    Just be sure that as you put that oil ring setup together that the expander ring ends up behind the other 3 rings.
    Second pic shows rings as they should be in the groove, don't have a "mule" ring set installed to take a pic of right now but you get the idea.

    Let me know if things are not looking or going right, try to figure something out.
    Love to make a house call, maybe one of these years.
    I do want to drive the Alcan highway and then do the Dalton to Prudhoe Bay, someday!!!!


    Every thing went together nice,
    Installed cylinders 2 & 4, and I could still turn the crank by hand, a little stiff, but not bad. But by the time I added cylinders 1 & 3. I have to use a strap wrench on the rope pulley to rotate the crankshaft..
    I checked the end gap of the rings in all the cylinders, and they are with in tolerance. There is no scratch marks, used lots of oil..
    It does get easy, when the pistons are at top dead center. For the few degrees..
    Is this normal..

    As to being easy at TDC, yes, as to being hard to turn when you get all 4 installed, I really don't know.
    It does seem surprising what effort it takes to turn a 2 over, or for that matter just to push and pull a ringed piston by hand in a cylinder.

    But once running the engine does not seem to care, I can only assume that the 4 is the same, just doubled.
    I recall putting my mitey mite engine together, V4 air cooled, it turned harder than I would have thought but in the end it was OK.

    I took off different cylinders, and with any of the 2 I could rotate by hand, but with all 4, It looks like I should have some good compression. It is just a dang tight fit

    have you done a compression check? should be 120psi min as I recall.

    Once I start the motor, what is your recommended method to break it in?

    I don't have any specific plan, with any engine I've major'd, just run it slow, check everything, increase, increase speed and load.
    Don't run full throttle or load right away. After some number of hours change and check oil for any material that shouldn't be there, cut open the oil filter and study the paper with a magnifier. It is normal to see small specs of Aluminum when doing a major on an Aluminum engine, I was concerned the first time I did that as I did see little tiny specs of AL in the filter, but was told by those smarter than I that this is normal, just check it the next several times and it should stop, and it did.

    there has been some things to think about... I have talked about some of this earlier, so excuse me if I am repeating some things...
    when my motor first started having 0 compression in cylinders 2 & 4. I pulled the heads and cylinders off, to attempt to get a better look at what was happening.
    one thing that i noticed was that I was able to compress the rings with my fingers and re-install the cylinder, with very little effort...
    and with a little oil the compression came right back. but as soon as the oil got washed out. the compression was gone.
    this was getting me kind of confused as to what was really going on. because there was no problem with cylinders 1 & 3.
    finally I disassembled the motor and measured the cylinder bores, and found out that the cylinders for pistons 2 & 4 were egged shaped,
    this is what Charles Witt, has been saying, when using the NON chrome rings, they will wear out the cylinder walls....
    "on a side note. when I opened up the 2A042 motor, it had chrome rings, and there was no measurable wear on the walls.. with 1800 hours on the meter..."
    even though I found a sweet deal on ebay for 4 pistons w/regular rings for 20 dollars +shipping. I opted to purchase & install double chrome rings.
    and they were a bear to install. the 4 piece oil ring, almost felt beyond to tight....

    The one thing that John Emery, stressed big time, was more than a few of his customers, and rebuilt their mule motor, and upon starting it. Had left off the top cover, even with the fan going, no air was being delivered across to the #1 cylinder, it would over heat and drop a valve. After a bit... "I could see that happening with my 2A042 genset. with the shrouds in place.. and the top cover removed. There was no air movement going across the cylinders.. That is why my head temps would spike so quick..."

    so that is where I am at for the moment. putting together a fan and shroud system, "where my motor is still stationary" so I can further test and play with it.. It would have been rather simple if the motor had came with its original shroud, and I had not changed a few things.
    So after the initial start, I have been working on a few different methods to keep the cylinder heads with in operating temps. I am hoping to have these things finalized in the next couple of weeks.

    on a side note, I was visiting with my brother that has a 6 cylinder Continental on his airboat, about head temps.. He mentioned that there has been times that he has had to shut his motor down. due to it overheating... it hasn't happened a lot, but there has been a time or two...
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    Last edited by Bart; 10-30-2019 at 10:32 PM. Reason: cleaning up the punctuation

  4. #4
    Member Bart's Avatar
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    Re: 4A084 inline motor rebuild

    thought i would put in a few more pictures.
    the biggest surprise I got, was looking at all the sludge that was in the bottom of the oil pan. if nothing else, I am glad to have got all that grit cleaned out.
    the crank journals has some wear, but they all are in tolerance.
    "It drives me crazy to see all the crankshafts for the smaller 2A042 motors available, but as of yet I have not located a supplier that has crankshafts for the 4A084 motor... "
    the nice thing now is even though the motor has had some issues in the past. now at least I have a starting point and know what I have..
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  5. #5
    Super Moderator Corky's Avatar
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    Re: 4A084 inline motor rebuild

    Yeah, that's some sludge build-up in there !!...I wouldn't have expected that either...I bought an extra crank with all the bearings from Saturn Surplus..Now if I could only find an NOS camshaft I'd feel better...Especially after reading about the camshaft bearing failure being common..

    Aluminum .120 14' X 76" hull
    Teledyne 4a084-4 engine
    Circle S 1.69:1 reduction
    67" Whirlwind "Razor X" prop



  6. #6
    Member Bart's Avatar
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    Re: 4A084 inline motor rebuild

    Quote Originally Posted by Corky View Post
    Yeah, that's some sludge build-up in there !!...I wouldn't have expected that either...I bought an extra crank with all the bearings from Saturn Surplus..Now if I could only find an NOS camshaft I'd feel better...Especially after reading about the camshaft bearing failure being common..
    yep. if my memory is correct. I called a day to late to get a crankshaft from Saturn Surplus, last fall. They sold their last one an day earlier.. I haven't called since to see if they restocked.. and they never had a camshaft in stock, at least for the last couple of years that I have purchased parts from them..

    that is one thing that I did not do yet is to update the camshaft bearing. "or apply some loctite like what is recommended.
    https://forums.g503.com/viewtopic.php?f=148&t=265091

    I thought that I would attempt to take the gear wheel off one of my 2A042 camshafts. with the pullers that I had, it really was not working. I sent some pictures of what I was doing to Charles Witt. to get some advise.
    found out I was using the wrong puller. I am needing to get a bearing puller, like the one below. which I didn't have at the time.


    also. I started thinking about once I have the gear off, where it is a good press fit on. How am I going to put it back together???
    I asked Charles about this. his thought, if I remember was I might need some heat on the gear so it would slide on..
    "What he does with the 2A042 motors, is just buy a new camshaft assemble with the new bushing and gear installed."
    so with the lack of 084 camshafts available. I am kind of leery about messing up the only camshaft.

    I may still take out the camshaft and at least apply some loctite to the outer bushing. as I think more about it. It should be something I should address... or it will be something always on the back of my mind...
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    Last edited by Bart; 10-30-2019 at 11:31 PM.

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