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Thread: Help! teledyne 4A084 Military Standard Engine modifications

  1. #1

    Help! teledyne 4A084 Military Standard Engine modifications

    I am considering the purchase of a teledyne 4a4084 engine to repower what used to be a golf cart but is evolving to a 4 passenger on/off road vehicle.

    other than removing the restrictor plate, what are the steps that must be done to modify it to it's 20 hp potential?

    Seems to be a versitile engine given modified for aircraft, airboats, generators, etc.

    I do have general mechanical knowledge but lack experience (and...sorry to say, the necessary confidence gained from experience) other than smaller 2 cycle outboards from laye 50s, 60s and 70s (30 hp and less).

    I do not want to "bite off more than I can chew" , so to speak. I have machine tools and can machine basic parts.

    Is it possible to obtain a mentor in this are?...please

    If works that the engine is doable, then I will, of course, need a far greater depth of knowledge than I have now (ie: choices for carburation, exhast etc).

    Lastly, are there other modification that could increase output above the 20 hp rating?

    thanks!

    the current village idiot

  2. #2
    Administrator Papee's Avatar
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    Re: Help! teledyne 4A084 Military Standard Engine modifications

    The motors are rated low by the military. They are about 40 hp out of the box. In your application you will want to keep all the shrouding for cooling. You can get a one inch shaft that bolts to the flywheel to use as an output shaft. The carbs on these engines are not made for varying rpms but to run a constant rpm so a carb upgrade is beneficial.

    Check out the intake mod and solex carb we are using in this forum for that. It is easily converted to 12 volt charging using a rectifier and you can find a starter (12v)that will mount in the stock position. Power to weight these are a good motor for a project like that with a lot of torque. With a set of new headers, intake and carb mods you could see close to 50 hp.

    You would also want to do away with the governer which is an easy mod, you just remove it and make a block off plate to cover where the part was removed.

    where are you located?
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  3. #3

    Re: Help! teledyne 4A084 Military Standard Engine modifications

    where are you located?[/QUOTE]

    I am in atlanta. I can get one unused for $350 + tax and drive about 90 miles and pick it up. I am unsure which ignition system it is (or something like that that is different between the years).

    I have looked at a possible yam air cooled snowmobile engine but biggest problem lies in developing a reverse gear. on elec and 2 cycles, rotation of motor/engine is reversed to obtain. I have looked at the Kohler engine and scanned the pages of the guys that modify them for garden tractor pulls which they basically double the output (ie 20 hp to 4 hp) but then those engines are no longer of the "durable" type, not water-resistent electrical nor have the redundant elecs of the teledyne. My hesitation lies in being unable to complete a 4A...but that's a different issue.

    I am looking for dependability, torque and power rather than speed, with certain saftey mods a golf cart can be tagged in Georgia for street use.

    I have seen the you tube videos and pics of 4A mods. I can see and read the mods. I just am unsure of how the mods were made...and being an inquisitive guy, why they were made. I know one basic premise...the volume of air in must also get out...efficiently.

  4. #4
    Administrator Papee's Avatar
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    Re: Help! teledyne 4A084 Military Standard Engine modifications

    We can help you with any of the engine questions but not much of the other parts of the build. With that said, at one time I started a project with a 4a032 which is the smaller brother of this engine. My plans were to use a snowmobile type drive into a hard mounted garden tractor transmission. Off the axles of the garden tractor axle where the tires would mount would be a "transaxle" to allow a suspension and to add width to the axle.
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  5. #5

    Re: Help! teledyne 4A084 Military Standard Engine modifications

    I have considered that. I have a garden tractor I paid $50 for and invested $8 for a starter gear and served me well for 3 years. needs a rebuid though. I need to raise up for clearance so I was going to weld up some "a" frame suspension and use coil over shocks. My guess was if the trans did not carry the body weight it should do fine. I guess can cut and weld on u joints.

    how far did you get or like me, was it one of those that just couldn't get completed?

    The village idiot

  6. #6
    Administrator Papee's Avatar
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    Re: Help! teledyne 4A084 Military Standard Engine modifications

    I changed the project a few times. It started out as a go cart. I put a full cage on it with the tractor rear then decided to put a suspension on it so I got a four wheeler and used the suspension and tires on it.

    edit: I got too busy with other projects and sold it less the motor.
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  7. #7

    Re: Help! teledyne 4A084 Military Standard Engine modifications

    Did you use a lawn tractor combination transmission/rear end or a transmission AND a transaxle. I looked at a site or two for lawn tractor pulls which seem to be dominated by cub cadet rear ends and perhaps their transmission and jacked up Kohler big block engines.

    I considered using a 35 hp OMC lower unit foward and reverse clutch dog gear set to drive primary var speed pulley but I had concerns about what torque it would take- a prop slipping in water and driving oversize tires didn't seem to be similar to me.

    on these 4As, are the intake and exhaust manifolds shop built? is there an ideal length and/or ID for them?
    How are carbs chosen and is there a closer to ideal setup?

    You mentioned 2 cylinders earlier. I visit a govt liq site and at warner robbins AFB (GA), there are a couple of generator sets with a 2 cylinder engine that looks similar to the 4 cyl 4As. are you aware of what hp are those rated at?

    It seems the 4A must be a very well built and dependable engine if one can install into a light aircraft with confidence.

    I have seen the rotax engines. What other engine are used for the mini airboats?

    I have 2 yamaha 650 engines with jet pumps I was saving for a lightweight small boat (15' - 16')...seems here in GA the river shoals and lower units do play well together.

    Thank You.

    the village idiot

  8. #8
    Administrator Papee's Avatar
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    Re: Help! teledyne 4A084 Military Standard Engine modifications

    Quote Originally Posted by rogerou812 View Post
    Did you use a lawn tractor combination transmission/rear end or a transmission AND a transaxle. I looked at a site or two for lawn tractor pulls which seem to be dominated by cub cadet rear ends and perhaps their transmission and jacked up Kohler big block engines.

    I considered using a 35 hp OMC lower unit foward and reverse clutch dog gear set to drive primary var speed pulley but I had concerns about what torque it would take- a prop slipping in water and driving oversize tires didn't seem to be similar to me.

    on these 4As, are the intake and exhaust manifolds shop built? is there an ideal length and/or ID for them?
    How are carbs chosen and is there a closer to ideal setup?

    You mentioned 2 cylinders earlier. I visit a govt liq site and at warner robbins AFB (GA), there are a couple of generator sets with a 2 cylinder engine that looks similar to the 4 cyl 4As. are you aware of what hp are those rated at?

    It seems the 4A must be a very well built and dependable engine if one can install into a light aircraft with confidence.

    I have seen the rotax engines. What other engine are used for the mini airboats?

    I have 2 yamaha 650 engines with jet pumps I was saving for a lightweight small boat (15' - 16')...seems here in GA the river shoals and lower units do play well together.

    Thank You.

    the village idiot
    The headers are made of either stainless or 3/4 conduit two into one. The length is about a foot or a little more. There are header builds in some of the boat builds. I'm not sure how much I covered it in my last build. These motors do like some back pressure so a muffler is needed.

    I mi offer the intakes for the Solex pict 3 conversion but if you can weld aluminum they are easily modified. There are a few threads on it here. So far that is the best choice Ive seen.

    There is a two cyl version, the 042 but I'm not sure of the hp on it. Saturn surplus has any of these motors available, if you decide on a motor I may be able to find you a used one with the shrouding.

    as far as airboat motors, you name it and it's most likely been tried even the Harley evo motors.
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  9. #9

    Re: Help! teledyne 4A084 Military Standard Engine modifications

    Are the air boat hulls generally all "shop built" hulls?

    I have built a couple of plywood over frame drift boats small craft mainly for trout fishing but am looking to go to composites (glass/kevlar/carbon over structural foam). Know of anyone whom went this route?

  10. #10
    Administrator Papee's Avatar
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    Re: Help! teledyne 4A084 Military Standard Engine modifications

    There are some out there that go that route but really there is no advantage in doing it. An aluminum or Fiberglas moulded hull would be lighter than a wood and glass hull. The number of garage welders is growing as far as building an aluminum hull and there are a slim number of guys who have laid up a fiberglass hull.

    The he biggest thing with a mini is weight,the lighter it is the better it floats. The better it floats the more easily it will plane. If the hull sits low in the water it takes a lot of thrust to get it out of the water.
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  11. #11

    Re: Help! teledyne 4A084 Military Standard Engine modifications

    I just want to say thanks for all of your effort and help.

  12. #12
    Junior Member Doozit20's Avatar
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    Re: Help! teledyne 4A084 Military Standard Engine modifications

    Hi and welcome to the forum. That sounds like a very cool rig your trying to build. A quick question on the drive system. Could you use a clutch and gearing from a snowmobile. Or do those have too high or an rpm to kick in?.
    Hull:10'6"x69" 1/2 deckover .100
    Motor:4a084 w/ stock carb
    Reduction:direct drive
    Prop:ultraprop 3 blade 59x10*
    Mods:Motorcycle exhaust

  13. #13

    Re: Help! teledyne 4A084 Military Standard Engine modifications

    The problem is reverse gearing. I looked at a yamaha (most say best dependability) air cooled 340 440 (must be same as early jet skis except air cooled) using a primary and secondary variable speed pulley system. back to same problem...no reverse. there is a place Surplus Center that buys overstocks and closeouts. They have a rear 2 speed w/reverse + output for a front differential (also have the front differential).

    The 2 cycles develop HP at higher rpms but with care they can be tuned to an rpm band.

    I liked the 4a since some have waterproof ignition and as 4 cylinder engines I bet there is more torque than comprable CID 2 cylinders. Also, most earlier gov't/military stuff had fairly rigorous specs.

    But what you suggested is a great idea! it's just that reverse thing. On elec carts they reverse polarity and on the 2 cycle cart engines they reverse the rotation...who needs a reverse gear when one can do that. probably be better off stripping it, selling off the parts and buying a welder and start from scratch. most of the time, ITS NEVER JUST EASY!

  14. #14
    Junior Member Doozit20's Avatar
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    Re: Help! teledyne 4A084 Military Standard Engine modifications

    I think the military made a mule using the 2a042. What about the trany off a blowed up quad bike with reverse of course.
    Hull:10'6"x69" 1/2 deckover .100
    Motor:4a084 w/ stock carb
    Reduction:direct drive
    Prop:ultraprop 3 blade 59x10*
    Mods:Motorcycle exhaust

  15. #15

    Re: Help! teledyne 4A084 Military Standard Engine modifications

    I havn't looked at many quads but those I have seen had trans that bolted to engine case like a motorcycle. I was going to use F/R dog gears off a 33 hp outboard between engine and var speed pulleys but I believe that need somewhere 75 hp+ for strength.

    perhaps a 3 or 4 speed trans and transaxle out of a Yugo would work.

    the village idiot

  16. #16
    Junior Member Doozit20's Avatar
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    I think the outboard thing might work if you rig up something like a clutch. But I dont know if it will hold up to to torque as you said earlier
    Hull:10'6"x69" 1/2 deckover .100
    Motor:4a084 w/ stock carb
    Reduction:direct drive
    Prop:ultraprop 3 blade 59x10*
    Mods:Motorcycle exhaust

  17. #17

    Re: Help! teledyne 4A084 Military Standard Engine modifications

    Anyone here I have a question regarding the arrow direction on pistons do I put them in according to barrow and motor rotation?

  18. #18
    Junior Member Doozit20's Avatar
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    Re: Help! teledyne 4A084 Military Standard Engine modifications

    Sorry but huh??? What arrow are you referring to?
    Hull:10'6"x69" 1/2 deckover .100
    Motor:4a084 w/ stock carb
    Reduction:direct drive
    Prop:ultraprop 3 blade 59x10*
    Mods:Motorcycle exhaust

  19. #19
    Member aerokirk's Avatar
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    Re: Help! teledyne 4A084 Military Standard Engine modifications

    Hello Goldenadept,

    Here is an excerpt from the 4a084 maintenance manual:

    NOTE


    Before positioning connecting rod on crankshaft, ensure arrow on piston is in direction of rotation. See crankcase area to left of cylinder for reference rotation arrow.

    This manual is posted on this site ... Papee has a sticky with all three manuals listed
    11'6" Marty Bray Hull
    4A084 Continental
    Circle "S" 1.69:1 Reducer
    67" Whirlwind Razor X Prop
    SS Rigging

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