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4.3 two stroke conversion...

This is a discussion on 4.3 two stroke conversion... within the Other Rides Tech forums, part of the General Discussion category; Found a free 4.3l, and I got the stupid idea that I could convert it to two stroke. Will somebody ...

  1. #1
    Registered User gianelli280's Avatar
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    4.3 two stroke conversion...


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    Found a free 4.3l, and I got the stupid idea that I could convert it to two stroke. Will somebody PLEASE tell me why I can't do this so I'll stop chasing this rabbit.

    Redneck theory sez... 1:1 timing gear ratio + intake reeds + expansion chambers = wheelies.

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    Registered User flyinbrian's Avatar
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    Re: 4.3 two stroke conversion...

    I assume you're just joking around, but since I love two strokes for their simplicity and power to weight/cc ratio it got my wheels turning.

    I suppose it could be done if you could cut holes in the sides of the cylinder walls for intake and exhaust. You would have endless obstacles, i.e. water jackets, lifter valley, etc. Come to think of it, how would you lubricate the crank? All of the V-6 two strokes I have ever worked on, (marine outboards, Mercury, Mariner, OMC/Bombardier, Yamaha), all have the intake on top of the crankshaft. In other words, the fuel/oil mix passes over the crank before it reaches the combustion chamber to lubricate the rod and main bearings, (both roller bearings).
    I suppose you could still lubricate via the stock oil pump.
    Suppose you cut, ground, and welded intake and exhaust ports in this motor. Where do you put the ports relative to the deck? This is how two-strokes do without a camshaft. The figuring out of piston timing, port location, and timing events are more than I can get my head around while typing this.
    Your heads would have no valves. They would be more or less a spark plug holder and a place for coolant to circulate.
    The intake would go through the lifter valley or along the outside of the block and enter the side wall of each cylinder.
    The exhaust would do the opposite of whatever the intake did.

    So good luck. I'm sure I missed a bunch, but these are my initial thoughts as I have done a good bit of work to V6 two strokes that were originally two strokes. Those V6's had anywhere from 150 to 330 horsepower and 2.0 to 2.5 liters.
    1993 K2500 Suburban. 454 poked and stroked to 496. Comp Cam roller valvetrain, JimD(454ss.com) bored TBI, Thorley headers, Edelbrock TBI intake ported and flowed. Innovate WBO2, TunerPro RT, Ostrich, Burn1.*Now running a Dynamic EFI EBL with a '7060 piggybacked to run the 4L80E.*

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    Registered User gianelli280's Avatar
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    Re: 4.3 two stroke conversion...

    I don't think I'm going to even attempt it and ruin a perfectly good block, but I wanted to know if it can or has been done before. I see what you mean about shutting down the heads, whereas the pistons themselves are the intake and exhaust valves, negating a camshaft, but i'd need forced induction to clear the cylinders before the second cycle is finished, right?

    I wouldn't be able to use regular oil for this operation, would i, since the piston will pass the intake port and get oil worked up in there.

    I'm pretty limited on my knowledge of two strokes, other than the maintenance i did on my dirt bike growing up, but I didn't get very deep into the mechanics of it. I asked my brother and he told me to check out detroit's two-stroke diesel, he said that might be pretty close to what i'd be shooting for, but i haven't had time to look into that yet.

    I absolutely love two strokes, as far as dirt bikes go, couldn't go back to a 4 once i had that ridiculous powerband, that's what started me thinking about this, but it's looking very impractical. Might just be a rebuild and straight to craigslist. Though my s10 could use a new powerplant.

    I have some time on my hands so if you have any wild ideas that might work i'm all ears, it's free after all!

    Check out crower's 6 stroke engine, i ran into this when doing a little research, pretty cool if you ask me.

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    FSC SOUTHEAST CHAPTER kirk's Avatar
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    Re: 4.3 two stroke conversion...

    Quote Originally Posted by flyinbrian View Post
    Your heads would have no valves.
    Depends on how you do it. Old Detroits had exhaust valves in the heads, with slots in the bottom of the cylinders for the inake.
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    Registered User flyinbrian's Avatar
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    Re: 4.3 two stroke conversion...

    Quote Originally Posted by kirk View Post
    Depends on how you do it. Old Detroits had exhaust valves in the heads, with slots in the bottom of the cylinders for the inake.
    I figured someone would chime in with diesel experience. My two-stroke hands on knowledge is limited to marine applications. If he were to make it like a V6 outboard motor this is the way it would work.
    MotoGP, before outlawing the two stroke, had rotary valve or valves from what I remember. But I have zero hands on with those.

    I am intrigued by this thread and wish someone would attempt it. At one time I tried to have everything two stroke, i.e. lawn mower, weed trimmer, leaf blower, etc...all so I could smell the Klotz smoke as much as possible. :)
    1993 K2500 Suburban. 454 poked and stroked to 496. Comp Cam roller valvetrain, JimD(454ss.com) bored TBI, Thorley headers, Edelbrock TBI intake ported and flowed. Innovate WBO2, TunerPro RT, Ostrich, Burn1.*Now running a Dynamic EFI EBL with a '7060 piggybacked to run the 4L80E.*

  6. #6
    Registered User gianelli280's Avatar
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    Re: 4.3 two stroke conversion...

    please don't egg me on hah! if we could come up with a good plan i'll try it, but the problem for me is funding on the forced induction, i really don't see a way around it.

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    Re: 4.3 two stroke conversion...

    If you truely want a 4.3L V-6 two stroke you are going to be designing it from scratch. Trying to use any part of the current engine is only going to make things harder. It's not a starting point, it's a hinderence. There's just so many obsticles there is unbelievable.

    I'm not saying don't have big dreams. But you'll end up with a terd of an engine without tens of thousands of dollars to throw away, full machining capabilities, engine modeling software (for deciding on primary compression ratio, secondary compression ratio, port timing, transfer port angles, sub and main exhaust port heights and cordial widths, squish band geometry, intake lengths and volumes, etc), and a dyno for testing dozens if not hundreds of variations. I've seen the process that goes into making a "new" 2 stroke engine. It takes a team of people thousands of man hours to get things ready to rock and roll.

    Just buy one of these.

    1750 cc (or 1.75L), 403 hp, 235 lb-ft. Doubt it'd do well in a truck though, maybe a really light track car.

    92 K1500 WT - Gone
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  8. #8
    Registered User stepsideben's Avatar
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    Re: 4.3 two stroke conversion...

    Quote Originally Posted by adam728 View Post
    If you truely want a 4.3L V-6 two stroke you are going to be designing it from scratch. Trying to use any part of the current engine is only going to make things harder. It's not a starting point, it's a hinderence. There's just so many obsticles there is unbelievable.

    I'm not saying don't have big dreams. But you'll end up with a terd of an engine without tens of thousands of dollars to throw away, full machining capabilities, engine modeling software (for deciding on primary compression ratio, secondary compression ratio, port timing, transfer port angles, sub and main exhaust port heights and cordial widths, squish band geometry, intake lengths and volumes, etc), and a dyno for testing dozens if not hundreds of variations. I've seen the process that goes into making a "new" 2 stroke engine. It takes a team of people thousands of man hours to get things ready to rock and roll.

    Just buy one of these.

    1750 cc (or 1.75L), 403 hp, 235 lb-ft. Doubt it'd do well in a truck though, maybe a really light track car.
    i think this would be fun in somthing like a geo metro
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  9. #9
    Mine is Louder Than Yours leveldowen's Avatar
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    Re: 4.3 two stroke conversion...

    I don't think a 1:1 cam timing ratio wouldn't be the only thing you need, you would need a 1:1 drive ratio for the distributor, and then you would need an entirely new camshaft with the intake and exhaust ground at different points so that they overlap to take advantage of the exhaust pressure pulling the intake charge in instead of the piston pulling the intake charge in as it would in a 4 stroke engine.
    Last edited by leveldowen; 06-13-2010 at 06:00 PM.
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    Re: 4.3 two stroke conversion...

    Quote Originally Posted by stepsideben View Post
    i think this would be fun in somthing like a geo metro
    I like the way this guy thinks.

  11. #11
    Offroad Engineerd Underpowered's Avatar
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    Re: 4.3 two stroke conversion...

    Quote Originally Posted by flyinbrian View Post
    I figured someone would chime in with diesel experience. My two-stroke hands on knowledge is limited to marine applications. If he were to make it like a V6 outboard motor this is the way it would work.
    MotoGP, before outlawing the two stroke, had rotary valve or valves from what I remember. But I have zero hands on with those.

    I am intrigued by this thread and wish someone would attempt it. At one time I tried to have everything two stroke, i.e. lawn mower, weed trimmer, leaf blower, etc...all so I could smell the Klotz smoke as much as possible. :)
    not only moto GP, but old 60's-70's 2 strokes used a rotary valve as well. they are a PITA to work on and never seem to seal corrrectly but it was a valve of sorts
    new tow Rig rattles and smokes
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    Re: 4.3 two stroke conversion...

    Quote Originally Posted by Underpowered View Post
    not only moto GP, but old 60's-70's 2 strokes used a rotary valve as well. they are a PITA to work on and never seem to seal corrrectly but it was a valve of sorts
    Rotax still sells rotary valved 2 strokes, mostly for small aircraft (ultralights). Ski Doo ran rotary Rotax's well into the 90's.

    92 K1500 WT - Gone
    92 C2500 - Current. Scottsdale, 350tbi, 4L80E, 14 bolt sf

 

 

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