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The Ratsun Rebuild a good idea?


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if you take an L16 that smokes apart and re ring it, add new seals and new gaskets, and possibly bearings do you trust it? This is obviously taking into consideration that tolerances are still in spec, no crazy gouges in the cylinder walls etc.... New freeze plugs? do anything else while its apart? important notes?... i've searched and searched but the consensus seems somewhat mixed... Is this just an idea for the person that wants something cheap to get them by for a few 3-5 years maybe until they do an actual rebuild/motor swap... or is this a legitimate long term option possibly?

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Not sure on an "L" motor but I did this on an "A" motor years ago and it is still going.

Gasket and seals, main and rod bearings, timing components, rings, freeze plugs, and I may have even taken the head to a machine shop but am not positive.

Not sure if this helps any but its my $.02 worth.

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As long as the cylinders are checked for bore wear and out of round and pass. That's two places at 90 to each other about 1/2" down from the deck, halfway down the piston travel and at the bottom of piston travel. Six points. Then hone carefully and use cast iron rings. The reason being that the chrome rings last longer but are harder and the cylinder is never going to be as perfect as a freshly over bored one and will wear out before seating. The cast iron rings are softer and will bed in faster. 


When cleaning the pistons ring lands, do not remove any deposits above the top ring. The most cylinder wear is where the rings reach the top of their travel and this will help seal in the combustion pressure.


Lap the valves. Grinding compound and an electric drill, it's easy and cheap and only takes your time to do. Improves the combustion chamber seal. Use a wire wheel to remove all deposits off the valve stem. Keep valves, springs keepers, rocker arms and lash pads in order so they go back in the same place. 


While valves are out most definitely replace the valve seals. This could be where a lot of the oil smoke is coming from. It's cheap and easy to do.


Wire wheel the combustion chamber deposits off but have a care as the head is soft aluminum. Do with the valves in to protect the seats. Clean the block and head surface carefully. You can't over clean them and the cleaner, the better the head gasket will seal.


I wouldn't bother measuring the main and rod bearing clearances. If there is wear, new bearings will close up the clearances anyway and if no wear it will be returned to stock clearances.


I imagine the engine will be removed? (although you can do this in the vehicle) if so the timing chain and guides are much easier to replace so you should. There are kits for this and the only advice is get a better quality 'made in Japan' one. With timing cover off it's also easier to replace the front crankshaft seal.


A full gasket set should contain front and rear crankshaft seals, oil pan, manifold, timing cover, valve seals, valve cover gasket and head gasket. I wouldn't change the thermostat housing gasket because of the risk of breaking off the mounting bolts. Don't cheap out on the rings or the main and rod bearings.


Borrow a good torque wrench for assembly. Use an assembly lube on all bearing contacts. Get a factory service manual (FSM) for a year that includes the L16 ('73 620, '68-'73 510 or '70-'72 521) if possible.

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Hone the cylinders with a ball hone, and all will be fine. New sprayed chrome rings will seal better than chromoly rings and last longer than regular cast rings. Hastings makes a nice set. Other than that, new seals and gaskets, should run like a champ!


If you want to polish the crank yourself, use 320 grit emery cloth. You can buy rolls on Amazon for $25.


If your bearing clearances are a tad loose, you can tighten them up by sanding the main or rod caps on a hard, flat surface with emery cloth. You can take up as much as a couple tenths this way, but not much more.

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If replacing the oil pump get the one from a '90 and up a KA24E or KA24DE powered D21 Hardbody truck. Externally the same but internally has longer rotors for higher volume and pressure at lower engine RPMs. Same top pressure. Highly recommend this swap if replacing anyway.



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Never hurts, if you do it yourself. Use the gasket and match the intake and exhaust ports then the intake and the exhaust manifolds. Not worth paying for it but you get the fun of hands on doing it and saying....



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