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The Ratsun Rebuild a good idea?


sick620

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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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  • 1 month later...

I am now in the middle of this process, very excited to try my first ratsun rebuild!

 

while engine is out of a datsun being rebuilt, is it a good idea to replace front cover gasket on the transmission? 

 

why is a flex hone preferred on ratsun? I've seen a lot of videos and read a lot on this topic and everyone elsewhere online is saying the 3 stone style hone is better because it helps to ensure the cylinder is straight with no areas that valley or peak etc, and although the flex hone gets the desired finish it may keep valleys etc intact ... I believe this is the argument they are making... I already purchased a flex hone but just wondering...

 

Cleaning block and head: I live in an apartment though I do have a garage which is great.. Block and head are disgusting, if you lived in a garage no access to garden hose how would you degrease your engine? Take down to car wash? Tub of diesel fuel? Simple green in your bathtub?... Trying to keep odor down, when I spray brake cleaner in the garage my entire 3 story townhouse smells outrageous, can't imagine degreasing an entire engine... 

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The cylinder should be measured for taper and wear first. A re-bore to a slight oversize and matching over size pistons eliminates cylinder high and low spots.  Also allows the use of chrome rings that work best on pristine round cylinders. Most of the wear will be where the piston rings stop at TDC. 

 

Definitely power wash down town. Wear rain gear and goggles. Scrape as much of the thick stuff off in advance. If you can, get a citrus degreaser and liberally spray down the night before the wash. I use a couple of squirts to clean hands. It's also food grade safe for cleaning kitchen appliances. Contains oil from orange peels. Have you ever peeled an orange with greasy hands? You'll know what I mean.

 

http://mobileimages.lowes.com/productimages/0914926a-0b7d-4428-886d-ae28eee947e5/07773448.jpg  

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Ball hone vs flat stone hone - the entire reason this is called a "Ratsun Rebuild" is because it is done on the cheap.

 

A ball hone is good for cleaning up the surface of a bore that is in good shape. On a budget build, one should assess the condition of the bore with a visual inspection before and after a ball hone is used. You can almost always see an imperfection. Damage can usually be felt with your fingernail. If there are imperfections that a ball hone cannot clean up, the next step is to measure them. If the imperfections can be measured, then the proper way to fix the damage is to use a power hone. Luckily for Datsun guys, the metal used in Nissan's castings was very good for the time. It's not common (like it is on Chevy and Ford V8s) to find a ridge at the top of the bore, and unless the motor was overheated, or a ring was broken, the surface of the bore should be relatively smooth. Taper in a bore can occur, but this is almost always accompanied by the ridge in the top. If there is a taper, but no ridge, then your block was born that way.

 

A stone hone is used when the bore needs to be trued up or straightened or have imperfections removed by a slight oversize. The type of three stone hone used for this is called a power hone and will change the size of the bore. Ideally, a power hone would be done with a torque plate bolted to the top of the block, simulating the shape of the bore when the head is bolted on.

 

Measuring the bore is only a relative measurement. The bore gauge is usually zeroed out at the smallest point of the bore and then run up and down the bore to measure taper. A couple thousandths is common. The measurement is also checked against the large measurement of the diameter of the piston skirt, again, a relative measurement. On a Ratsun Rebuild, anything up to about .010" could be ok. Any more than that and there may be problems.

 

In a nutshell, if the bore looks and feels fine, and you have no intention of going to a larger piston, why even measure it? Ignorance is bliss. Hone it with the ball hone. Make sure there's a nice cross hatch, use a good sprayed chrome ring and be done.

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o

13 hours ago, Stoffregen Motorsports said:

Leave them in the head. The only time you would ever remove them is if you're having the top of the head cut.

ok awesome seemed like a waste of time to screw them all the way out... Thanks for all the information.. I ordered a how to rebuild nissan datsun engines book, I now have everything i'm going to need for my L16...

 

head is off started cleaning, head looks great, cam looks great... cant catch fingernail anywhere in cylinders, walls look fine, tops of pistons look fine.... Cleaning all of this will be a nightmare, that's by far going to be the hardest part of this job.. caked on sludge all over exterior... I don't know why I've always been so scared to conquer a job like this so far seems very strait forward except for the cleaning 😔 😅

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ok hold on I spoke too soon there is a ridge at the top of every cylinder the front and rear cylinder you can catch a finger nail on it barely but only on passenger side of cylinder..middle two cylinders you can’t feel it really at all anywhere… the other two you can feel it around the whole top but only barely catch fingernail on left side… tried cleaning to see if it’s carbo buildup or something but definitely not 

 

 

Edited by sick620
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That's the topmost point of ring travel and where the most wear is. Least wear is at the bottom of piston travel. The difference is the taper allowance 0.0006". Oval (out of round) of the bore is also 0.0006" and maximum bore wear is 0.0079".

 

I've done a few cheap hone and ring jobs and got another 10k miles before I was right back where I started and another 10k till it was serious. Should have just had it bored and gone to an over size piston and had a new engine capable of a couple of hundred k miles.

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You can have the ridge power honed, but that requires the same amount of effort as having it bored and honed with new pistons. Literally, the same wait time, the same machine, everything but the new parts. Installing the rods on the pistons is another job for the machine shop, unless you have a rod vise and a piston press, which you can make easily at home. If after honing out the ridge, the bores are still within spec, you'll save a few hundred bucks by being able to re-use your pistons and not having to have the new ones installed on the rods.

 

I draw the line at the ridge in the top of the bore. A ridge can break rings.

 

So your Ratsun rebuild has just hit dead man's curve. Continue or change course?

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Ok I read your responses and decided on a course change! friend hooked me up with a great deal on the 720 with l20b and 5 speed, and an extra z20 complete in the bed removed from a good running and driving truck… 

 

so either the l20b is going in the 521 or the z20 I’m leaning towards the z20 because it’s out of a 720 so it’ll bolt right in, it has a brand new clutch kit with it, I’ll just use the l16 tranny for now bend the shifter and make a diy transmission mount to deal with the lean seeing as it will mount at an angle to the z motor. 
 

or I rebuild l20b from 720 and put it in 521 instead and I put z20 in the 720 and 720 will now have the gangster lean on the transmission…

 

will main and rod bearings for l16 work on l20b? Seems like just the rod bearings interchange right? Gasket set definitely works, clutch kit… are l20b and truck l16 both 240mm flywheel? All my rebuild parts should work to rebuild the l20b minus the rings and main bearings correct?
 

if you have any better idea on what to do with all these parts let me know 

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Edited by sick620
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Q9xYbRS.jpg

 

Look between the two pair of exhaust pipes for the engine size. Confirm it's a Z20. Could be a Z24. You never know.

 

 

Z20 won't work with an L transmission. Only as an absolute last resort. The Z20 from the 720 has a monster 240mm clutch and pressure plate that (I think) will rub the tiny 521 bell housing.

 

Do you have a spare L20B head? Put it, the timing chain, engine brackets and 521 oil pan and pick up on the Z20 block and this converts 

it to a long rod 9.9 compression L20B. Now the 240mm clutch can be used on the L series 5 speed with no lean. Win Win.

 

No the L16/18 main bearings will not fit an L20B. They are smaller diameter. L16/18 rod bearings will work on L20B, L24, L26, L28, Z20, Z22 and Z24.

 

Some L16 gaskets will work but not the head gasket or the timing cover.

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1 hour ago, datzenmike said:

Q9xYbRS.jpg

 

Look between the two pair of exhaust pipes for the engine size. Confirm it's a Z20. Could be a Z24. You never know.

 

 

Z20 won't work with an L transmission. Only as an absolute last resort. The Z20 from the 720 has a monster 240mm clutch and pressure plate that (I think) will rub the tiny 521 bell housing.

 

Do you have a spare L20B head? Put it, the timing chain, engine brackets and 521 oil pan and pick up on the Z20 block and this converts 

it to a long rod 9.9 compression L20B. Now the 240mm clutch can be used on the L series 5 speed with no lean. Win Win.

 

No the L16/18 main bearings will not fit an L20B. They are smaller diameter. L16/18 rod bearings will work on L20B, L24, L26, L28, Z20, Z22 and Z24.

 

Some L16 gaskets will work but not the head gasket or the timing cover.

Yea already confirmed its a z20 … only extra head I have is the 210 l16 head, but I could take the w58 l20b head off the l20b onto the z20… 

 

ok so that settles it … I’ll put the l20b from 720 rebuild it the ratsun way stick it in 521…. Rebuild the z20 also ratsun way and put a lseries head on it and put it in the 720 and make the high comp engine … what’s stock compression for l20b with w58 head ?… what would happen if I put 210 head on either of the motors? 

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W58 L20B is 8.4 compression.

 

If putting the L20B from the 720 into the 521 what head are you going to put on the Z20????

 

You should keep the L series 5 speed with the L20B. The 521 has 4.375 differential, you need the over driver 5th.

 

Z20 won't work without Z series transmission.

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If I did that (l20b from 720 into 521) I’d probably just have to wait and keep an eye out for an l20b head … I don’t mind running the 521 as a 4speed geared low for a while to get the truck on the road… didn’t you just say that the z20 could be made to sit at the correct angle with proper Lhead and mounts so it could work with the L series 5 speed? 

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