Datsun Roadster Forum-311s.org

I'm looking another motor to rebuild. I want a 3-main r16. Is there an easy way to tell if a motor is a 3-main by just looking from the outside? I'm guessing engines with a number lower than "certain number" will all be 3-main. Any help is greatly appreciated.

Thanks.

If anyone has one, I'm looking for one that is complete or close to complete.

Engine s.n. Less than 40000. As I recall. There are a couple external casting differences, I'll try to put up some photos. I'm sure Mike Young has one, he isn't real far away. I would ship you one but the freight would be kinda expensive.

Also if it as a long tube (rear crankcase vent) on the left rear below the #4 exhaust running down vertically, it probably is a 3-main. 5's typically had a freeze plug there. (Not an absolute indication, but likely)

US course thread and SAE fasteners (not metric)jt

I have a new one in the Los Angeles area. It has never had a serial number stamped on the block.
BRAND NEW 1600 3-MAIN CYLINDER BLOCK Never used empty block with cosmoline in bores. Price is $265.00.

Also have a new set of 4 factory rods and pistons that were removed from a new short block and never run. Price is $500

Stan
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Man, that's a bargain on the new 3-main block....You'd have over 200 in prepping a used block.

I just sent one to the scrap yard.

I have 3 or 4 .
Are you looking for a vin in a certain range
Arnold

Thanks for the help, I'm building a stroker motor, so I don't think I want to start from a brand new block. Stan, if you were close I'd pick that up, but the price plus shipping is more than I want to spend for the motor. I see them for sale locally every once in a while for $100-250 or so in running condition, I just want to know how to identify if the the motor is a 3 main or not when i go to check one out. Arnold, vin doesn't matter as long as its a 3 main, if the price and shipping costs are not to bad I'll take the one in the best shape.

Thanks again,
Todd

Todd, on the R-16 block, look on the distributor side and a 3-main block will have "Nissan" cast into it and a 5 main block will have both "Nissan" and "Japan" cast into it....

What's going to be your method of stroking? If going the usual route of using a modified U20 crank, won't you need a 5main? The U20 is a 5main crank. I also understand that the U20 crank is very nice for its time, being forged steel and fully counter balanced. Not sure what the attraction was with the 3main, which I think is less robust and smooth running? I'm no expert, just expressing what I've heard...

I'm not 100% set on the 3 main, mainly trying to educate myself on identifying them (like I said, I have seen them very cheap, even free). I have a g15 crank that I read can be mated to the r16 to make 1800cc's.

Unless I am mistaken, you will need the G15 rods too.

I used the R16 rods, which are longer, and went with custom flat top pistons which are each almost 200 grams lighter than the stock pistons.
It's a noticeable improvement over the 1600 in power, but since I've built it I've come to the conclusion that the 5 main 2L stroker would be easier and cheaper to build, if you stick to the stock parts.
When you start going to aftermarket custom parts, the costs will be near the same but you have potentially 15 - 25 more available horsepower with the extra displacement. as well as the added low end torque which is always nice to have.

Don't get me wrong tho, my 1800 is quite fun and pulls hard to 6500 rpm where I limit it.

If you go 3 main, Stan's setup is a bargain, even with shipping. Beyond cleaning the Cosmoline off the block, it's ready to assemble with no machine work needed, whereas on any used block you don't know until you clean it up and measure everything. Try Uship.com see if you can find a shipper, or it might be light enough for Greyhound freight.
The 5 main /U20 is simpler, 5 main blocks (and even whole H20's sometimes) are easy to find and someone may want that G15 crank to cover some of the cost. If you find a later H20, not an H20-II, you can sell off some of the H20 parts, like the electronic distributor and cover some $$. Get a R16 head and a diesel 5 speed transmission and you are golden.

For the 3 main stroker, do you use R16 rods or the G15 rods?