Hot tanking is no longer what it used to be.  Nasty chemicals are being regulated.  Do a search on it and you'll find stories about today's cleaning processes.  You might do more damage trying to clean it than just doing the minimum needed.  It's just going to get dirty again anyway.

Kind of looks like old antifreeze residue.  Whoever told you the block was "done" should not be listened to in the future.  If the passages aren't blocked it will probably be fine.

  On 12/7/2020 at 7:36 PM, Zed Head said:

Hot tanking is no longer what it used to be.  Nasty chemicals are being regulated.  Do a search on it and you'll find stories about today's cleaning processes.  You might do more damage trying to clean it than just doing the minimum needed.  It's just going to get dirty again anyway.

Kind of looks like old antifreeze residue.  Whoever told you the block was "done" should not be listened to in the future.  If the passages aren't blocked it will probably be fine.

Yeah, the thing is that it is completely clogged, there is no flow between left side and right. I don't have any trusted machinist to take the engine either, i was asking around the area and the price for a hot tank is 80$-120$ and that is all the cleaning methods they offer.

Not sure the coolant is supposed to flow left to right.

I'd pour water in the inlet at the pump area and see where it goes.  Stand the block on end and run some water through the front cover inlet where everything starts.  It should come out the holes that connect to the head.  That's the path.

Completely blocked coolant passages is not as common as people think, I think.  You hear/read the stories about stop leak usage but most of what people find in their blocks is just stuff that dropped out in the dead flow areas.   I've never seen a story from anyone who had overheating problems and found that clogged coolant passages in the block was the cause.  A better radiator and a good water pump is usually the fix.  The clogged passages stories are what people see and think must happen, "what is all this stuff in here" (no offense), but the coolant passages are really very crude.  It's a big open cavity between the block walls and the cylinder bores.  Most of the cooling happens at the top of the block and in the head.

Anyway, I wouldn't overthink it if it was mine.

What if you fill the block as much as you can with CLR and let the block sit for a couple hours (verify iron use on data sheet), you should observe it break through some of the gunk, and can flush and repeat this process.

  On 12/7/2020 at 7:54 PM, Zed Head said:

Not sure the coolant is supposed to flow left to right.

I'd pour water in the inlet at the pump area and see where it goes.  Stand the block on end and run some water through the front cover inlet where everything starts.  It should come out the holes that connect to the head.  That's the path.

Completely blocked coolant passages is not as common as people think, I think.  You hear/read the stories about stop leak usage but most of what people find in their blocks is just stuff that dropped out in the dead flow areas.   I've never seen a story from anyone who had overheating problems and found that clogged coolant passages in the block was the cause.  A better radiator and a good water pump is usually the fix.  The clogged passages stories are what people see and think must happen, "what is all this stuff in here" (no offense), but the coolant passages are really very crude.  It's a big open cavity between the block walls and the cylinder bores.  Most of the cooling happens at the top of the block and in the head.

Anyway, I wouldn't overthink it if it was mine.

Is the big port the inlet? I dont have the core plugs in, it just comes out of them

Here's a good web page with a video.  He sprays water in from the top holes and you can see it coming out the core plug areas.

Some long skinny brushes, a hose, and time will probably get you feeling confident.

http://www.kangamotorsports.com/blog/datsun-engine-block-cleaning

  On 12/7/2020 at 8:42 PM, Zed Head said:

Here's a good web page with a video.  He sprays water in from the top holes and you can see it coming out the core plug areas.

Some long skinny brushes, a hose, and time will probably get you feeling confident.

http://www.kangamotorsports.com/blog/datsun-engine-block-cleaning

Thank you, i also found a good diagram on the manual of the coolant flow. My only question left would be the flow between cylinders, is it supposed to be open for all as in the pic or closed? I looked at alternatives to hot tanking and i found the baking thing(idk the exact name) but it cost about 200$. I still have to figure out how the rest of the block will go, i would love to reuse my old pistons, but that's for another topic, i have never gone to a machinist or rebuild anything before :p.

 

What type of engine block do you have, N42 or F54?  There's quite a bit of discussion around the internet about "siamesed" cylinders.  Apparently the early blocks were blocked off between cylinders and later blocks were open.  Edit - this might be backward.  See #22 below.

In your second picture what you're showing as a blockage is really just the casting itself, I think.  Steel.  Poke a screwdriver in there.

I haven't seen a cutaway of an L engine engine block but the way it should be is that the lower portion of the cooling passage would be open, that's where you'd get left to right flow (actually front to back but shared at the bottom), but the upper portion (where the core plugs are) would be isolated by cylinder so that coolant is forced to flow upward and in to the head.  Like a manifold, with the open bottom "plenum" pressurized by the pump.  

A block cutaway would be interesting I think that there might be one on the site.  Somebody cut an engine in half and made a three cylinder L engine.  It's on the site somewhere.

You should buy Monroe's How to Rebuild book.  It's worth the money and time to read it.

https://www.amazon.com/Rebuild-Your-Nissan-Datsun-Engine/dp/1931128030/ref=sr_1_1?dchild=1&keywords=How+to+Rebuild+Your+Nissan+%26+Datsun+OHC+Engine&qid=1607375412&s=digital-text&sr=1-1-catcorr

 

Edited December 7, 20204 yr by Zed Head

Here's the cutaway engine thread.  Not sure it gets in to cooling areas, I have to watch the video again.

 

More block confusion.

https://datsunzgarage.us/engine/

I would try to find a pressure washer to borrow and go at it. I bet most of that will wash out

Just an example of a block with no passage between cylinders.

 

Edited December 7, 20204 yr by Zed Head