Stroking a K motor

[parrot]

So, I thought I would stroke my existing K motor in the KE15 by installing a 3K crank. The original motor failed due to serious blocking of the water jacket between cylinder 3 & 4. Picked up a grotty 3K bottom end for $1.50 on eBay a while back to donate the crank. Sent the various bits off to the machine shop for tanking/overhaul/boring to 40 thou and balancing etc. The block came back still seriously blocked solid, so I spent hours with various implements chipping out the rust and scale through the waterways and core plug holes, then had it ultrasonically cleaned. The space between the cylinders still wasn’t great but that’s how they are.  As others have said, the water flow suffers at the back of the engine.

So how did I get on?

 

Not good!  I’ve done some research and have a Japanese booklet that details the changes made when they went from the Ke10/15/16 to the KE11/17/18. 
 

As you can see they not only increased the stroke, but the block is taller by 2.5mm…….

So looks like I’ll have to get the 3K block out and start over with that.

 

[altezzaclub]

So you will be adding Banjo's water-line to the back of the head too?

Can you get shorter rods?

 

 

[Banjo]

Water flow issues at the back of the head, have always been a problem.

The original moulds for manufacturing K Series heads, were made in a couple of styles.  Whether it is a block or a head; there is a need to remove the sand inside the finished product, before the bare casting starts to get machined. It's those holes that get filled with "Welsh Plugs", in the block.  The head on the other hand, already had a large hole right in the front of the head, where the thermostat housing attaches, & the coolant exits the engine. It needed a hole in the casting, to remove the sand at the rear of the head.  There were some K series aluminium heads that had the equivalent of a large Welsh plug. The best head was one that had a bolt on plate, with four (4) off 10mm bolts.

   

This is a reasonably large hole, which you can release a lot of crud through.

It is also an ideal spot to fit an additional outlet to; to feed coolant back to the thermostat housing, from of the rear of the head & engine.  There were some early model Corollas, that took the cabin hot water heater feed from this point.  I also have a 4K-U engine, with a factory fitted coolant feed point from the rear of the head, back to thermostat housing at the front; running through a factory fitted pipe running down the side of the engine, just below the spark plugs.

I've also modified my 5K engine, to have a return pipe, running just behind the inlet manifold.

 

 

Tests I've carried out before & after fitment, indicated the real reduction in temperature at the back of the head.  I think I documented it on here somewhere; but off memory, it was about a 15 deg C reduction.

Cheers Banjo

 

 

Edited September 19, 2025 by Banjo

[parrot]

Have spent the afternoon pulling out the 3K block from it's hidy hole and getting it ready to be dipped.  Everything else in the motor has been balanced etc, and realistically the only reason for keeping the block was for originality.  Happily the 3K block looks reasonably good as far as the water jacket is concerned.  I'm tempted to run Banjo's modification but slightly more fiddly with the bigport head as it doesn't have the bolt on plate.  I know I could get the machine shop to tap some hoes to retrofit the plate, but I might have a think about that.  Coolant, yearly drains and dosing with thermocure evaporust may do the trick.  Realistically the car isn't going to do many kms each year.

There is a light score in No. 4 bore so I'll see what the machinist thinks we should bore it to.  

Haven't been able to drive for the last 3 mths due to a health issue, but hoping to get clearance for that on Wednesday which will make things much easier.  I'm a bit over buses and trains.

[altezzaclub]

"Haven't been able to drive for the last 3 mths due to a health issue,"

I hope they sort it out, that would take all the fun out of life!

[Banjo]

Hi Pete,

             So sorry to hear You have "a health issue".  Join the club !  Getting back behind the steering wheel, will certainly help. I did a recent trip to Sydney & back, from Brisbane, & it was really good for the moral. I find, when You are on the open road, travelling close to the speed limit, You are concentrating so much on the job at hand; that all other issues seem to be forgotten about, for the time being. 

I've tried a few coolant water additives, over the years, but not Thermocure Evaporust.

Had a quick look on Google last night, & found a utube guy with a BMW, who did a clean, & the results were really good.

https://www.youtube.com/watch?v=aq3brzIA3e0

What I like about this product, is that it keeps giving for quite a while. In another video, a guy didn't throw away, the waste from the coolant system.  He left it in a plastic tub, & just threw in any metal tools that had a bit of rust on them. After about a week, He took them out, & rinsed them, & they looked like new. 

Really a problem in Brisbane & Qld. in general, where our humidity levels are higher.

P.S.   What is it about BMW water pumps ?   I had to change mine, in my BMW; that had a failed bearing like this guys. The seal breaks down, & once there is coolant in there; it is "bye bye bearing".

Cheers Banjo

 

 

 

 

 

Edited September 19, 2025 by Banjo

[parrot]

So cleared to drive last Wednesday and first trip was to the engine machinist!  Then the pie shop.

Now to wait for his assessment of the $1.50 block.  

Have ordered another set of crankshaft mains bolts through Impex along with various other things.  I'm also rebuilding the front struts with the KE55/70 brake conversion so various bits and bobs in the meantime.  

One thing, I wasn't particularly impressed with the variable size ring compressor I had.  So after watching Banjo's linked post about piston ring gapping I've elected to get a tapered one size 75mm tool.

[Banjo]

Good to hear You are "back on the road" !

Chers Banjo