How necessary is balancing?

Dude just buy a running motor and drop it in. You cant take a crank and other stuff from one engine and just "drop it in" the other.

You will probably have to have the main caps line bored, the crankshaft will need to be machined, you'll need oversized bearings, and that's if it can be used.

You can find a running used engine for about 2k dollars, drop it in your car and be driving in a few days. If you keep on the path you're on now I guarantee it wont be ready by January.

 

Thanks for the thoughts. As tempting as getting a used JDM engine is at this point (it did occur to me...), it’s not really an option since everything is bought and I’m not keen to return parts and lose some money.

I was intending on taking the crankshaft to the machine shop The dude at the shop didn’t seem concerned about the idea of transferring it. My main concern is just that since a rod broke it may have damaged that crank. I’m aiming to get it all disassembled in the next few days.

 

https://www.mazdaspeeds.org/index.php?threads/johnnytightlips-build-maximum-carnage.7025/

My motor blew a hole through the block and the crank was still in good shape and has been going strong over a year at 500+ so there is hope.

 

Just keep the main caps with the block and you should be fine on the crank side

 

Are you saying to make sure I keep the main bearing cap with the specific block? Or use the main cap that corresponds to the crankshaft?

 

You keep the main caps corresponding to the block

 

This

 

Hey

I'm old

I know your future self, and he asked me to tell you a story about a nail,horse,and war..
But I thought fuck that, I'll try to be useful

You know the meme about a downpipe, fuel pump internals, and a bad time?


Here is the Ironical part

the internals should come with rods.

As in, once you have said DP, and internals, you can tune well past what the OEM rods can take. so, if you build it with OEM rods, you can drive those pretty pistons as hard as you trust your foot, or tuner (mapper) basically you have to ensure you dont command any significant load <2750 rpm. which will make a lumpy tork curve and less DD fun.

Champagne taste and beer budget. is what my dad once said


look about for some used K1 rods, they ain't bad, and proly well inside your flex zone of cash. stock head bolts will be fine, there is some money
when you broke you learn how to shop

 

That was a chuckle I’m leaning toward going ahead and getting the Manley h-beam rods, but I’ll have a look for some used K1 as you suggest.

 

I went ahead and ordered the Manley H-Beam rods.

I remembered that my goal with building this motor instead of buying a good used one was to use better quality internals for more reliability. I got a little sidetracked when the machine shop dude said to get forged pistons and that the rods don’t matter. Even if that’s the case, my goal wasn’t OEM.

 

Turns out the Manley rods wouldn’t come until potentially after Christmas so I decided to get the K1 rods instead. That two week delay could complicate things.

 

I weighed one K1 rod and Manley piston (with wrist pin) and together they’re about 160grams lighter than OEM, with the K1 rod being about 120grams of that.

Is that a good thing? Or does it really not matter in this application?

 

Lighter rods and pistons equals more power because the engine has to work less to turn just as fast. It's not exactly like you would see an increase in power off of those components alone (unless you got higher compression) or had a lighter flywheel.

Basically it frees up horsepower it doesnt add it. The pistons and rods can weigh less but be stronger if made from a stronger metal/process.

 

It would affect the primary balance, but not as much as you think.
the piston/gudgeon pin are all reciporcating mass, needing opposing mas to balance.
only some of the rod counts into the equation. there is a not super painful way of calcing that, but not residing inside my skull