hahaha, no I dont know how to measure oil clearance actually.

I did apply assembly grease, so I expected them to be somewhat stiffer. However, now I worry that the bearings are too 'tight'. So I guess measuring oil clearance is something I need to learn.

As I am installing the front case I realized that the front balance shaft doesn't 'fall' to identify which turn is the appropriate timing mark. I can turn it, but it certainly doesn't free fall.

Now I need to figure out if that is just because there is only assembly grease instead of oil, or if that is something that requires the bearings removed and reinstalled.

What would you expect with assembly grease only on the bearings?

 

The balance shaft oil clearance is actually very tight. Much tighter than the connecting rod oil clearances. The thickness (viscosity) of the assembly lube you used may hinder the balance shafts spinning freely but if you were to use regular engine oil on the shafts the balance shaft counterweights should still be able to rotate the shafts via gravity alone. I would take out the balance shafts and visually inspect both the bearing and shaft oil surfaces to make sure there is no scoring or signs of mechanical interference between the shaft and the bearing surfaces. Then reinstall them with a coat of engine oil on the bearing surfaces and check to see if they spin freely from the force of gravity on the counterbalance weights. Here is a youtube video of a mechanic spinning the balance shaft to find the proper counterbalance location:


In the video you get an idea of how the balance shaft spins freely by hand.

You don't want to install them if there is metal on metal contact due to the bearing lip being deformed from being pressed in, this will most likely cause premature balance shaft failure and cause your engine oil to get metal debris in the supply.

 

Stock dampener is used in most big builds, stroker no stroker.

Completely misguided statement that you have to replace it: read discussions rather then taking one mans input for fact.

Benefit of aftermarket dampeners was never quantified, ie measured and verified.
It’s speculation- some of it plausible - but nobody denies stock to be great.

 

"You don't want to install them if there is metal on metal contact due to the bearing lip being deformed from being pressed in"

So I checked that there was no friction or edges. Actually I did have the one of the bearings deform slightly causing the shaft to only go in part way easily. I took that bearing out again, and put in a brand new OEM bearing. So theoretically I checked carefully but even when in neight shaft spins freely. As if the bearings were 1/2 thousands smaller than the ones that came out years ago.

The rear shaft was easy to confirm that it was not spinning freely. Should that shaft also fall with gravity as easily as the oil pump or front shaft as shown in the video?

Right now I am only identifying the oil pump side shaft as too stiff.

Is there anything understood between OEM vs the ACL bearings? tolerances, etc?

 

I was able to use ACL bearings with no issues. Both shafts should be able to rotate freely just like in the video.

 

I have taken both shafts out again and inspecting the shafts themselves seems like they may have some rough surfaces at the edge of the bearing races. I probably need a machine shop to polish them. Is it possible to do that myself, or DIY somehow?

I can't tell if the bearing themselves that are in the block are damaged in any way, but they went in easy enough. The OEM bearing however has a noticeable lip in the inside where the seem is. But the ACL bearing does not have that 'bump'.

however it feels like maybe the bearing gets smaller as its inserted. They certainly don't just fall to rest via gravity. They both require force to turn.

 

My OEM never replaced shaft bearings don't "fall" without a little force.

I would say it's normal.

 

So if I am understanding this correctly as I am going through a rebuild process myself. The balance shaft is recommended to be removed if going with forged internals ( Eagle H-rods / Wiseco HD Pistons )? Why is this? I was going to keep the balance shaft.

I apologize if I understood this incorrectly lol.