This is probably coming about 10 years after it really should have been documented but I'm going to post it anyway in the hopes these crazy rumors of the Z6 having better oil pump will finally die.

Y7 on the left, Z6 on the right:



With the covers off:



Bare housings:



Z6 oil pump gears in Y7 oil pump housing:



Relief springs:



Minor difference here in terms of the Z6 having larger studs for the pickup tube:




The real difference is right here, the crankshaft. Note how the Z6 crank (bottom) has two oil holes per journal to the Y7's (top) one. Also note the scored crank where the #4 rod bearing spun.



I hope this will at long last dispel any myths about the Z6 somehow having a superior oil pump, literally the only differences are the pump body due to having different dipstick locations, the Y7/Y8 needing the boss for the CKF sensor, and the Z6 for some reason has larger pickup tube studs (8mm vs 6mm)

 

Thanks.

Why did Honda reduce the number of oil holes in the Y7 crankshaft?

Can I assume that the Y8 crankshaft also has only one oil hole?

 

My guess is either to save on manufacturing costs or to cut down on parasitic loss to make a little more power. I really don't know for sure, but I do know the Y7/Y8 really is more prone to spinning rod bearings.

Yes it does, exactly the same crank and rods as a Y7. And on that note, something else I found was the Y7 and Z6 rods are also the same. The Z6 does not as some people have said for years have "beefier" rods)

 

I'll add the link to the FAQs sticky.

 

Nice work! So all else aside can the cranks be directly swapped? Or the Y7/Y8 crank be modified to match?

 

Thanks Ron I intended to do this myself but hadn't gotten to it yet.

Yes. That was actually the reason the Y7 crank came out. I didn't know it had a spun bearing till after I took it apart, the Z6 crank was strictly meant to be a preventative measure as the engine is going in a circle track car.

It can't The holes in the Y7/Y8 crank are drilled at approximately a 45° angle. The Z6 crank on the other hand have the holes drilled at a right angle to crank and they go clear through from one side to the other.

Basically if you want a Y7/Y8 that will take the same abuse a stock Z6 will swap over a Z6 crank.

 

The cranks can be swapped without problems.

 

Any idea where these numbers were derived from? In searching around I can't really find a source but if you search for "D series oil pump flow rates" it pops up every where, its probably where most of those ideas originated from:

D16A6 Oil pump flows 46.4 qt/min@6250rpm
D16Z6 Oil pump flows 47.6 qt/min@6000rpm
D16Y8 Oil pump flows 35.3 qt/min@6800rpm

 

None. Somehow I'm guessing the flow wasn't measured at the pump. The pumps use the same gears, same relief spring, they have the same size passages so the idea that the Z6 pump somehow flows an extra 12qt/min is ludicrous to me.

 

They're also rated at different RPM's, which in and of itself is enough to call that list disingenuous at best.

 

I noticed that.