Hello! I've been doing some homework, and I'm a little alarmed at how tight Nissan specs the oil clearances. Less the 1 thou on the mains, and the same for the big ends. How do these things live with abuse??? The main tunnel can't grow too much with heat?? Big ends is pretty run of the mill econobox specs.

I've built many high power 6 cyl engines, rb,2j and my VQ, all over 1000 to the wheels. And they all pretty much run around 3.5 on the mains and 2.5 on the big ends, and have great bearing life.

Is there a preferred "spec" that a built VH or VK is adjusted to? Again, over 1000hp, and 8-9k rpm, etc etc.

Dave.

I can totally agree. I ran bigends and mains in two blocks due to this and 15psi.

Ended up on the third block giving all the bearings 4 thou clearance, feeding mains directly from factory oil pump and backed boost off to 12psi.

This has held together now for about 4 years, except for the melted piston from a burnout comp.



For a rough rebuild I sanded the bore up in place and whacked a second hand piston and ring back in there.

How rough is that! Still got good compression.

This must be why they are known for throwing bad bottom end wear numbers

Th same way a F1 engine deals with abuse. Closer tolerances, more precise machining, better balancing.

It's not a 60's SBC.

AZhitman wrote: ↑

Tue Sep 01, 2020 3:46 pm

Th same way a F1 engine deals with abuse. Closer tolerances, more precise machining, better balancing.

It's not a 60's SBC.

Good point, I'd tend to agree, only issue is the VK45 in some applications is known for throwing poor UOA and bottom end wear numbers. And it doesn't even seem uncommon that some escalate to rod knock! Mine did..

No disagreement here. Fine engine that was way ahead of its time... but a finicky and temperamental one as well.

Yes, far cry from say, a VQ of any variation which just takes all the abuse you can throw at it it seems.