APE Heavy Duty Engine Studs.

:huh: I run top end oil restrictors on all my turbo Z's along with ape H. D. studs......I've never had a problem with too little oil to the head/cams :S my .02

4TheKZ1000 wrote: I looked into this issue and here again is the facts getting in the way of a good story.

I ran my bike with factory studs until warm. 3-psi oil pressure.
I ran my bike with APE Studs until warm. 7-psi oil pressure.

The oil pressure is taken before oil enters stud passage.

The increase in psi is a clear sign of restriction in the oiling system.

Stock Stud Diameter: 8.0 mm - measured in the middle of stud.
APE Stud Diameter: 9.50 mm - measured in the middle of stud.

Stud oil passage Hole ( Cylinder Block ) narrowest point: 10.40 mm
This was found in middle of block, were castings line or convergence was found

Stud oil passage hole ( Cylinder Block ) widest point: 10.80 mm

Measured several time with digital gauge.

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UPDATE:

I ended up drilling the entire length of the cylinder oil passage out to 1/2 inch or 12.60 mm.

I also drilled the first 1/4 inch of the head oil passage bottom up to the oil feed holes to 1/2 inch or 12.60 mm.

It brought the oil pressure back down from 7 to 3.5 psi at idle. When I bang though the gears it runs about 9 psi. I am getting a lot more oil to the head under acceleration, no way that can be a bad thing. There are no leaks.

I went from 2.40mm stock oil passage to stud clearance to a 3.10mm modified oil passage to stud clearance.

Ok, so here are the numbers. I don't just listen to others make an argument based on what this guy did or what they were told. I did the homework and the modification and think I made a case that holds water...... I will let you make the call if it is an improvement or not.

Does this need to be done: NO. As many have said, 10's of thousands of these stud kits have been sold without problem. Some of the forum guys run them just fine and never burned down a cam. If there was a major problem, it would have come to light by now.

As Larry said, you guys just like to F__k with your bikes ..... and he is 100% right. Its a street mod and no improvement has been spared. If I can improve it, I will. In my mind this is a KZ 1000% improvement.

When I mentioned this in the Orient express thread it was based on my findings from years ago on a particular tight casting that was probably the exception than the norm BUT I always check those oil passages now as a matter of course, just in case, and on something like that drag bike with std block and no external oiler it's a small detail that took minutes to do, cost nothing and could save the top end and $$$$ in an extreme circumstance.
Ok! there have been countless HD studs sold with no problem and I don't go drilling out every block for the sake of it but with the increasing trend for them to be needlessly fitted in stock engines as a replacement for the std ones there is possibly a slight increased chance of oil starvation to some motors.
Maybe this explains why some cam bearing shells show signs of overheating and bubbling of the white metal or maybe not.
Either way, as long as it doesn't have a negative effect it's worth looking at when the motors apart and no harm done.

I don't really care what larry says, does or thinks. Its free to drill out the holes. Its not like its a epidemic and everyone running hd studs to tear there motor down immediately. lol But while its apart, why not? NO, it probably hasn't caused engine failure. But the way I look at it, Its free to drill it out while its apart. Its cheap insurance, And I guarantee the more oil you get to the head the better, Espically when its already restricted.