Squirt hole or no squirt hole?
Thanks FABO, always great feedback from the community. You all confirmed what I was thinking. Anything that moves a little more oil around the inside of the motor can’t be bad. For those who were wondering, Sealed Power makes rod bearings with the notch for the squirt holes.
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Just so anyone else who comes along and reads this will know...as RustyRatRod posted above that squirt hole was to put MORE oil on the cylinder walls. That was great science then, but bad practice today. And I’m not trying to talk you out of anything.
Cylinder honing and piston rings from the 60’s, 70’s and even the 80’s are Stone Age compared to what we have today. Not even close. Today, the last thing you want (or need) is oil blowing out of the rods onto the cylinder walls. All oil retention for ring and piston skirt lubrication is controlled by the honing process...that is the surface geometry including cross hatch angle.
Today’s cylinder wall finishes SHOULD have a measured surface finish that has the correct valley depth (Rk, Rpk, Rvk) and a plateau surface (part of the RA measurement) that gives the proper bearing area for ring seal and the correct valley depths for oil retention.
Crosshatch angle matters because the de facto 45 degree included angle is ok for quite a few applications. But, today it’s more involved than that.
A steeper included angle (say 50 degrees) will rotate the rings faster, which may be good, or not so good, depending on the application. As engine RPM increases, that 45 degree crosshatch may be too steep and cause the rings to rotate too quickly. So maybe a 40 degree crosshatch is called for.
The other fact of crosshatch angle is oil retention, or more correctly stated, how much oil is pulled down by the scraper (second) ring as the piston goes up and down. The steeper the crosshatch angle, the faster the rings turn, but it also allows an easier path for the scraper to pull oil down off the cylinder wall and back to the pan. The opposite is true. A flatter crosshatch angle will retard oil migration down the crosshatch and slows ring rotation.
So many times with power adders or certainly with alcohol based fuels and/or high RPM you need to flatten the crosshatch angle down to keep some oil on the cylinder walls.
My point is the days of just running a hone down the bore and calling it good are long gone. Even with the archaic 5/64 ring pack, there is power, reliability and ring seal gains to be found in a decent hone. As we slowly crawl away from (we should be sprinting to get there but adaptation to technology is hard for some...for me it’s computers and phones...I hate this junk so I’m slow to warm up to new stuff, but in the automotive world and specifically engine building I go for new tech like a baby to the teat) the old, nasty, thick ring packs to the new, thinner, better sealing, lighter ring packs the surface finish of the cylinder walls should follow that technology.
And to that end, even a marginal cylinder finish today requires much less oil on the cylinder walls than it did back in the day.
If your engine shop doesn’t have and use a profilometer on its bores (and deck surfaces too) you need to find a better shop.
In 1995 a profilometer was considered a luxury. Today it is mandatory if you want to know what you have and if what you have is the correct surface geometry.
Just my .02 for the day, and it worth less than you paid for it.
