While visiting an FE Engine site I encountered a question from an inexperienced member asking a simple but thought provoking question. It seems his old rod bearings had a V notch on the mating edge, opposite from the tang that aligned with the rod bolt. (see photo). His new bearings had no such notch. He wondered if he could use the new bearings as they come or should he add the notch like the factory bearings had. They align with the squirt holes in the rod that I’ve always understood provided some oil to the cam lobes. I seem to remember those notches in the factory bearings I’ve removed during various rebuilds over the years. I have my 389 Pontiac short block assembled but I haven’t put the pan on yet. So I looked at a new rod bearing. No notch. I already tossed the old ones so I couldn’t check. So I’m wondering if the lack of oil notches in replacement bearings might be a factor in the cam/lifter failures we’ve all seen in recent years. Would it be a good idea to add a small oil path (notch) in the bearing to feed the notch in the rod?
As a lifelong Chevy guy I can tell you that the SBC oil notches in the rod caps were eliminated in the late ‘60’s, apparently Chevy engineers deemed them unnecessary. If someone felt they wanted to add them in newer rods or bearings that came without them it won’t be detrimental but also may have no real benefit. JMO
The gentleman who posed the FE question was leaning towards adding them to his bearings and I was thinking of doing the same to my Pontiac. I figure that it can't hurt. It might cost a pound or two in oil pressure, but it just might be the little touch that helps prevent a flat cam. I consider that a good trade.
I wouldn’t do any cutting through the shell and bearing material overlay for fear of destroying the bond between the base material and the overlay. You’re probably going to introduce at least some level of micro cracks in one or more of the 16 cuts you make, so why risk it? You probably won’t see the micro cracks and delamination with the naked eye, but there’s a chance they will open up under load at some point.
Pretty sure the bearing company knows more about them then we do, leave them alone. I've built plenty of Pontiac with no oiling issues. The oil is coming out of the crank, just what it is the notch would do for oiling?
The tang was an insurance policy against the rod bearing spinning under adverse conditions such as extreme rpm when the rod distorts some.
That’s always a strong argument, but in these days of cost cutting, eliminating a production step is mighty tempting to the bean counters. It doesn’t affect the rod bearings performance but it could affect the factory’s plan for additional cam lobe oiling as the RPM rises. Then again, I’m sure there’s plenty of oil slinging from the rod journal due to rod side clearance. I’m in no way metallurgically savvy enough to know about the makeup of the bearings themselves but many race engines get their bearings clearanced on one side for changes in the journal radius. I wouldn’t think that a small notch in the end surface would hurt. But it might.
I agree with Finn regarding the potential for delamination at the edge of the shell. I also fail to understand how the notch on the edge of the bearing affects oil to the cam or oil distribution whatsoever.
As you can see, this question was somewhat thought provoking. Why did the aftermarket suppliers do away with a design feature that the factory engineers decided was worth the cost. In my case, there apparently weren’t any factory oiling notches in the rod bearings. The tangs are machined into the same side of the rods as the squirt holes. They would have to be very narrow notches. The notches in the Ford bearings I read about appeared to be a 1/8” x1/8” V shaped notch. So why have squirt holes if there’s no direct path to feed oil to them? It doesn’t really matter, just pondering the mysteries of our automotive universe…..
Engineers had nothing to do with it. Bean counters figured out they could save 1/4 of $.01 on the cost of the rod and the benefit was less oil on the cam would wear it out prematurely so they could sell more repairs. I used a triangular file on the rod cap putting it back in. Just enough oil went around the bolt. None of my rebuild engines ever lost a cam.
I guess I read too many “How to build a (your engine here)” articles. Most stock engines I have messed with have little squirt holes in the connecting rod parting surfaces on one side. From what I have read, these holes point towards the cam. The holes are supposedly there to lubricate the opposing cylinder wall and the cam as the crank rotates. Is that an old wives tale? Have I been doing it wrong all these years?
Oh yes of course! It’s been a while since I had my head into an engine that deep. In that case I’d expect to shell to have a hole a little further up, about near the 45* location.
Come to think of it, I haven’t rebuilt any engines beyond 1969. I think I did a GM 60 degree V6 once but other than that most everything that I tore into was old. I’m not primarily an engine guy, I know enough to fix my own junk (I thought) but no one’s asking me to be their engine builder.
The tang is solely there to properly locate the bearing shell and cap. It’s an assembly aid. If you’re relying on the tang to stop the bearing from spinning, you have other issues. Bearing crush is what stops spinning..
Im probably wrong but I thought on pontiacs that hole squirted oil onto the cylinder wall for the piston skirt. Then discontinued it because it caused a small amount of oil consumption. I think I read that somewhere... maybe I dreamed it...
Whether that v-groove was meant to spray oil at the cylinder wall or cam I don’t think it’s necessary any longer, even Carrillo, among other HP rod manufacturers don’t put that detail into their rods. And with the price of Carrillo or other reputable rods if they felt it was necessary they no doubt would include the notch. Adding a notch won’t hurt anything but whether or not it helped the OEM’s sell more cams is debatable.
If the side clearance on the rods is correct then there will be plenty of oil getting thrown everywhere.
I think there is a direct path very briefly as the oil hole in the crank passes the squirt hole. It provides a metered flow every revolution. I seem to recall this from years ago but don't have a rod and crank available to verify the placement.
Cabrillo and other premium rod providers build primarily for strength and expect a performance engine to get more inspections and maintenance than a typical street engine but seeing as how Chevy did away with the squirt holes years ago, they probably weren’t mandatory. My thought, as I read the other gentleman’s post was, did the elimination of the squirt holes in the aftermarket bearings happen to coincide with the increase in camshaft failures. But if Chevrolet stopped them in the 60s, then there’s no correlation.
@dogwalkin that's what I always heard too. Built a few Pontiacs in my day and I remember the rods always installed one way and that was because of the spurt hole, "IF" I remember it always faced in, this was the oil out of it would find some of its way onto the top inside of the cylinder walls and cam. Makes sense since oil runs downhill, help keep the top side of the cylinder oiled. I always ran clevite bearings and they always had them. Honestly if it were me I'd put them back into the bearing... . ..
I think that was the design for engines with the squirt holes and a notch in the bearing shells but the path gets shut off when you install a bearing with no notch. I like that metered flow approach.
Careful, that whole discussion about flat cams and todays oils will spin this thread sideways faster than Bill Jenkins could row a four speed!
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