Oil Squirter Notches in Rod Bearings

[Blown7]

Yeah, I was thinking about that too. But, didn't AMC design the engines to have squirter holes in the bearings?

Our rod bearings didn't look so hot after only 300 miles on the last rebuild, and there were no holes in the bearings. But, seeing some of the other mistakes the machine shop made, I don't know how good of a job they did on the crank and bearings, so I don't know what might have been the cause.

Squirter holes are a carryover from the 1950's when engine designers thought the extra oil was necessary on the bores. since the 1970's engine designers have found then to be unnecessary. I don't have them and my bores are just like new.

Have you posted any pics of the old bearings?


Jeff

[1980_Cj7]

Jeff, no, I never got any pics of the old bearings. I don't know if the new shop saved them for me or not. I'll ask when I take these new ones back tomorrow. I know they didn't look that great to me, and the new shop concurred. There was no copper showing or anything, but they were showing uneven wear/shining spots. I think it was to one side if I recall. I'll try to get them and post some pics.

Now you have me wondering if I should go with the squirter holes or not. I could always just eat the cost of the set I modded, and put ones in without the holes. The new shop didn't feel they were needed either. Decisions, decisions.

[jeep_man_401]

I know they didn't look that great to me, and the new shop concurred. There was no copper showing or anything, but they were showing uneven wear/shining spots. I think it was to one side if I recall. I'll try to get them and post some pics.

Isn't uneven or wear on one side signs of a not correctly seated bearing and/or bent rod?

If the engine won't see a ton of HP or turn super high I wouldn't worry about the bearing holes. It still has to go through the little squirt hole. I think maybe some more study is needed on this.

I would suppose the rods for the stroker motors don't have the squirt hole. What was the cause of the old bearings going? Did they have the squirt hole?

[Blown7]

There was no copper showing or anything, but they were showing uneven wear/shining spots. I think it was to one side if I recall. I'll try to get them and post some pics.

Usually shiny areas to one side is indicative of oil overheating problems. If the shine is to the connecting rod to connecting rod side, it indicates not enough rod to rod clearance. If it is to the cheek side there is not enough radius in the crank throw.

Jeff

[Blown7]

Not to sound negative, but I think you may bleed off too much oil from the connecting rod journal with that big of a groove. The squirter hole only lines up with the oiling hole on the crankshaft under pressure once every revolution. Connecting rod width is controlled so that the oil stayes on the journal long enough to act as a barrier for high loads and heat disappation. Usually the width is kept within .003 thousanths to control the bleed.
I think your looking to save the pistons and bores (which I think is counter productive and yes I remember your last problems) at the expense of the connecting rod bearings and crankshaft.

You have to remember your connecting rod only gets oil every 360 degrees of crankshaft rotation, unless you have a cross drilled crank.
Just my two cents FWIW.

Jeff

Let's explore this a little further.

If you look at the timing of the oil flow through the rod journal passages on a standard crank (not cross-drilled) with half groove main bearings, the rod passages are fed oil through only 180 degrees crank rotation - and it looks to me that the timing of this oil flow relative to the power stroke is random at each journal.

I don't think these squirters are actually applying oil directly to the bores at all, rather, they simply add more total windage. Well, leakage past the edges of the rod bearings ought to do this job sufficiently.

My machine shop gurus suggest that the rod squirters are not necessary with todays oils and in fact may lead to excessive oil consumption by overwashing the bores. It does seem to me that not allowing flow through the squirters would help maintain film strength on the rod bearings, especially if they are not getting oil pressure through the full 360 degrees of rotation.

I am still torn on the full groove main bearing idea, simply because of my observation on two high time engines that had them and they did not seem to be worn excessively.

I do not however fully understand the dynamics of 180 degree rod journal oiling. As I said the timing of this seems random to me from one rod journal to the next - some start oiling just after combustion and some long after (maybe it does not matter). It does however seem obvious that full groove bearings or cross-drilled cranks would be feeding the rod journals at all times, and I cannot imagine why that would be a bad idea since it does seem as though the rod bearings suffer the most.

What say you?

Found the formulas it's under Journal Bearing Lubrication analysis in the Machinerys Handbook.

First find l/d ratio= length of bearing including shaft deflection and misalignment (should be maintained below .0003 thousands per inch of length.
Bearing pressure PSI = Pb= W divided by Kd
Oil Temperature rise thru bearing try to keep under 20 degrees F
Sleeve bearing pressure for a auto engine between 500-700 PSI for the mains
800-1500 for a diesel
Torque parameter vs. Eccentricity Ratio for a stock 401
l/d ratio is 1.375 = 3.6 torque parameter
Then flow factor of oil=q

Much more things involved and you have to do your own figures but add hydrodynamic action plus the highest RPM of the engine to find the bearing speed in FPM.


To make a long story short, in my case I need to run SAE 50 oil at 6000RPM with .0032 Main clearance to take the hit of Nitrous with non full groove bearings without overloading the bearing.

Jeff

[1980_Cj7]

I just got a picture in my head of Albert Einstein at a chalk board...trying to figure out if he should use oil squirters in his 401!

I had the rod bearings bagged and numbered which rod they came off of, when I took the engine to the new machine shop, but I don't know if they kept them like that...or kept them at all for that matter. I'll ask tonite, and try to retrieve them.

The other thing I was thinking, is that although the hole in the bearing looks pretty big, look at the path the oil has to take from there. The "V" in the rod is smaller, then the groove around the rod bolt is even smaller yet. So, the path necks down noticeably.

I'm gonna talk to the machine shop tonite and see what they think. I also need to ask them how much experience they have with AMC's though. You'd think there wouldn't be that much difference from one brand of engine to another, as they all operate basically the same, but I'm really starting to wonder.

[1980_Cj7]

Well, just returned from the machine shop. After a lengthy discussion with a man with a lot of experience that I highly respect , I decided NOT to use the bearings with the squirter holes. He told me, as have some of you, that it was old technology that has been gotten away from. He said he's watched engines running with no oil pans (I forget what he said was hooked up to them) and said you wouldn't believe the amount of oil flying everywhere. So, for the sake of not wanting to take any oil away from the rod bearings, I told him to just put bearings in without the holes.

Anybody in the market for a good buy on a set of brand new "custom" .020 over rod bearings with oil squirter holes??? I'll make you a real good deal.

I told him to make this to be the best engine he's ever built, becuz I ain't doin this again! I almost wish I'd never heard of a 401, but hopefully, soon, when we have it back in the Jeep and are almost keeping up with Fuzz, we'll forget about all this. Heck, if it was easy, everybody would have one, right?

[82Waggy]

I told him to make this to be the best engine he's ever built, becuz I ain't doin this again! I almost wish I'd never heard of a 401, but hopefully, soon, when we have it back in the Jeep and are almost keeping up with Fuzz, we'll forget about all this. Heck, if it was easy, everybody would have one, right?

These issues you have been having are not unique to the 401, or any AMC for that matter. Bad machinists are everywhere.

Last summer my buddy had a set of 351 Cleveland heads rebuilt, blueprinted the whole motor. They did not hone the new bronze valve guides for sufficient stem clearance. During cam break in at 2000rpm an exhaust valve seized, bent pushrods and valve stems, filled the engine with bronze dust, and stuck two valves open. Can you say" DO OVER"!

Tore it all back down, cleaned it out, new bearings again, reworked the valve guides, new gasket set again, more dollars. Been running great ever since (for a Cleveland anyway). We put KB pistons in it by the way.

Never time to do it right. Always time to do it over.

[seth gordon]

The oil squirt holes are thought to put some oil on the cylinder bore and also some on the cam lobes; how efficient or important this oiling system is could be argued. What is known is that factory cranks must have the oil holes radiused & chamfered. The use of full groove bearings is definitely not recommended. At one time, Randall engineering recommended that the main journals be grooved. Currently, cross-drilling the crank is the general method for avoiding oil starvation.

Seth