I had a big block come apart on the dyno years ago. It had good oil pressure when it spun a rod bearing. We never figured it out exactly but part of the problem in my case might have been poor oil volume. Pressure was high but volume might have been too low. The other issue in my case was tight clearances and heavy oil. I used some 20/50w which might have contributed to the problem. I was also using a fairly inexpensive connecting rod which might have been part of the problem. Hard to say when just one fails. Could be something about that particular rod or it could be something about the oiling to that one rod.

I think .002 is fine with high quality machine work but the taper side to side, roundness, big end bore... all need to be very acurate to get away with it consistently. If you machine shop can't deliver very high quality machine work than better to have a little extra clearance.

Your oil pressure was a little high, especially at idle, I wonder if you had a restriction somewhere?

Also rule of thumb for oil pressure is 10psi per 1000 rpm , 55psi at 6000 is a little low especially with that thick oil .... but that could have been the bearing going away at that point ?

What oil mods did you do Dave and why not try 10-30. I switched over from 20-50 years ago and my engines love it.

You also may want to step up to SPS2000 (ARP)rod bolts. Cheap insurance.

I was always under the impression that when the bolts were changed the rods got resized.

I have run coated bearings that tight without any problems, and at higher RPM. I was running 10W-30 oil, but 15W should have been fine. Mine have all been big blocks with full groove main bearings to improve rod oiling.

It does not matter what the first number is when looking at the grade of an oil. I don't remember off the top of my head but the winter grade is checked at 32* and colder as the number goes lower. He was still using a 50 grade oil. I don't know where Gibbs oil is blended at, but if it is on the high side ( so almost a 60) that oil was too thick for that clearance. The spread for any given grade of oil is very wide. Cheap oils run in huge blends can vary in grade from lot to lot. One lot may grade at the top (almost a 60) and the next lot may be on the low side (almost a 40).

There is a reason some oils are $8.00 a quart and some are $24.00. It pays to spend some time researching who these companies are, what base stocks they are using (probably the LEAST important part of any oil...but the company can save $$$$ using a cheaper base stock), what the additive pack is and where they put the oil in reference to grade.

When you start talking about squeezing down clearances and things like that, or using alternative fuels, it pays to do some research. And get on the phone and talk to themes guys. Every oil guy I have ever spoken to has been very frank about the questions I ask.

I think the single groove main and the plugged driver side oil galley contributed to the high oil pressure.

I called Gibbs and told them the combo and bearing clearance and they recommended the xp4 15/50. So that's what I used. I have always used a 20/50 because of all the internal leaks. Lifters being the biggest leak.

15/50 is only 15 vs 20 when cold. Hot 50 is 50. Personally on non power adder stuff i see no reason not to run 5W30 unless it is a combo that runs a lot of oil temperature.
Doug

Sorry to read this.

It's a shame, I just let a stock bore 360 go for a song because I was tired of looking at it.

You can't fault a guy for doing what you are told. I tried to see where that 50 Is supposed to measure at but they don't give it out. Or I just can't find it.

I don't think many other oil companies would call out a 50 for those clearances but I could be wrong.

I had 20-50 VR1 to use in mine but after soaking the roller lifters in it and seeing how thick it was went with Brad Penn break in oil on the dyno. I'll use their 10-30 now that it has been ran.

I can tell you this, when using 20/50 hot oil pressure was 15-20 at idle and 55 thru the traps using full groove bearings. I didn't know what to expect for oil pressure on Dyno with single groove and plugged oil galley Dr side. Thought too much would be better than not enough or too low.

Oil mods were open up all oil galleys. 1/2 and 5/16 from oil pick up thru main rear cap to plugging the Dr side galley which only feeds the lifter galley.

Dave... those pressures are VERY high for those
clearances... I have never had over 70# cold and
25-30 hot.. when pressure is high you are reducing
the flow.. remember pressure is a restriction in
flow... I use the half groove mains and turn higher
rpms... but I do use .003 and .003 on my clearances
on all my junk... I balance out my oil pressure once
I see what it is both hot and cold... but I wouldnt
make a dyno pull or a pass with the pressure you stated

15W/50 is NOT like straight 50W. Straight 50 is like syrup when it's cold. To put it simply, or at least how it was explained to me, was that multi viscosity oil, the first number is basically the Winter or cold viscosity, with lube qualities of the heavier weight when the motor reaches 212*. For the oil to actually get to the 50W viscosity takes the high temps. This is done with "viscosity modifiers". The cold or Winter viscosity number is based on how hard the oil is to pump through a given orifice at low temps and has to meet pumping pressure requirements based on temps and test orifice size. So what does all that mean? Simply put the 15W/50 oil MUST pass SAE J300 standards of a straight SAE15 to be labeled as such, as well as passing the 50W SAE J300 standard at 212* So that said, based on average dyno room temps and his bearing clearance, no way should 15W/50 be too heavy when cold. Factory motors used to run as tight as his and straight 30 was what most everything came with back then and they weren't grabbing bearings, even in extremely cold temps.

I don't know what caused his issue, but I highly doubt it was the viscosity of the oil, the lack of full groove bearings, or similar.

Of all people, the ones at Gibbs, who he called, should know the characteristics of their oil.

I dont care what the viscosity is.. his pressure is
HIGH... pressure is a restriction in flow... PERIOD

I understand that......but some were saying the 15W/50 was like 50W when cold and it is NOT. Would you think straight 15W was too thick given his combo?......No and neither would anyone else and that is the SAE standard that 15W/50 oil MUST meet when cold. My point was that is wasn't the oil that caused the problem.

He said he had .002. Well how was that checked? With plasti-gauge or with mics. And if mics were used, was it only checked 90* from the parting line in a torqued rod, or in several places. The rod could have been out of round, or the crank pin had taper or wasn't round. .002 in one spot, doesn't mean it had .002 everywhere. I still think it was just tight for some reason. If you want to run em tight, that's fine, but it better be right everywhere