Too much bearing clearance?
Originally Posted by racer7088
You'll be totally fine. Your NOS tune is what you need to worry about. I would have reversed those specs with the rods at .0025 and the mains at .0020 but they are both within range and the crank and rods will live longer than running them tighter even though you may see lower oil pressure than a dead stock engine. Less pressure in your case if from more oil flow through the bearings.
I agree, your clearances will be fine. I'd run a 40 or 50 weight oil though. My clearances are .0016"-.0018" on the mains, and .0018" on the rods. I run 10w40 oil and see 55psi at idle, and 65 at cruise.
Thread Starter
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From: St. Louis, MO
Well, I got the motor in. In addition to a major oil leak coming from the rear, my oil psi is only at 20 psi using 10w40 and it don't rise like it should when driving. It rose maybe 10 psi when I was up at around 4000rpm. Could a old/bad oil sending unit make the gauge read incorrectly? I forgot to change that out. 
FormerVendor
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Originally Posted by shortdog
Well, I got the motor in. In addition to a major oil leak coming from the rear, my oil psi is only at 20 psi using 10w40 and it don't rise like it should when driving. It rose maybe 10 psi when I was up at around 4000rpm. Could a old/bad oil sending unit make the gauge read incorrectly? I forgot to change that out.
I had the same thing a long time ago and it was the oil pressure sending unit was broke but not all the way around . The oil pressure is a variable resistor ,the lower part of the sending unit is sealed with a diaphragm that raises up and down with pressure and there a rod that is pushing against it ,the rod moves the resistor up and down and then move the needle ,Now if its cracked the rod will not move enough and cause a falls reading
Thread Starter
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From: St. Louis, MO
Well, I just just fix my oil leak and pressure problem with a part I should've replaced in the first place: You guessed it, the oil sending unit. I reached back behind the intake, removed it and it practically fell apart in my hand. This $40 part was the same problem I had on my last motor. With the new part installed, my oil pressure went up around 60psi on a cold start and 35-40 hot. Thanks everyone. 
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Originally Posted by GOaT Cheese
.030 rod side clearance would be catastrophic in any engine that is not designed and built specifically for that type of oil wash. When I say that bearing clearance is not as much of a factor I am assuming a realistic parameter, such as a working spec of .0009 to .002. With a rod bearing clearance range of .0009-.0020, the side clearance will have a much greater affect on oil presssure than will moving the bearing clearance around within the specified range.
This is simply just wrong. Many high performance engines will run close to this spec and beyond. I have ran several aluminum rod engines with .045-.080" (not actually by choice, but because of the way the crank was ground on the cheek clearances) and had 0 problems and wonderful oil psi both hot and cold and both at idle and HIGH RPM. Sometimes experience well outweighs what you read in a book.
Lots of things work out to be like this in this area of performance rebuilding. OE stock specs are not always what is preferred when building High Performance, alot of times YES, always NO. 
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Aluminum rods are a completely different scenario. Everything needs to be alot looser with aluminum. And speaking from experience of many years now, I have FOUND, not read, that .030 rod side clearance on a steel rod engine is too much. I guess it comes down to differences in engine building techniques. I have always liked building tight engines that are assembled perfectly.
Originally Posted by GOaT Cheese
the rod side clearance will have the most effect on low speed oil pressure.
Bret
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Let me clarify my position. If the rod side clearance is excessive ( .025"+), at high RPM a "pinwheeling" affect takes place. This "pinwheeling" actually sucks, or throws, too much oil out of the rod journal through the excessive side clearance. Centrifigul evacuation if you will of the rod journals oil supply. Not good in my book. Through EXPERIENCE, I have found that on a steel rod engine, a rod side clearance of between .012 and .015 works the best.
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I can't go back and read all this stuff but I guess I already said that NASCAR and F1 have run pin guided rods that have fairly huge side clearance sometimes as much as .100 and they do not have oiling problems either. The bearing clearance will set the oil flow out of the rods unless you can run some extremely tight side clearance and the rod journals on the crank were made consistently higher.
If you had the same .002 of oil clearance and then had .008 side clearance the side clearance will be just as much of a limit to oil flow. The same with .003 of oil clearance and then had .012 side clearance. If you have .015 and you still have the normal .002-.003 oil clearance then the bearings are limiting the oil flow more.
If you had the same .002 of oil clearance and then had .008 side clearance the side clearance will be just as much of a limit to oil flow. The same with .003 of oil clearance and then had .012 side clearance. If you have .015 and you still have the normal .002-.003 oil clearance then the bearings are limiting the oil flow more.
Originally Posted by GOaT Cheese
Let me clarify my position. If the rod side clearance is excessive ( .025"+), at high RPM a "pinwheeling" affect takes place. This "pinwheeling" actually sucks, or throws, too much oil out of the rod journal through the excessive side clearance. Centrifigul evacuation if you will of the rod journals oil supply. Not good in my book. Through EXPERIENCE, I have found that on a steel rod engine, a rod side clearance of between .012 and .015 works the best.
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Unless I'm mistaken, "pinwheeling" only occurs in cross drilled cranks and
impedes oil flow to the bearings at high RPM?
Maybe I have the term mixed up with another...I recall reading that recently.
impedes oil flow to the bearings at high RPM?
Maybe I have the term mixed up with another...I recall reading that recently.
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Originally Posted by Adrenaline_Z
Unless I'm mistaken, "pinwheeling" only occurs in cross drilled cranks and
impedes oil flow to the bearings at high RPM?
Maybe I have the term mixed up with another...I recall reading that recently.
impedes oil flow to the bearings at high RPM?
Maybe I have the term mixed up with another...I recall reading that recently.
Originally Posted by GOaT Cheese
Let me clarify my position. If the rod side clearance is excessive ( .025"+), at high RPM a "pinwheeling" affect takes place. This "pinwheeling" actually sucks, or throws, too much oil out of the rod journal through the excessive side clearance. Centrifigul evacuation if you will of the rod journals oil supply. Not good in my book. Through EXPERIENCE, I have found that on a steel rod engine, a rod side clearance of between .012 and .015 works the best.
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Originally Posted by edcmat-l1
If the side clearance is that critical to oil pressure, would 2 different engines, both with the same bearing clearances, but 2 different side clearances, one loose one tight, have 2 different oil pressures? Identical engines, nothing dif but rod side clearance.
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Originally Posted by GOaT Cheese
Yes, I believe so. I have never done that experiment in a controlled environment, with two seperate identical engines. But I have had customers bring me "fresh" engines from other shops, that had low oil pressure, and upon disassembly I found excessive side clearance. corrected the issue, and had proper oil pressure afterwards.
99 per cent of these aftermarket cranks and rods have around .020 -.025 side clearance and if you run tighter oil clearance they will have higher oil pressures. They also are more likely to spin a bearing if they are too tight even though the oil pressure will always show higher when you tighten the clearances up. If you go under .001 clearance and use the right springs you can achieve over 100 PSI oil pressure and can almost blow the filter right off the engine as well as probably spinning all the bearings.
High oil pressure does not mean that you are getting the right amount of oil by the bearings and also does not mean you have the right clearance but rather it is just a measure of restriction and oil viscosity really.
If you run the right clearances you will have lower oil pressure than our example above and also will not have any bearing problems with higher rpm and more power. Oil pressure is a measure of restriction and if you have much higher oil pressure it means less oil is flowing through the bearings if nothing else has changed not more.
FormerVendor
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From: Houston, Tx.
Originally Posted by GOaT Cheese
Yes, I believe so. I have never done that experiment in a controlled environment, with two seperate identical engines. But I have had customers bring me "fresh" engines from other shops, that had low oil pressure, and upon disassembly I found excessive side clearance. corrected the issue, and had proper oil pressure afterwards.
Saying all this I don't mind having tighter than .0025 side clearance either but more engine builders I know LIKE the side clearance to be .020-.025 so 90 percent of your aftermarket rods are made like that. A SBC rod journal is 1.900 across and the rods are usually .940 wide so you are right at .020 basically right away and the journal width is usually even a little over 1.900 in reality so you end up at .020-.025 usually.