NSTY WS6

iTrader: (5)

This is good info. I've been looking for this. Erik, why would he need to worry about his nitrous tune? I am also going to be running a forged 347, stock 02 crank and callies compstars. What would you suggest? How much hp can you get by having a lil more clearance in the mains/rods?

Ferocity02

iTrader: (60)

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.

shortdog

iTrader: (1)

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.

racer7088

Could be something jamming the oil pump bypass. Also the pickup may be bottomed out of something blocking it. Also could be the O-Ring allowing the pump to suck air. There's many possibilities.

mikey

iTrader: (6)

What is your oil pickup to pan clearance?

ls1408cp

iTrader: (37)

thats what I just said on the local board. He just needs to go though and check everything.

Randy WS6

iTrader: (69)

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

shortdog

iTrader: (1)

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.

helicoil

iTrader: (104)

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.

GOaT Cheese

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.

SStrokerAce

iTrader: (2)

No it's not.... it's the clearance between the journal surface and the bearing as Erik said.

Bret

GOaT Cheese

I disagree.

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.

racer7088

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.

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.

GOaT Cheese

It is exagerated in cross drilled cranks, but it occurs on all setups. I simply believe that anything over .020 (give or take) is excessive rod side clearance for 99% of all street strip, and even alot of max effort drag race applications. Racer likes to argue that NASCAR and F1 use cheek clearances up to .100, on those applications, with the dry sump oil systems that some of those engines use, I'm sure it works fine. It simply comes down to How I build my engines for myself and customers alike.

edcmat-l1

iTrader: (10)

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.

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.

racer7088

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.

racer7088

We do that kind of controlled experiment all the time on the engine dyno and side clearance has little to nothing to do with it. You run the same .025 side clearance and rods and mains at .0015-.0020 oil clearance and then the same engine at .0030-.0035 oil clearance and its a dramatic difference in oil pressure especially at hot idle when the pump isn't spinning as fast. One will have 50 psi and one will have 10 psi at idle

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.