Guys I need some advise on bearings..

[MadBill]

BUT'
Bill,
Does the circle of an expanded piece of aluminum grow to be larger in diameter, or does it grow to be smaller?..
Ed

As needfor says, the hole gets bigger. The reason I mentioned just the difference in the coefficients is that if the crank and rod were both steel and were at the same running temperature, the clearance would remain essentially unchanged regardless of what the temperature was.

[Ron C.]

Hi Chad, just jumped on here and glad to see you sending it back for that adjustment. I've run into the same deal a couple of times when coating bearings. We both know what it takes to build a competitive engine. And if that's not good enough you can research on this board and read what Darin Morgan says. So stay on course and be comfortable with what your doing.
Blessings........Ron Clevenger.

[dbusch]

wow...and i was thinking about closing up my Honda rod journal clearance from .0023 to .002 or.0018"!!!

[maxracesoftware]

wow...and i was thinking about closing up my Honda rod journal clearance from .0023 to .002 or.0018"!!!

every Engine that has had "Bearing Failures"
on my Dyno ... has been that .002" to .0025" stuff

i Dyno for a bunch of Local Racers and Engine Builders,
as the aftermarket CNC Heads are getting better,
and the ease of just about bolting together a 632 +CID BBC
and making great TQ + HP,
as the RPM levels , TQ, and HP has went way upwards,
the average Racer assembling his engine at .002 to .0025"
has been the most failures on my Dyno so far.

It wasn't as much a problem running .002" or so
when they were making 700-800 HP and lower Power Curves,
less stroke....now as they are building larger CID engines,
turning much higher RPMs and 900-1300+ HP (1500-1600+ w/NOS)
they've went to .003-.004 clearances with great success, no failures.

the Engine Builders i now Dyno for, all run .003 to .004
and strive for .0035"...since they've all switched to .003-.004
i have not had 1 more Bearing failure on my Dyno since !

i personally use .0035 and up to .004 on all my Engines,
i have never had a bearing failures yet !!
Bearings always look brand new.

i just think the average Builder out there without all the Hi-Tech equipment
to check and triple check every Engine component is much better off
with .003 to .0035 -.004 clearances

i'm glad to see Darin Morgan + Reher-Morrison recommend the same.

[Ron C.]

And in the real racing world things don't always theroy out as most will already know. There are conditions were very large rod bearing clearances are used because they do actually close up when race load is applied. For that reason Brad Anderson blown alcohol engines leave the shop with .006 to .0065 rod bearing clearances. Running less has caused seizer problems. It's one of those questions and answers that have to be qualified before answering.
That's my thought's anyway.......blessings........Ron Clevenger.

[Ed-vancedEngines]

Well, I enjoyed this thread, while it lasted. Looks like it is getting ready to play out though.

Here was the engine combination that Chad begun the thread with, and we all, myself included have changed it into talking about mega-cube mega-horsepower engines.

Usually when a good and sucessful engine builder is even asking others for opinion other than what thier gut feels is right, he is trying to justify going against what is proven to be sucessfull for him. I am glad that Chad is sticking with what he knows will work. I do however think that with his 4 cylinder that what he asked about should have also worked with his lightweight oils.

First off, I'm a huge fan of .0030- .0035 rod and main clearance. But, I'm in sort of a bind. I'm putting together my 4 cylinder. It's a KRP block, Moldex crank, GRP rods, 15.2 compression, external oil pump, lots of vacuum. SB2.2 head, Hogan manifold w/ Book dominator. Comp deal, 10k plus rpm. Ultra LW oil.

I thought I might provoke some of you into describing or explaining why the hole would not grow to be smaller. That answer, I do not know. It does seem reasonable to me that the metal would grow in all directions. Engines show me different, but I still wonder.

Ed

By the way, Chad,
How do you find thew Molex webpage? Or do they have one. If not, What is thier phone number?

[Milan..]

Ed , I think those are good questions , I have measured the bore of an aluminum rod after heating it in an oven , to only about 140 deg. And it grew .0002 , then why do most builders want to start with more vertical clearance. And a looser pin too? I like the material expands in all directions thing. Then the pinned lower bearing on a aluminum rod holds the bearing because the hotter it gets the looser it gets?? Thanks Milan

[rskrause]

Food for thought here. I think the common ground has been identified - proper bearing clearance depends on what you are building. A daily driver, a street strip car, a bracket motor, a mountain race motor, or a blown alcohol setup. The OEM motors are in the .0020" range now with recommendations for 5W-30. The daily driver, street strip and bracket motors my buddies and I build have always done fine with 0.0025" on the mains. We run 5W or 10W-30 on the street and street strip stuff and 20W-50 semi-synthetic racing oil on the bracket cars. I don't plan to change this. But if I ever have the opportunity to build a high hp setup, I think I will open things up a bit.

The light oil and the big clearances still has me a little confused.

Richard Krause

[user-9274568]

Ed

Moldex Crankshaft Co.
25229 W. Warren
Dearborn Heights, MI. 48127
313 561-7676

No web site. Prices are fair, work is excellent. This is a 4340 billet, nitride and magnafluxed. drilled pins, balanced, LW. It cost me $1845 to the door. Scat and Crower were $2800+.

[Ron C.]

Ed, Richards comments were my point. The thread was already drifting and my point was.....application is important in clearancing.

I run a 565 big chief centrifical blow gas deal. And I run about in the middle of the .003 to .0035 deal with coated bearings/al rods. This motor makes 1900hp and I run 30 wt Redline syn racing oil. That oil mets a 10/30 spec. actually. The bearings always look good enough to put them back in.
It seems to work for me and I have tried tighter (sub .003) clearances with not good results. Just sharing my story.
Blessings........Ron Clevenger.

[MadBill]

...I thought I might provoke some of you into describing or explaining why the hole would not grow to be smaller. That answer, I do not know. It does seem reasonable to me that the metal would grow in all directions. Engines show me different, but I still wonder...

How about a thought experiment?

First, from textbooks or the net, e.g. http://hyperphysics.phy-astr.gsu.edu/hb ... thexp.html , we find that for a typical steel alloy the coefficient of thermal expansion is about 7.2 parts per million per unit length per degree F.
Therefore a 3' length of very small diameter steel rod, heated from room temperature to 1070° F., would grow in length by 36 x 1000 x 7.2/1,000,000 = 0.259".

If we were to form this rod into a perfect circle, join the ends and repeat the experiment, the circle formed would be 36/3.14 = 11.459" diameter at room temperature. Heating it to 1070° F. would still cause it to grow 0.259" in 'length', but because it is now a circle, this would become circumferential growth, equivalent to a diameter change of 0.259"/3.14 = 0.082". Because the wire is very thin (this is a thought experiment, so let's call it 0.001"), there is no appreciable 'lateral' expansion of the wire (.001" x 1000 x 7.2/1,000,000 = 0.000007"), so the ID and the OD of the circle must both increase by 0.082"

Not coincidentally, this is also the diameter change which would occur if the initial circle were a solid disc 11.459" in diameter (11.459 x 1000 x 7.2/1,000,000 = 0.082"). If it helps, one can visualize the solid disc as being made up of millions of infinitely thin concentric circles of material, each reacting to the temperature change exactly as did our original wire.

Thus, any hole in an object will grow in diameter with temperature at the same rate as the parent material.

[user-z68766209]

Years ago I did some testing on bearing clearance for a bearing
manufacture using steel rods.
My question is on your rod bearing clearance you say you shoot
for .003-.0035 that is vertical? what do you have X'ing say about
.250 down from the parting line?
Brian B
Dakota Parts Warehouse
The Ferrea Valve Guy
877-235-2832

[Ed-vancedEngines]

Bill,
This is good *Sink your Teeth into info* which by practice I know to be true without knowing the formula or equations. I do see it in ring gears when setting up gears. I see it in bearings and gears when pressing them on shafts etc.

But a What If. What is the hole was not in a circular part? In other words what if the hole were in a solid flat piece of thick steel or aluminum? Isn't that what an aluminum rod is? Isn't it basically a flat piece of thick aluminum plate before maching? Not talking about the Forged Aluminum Rods but am talking about those that are machine cut from a flat sheet of raw material.

Pleae do not misunderstand me as getting arguentive. I am not. I am just not a person that always accepts the easy answers or the status quo of what is always known common lines of thinking. To say I am a little wierd in things I have done with engines through out my life is putting it mildly. I guess this traight about me does extend into almost everything though. This trait has led me to spend yeras in exploration and research about the Holy Bible, known and common accepted ideas or thought processes and to really dig deep for what I can see as truths. My recently deceased wonderful mother used to say "Eddie you would argue with a sign post" She was right. I seldom accept anything at face value, or because it is what everyone else is doing.

Ed

[bigjoe1]

I always use coated bearings, and I have found you can be .0008 to a full thousand tighter with no ill effects. Like you set it up at .0035 non coated, and the coating looses .0008 or so. It works just fine. I run Royal Purple number 9, or sometimes # 11. JOE SHERMAN RACING

[performance crankshaftinc]

seems to me the most overlooked aspect of running lots of clearance is the flow of oil in gallons per minute through the engine .. meaning more windage (HP loss) and the most important the oil filters ability to filter that volume of oil , most filters wont , and the pressure differental usually opens the bypass valve and you end up with bearings that have lots of trash in them .... .0025 has always been a compromise of the bearings ability to carry a load and the oils ability to dissapate heat .. .002 being the maxium load carrying using a large amount of bearing surface area .. .003 removing the most heat from the journal/bearing ... .0025 being the logical compromise ... I have had the wonderful experience of tearing down many engines , circle track and drag race .. When you get close to .002 the bearings have a shine, almost to a wiped lok , but not failed ... past .003 most all have trash in them unless the vehicle ran a dual filter....... at .0025 you wont need your HV pump (dry sump excluded) and your cam gear will be all the happier....not knowing the application , but suspecting a SBC small journal crank , that is where I would be .. if it were a BBC 632 or so , I might be a bit on the bigger side...A longer stroke and a higher HP I tend to think the crank is going to bend and flex a lot more , then experience is the best teacher..what ever works .....PCI