burntblkZ

iTrader: (5)

So I tore down a engine that has been running for about 3 years now. It was used in a drag car and has somewhere around 200 passes. The engine is a 6.0l iron block, forged rods and pistons, stock crank. I tore it apart to replace main and rod bearings but I do not want to put it back together untill I find out what caused the bearing to look like this. I originally put the engine together, I had the block align bored (arp studs installed) and rotating assy balanced etc. at the machine shop and was told everything is good to go, even micd everything when I got it back. The stock crank that is in this engine came out of an engine that broke #6 piston. Could the crank be slightly bend?? any input is appriciated.

bearings placed in order #1 starting at left.

87silverbullet

iTrader: (11)

What kind of oil pressure did you have? What kind of oil pump? What clearances did you have on the mains? What did the rod bearings look like?

O2Form

Looks like it was dirty for sure.

burntblkZ

iTrader: (5)

Oil pressure was 60@ idle and 80+@ WOT. Oil pump is a ligenfelter high volume (ported stock basically) all 5 mains were between .0025-.003". rod bearings looked better except for #6 and #5 cyl witch had some copper showing on both top and bottom.

PREDATOR-Z

oil starvation

87silverbullet

iTrader: (11)

It looks like it got hot too. There is some bluing on the thrust bearing.

65panel5.3

what weight of oil were ya running?

burntblkZ

iTrader: (5)

The engine was shifted @7500rpm,Is a stock style pump not reliable this high? What would need to be done to get more oil?


10w-30 rotella

PREDATOR-Z

Could be the oil did not have time to return to crankcase. The pump simply sucks it dry.
You said 200 passes at the track. Does the car lift the front?

burntblkZ

iTrader: (5)

sometimes the tires a couple inches

PREDATOR-Z

That and 7500rpm can contribute to what I described.

racer7088

We do engines like this all day long and they have no issues going 7500 rpm. Some are going on 7 years old at this point. Mains were probably too tight would be my guess or other issues. We usually run 15W50 in drag stuff with a lil more clearance but not much.

C/Performance

It looks like:

MISALIGNMENT OF SHAFT AND HOUSING
There are a number of causes that give rise to misalignment of the crankshaft and
cylinder-block housings, such as improper machining, bent crankshaft, distorted
cylinder block, etc. These defects result in localized wear, which tends to be
greatest on some of the main bearings and less pronounced on others.
Recommendation: ensure that cylinder-block and crankshaft machining
tolerances are in accordance with the engine manufacturer’s specifications.

65panel5.3

Id definately go for a thicker oil and maybe a little more clearance on the mains, ive had good luck running a 15/40 but 15/50 may be a good choice as RACER said it helps cushion the mains a little more at that sorta rpm. I took out a set of mains on a 400sbc from running too thin of oil, switched to the 15/40 and never had another problem.

burntblkZ

iTrader: (5)

Thanks for the input guys.
Im going to use a known good crank and have the block checked again. along with thicker oil and loosining up the tolerances a tad. And more oil!
Whats the maximum amount of oil I can run in it with a f-body pan?

kevin kuether

iTrader: (1)

You want to watch running too heavy weight of oil as it can take longer for it to return back to the pan and then starve the engine.

C/Performance

Kevin has a very good strong point on heavy weight oil.

Here is why you need to use the correct oil viscosity for your engine !
Viscosity is a measure of oil’s ability to flow through a certain size orifice at a designated temperature.
It takes more hp to run a thicker oil, and it doesn't mean thicker oil is always better.
With out getting to deep in to this.I will briefly explain.

Multi-viscosity means the oil meets two viscosity requirements, one at a low temperature
depending on the first number of the viscosity grade, and a second at 212oF for the second number in the viscosity grade. What all of this means is that an SAE 20W/50 oil flows like an SAE 50 oil at 212oF and flows like an SAE 20W oil at 14oF. This provides the best of both worlds; good lubricant flow at low temperatures to get to the critical areas quickly, and adequate film thickness to protect those same critical areas at high temperatures because the oil does not “thin-out !!!!
Here is an example:
Let’s take a look at straight grade oil used in a racing engine and see if there are any undesirable conditions that develop.
A good example of this is the racer that uses a straight grade SAE 50 oil, then heats it to 212oF with a heating blanket around the dry sump tank or has a heating element in the tank. The engine is cold and is fired up for qualifying and run one lap to warm up and one lap for time. But what happens to that 212oF oil when it hits that 70o or 80o cast iron block? You can bet pole money that it cools down significantly and gets thicker.
Cool (thick) oil does not flow as freely as hot oil, so the pump may max out on pressure and start to bypass.
Why heat oil up only to have it cool down? When it cools down after hitting the cold cast iron and pressure increases to the point of bypassing, power is wasted pumping and bypassing thick oil when that power could have been more effectively used at the rear wheels. Bypassing oil at the pump also reduces oil flow to the bearings.

S10xGN

iTrader: (11)

Would this "misalignment" be something one could feel while rotating the crank (properly torqued and w/o rods) during assembly?

C/Performance

The correct way to check for main bearing bore alignment is to have an accurate straight bar that is laid on the main bearing saddles. Then the space between the bore and the straight bar is measured. If the space is larger than what the manufacturer recommends, line boring is required.

If you want to check for the main bore alignment yourself, you can lay the crankshaft into the inverted engine block with the new bearings in place. Measure the effort to turn the crankshaft. Now install the bearing caps in place and torque them to specs. Again measure the effort required to turn it now. If the effort gets noticeably harder, the block, needs line boring. You should also inspect the old main bearings. Any unusual wear patterns are another sign that line boring is needed.