Bad weekend (discussion about running bearings)

[darinz]

Ok the bad news. First race of the season and it appears I've a big end problem. We are pulling the motor this week/weekend and will have a look but I'm pretty sure a big end bearing have packed it in.

So a couple of questions.Anyone done this and not had to replace the crank and or rod?

Can you machine the factory pistons to drop compression a bit?

I'd rather rebuild this motor and know what I have than just thriw another unknown motor in and take my chances but it comes back to cost at present.

Any ideas and anyone have a few spares part lying around if I need them?

[Raxephon]

So a couple of questions.Anyone done this and not had to replace the crank and or rod?

Depends on how far gone it is. Realistically you should replace any thing that seems worn excessively or is too far out of factory spec.

Can you machine the factory pistons to drop compression a bit?

No.You won't achieve your goal that way. You'll just be replacing pistons sooner.

You can play around abit with Singh(sp?) grooves but then you start getting into the "quench" area of the combustion chamber.

Any ideas and anyone have a few spares part lying around if I need them?

If you need anything used but still within OEM spec, let me know.

I have a block that I'm boring out to 5000cc, so I have a spare set of pistons and rods.

I have more OEM parts than I'll ever need, so I let them go cheaply to any NICO member in the Q45 or VH/VK forums.

(I'm a big believer in karma, and given the fact that I have an amazing wife, lots of machines(toys) to tinker with, and a kick a** job, I try to help out as many people,(non-douchebags, just people), as I can, to try to pay the universe back for what it has been kind enough to give me.)

(EDIT: Sorry for the run on sentences. I haven't slept in 2 days due to pain.)
Modified by Raxephon at 8:02 PM 3/17/2009

[darinz]

OK the bad news is that #6 big end had spun and all other big ends are worn badly. As are the main bearings!The good news is that it appears the crank will be OK. It appears only one big end (#6) has done any damage to the crank and it doesn't appear too bad.So hopefully it will be a polish of the crank, new bearings, one new rod, rings and that will be it.

HOPEFULLY

[Orphan]

Lol whats with VH's and big ends Seems everyone is having that problem lately.

[Carl H]

a serious question for every one...is everyone running the engine to the 'high' line on the dipstick if on stock oil pan?with my vh i have run it with about .75qt extra in the pan so its above the 'high' line...perhaps these engines are suceptible to oil surge?

[darinz]

I run mine to the high line on the factory dip stick but I have had mine on a near vertical angle winch up a very step bank and it lost oil pressure that time. That was a year ago but it would appear some damage had to have been done.Before we put it back in I'm going to build an extra deep sump for it. I want to increase the oil capacity by another 2ish liters and also shif the pick up to the middle/rear.But yeah, quite few have done big ends haven't they? Has everyone identified the problem? I know I've had oil pressure issues on 3 different occasions so mine's pretty easy cause but what about others?

[Mettler]

Hmmm this is starting to get me worried a bit, might be time to design a better pan & oil pickup setup... cos I really cbf with running a big end!

[SuperHatch]

FWIW, my engine was run with the oil 1/2 qt. over the high line and it was on the dyno when the big end spun, so no oil slosh or loss of pressure.

I think the biggest issues are the condition these used motors are in and how tight the tolerances are from the factory.

[gs14racer]

I think the biggest issues are the condition these used motors are in and how tight the tolerances are from the factory.

Stephen hit the nail on the head, nissan runs really tight clearances on almost all theyre motors, they love to spin bearings after they have some mileage then we abuse them for a few thousand miles and they die.

[Orphan]

So basically get a low KM engine that looks clean as inside? Does anyone have comment on the OEM bearings if you were to rebuild the engine.

[Mettler]

My only comment on the OEM bearings is that they're too damn expensive!

So if it's not caused by pressure loss, then I wonder if a modification to the rods allowing bearings to be used with a deeper locating bit could help prevent it?

Or would that just cause additional damage to the big end journal on the crank if there was to be a clearance/wear issue?

[gs14racer]

When you rebuild them you can make the clearances looser.

[Carl H]

im not sure i believe in the whole 'tight clearances' theroy...i have seen NUMEROUS high mileage rb engines make great power and never spin bearings.granted nissan's bearing clearances are silly tight (anyone who has had to order oem bearings knows this) even if they loosen up some they shouldnt spin the bearing.i honestly think that the problem may lie in the pan and pickup, perhaps the intake on the pickup simply isnt large enough to support high flow.take a look at the differences in oil pickups with the sr engine, the s13 sr has a noticably smaller inlet and less 'robust' design than the s14 sr and everyone hears about the redtops spinning bearings but not many blacktops seem to suffer this fate.

[kingkilburn]

Is it time for dry/accusump?

[Carl H]

fwiw...the sr strainer differences:s13 sr20det

s14 sr20det:

notice the large differences in opening...anyone have a pic handy of the vh45's oil strainer?

[tmorgan4]

Best one I've got....



The VH pick-up "slot" is a lot longer than the two shown above however it may be narrower.

[SuperHatch]

FWIW, if the strainer was restricting flow, the pressure would drop.

Pressure doesn't drop, ergo the strainer isn't a restriction.

The redesigned SR pickup still allows oil flow in the event that the pan is crushed up into the pickup.

[darinz]

FYI, there is evidence that my #6 piston had been hitting the head. That was the noise that I could hear! Other than that, it was running a little bit rough and was down on power but to be honest I thought it was a spark plug breaking down! When you look at the damage inside, that is really scary! It makes me think it has been like this a long time and there was basically no obvious signs. Oil pressure dropped a bit once hot but was still basically within factory specs. It is starting to make think that replacing the bearing fairly early in life (relatively speaking) should be a standard practice. Like we are all noticing, quite afew guys have had this problem so just replacing the bearing could be a very cheap insurance policy! Are we finding that the bearings have a life span that is much shorter than the rest of the motor?

[Mettler]

I'm pretty sure a guy on here spun a bearing after a reasonably recent rebuild... anyone else remember about that and who it was?

BTW the VH oil pickup slot is 40mm x 15.5mm (with rounded ends). This produces a surface area of 568.44 square millimeters.

The oil passageways through the filter housing are 16mm in diameter, which results in a surface area of 201.06 square millimeters.

So clearly the pickup has more than enough of an opening to be getting oil through... and as has been remarked on by a couple of guys now, they've spun bearings despite retaining decent oil pressure. I'm gonna call a stockcar engine builder and find out their thoughts!

[darinz]

zx450 or something wasn't it?

[Mettler]

Ok I spoke to a guy who builds superstockcar VH engines and got his opinion, he had the following to say...

Firstly, he says the oil pump is too massive, pumps too much oil and produces too much pressure when at sustained revs. They actually run a different sprocket to drive the oil pump to run it a bit slower. He said 80-85psi is just too high, they back them off to about 70.

The other thing he mentioned was that the oil has a bit of a mazelike pathway from the filter housing all the way to the back of the block and up to the middle rail where it feeds the mains.

They don't bother with this, and plumb a line from the filter straight into the front of this rail in the front of the block (under the water pump) using a modified -12 fitting.

Fairly interesting, he wasn't as concerned about tight clearances as he was the oil pressure. He mentioned they clearance them to about 2 thou (0.0508mm).

I asked him about the idea of using a lighter spring in the bypass valve to back off the pressure, but he said that despite doing this, the oil is still gonna get swirled around and aerated a bit by having to pass through all those channels.

I also asked him about running a twin turbo setup and whether the additional oiling to the turbos would be enough to drop the pressure favourably, and he said he'd still probably want to back that pressure off a bit. It's fairly interesting, the extent to which the stockcar guys change things about the VH for use in this type of application.

He did mention that initially they ran a motor close to stock and it worked awesomely for over 40 stockcar meets until the car took a big hit, was flipped upside down, and the driver knocked unconscious with his foot flat to the floor. Obviously it ran the bearings then. They slapped in a new crank, full fresh rebuild etc... but the motor wouldn't stop running bearings from then on... so they did the other mods I mentioned above and it's been mint ever since.

Food for thought!

[XJared]

Is everyone that spun bearings running a totally stock pan and pickup?

[Mettler]

s*** that just jogged my memory... a friend did a ground up rebuild on his RB30DET recently and not long after running it in, it spun a bearing.

They did a full inspection and it took some time to figure out the cause... but then they discovered they had used a nitrile o-ring on the oil pickup where it bolts to the block... and it had deteriorated from temperature and exposure to oil, allowing air to be sucked past it into the oil supply to the pump. Obviously bubbly aerated oil kills bearings.

Nobody here has even mentioned this... so I suggest you guys with run bearings check out the condition of your o-rings on your oil pickups, and also determine whether they are nitrile or viton... you want to be using viton o-rings in any harsh temperature or chemical environments!

At the same time, check & replace the o-rings on your oil pump with viton too!

I bet this could be the cause!

[Carl H]

ha, a nissan pump that drains the pan faster than it can return the oil to it...who'd have thought!

[Mettler]

No kidding! The RB30 boys have to run oil restrictors to prevent them emptying the sump and filling the head up with oil when doing extended burnouts :P

[efeezie]

Yeah some of the DOHC 4.6 ford(which is very similar to the VH) guys have had problems with the the timing chain slinging too much oil up into the heads causing bearing failure.

Maybe a bigger capacity oil pan would help out quite a bit.

[darinz]

s*** that just jogged my memory... a friend did a ground up rebuild on his RB30DET recently and not long after running it in, it spun a bearing.

They did a full inspection and it took some time to figure out the cause... but then they discovered they had used a nitrile o-ring on the oil pickup where it bolts to the block... and it had deteriorated from temperature and exposure to oil, allowing air to be sucked past it into the oil supply to the pump. Obviously bubbly aerated oil kills bearings.

Nobody here has even mentioned this... so I suggest you guys with run bearings check out the condition of your o-rings on your oil pickups, and also determine whether they are nitrile or viton... you want to be using viton o-rings in any harsh temperature or chemical environments!

At the same time, check & replace the o-rings on your oil pump with viton too!

I bet this could be the cause!

So I wonder if running avgas all the time has killed the seals? Interesting thought. My motor hasn't been apart so all O rings are still factory?The racing I do is very much an all or nothing kind of thing, so go from full throttle to not much, maybe idle a bit and then back up to everything. I wouldn't have thought that I'd be on the throttle long enough to empty the sump, particulary with how faster my truck accelerates!

I'm definitely increasing the oil pan volume, now must change all the 'O' rings to be sure.Now the extended oil pathway is interesting. Since I have the motor completely apart we should look into this. I've got a guy who is a very (very) experienced (motorsport) engine builder. He's also played with RB oil pumps so I'll talk to him about this.

[CrazyTrance]

Here's a little better picture of the size of the opening in the pickup tube from my spare/mock up engine.

[maxnix]

As long as the passages are sufficient, there is no way to empty the sump. The extra pressure was probably sufficient to enable a full flow throught those convuluted passages.

If over filled, there will be crank slap and subsequent foaming.

[SuperHatch]

So if it's not caused by pressure loss, then I wonder if a modification to the rods allowing bearings to be used with a deeper locating bit could help prevent it?

Just to see if everyone on this thread is on the same page.

For me to consider a bearing "spun" it doesn't actually need to physically spin in the journal. Sufficient metal to metal contact to wear down the bearing and cause loose enough tolerances to produce an audible noise is "spun" in my book.

FWIW, if you have any wear on your bearings at all, something in the engine went wrong, weather it be contaminated oil causing bearing wear, loss of thin film coating causeing metal to metal contact, or deformation of the big end/main cap from increased loads (RPM/Boost) that cause the journal to elongate. Bearings should never "wear out" in a properly set up motor.

That being said Mettler, I don't think the issue has anything to do with the bearings physically spinning in the journals. Its a good idea to keep in the back of your mind, but not the main issue at hand.

This is again, why I believe a large portion of the problem has to do with the tight clearances. The slightest deformation of the big end of the rod from increased high RPM use will cause metal to metal contact and ruin the bearing. An increased clearance will allow for more deformation before failure. It will also allow the use of a heavier weight racing oil that will stand up to the abuse better.