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What happened to your ChampCar today 2021 ??


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27 minutes ago, RandomTask said:

Huh? I have never heard of this. You know on SBCs the oil flows through the cam bearings to the main bearings, right? If I restricted oil at the cam it would also restrict at the mains. 

 

 

It's a smaller feed hole in the cam bearing itself. Stock bearings feed more oil than necessary to the cam journals, taking supply from the mains. This doesn't restrict oil to the mains. Not an unusual circle track mod.

 

Described in more detail here;

 

https://www.speed-talk.com/forum/viewtopic.php?f=1&t=59666

 

Post 3 and 7, with a clarification in 7, explains it pretty well. Other stuff in that thread may give you some ideas as well.

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22 hours ago, RandomTask said:

.0015 on the crank journals and .0027 on the rods. 

Not sure where you got those numbers but I certainly wouldn't recommend them. 

 

For the typical level of precision expected from the local machine shop, use 0.0010-0.0011" per inch of journal diameter as a starting point for bearing clearance. That will give you a good balance between load capability and flow volume for cooling (the two jobs of oil). Your mains should be 0.0025-0.0027", and the rear main can be closer to 0.0030" because of the width and thrust surface. Your rods should be 0.0020-0.0022". That will give your oiling system a better balance of pressure and volume throughout the system. Your present numbers won't. 

 

Too small on the clearances and you'll overheat the oil at the bearing surface (not enough flow for proper cooling) and the oil film will be too thin, leading to bearing failure. Sounds like that's what you're getting on your mains. 

 

Too large on the clearances and the load bearing of the hydrodynamic wedge goes down, plus the volume of oil moving through the bearing drops the system pressure without providing any benefit. Also, too much rod bearing clearance sprays extra oil on the cylinder walls and increases the work of the oil rings. 

 

Get your machine shop to use these clearances.

Edited by mender
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1 hour ago, Bandit said:

It's a smaller feed hole in the cam bearing itself. Stock bearings feed more oil than necessary to the cam journals, taking supply from the mains. This doesn't restrict oil to the mains. Not an unusual circle track mod.

 

Described in more detail here;

 

https://www.speed-talk.com/forum/viewtopic.php?f=1&t=59666

 

Post 3 and 7, with a clarification in 7, explains it pretty well. Other stuff in that thread may give you some ideas as well.

Gotcha. I have a HV pump; not worried about that. Jokingly asked the machinist what noise the oil would make if it starts cutting into the oil. Else, I'll have to fill it up until I lose power then drain half a quart :P

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1 hour ago, mender said:

Not sure where you got those numbers but I certainly wouldn't recommend them. 

 

For the typical level of precision expected from the local machine shop, use 0.0010-0.0011" per inch of journal diameter as a starting point for bearing clearance. That will give you a good balance between load capability and flow volume for cooling (the two jobs of oil). Your mains should be 0.0025-0.0027", and the rear main can be closer to 0.0030" because of the width and thrust surface. Your rods should be 0.0020-0.0022". That will give your oiling system a better balance of pressure and volume throughout the system. Your present numbers won't. 

 

Too small on the clearances and you'll overheat the oil at the bearing surface (not enough flow for proper cooling) and the oil film will be too thin, leading to bearing failure. Sounds like that's what you're getting on your mains. 

 

Too large on the clearances and the load bearing of the hydrodynamic wedge goes down, plus the volume of oil moving through the bearing drops the system pressure without providing any benefit. Also, too much rod bearing clearance sprays extra oil on the cylinder walls and increases the work of the oil rings. 

 

Get your machine shop to use these clearances.

These are straight out of the corvette FSM; it states the mains (could) go down to .0009" clearance. There's also tons of other dimensions that need to be kept; I'll mic it all out. 

The rods should be looser than the mains to promote oil to them. 

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2 hours ago, mender said:

Not sure where you got those numbers but I certainly wouldn't recommend them. 

 

For the typical level of precision expected from the local machine shop, use 0.0010-0.0011" per inch of journal diameter as a starting point for bearing clearance. That will give you a good balance between load capability and flow volume for cooling (the two jobs of oil). Your mains should be 0.0025-0.0027", and the rear main can be closer to 0.0030" because of the width and thrust surface. Your rods should be 0.0020-0.0022". That will give your oiling system a better balance of pressure and volume throughout the system. Your present numbers won't. 

 

Too small on the clearances and you'll overheat the oil at the bearing surface (not enough flow for proper cooling) and the oil film will be too thin, leading to bearing failure. Sounds like that's what you're getting on your mains. 

 

Too large on the clearances and the load bearing of the hydrodynamic wedge goes down, plus the volume of oil moving through the bearing drops the system pressure without providing any benefit. Also, too much rod bearing clearance sprays extra oil on the cylinder walls and increases the work of the oil rings. 

 

Get your machine shop to use these clearances.

Was waiting for this response.

Thanks for refreshing my memory on recommended clearances 'rule of thumb.'

 @mender

Edited by mcoppola
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1 hour ago, RandomTask said:

These are straight out of the corvette FSM; it states the mains (could) go down to .0009" clearance. There's also tons of other dimensions that need to be kept; I'll mic it all out. 

The rods should be looser than the mains to promote oil to them. 

 

I learned a long time ago that building a racing engine to factory bearing tolerances generally leads to bearing failure.  Same goes for piston to wall clearance.  Subaru for example says minimum piston/wall clearance for EJ turbo engines is 0.000....

 

The clearances are too tight, and the sustained high loads/revs causes failure.  High mileage (50K+) street engines work well for racing because they've self adjusted their clearances.  

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1 hour ago, RandomTask said:

These are straight out of the corvette FSM; it states the mains (could) go down to .0009" clearance. There's also tons of other dimensions that need to be kept; I'll mic it all out. 

The rods should be looser than the mains to promote oil to them. 

The FSM isn't about building engines for racing. Using those specs will not end well for you. 

 

I've been building racing engines for over 30 years so I know my stuff. Reread my post, use those numbers. Have your machine shop order in the H series bearings and size things to the specs I gave you. If they argue, find another machine shop.

 

This is basic stuff. We can get into much more depth but you don't have to reinvent the wheel - or the SBC oiling system.

 

Here's an article by some no-name by the name of David Vizard:

https://www.chevydiy.com/lubrication-systems-cheat-sheet-for-chevy-small-block-engines/

 

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36 minutes ago, mcoppola said:

Was waiting for this response.

Thanks for refreshing my memory on recommended clearances 'rule of thumb.'

 @mender

No problem, Mike!

 

You probably know from working at that Furd place (:P) that the quality of the machine work and the quality of the parts used is a major factor in deciding the final bearing clearances. Sure, the Cup guys are using smaller clearances but they have the precision in their grinds and the high-dollar parts needed to maintain the critical dimensions under high loads and rpm.

 

 

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56 minutes ago, Ian said:

The clearances are too tight, and the sustained high loads/revs causes failure.  High mileage (50K+) street engines work well for racing because they've self adjusted their clearances.  

Race engines should be like the town moped.

 

Loose.

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41 minutes ago, mender said:

The FSM isn't about building engines for racing. Using those specs will not end well for you. 

 

I've been building racing engines for over 30 years so I know my stuff. Reread my post, use those numbers. Have your machine shop order in the H series bearings and size things to the specs I gave you. If they argue, find another machine shop.

 

This is basic stuff. We can get into much more depth but you don't have to reinvent the wheel - or the SBC oiling system.

 

Here's an article by some no-name by the name of David Vizard:

https://www.chevydiy.com/lubrication-systems-cheat-sheet-for-chevy-small-block-engines/

 

So if I use those numbers and my motor blows, you willing to fix it? 

I'll ask my machinist but for losing oil pressure at full tilt numerous times, I was surprised how good of shape it was in. 

Edited by RandomTask
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1 minute ago, RandomTask said:

So if I use those numbers and my motor blows, you willing to fix it? 

I'll try one more time.

 

Professional engine builder for over thirty years, owning and running my own engine building shop for twenty years, NASCAR crew and car chief for five years, and a very loyal customer base because my engines make power, don't blow up, and last an entire racing season making over 2 hp/cid at 8200 rpm. And you?

 

To be blunt, you'd be wise to use the numbers I gave you for free. I'm trying to save you money.

 

 

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13 minutes ago, mender said:

I'll try one more time.

 

Professional engine builder for over thirty years, owning and running my own engine building shop for twenty years, NASCAR crew and car chief for five years, and a very loyal customer base because my engines make power, don't blow up, and last an entire racing season making over 2 hp/cid at 8200 rpm. And you?

 

To be blunt, you'd be wise to use the numbers I gave you for free. I'm trying to save you money.

 

 

 

. . . and you threw all those credentials in the trash when you decided to race a Fiero ;)

 

I'm a mechanical engineer. I simply become dubious when someone says "I know better than the entire engineering staff at GM"

 

I'm not going to get into a pissing match to flash credentials. Appreciate your input, I'll take note 🍻

 

Edited by RandomTask
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Just now, RandomTask said:

I'm a mechanical engineer. I simply become dubious when someone says "I know better than the entire engineering staff at GM".

You better hit the books again if you think a FSM is about building race engines.

 

Don't let your formal education get in the way of learning.

 

 

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Mender's clearance numbers are pretty much standard in the industry for a SBC. They are not unusual and frankly are the numbers I'd suspect most machine shops use for a performance 350.

 

A quick google search will show as much.

Quote

Generally speaking, bearing clearance should be 0.001-inch for every inch of journal diameter. Let's take the traditional 350 small-block as an example. The factory specs include 2.450-inch main bearing journals and 2.100-inch rod journals, which means the target bearing clearance should be about 0.0024-inch (0.0025 is the common spec) on main bearings and 0.0021-inch on the rod bearings. Again, in general terms, it's better to have the clearance slightly larger to ensure optimal performance and oil temperature, particularly if the engine is built for higher performance.

 

http://www.superchevy.com/how-to/engines-drivetrain/1907-ten-important-facts-engine-bearing-clearance

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10 minutes ago, RandomTask said:

And don't let your hubris let you think you're always the smartest man in the room. 

Not to be too immodest, but I usually am. :)

 

* One time that I wasn't for sure: I was training with an Indy car engine builder. He was not only smart, he had the experience of working for Cosworth building engines and such. I learned a lot, and have learned a fair bit more since then. Thirty years of learning.

 

We didn't use a Corvette FSM, not even once. Think about that. :)

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7 hours ago, mender said:

Not to be too immodest, but I usually am. :)

 

* One time that I wasn't for sure: I was training with an Indy car engine builder. He was not only smart, he had the experience of working for Cosworth building engines and such. I learned a lot, and have learned a fair bit more since then. Thirty years of learning.

 

We didn't use a Corvette FSM, not even once. Think about that. :)

What series in NASCAR did you run? 

Edited by RandomTask
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7 hours ago, Bandit said:

Mender's clearance numbers are pretty much standard in the industry for a SBC. They are not unusual and frankly are the numbers I'd suspect most machine shops use for a performance 350.

 

A quick google search will show as much.

 

http://www.superchevy.com/how-to/engines-drivetrain/1907-ten-important-facts-engine-bearing-clearance


It's a "rule" of thumb that I've been aware of since I built my first SBC at 16. There's plenty else that goes into a build, oil that I'm running, oil temps I'm after, bearings I'm running, machine work done, etc. 


My motor has countless daily hours and about ~140 race hours on it. It's been run at full tilt w/ zero oil pressure (drain plug fell off). It's been run low (<10psi) on oil pressure in turns countless times from something going on with the pan. And even with this, the rod bearings are perfect and the mains had only the slightest scoring. 

Appreciate everyone's input.


 

 

 

Edited by RandomTask
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20 hours ago, RandomTask said:


FSM calls for .0009 to .0021 for the crank journals and .0010 to .0030 for the rods. 

Whats a 'cheater pan'? The canton I have has trap doors on it. 

that's the one I mean. I call it cheating because before pans were points you had to make one. We run the Speedway version. Works well.  And I'll admit, I have never heard of restricting the oil flow from the cam bearings either. But I'm a Mopar guy, but Bandit and Mender know their stuff....

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2 hours ago, RandomTask said:

What series in NASCAR did you run? 

The top national level here in Canada, various names over the years but now known as the Pinty's series. 

Edited by mender
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2 hours ago, RandomTask said:


It's a "rule" of thumb that I've been aware of since I built my first SBC at 16. There's plenty else that goes into a build, oil that I'm running, oil temps I'm after, bearings I'm running, machine work done, etc. 


My motor has countless daily hours and about ~140 race hours on it. It's been run at full tilt w/ zero oil pressure (drain plug fell off). It's been run low (<10psi) on oil pressure in turns countless times from something going on with the pan. And even with this, the rod bearings are perfect and the mains had only the slightest scoring. 

Appreciate everyone's input.

I didn't develop those numbers but have seen how well they work, and also what happens when engine builders start moving away from them. 

 

I get a fair bit of work from racers who have had engine issues and have asked around. First thing is to do a postmortem and figure out whether the failure was due to part selection, machining, or assembly error. From there, I see whether the trail leads to support systems and/or running conditions. That includes oil type and temp, pan design, cooling system, fuel and ignition, and of course driver habits.

 

The fact that you have more wear on some of your bearings than others tells me that those bearings are not getting the treatment they need. In your case, the clearances that you are using are the culprit. The main clearances are too tight by about a thou. If you're having problems with rod bearings when running them at 0.0020-0.0022" clearance, either lower your rpm, get better rods or a better machine shop because something is moving or isn't consistent. Fix the problem the right way and don't build in other problems as a crutch.

 

I'm assuming you're using proper measurement tools that get calibrated regularly, and the numbers you're providing are accurate. I'm also assuming a reasonably good machine shop, one that does some race engine work and has decent equipment and operators. A quick tour through the shop will tell you a lot.

 

If you want to play with pet theories, start off by using smaller increments and make sure you're being objective about what you're doing and seeing. As you've seen, a SBC (and most engines) will survive quite a bit of abuse before failing, but don't ignore the warning signs. 

 

 

 

Edited by mender
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1 hour ago, TiredBirds said:

that's the one I mean. I call it cheating because before pans were points you had to make one. We run the Speedway version. Works well.  And I'll admit, I have never heard of restricting the oil flow from the cam bearings either. But I'm a Mopar guy, but Bandit and Mender know their stuff....

But you've heard of running an external oil line from the pan on RBs to bypass the internal oil passages, right? Each engine has its quirks. :)

Edited by mender
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