Thread: 302 oil pressure

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So, if I like synthetic oil and it's reduced friction and other advertising hype, what changes can I make in my bearing clearances, and should I use an "h" bearing, or stick with the standard bearing material???? PS We are talking a 7500 RPM race engine, steel crank, powder rods, solid cam???? Can I design for reduced friction and increased bottom end longevity????

I don't think bearing (or clearance) changes are necessarily going to reduce friction and increase longevity. What are you doing now (both bearing and lubricant) and is it giving you satisfactory results?

Bob is correct. Moreover there is a delicate balance of design trades with hydrodynamic bearings. Classical bearing design generally involves calculation of the Sommerfield Number;

S=(R/C)^2*(u N / P)

where R is the journal diameter, C is the radial clearance, u is the absolute viscosity, N is the shaft speed, and P is the film pressure required to carry load. In general higher S numbers lead to higher friction coefficients and flow requirements. Lower S numbers lead to lower oil film thickness also. So for example if you increase the clearance you may think the friction should go down. But now you have changed a lot of other characteristics of the bearing such as load capacity and minimum oil film thickness required to carry that load. To maintain the same load capacity at the same film thickness you now need to increase the viscosity which tends to negate the desired effect of lower friction.

In addition the main journals need to supply the rods with oil also and messing around with the clearance will have an effect on that as well. In my experience that effect will be negative.

Kitz says don't mess around with the bearing clearances too much at all. If you feel the need to experiment, do all your messing with viscosity and oil types/grades.

Regards

I'll run all of these theories past the kid at the local Autozone and get back to you guys with his opinion.

Don

Originally Posted by Dave Severson

So, if I like synthetic oil and it's reduced friction and other advertising hype, what changes can I make in my bearing clearances, and should I use an "h" bearing, or stick with the standard bearing material???? PS We are talking a 7500 RPM race engine, steel crank, powder rods, solid cam???? Can I design for reduced friction and increased bottom end longevity????

Dave,you would think I was nuts if I told you what we do to make our engines live at 7,500.
First off all if you use all synthetic you make be down more than a little on your oil at the end of the race.
We don't run a lot of it.
We do blend it with the Valvaline 20-w50 race oil.
We have not spun a rod or main bearing in over 5 yrs. in our IMCA mod. engines.
We use 2.5 thousands clearance on the rods based on a 2.1 rod size and 3.25 thousands of clearance based on a 350 main size.
We side clearance the rods so we have 20 thousands between each rod assembly.
Crazy but it is track proven.

Originally Posted by DennyW

On this road runner engine that will run between 62-6500, we are using sheafer oil blend. Rods at 2, mains at 2.5. Side clearance 15. full floating rods.

Have you tried the V bearings ?

No we have not.
I have heard other racers say they worked very well for them.
We have used some of the coated bearings when the crank was on the loose side to take up some extra clearance in street cars and have good luck with them.
My only worry is at hi-rpm/hi-load applications that the coated bearings might start to lose their coating.

In the turbine-generator industry (gas or steam) it is common practice to build up old journals with chrome. Although these journal bearings have comparable surface speeds to high performance gasoline engines they lack one very important operational factor; and that is fatigue.

Our automotive engines pound the crap out of all the bearings, particularly the crank and rod bearings. I have applied some coatings to hydrostatic and hydrodynamic bearing journals that might well hold up and work well. But you need to be rather wealthy to afford such procedures. And I ain't at all sure it would win you races or reduce costs in the end ...........

Kitz

Originally Posted by kitz

In the turbine-generator industry (gas or steam) it is common practice to build up old journals with chrome. Although these journal bearings have comparable surface speeds to high performance gasoline engines they lack one very important operational factor; and that is fatigue.

Our automotive engines pound the crap out of all the bearings, particularly the crank and rod bearings. I have applied some coatings to hydrostatic and hydrodynamic bearing journals that might well hold up and work well. But you need to be rather wealthy to afford such procedures. And I ain't at all sure it would win you races or reduce costs in the end ...........

Kitz

We use to hard chrome the cranks but now we can buy a good 4340 crank for less than $500.

we can now adays get a good 4340 crank and rods, plus forged pistons and bearings and rings for less than $900

but actually even me being one of the young guys i have hard chromed a crank because it was the cheapest way to fix my crank that got chewed up..... crank lasted about the life of the motor

Originally Posted by Bob Parmenter

I don't think bearing (or clearance) changes are necessarily going to reduce friction and increase longevity. What are you doing now (both bearing and lubricant) and is it giving you satisfactory results?

We run the H bearings, and Mobil 1 15w-50. Engine looks great, bearings are super. Just wondering if I can free things up a bit...


Erik, I run my Ford mains loose, usually about 3. Guess it works on a Chevy, too. With the Super Stock and a Chevy, we will be stuck running the GM Powder rods, do they like the extra side clearance, too???

Now, because of loophole in the rules, we are considering a 360 Chrysler engine..... Engine builder is figuring out some combinations for us now... Will be interesting to look at them. It's all going to come down to horsepower and torque we can make within the very confining rules. That, and a potential new sponsor talking some major $$$$ with a Mopar in the car....

Originally Posted by Dave Severson

We run the H bearings, and Mobil 1 15w-50. Engine looks great, bearings are super. Just wondering if I can free things up a bit...


Erik, I run my Ford mains loose, usually about 3. Guess it works on a Chevy, too. With the Super Stock and a Chevy, we will be stuck running the GM Powder rods, do they like the extra side clearance, too???

Now, because of loophole in the rules, we are considering a 360 Chrysler engine..... Engine builder is figuring out some combinations for us now... Will be interesting to look at them. It's all going to come down to horsepower and torque we can make within the very confining rules. That, and a potential new sponsor talking some major $$$$ with a Mopar in the car....

Yes, Dave I would run a min. of 15 tho..Don't be afraid to shim up the oil pump spring a little or go to the super stiff spring.
All the syn. oil makes me nervous.
We don't run any valve stem seals at all.
I am guessing you guys do run the valve stem seals.
Because if you did'nt run them your oil would be down a lot at the end of the race.

Originally Posted by Dave Severson

We run the H bearings, and Mobil 1 15w-50. Engine looks great, bearings are super. Just wondering if I can free things up a bit...
....

If by saying "free things up a bit" you mean you're looking for more power then you'll have to be open to changing from "old think". Cold start and low temp operating (which means the 15w part of the vis range on your oil) doesn't mean much in race engines, unless you tell me differently I'd guess you're operating in the "max temp" end of the spectrum, so for practical purposes you're running an SAE 50, and just for comparison that's at the heavy end of say an SAE 80w90 gear lube. Odds are you're running 60 or so psi (with a stock style pump)with the skinny pedal down which means you're dumping over the relief all the time (at least at the higher rpms). If you've got a "high pressure" pump, that just means the point at which the force of the oil flow opens the relief is higher, so it will mean more resistence to flow (the definition of pressure in a fluid system) so it would read something around 75 pounds (does absolutely nothing positive for oiling performance, just heats the oil more). Now, this is where folks get all self righteous and say how successful they've been doing yada yada. And I wouldn't doubt most of them, they probably have been successful. But that's more of a testiment to how tolerant most engines are of a wide variety of applications when the measuring stick has a lot of latitude.

Testimonials like that are interesting but of dubious value. One of my life's careers was in field engineering for fuels and lubes, and through that I had the opportunity to hear just about every kind of oil performance testimonial and it's equal/opposite counter testimony. e.g. "Pennzoil sucks I can prove it................Pennzoil is the only one you can count on, I can prove it". These types of statements very often came from folks in similar application situations, with apparently equal success in operating a fleet, race team, or whatever type of application was appropriate. So pardon my cynicism.

Back in the '80's we had a hard time convincing some of the old timers in NASCAR to run a less viscous oil in qualifying because they were losing power to pumping losses in fluid friction using the heavier oils. The smarter ones caught on (most generally the more dominant teams) quick and, in a mode where 10ths of a second are important, every little bit helped. Then for the race itself they'd revert to a more viscous oil because of the prolonged operation at higher temp.

To some that seemed like radical think, yet today they've gone even further. I've been away from it as a career for over 16 years, so I keep in touch by surfing the net. You might want to read this to get a feel for where things have gone; http://www.joegibbsracingoil.com/datasheets/81106.php . After reading that page, click on their "products" tab at the top and see what viscosity grades they're using in engines that turn higher rpms than you've indicated, and probably for longer periods and higher temps (?) than your race car. These guys invest a lot of time, money, engineering, and experimentation in power developement, with reliability being one of their major performance criteria. Yeah, they probably overhaul their engines more than you would ever think of, but they do it less so because of damage incurred (most of which is valve train related rather than bearing failure), rather more for maintaining peak performance in a hyper competitive venue where a lot of money is at stake (their measuring stick is VERY tightly defined).

One additional note about oil selection. In the past we were able to use "conventional" oils (i.e. the same ones that were generally available in the local stores) with considerable success. Today, if you're running flat rather than roller lifters, that is going to have to change. The additive in all qualified engine oils in years past that was most effective for protecting camshafts/lifters (zinc dialkyldithiophosphate or zddp) is not especially good for contemporary emmissions equipment longevity standards, so the amount in the newest of engine oils has been reduced. For roller lifters that's not much of an issue, but the higher frictional characteristics of "flat" tappet/lobe interface will not be happy with the lower levels of zddp in more severe useage. Quick note, no reason to panic if you've used the newer oil, it won't contribute to immediate damage, but you should look for a better replacement for next time. The way to identify oils with lower zddp is the API rating (decent explanation here; http://www.advanceautoparts.com/engl...0030901og.html) on the lid or side of the bottle. If it's SL you probably don't want to use it long term. The compromise is if the oil also (or only) has a hd diesel (or C for commercial) rating. Currently these oils have a higher zddp level, but that will change when diesels require cat converters. Looks like, in the longer haul, we'll end up having to use "specialty" oils blended for non emissions/high performance/off road applications. As much as I generally think "snake oils" and "magic potions" are an unnecessary placebo for the uninformed, this situation may become a reasonable rationale for their use. We'll see in time.

Denny, due to the length of my post and trying to remember all the points to make (you can identify, can't you? ) I had intended to add a disclaimer to the Gibbs reference but "forgot". Now that you've reminded me here it is; As with most links I put up my intent is usually not to endorse exclusive use of that product/system/whatever, but to use it as a learning tool to be applied however the reader sees fit. There are certainly other products that will work as effectively, but you may not be able to identify them without some knowledge to aid your choosing.

If I remember correctly Gibbs has a sponsorship tie in with Shell. Very likely they are making the oil for him to re-market. As for the additives package in the base oil, there are only a small handful of companies around the world who produce oil additives so the technology employed at Gibbs is not proprietary to him. If you think about that statement, it would also be enlightening about the "snake oil" segment of the market.

Originally Posted by Bob Parmenter

If by saying "free things up a bit" you mean you're looking for more power then you'll have to be open to changing from "old think". Cold start and low temp operating (which means the 15w part of the vis range on your oil) doesn't mean much in race engines, unless you tell me differently I'd guess you're operating in the "max temp" end of the spectrum, so for practical purposes you're running an SAE 50, and just for comparison that's at the heavy end of say an SAE 80w90 gear lube. Odds are you're running 60 or so psi (with a stock style pump)with the skinny pedal down which means you're dumping over the relief all the time (at least at the higher rpms). If you've got a "high pressure" pump, that just means the point at which the force of the oil flow opens the relief is higher, so it will mean more resistence to flow (the definition of pressure in a fluid system) so it would read something around 75 pounds (does absolutely nothing positive for oiling performance, just heats the oil more). Now, this is where folks get all self righteous and say how successful they've been doing yada yada. And I wouldn't doubt most of them, they probably have been successful. But that's more of a testiment to how tolerant most engines are of a wide variety of applications when the measuring stick has a lot of latitude.

Testimonials like that are interesting but of dubious value. One of my life's careers was in field engineering for fuels and lubes, and through that I had the opportunity to hear just about every kind of oil performance testimonial and it's equal/opposite counter testimony. e.g. "Pennzoil sucks I can prove it................Pennzoil is the only one you can count on, I can prove it". These types of statements very often came from folks in similar application situations, with apparently equal success in operating a fleet, race team, or whatever type of application was appropriate. So pardon my cynicism.

Back in the '80's we had a hard time convincing some of the old timers in NASCAR to run a less viscous oil in qualifying because they were losing power to pumping losses in fluid friction using the heavier oils. The smarter ones caught on (most generally the more dominant teams) quick and, in a mode where 10ths of a second are important, every little bit helped. Then for the race itself they'd revert to a more viscous oil because of the prolonged operation at higher temp.

To some that seemed like radical think, yet today they've gone even further. I've been away from it as a career for over 16 years, so I keep in touch by surfing the net. You might want to read this to get a feel for where things have gone; http://www.joegibbsracingoil.com/datasheets/81106.php . After reading that page, click on their "products" tab at the top and see what viscosity grades they're using in engines that turn higher rpms than you've indicated, and probably for longer periods and higher temps (?) than your race car. These guys invest a lot of time, money, engineering, and experimentation in power developement, with reliability being one of their major performance criteria. Yeah, they probably overhaul their engines more than you would ever think of, but they do it less so because of damage incurred (most of which is valve train related rather than bearing failure), rather more for maintaining peak performance in a hyper competitive venue where a lot of money is at stake (their measuring stick is VERY tightly defined).

One additional note about oil selection. In the past we were able to use "conventional" oils (i.e. the same ones that were generally available in the local stores) with considerable success. Today, if you're running flat rather than roller lifters, that is going to have to change. The additive in all qualified engine oils in years past that was most effective for protecting camshafts/lifters (zinc dialkyldithiophosphate or zddp) is not especially good for contemporary emmissions equipment longevity standards, so the amount in the newest of engine oils has been reduced. For roller lifters that's not much of an issue, but the higher frictional characteristics of "flat" tappet/lobe interface will not be happy with the lower levels of zddp in more severe useage. Quick note, no reason to panic if you've used the newer oil, it won't contribute to immediate damage, but you should look for a better replacement for next time. The way to identify oils with lower zddp is the API rating (decent explanation here; http://www.advanceautoparts.com/engl...0030901og.html) on the lid or side of the bottle. If it's SL you probably don't want to use it long term. The compromise is if the oil also (or only) has a hd diesel (or C for commercial) rating. Currently these oils have a higher zddp level, but that will change when diesels require cat converters. Looks like, in the longer haul, we'll end up having to use "specialty" oils blended for non emissions/high performance/off road applications. As much as I generally think "snake oils" and "magic potions" are an unnecessary placebo for the uninformed, this situation may become a reasonable rationale for their use. We'll see in time.

Bob,part of the reason we run the oil pressure clear up there is the drivers.
When a driver is going down the back stretch turning well over 7,500 rpm he likes oil pressure.
In other words when he is use to seeing 65 lbs. for many years and now he see's 40 lbs. he will be more than a little nervous.
I understand the whole idea about oil viscosity = hp.
I also understand that the higher oil pressure means more friction and more heat.I also understand that to much pressure will also imbed dirt in to the babbit.
I also understand that to much oil pressure can lead to the oil becoming more un-stable ie-foaming and such.
If we ran on gas we would not be running a 20-w50 we would run say a 10-w 30 race blend instead.
The alcohol dilutes the oil so badly in other words makes it very thin we don't feel it is in our best intrest to drop the oil weight down to say 10-w30. because we run it on the rich side so we don't burn any holes in the pistons.

Originally Posted by erik erikson

If we ran on gas we would not be running a 20-w50 we would run say a 10-w 30 race blend instead.
The alcohol dilutes the oil so badly in other words makes it very thin we don't feel it is in our best intrest to drop the oil weight down to say 10-w30. because we run it on the rich side so we don't burn any holes in the pistons.

Excellent use of practical, and justifiable, application factor(s). I think it's important that other readers have a better understanding of such things so that they don't inadvertently take an application scenario that isn't appropriate for their situation and mistakenly misapply it.