About time to make the switch to lighter oil?

So I have been playing with high performance engines now for 45 years or so. One of the earliest lessons drummed in to my impressionable brain back at the beginning was the thing about using 20/50 or even 60 weight oil in any serious racing engine.

In spite of repeated exposure to multiple experts since then I have resisted the urge to change.

I have recently come to the realization that I need to move in to the 21st century.

So the question is... How does one decide which of the new miracle products to choose.

I have been eyeing up the Lucas synthetic line but have no idea how to choose which weight.

5-30 10-30 even 20-50 whatttt....

600 inch SVO block, dry sump, Drag race, steel rods, .003 -.004 bearing clearances.

Any advice from the panel?

Well I'm in the same boat....... I've been on 20/50 green oil and hate to fix what ain't broke.

If you run tight clearances, you can run the thin stuff, like 0W-5, or a 0W-20, the stuff is almost like water!!
I always run 10W-30 in my stuff....not too thick, not too thin, just a good middle ground I guess.

From my experience tolerances and available oil volumn dictate what oils you can use.

In my opinion ... wide bearing clearances are simply a band aid for suspect parts or bad machine work or not good assembly.  Tighter clearances need to be more exact.

Parts today are more stable and stronger than they ever were and great oil in lighter weights is available ... I think it makes no sense to not take advantage of that.

Although, it usually seems to be all about money and how cheap can I do it.

rmcomprandy wrote:In my opinion ... wide bearing clearances are simply a band aid for suspect parts or bad machine work or not good assembly.  Tighter clearances need to be more exact.

Parts today are more stable and stronger than they ever were and great oil in lighter weights is available ... I think it makes no sense to not take advantage of that.

Although, it usually seems to be all about money and how cheap can I do it.

what is tighter clearance in your opinion? I have always went with .001 per 1" of journal and it's worked . I know some like more but they also run molasses for oil, 50wt!

cool40 wrote:

rmcomprandy wrote:In my opinion ... wide bearing clearances are simply a band aid for suspect parts or bad machine work or not good assembly.  Tighter clearances need to be more exact.

Parts today are more stable and stronger than they ever were and great oil in lighter weights is available ... I think it makes no sense to not take advantage of that.

Although, it usually seems to be all about money and how cheap can I do it.

 what is tighter clearance in your opinion? I have always went with .001 per 1" of journal and it's worked . I know some like more but they also run molasses for oil, 50wt!

I am told by bearing makers who sell, a lot of bearings to Nascar race teams that most of the time .8 x shaft diameter and even .7 is used in 500 mile race engines using well researched thinner oil. That is an engine with 1.881" journals holding 900+ horsepower for hours of wide open throttle running.

rmcomprandy wrote:

I am told by bearing makers who sell, a lot of bearings to Nascar race teams that most of the time .8 x shaft diameter and even .7 is used in 500 mile race engines using well researched thinner oil. That is an engine with 1.881" journals holding 900+ horsepower for hours of wide open throttle running.

With the absolute best machinists and the absolute best machines without any temperature cycles.  Then a complete rebuild after that race.  Makes a huge difference.   You're not going to find any race engine builder that sets BB 2.200 rod bearings at .0154 on the open market.[/quote]

Thick oil and big clearances worked and saved engines back when stock rods were distorting and pinching the bearings at the parting line, and blocks were moving and caps were walking and pulling in at the parting line.

But with good rods and blocks, their is really no reason to do this now days. I am still bad to run clearances wider than needed, just because I have never had a problem doing it.

With good parts if a thinner oil will hold your pressure where it needs to be, then it should be ok to run it.

If not then your oil clearances should be tightened up to be able to run it.

I have noticed that big diesel engines are no longer running the high 100 psi pressure they used to. we have a 15 liter Cummins that runs at 45 lb hot. Rep said that was the norm now.

I have been slowly tightening clearances up my personal stuff. With good results. and running thinner oil.

Curt wrote:

rmcomprandy wrote:

I am told by bearing makers who sell, a lot of bearings to Nascar race teams that most of the time .8 x shaft diameter and even .7 is used in 500 mile race engines using well researched thinner oil. That is an engine with 1.881" journals holding 900+ horsepower for hours of wide open throttle running.

With the absolute best machinists and the absolute best machines without any temperature cycles.  Then a complete rebuild after that race.  Makes a huge difference.   You're not going to find any race engine builder that sets BB 2.200 rod bearings at .0154 on the open market.

[/quote]

Those who build NASCAR engines are not to be considered "race engine" builders  ... really?  
.0154" with a 2.200" journal is way, WAY to big; you probably meant to type .00154".  

In the lower NASCAR & CASCAR "short track" class engines with 2.100" rod journals using all good bottom-end stuff, an oil clearance of .0015"/.0017" is the norm and they have those engines refreshed after hundreds of heat cycles, maybe twice a season. The power level is a whole lot less, though.

You may do anything you want and disagree as some others probably will, also ... but, that will not change today's realities.

You go setting up the BBF big engine with real tight tolerances you could be asking for trouble

rmcomprandy wrote:
Those who build NASCAR engines are not to be considered "race engine" builders  ... really?  
.0154" with a 2.200" journal is way, WAY to big; you probably meant to type .00154".  

In the lower NASCAR & CASCAR "short track" class engines with 2.100" rod journals using all good bottom-end stuff, an oil clearance of .0015"/.0017" is the norm and they have those engines refreshed after hundreds of heat cycles, maybe twice a season. The power level is a whole lot less, though.

You may do anything you want and disagree as some others probably will, also ... but, that will not change today's realities.

I don't consider the NASCAR shop a "race engine" builder, more like an artist with the very best paints and canvases. And those engines are not built with the same parts that we get away with. And when was the last time that you machined a crank that you knew exactly how much the journals would measure at engine temp inside the block? I guarantee you the NASCAR engineers know.

I would challenge you to build the OP a 600" BBF Ford that will be competitive with those clearances. Guaranteed not to spin a bearing of course.

Thank you for correcting my error on the decimal place.

rmcomprandy wrote:

cool40 wrote:

rmcomprandy wrote:In my opinion ... wide bearing clearances are simply a band aid for suspect parts or bad machine work or not good assembly.  Tighter clearances need to be more exact.

Parts today are more stable and stronger than they ever were and great oil in lighter weights is available ... I think it makes no sense to not take advantage of that.

Although, it usually seems to be all about money and how cheap can I do it.

 what is tighter clearance in your opinion? I have always went with .001 per 1" of journal and it's worked . I know some like more but they also run molasses for oil, 50wt!

I am told by bearing makers who sell, a lot of bearings to Nascar race teams that most of the time .8 x shaft diameter and even .7 is used in 500 mile race engines using well researched thinner oil. That is an engine with 1.881" journals holding 900+ horsepower for hours of wide open throttle running.

That's also with engine builders who can air gauge their bearings and check tolerances accurately to the tenth. I would never use .0007 or 8 per diameter with conventional measuring tools. I use .001 as a minimum and adjust from there. On paper, some "ideal" tolerances are acceptable but in reality and application, there are considerations to be taken.

Curt wrote:

rmcomprandy wrote:

I am told by bearing makers who sell, a lot of bearings to Nascar race teams that most of the time .8 x shaft diameter and even .7 is used in 500 mile race engines using well researched thinner oil. That is an engine with 1.881" journals holding 900+ horsepower for hours of wide open throttle running.

With the absolute best machinists and the absolute best machines without any temperature cycles.  Then a complete rebuild after that race.  Makes a huge difference.   You're not going to find any race engine builder that sets BB 2.200 rod bearings at .0154 on the open market.

I hope not...

rmcomprandy wrote:

Curt wrote:

rmcomprandy wrote:

I am told by bearing makers who sell, a lot of bearings to Nascar race teams that most of the time .8 x shaft diameter and even .7 is used in 500 mile race engines using well researched thinner oil. That is an engine with 1.881" journals holding 900+ horsepower for hours of wide open throttle running.

With the absolute best machinists and the absolute best machines without any temperature cycles.  Then a complete rebuild after that race.  Makes a huge difference.   You're not going to find any race engine builder that sets BB 2.200 rod bearings at .0154 on the open market.

Those who build NASCAR engines are not to be considered "race engine" builders  ... really?  
.0154" with a 2.200" journal is way, WAY to big; you probably meant to type .00154".  

In the lower NASCAR & CASCAR "short track" class engines with 2.100" rod journals using all good bottom-end stuff, an oil clearance of .0015"/.0017" is the norm and they have those engines refreshed after hundreds of heat cycles, maybe twice a season. The power level is a whole lot less, though.

You may do anything you want and disagree as some others probably will, also ... but, that will not change today's realities.

This is pointless to the regular guy building an engine in his garage, or even for 90% of professional engine builders. I would challenge you to keep +/- a tenth with hand held measuring tools and when you're pushing tolerances that tight, you better be able to hold them tighter than that. Ain't gonna happen, plus, there's absolutely no need to. No one here is looking for the one or two HP that MIGHT be gained by using those kinds of tolerances. You sure don't need them on a drag engine or a hot street engine. Practicality, reliability, longevity will all trump a couple HP any day for 99.999% of the racing and performance community. You have to pick your battles.

To the OP; with those bearing clearances you'll probably need to stay with a heavier oil but being that this is a drag race deal I would look at some of the full synthetic 40wt oils available. There might be some decent power to gain there. The biggest problem with that much clearance is the amount of oil that is being thrown around in the crankcase. That causes a lot of parasitic drag on a rotating assemble and it's a lot of oil suspended inside the engine and not back in the pan where it belongs. Sometimes those sort of clearances are necessary and it's a reasonable compromise but for a NA drag engine it's really not necessary. You don't have the forces acting on your rotating assembly that need those clearances and you don't have the oil temps that would dictate running a high viscosity oil like that.
Having said all that, we use Joe Gibbs/Driven oil exclusively here. I recommend their products highly.

You guys all seem to be missing my point ... that it IS done often.
Whether or not a guy with his garage build can do it is another subject altogether.

I have built several 562 to 604 big block Fords with .0024" main and .0018" rod clearances but, they all NEED to use really good quality parts and 10W-30 or thinner oil.
There is one aluminum block big block Ford engine out there at 588 cubes and around 1,000 horsepower, (not a lot but, substantial), running .0019" MAIN bearing clearance which I have refreshed over 4 times now over the past 6 years and only needed to change a few bearings along with whatever else. That engine uses 15W-40 oil however, that NEEDS to be fully warmed with oil temps over 140 before full power is applied and 100 degrees before it is even started.

There is a very large difference between a high power, redone OEM engine and a RACE engine.
Over 20 years ago, I built engines for a very well known GTP 12/24 hour endurance race car which had a Chevrolet aluminum block and ran .0009" main bearing clearance, (at room temperature), and it NEVER lost an engine.

Granted, tight clearances will require certain things and procedures be followed but, anybody really serious about their type racing won't mind that extra attention which keeps everything right.
The everyday person won't tolerate that so, of course, you adjust their build accordingly.

dfree383 wrote:You go setting up the BBF big engine with real tight tolerances you could be asking for trouble

The BRAND has absolutely nothing to do with it.
It is all just metal and the running dimensions under stress should be the only thing which matters; if the parts and oiling system are up to the task.

I have learned the mindset of most Big Block Ford people and they are simply unwilling to perform the necessary steps in order to be able to run those tighter clearances.  
I understand all this however, closing your eyes to what is happening throughout the rest of the industry is just the hard headed arrogance of the "if it ain't broke, don't fix it" people who think that also means not to take any advantage of any evolutions or advancements either.

It really is the choice of people to do whatever they wish; whatever makes them happiest is all that really matters.

rmcomprandy wrote:

dfree383 wrote:You go setting up the BBF big engine with real tight tolerances you could be asking for trouble

The BRAND has absolutely nothing to do with it.
It is all just metal and the running dimensions under stress should be the only thing which matters; if the parts and oiling system are up to the task.

I have learned the mindset of most Big Block Ford people and they are simply unwilling to perform the necessary steps in order to be able to run those tighter clearances.  
I understand all this however, closing your eyes to what is happening throughout the rest of the industry is just the hard headed arrogance of the "if it ain't broke, don't fix it" people who think that also means not to take any advantage of any evolutions or advancements either.

It really is the choice of people to do whatever they wish; whatever makes them happiest is all that really matters.

If I would run those tight tolerances in my 638 with the parts I have it would be a pile of scrap already, but go ahead and run .0025 main clearance on a 4.75 crank and 1200 hp and see what you end up with.

Ask Kaase what main and rod clearances they use on the 820" stuff, they are a way different animal than a 350" NASCAR or a 500" PS engine.

The clearances need to fit the application and use.

rmcomprandy wrote:

I have learned the mindset of most Big Block Ford people and they are simply unwilling to perform the necessary steps in order to be able to run those tighter clearances.  
I understand all this however, closing your eyes to what is happening throughout the rest of the industry is just the hard headed arrogance of the "if it ain't broke, don't fix it" people who think that also means not to take any advantage of any evolutions or advancements either.

Open our eyes!  What are the necessary steps? Costs?  
What do these evolutions and advancements mean? More power? Longevity?

What is the benefit to the average BBF builder to going 0.001" tighter on bearing clearances and thinner on oil?

68galaxie wrote:

rmcomprandy wrote:

I have learned the mindset of most Big Block Ford people and they are simply unwilling to perform the necessary steps in order to be able to run those tighter clearances.  
I understand all this however, closing your eyes to what is happening throughout the rest of the industry is just the hard headed arrogance of the "if it ain't broke, don't fix it" people who think that also means not to take any advantage of any evolutions or advancements either.

Open our eyes!  What are the necessary steps? Costs?  
What do these evolutions and advancements mean? More power? Longevity?

What is the benefit to the average BBF builder to going 0.001" tighter on bearing clearances and thinner on oil?

Those benefits certainly may not be required or even wanted by the everyday person who bracket races once in a while.

There are many benefits to the engine NEEDING less oil flow volume.
Thinner oil, (with correct clearances for that oil), "flying around" in the crankcase will mean less oil control problems, less mass oil volume needed, less oil aeration, less chance that any oil will by-pass at the filter, a smaller required oil pump, lower tension rings and of course a bit more power because of all this.
But, a lot of people don't care about such stuff; especially drag racers who only worry about very short time Wide Open Throttle running, with relatively cold engine oil.

Of course it all will usually cost much more money so, certainly people pinching pennies won't want any of that.

Parts distortion with very high torque engines is why those engines will need to use larger clearances.
Even needing piston guided rods with .060" rod side clearance because, with that large amount of torque and the long stroke crankshaft, (having small journals and no overlap), will actually get about .040" shorter in that engine when running 6.500 RPM.

Thank you for the explanation.

It just sounded like any persons or builders who chose not to run tight bearing clearances and thin oils was living in the 1970's and was a luddite - not wanting to accept a/the more modern approach to bearing clearances.

Cheers

bosshoss wrote:So I have been playing with high performance engines now for 45 years or so. One of the earliest lessons drummed in to my impressionable brain back at the beginning was the thing about using 20/50 or even 60 weight oil in any serious racing engine.

In spite of repeated exposure to multiple experts since then I have resisted the urge to change.

I have recently come to the realization that I need to move in to the 21st century.

So the question is...  How does one decide which of the new miracle products to choose.

I have been eyeing up the Lucas synthetic line but have no idea how to choose which weight.

5-30  10-30 even 20-50  whatttt....

600 inch SVO block, dry sump, Drag race, steel rods, .003 -.004 bearing clearances.

Any advice from the panel?

Straight wt oils like 40-50-60 are not the way to go for sure.

If you are using something like VR-1 mineral oil 10w-30 or 20w-50 works good but, leaves some power on the table. At my budget level I do not see that as an issue unless a guy was running some bad fast class deal.

If a guy wants to lay a number down on a dyno the thin syn stuff is the way to go....just a matter of budget.

.0028"ish on the rods and .003" with aluminum works on most stuff I've been involved with. .0033 - .0035" on the mains....until there is a shit load of 'spray' involved.... .004" ain't out of the question at that point. I think Blake was trying to address the subject of how flexable our parts are.

.0002" more clearance than it needs is not shit......0002" less than it needs is a rod under the rear wheel.

thanks for all the responses guys. Gives me a lot of food for thought. I don't consider myself a professional engine builder by any stretch. I do the best I can. Assemble all my stuff in my shop at home. Measure everything as carefully as I can. I have had decent success over the years. A few failures of course, mostly of my own making. Lessons learned.

I like the sound of less windage and lower overall oil flow. Next set of bearings will be a little tighter and will step out with maybe a 10-40 synthetic.

thanks guys

IMO........the dry sump is a game changer in regards to the oil control stuff. I have used 10/30 in place of 20/50 and saw very little difference in psi with hot oil. The external pump can usually be adjusted to do what you need it to. Just my .02......