One more time, rod side clearance

General engine tech -- Drag Racing to Circle Track

Moderator: Team

User avatar
MadBill
Guru
Guru
Posts: 13399
Joined: Tue Nov 15, 2005 10:41 am
Location: The Great White North

Re: One more time, rod side clearance

Post by MadBill » Fri Apr 06, 2018 8:34 pm

One situation in which more side clearance could result in more oil outflow would be if the radial clearances were large, such that the tight side clearances were effectively doing the metering... :-k
Felix, qui potuit rerum cognscere causas.

Happy is he who can discover the cause of things.

Charliesauto
Member
Member
Posts: 90
Joined: Wed Sep 03, 2014 2:01 am

Re: One more time, rod side clearance

Post by Charliesauto » Fri Apr 06, 2018 8:47 pm

LSP wrote:
Fri Apr 06, 2018 8:27 pm
My case might be considered a "tweener".

LS1
OE wet oil pump
OE wet oil pan with accel baffle
Manley H-Lite rods, narrowed to .710" at big end, .680" wide rod bearings, guided at small end
K1 LS1 crankshaft
3mm - 7 lb. Hastings oil ring
5800-8300 rpm

Charcoal gray piston tops and chambers upon teardown.

Everyone can believe what they want, just giving another example to think about.
That computes to about 1/2" of side clearance, in conjunction with a 7lb oil ring. According to my detractor above, that thing should consume all the oil in the pan before you get out of the driveway.

LSP
Pro
Pro
Posts: 274
Joined: Tue Mar 16, 2010 12:33 pm
Location: Charlotte

Re: One more time, rod side clearance

Post by LSP » Fri Apr 06, 2018 9:00 pm

Charliesauto wrote:
Fri Apr 06, 2018 8:47 pm
LSP wrote:
Fri Apr 06, 2018 8:27 pm
My case might be considered a "tweener".

LS1
OE wet oil pump
OE wet oil pan with accel baffle
Manley H-Lite rods, narrowed to .710" at big end, .680" wide rod bearings, guided at small end
K1 LS1 crankshaft
3mm - 7 lb. Hastings oil ring
5800-8300 rpm

Charcoal gray piston tops and chambers upon teardown.

Everyone can believe what they want, just giving another example to think about.
That computes to about 1/2" of side clearance, in conjunction with a 7lb oil ring. According to my detractor above, that thing should consume all the oil in the pan before you get out of the driveway.
I wanted to see how far I could the rod side clearance thing, if it had an oil pan failure I was ok with it. Only thing I saw that was a concern were the rod bearings shining up right where the eccentricity kicks in, but after all, it was a set of $550 rods that aren't all that robust at the parting lines.
Wish I had time to be a Guru

Charliesauto
Member
Member
Posts: 90
Joined: Wed Sep 03, 2014 2:01 am

Re: One more time, rod side clearance

Post by Charliesauto » Fri Apr 06, 2018 9:04 pm

Newold1 wrote:
Fri Apr 06, 2018 7:33 pm
Your contention that "excess" side clearance has no affect on oil consumption in an engine based on the single point that some Nascar engines in the past had very large rod side clearance and it was not an issue or reality ! Wow, this tells me you have almost no real experience building performance engines in my opinion!

I have seen the affects of excessive rod clearances in some fleet engines that I was asked to determine why the engines were consuming way to much oil and the excessive oil contamination in the combustion chambers was leading to detonation, carbon scoring of the cylinder walls and coking and sticking of the rings in piston grooves! After we discovered the excess rod side clearances we installed new properly clearanced rods, cleaned up the pistons and chambers, installed new rings and broke the glaze on the cylinder faces and reassembled the engines with all original bearing sets and seals and the oil consumption and oil contamination problems stopped immediately with no changes in ring types or tensions, no reduction in oil pressures and just eliminating the rod side clearance issue.

You cannot and should not make comparisons here for performance enthusiasts, hobby type engine builders and users that you can use Nascar engine building experimentation and exotic parts and build techniques and use those on most all the engine users that draw from and use a lot of information disseminated here on Speedtalk. I am sure that all the very knowledge professional engine builders here on Speedtalk know that excessive rod side clearance is a problem and that is why I am pretty sure that few of them set their builds up that way.

Please remember that all Nascar engine builders are building and prepping very specialized V-8's that have almost nothing in common with any other racing family of engines and they do not share direct information of how they design, build and equip their team engines! Almost all heir employees know that if their special information and data is leaked, their jobs are at serious risk! Comparing today's Nascar Cup engines to all the other engines that contributors here on Speedtalk are asking about or discussing is like comparing a brain surgeon to a chiropractor!

This is some of the internet fed and spread misinformation and comments that make the internet forums dangerous places to get good build information.

Sorry to be so blunt, but let's be careful and correct when we share information.
Only been building racing engines for thirty years, I am sure that pales in comparison to most on here.

When the original poster ask his question in this forum(Speedtalk) I assumed we were discussing a race engine or at least something performance oriented.

I have built numerous piston guided wet sump circle track engines with side clearances from .240" - .300". I observed no difference in oil consumption compared to engines of the same configuration, application and ring package and having more conventional side clearance(.015"-.020").

I still say the radial clearance of the rod bearing dictates the total oil flow from the rod bearing/crank interface. Assuming you have not done something ridiculous like standard bearings on a .010" undersize journal.

LSP
Pro
Pro
Posts: 274
Joined: Tue Mar 16, 2010 12:33 pm
Location: Charlotte

Re: One more time, rod side clearance

Post by LSP » Fri Apr 06, 2018 9:26 pm

LSP wrote:
Fri Apr 06, 2018 9:00 pm
Charliesauto wrote:
Fri Apr 06, 2018 8:47 pm
LSP wrote:
Fri Apr 06, 2018 8:27 pm
My case might be considered a "tweener".

LS1
OE wet oil pump
OE wet oil pan with accel baffle
Manley H-Lite rods, narrowed to .710" at big end, .680" wide rod bearings, guided at small end
K1 LS1 crankshaft
3mm - 7 lb. Hastings oil ring
5800-8300 rpm

Charcoal gray piston tops and chambers upon teardown.

Everyone can believe what they want, just giving another example to think about.
That computes to about 1/2" of side clearance, in conjunction with a 7lb oil ring. According to my detractor above, that thing should consume all the oil in the pan before you get out of the driveway.
I wanted to see how far I could take the rod side clearance thing, if it had an oil pan failure I was ok with it. Only thing I saw that was a concern were the rod bearings shining up right where the eccentricity kicks in, but after all, it was a set of $550 rods that aren't all that robust at the parting lines.
Wish I had time to be a Guru

LSP
Pro
Pro
Posts: 274
Joined: Tue Mar 16, 2010 12:33 pm
Location: Charlotte

Re: One more time, rod side clearance

Post by LSP » Fri Apr 06, 2018 9:27 pm

LSP wrote:
Fri Apr 06, 2018 9:00 pm
Charliesauto wrote:
Fri Apr 06, 2018 8:47 pm
LSP wrote:
Fri Apr 06, 2018 8:27 pm
My case might be considered a "tweener".

LS1
OE wet oil pump
OE wet oil pan with accel baffle
Manley H-Lite rods, narrowed to .710" at big end, .680" wide rod bearings, guided at small end
K1 LS1 crankshaft
3mm - 7 lb. Hastings oil ring
5800-8300 rpm

Charcoal gray piston tops and chambers upon teardown.

Everyone can believe what they want, just giving another example to think about.
That computes to about 1/2" of side clearance, in conjunction with a 7lb oil ring. According to my detractor above, that thing should consume all the oil in the pan before you get out of the driveway.
I wanted to see how far I could take the rod side clearance thing, if it had an oil pan failure I was ok with it. Only thing I saw that was a concern were the rod bearings shining up right where the eccentricity kicks in, but after all, it was a set of $550 rods that aren't all that robust at the parting lines.
Wish I had time to be a Guru

LSP
Pro
Pro
Posts: 274
Joined: Tue Mar 16, 2010 12:33 pm
Location: Charlotte

Re: One more time, rod side clearance

Post by LSP » Fri Apr 06, 2018 9:29 pm

Sorry for the multiple posts, tried to make a correction and somehow copied/pasted, and couldn't delete.
Wish I had time to be a Guru

Newold1
Guru
Guru
Posts: 1262
Joined: Fri Apr 08, 2016 9:50 am

Re: One more time, rod side clearance

Post by Newold1 » Fri Apr 06, 2018 10:08 pm

Charliesauto

My point was to say that the thread all of a sudden with your question about piston guided rod setups went from an enthusiast asking if excessive side clearance with NON_PISTON GUIDED ROD SETUPS and standard side clearances to one pointing out that Nascar shops and your builds were using large rod side clearances on piston guided builds without explanning to users how a piston guided rod set up is different from a standard piston rod combo and some readers are going to possibly wrongly assume they can run those type of clearances on regular piston rod builds without excessive oil splash and burn. That's a point I disagree with and from my experiences has not worked well.

I apologize for attacking your engine building experience that was a cheap shot without me knowing your experience.

Since piston guided rod clearance has now moved into this post maybe you with your experience could post a picture of such a piston and rod example so readers here not familiar with this type of setup could see how your using it in your builds. I also see that your builds using this are deep skirt LS engine blocks and that might have an influence on how the oil volume from the big end of the rod is not splashed as much on the shorter cylinder walls in that engine versus older short skirt blocks. I personally have not seen an LS based race engine with a piston guided rod set up so I can't speak to that use.

groberts101
Guru
Guru
Posts: 1879
Joined: Sat Mar 08, 2008 3:08 pm
Location: Minneapolis

Re: One more time, rod side clearance

Post by groberts101 » Fri Apr 06, 2018 10:24 pm

Charliesauto wrote:
Fri Apr 06, 2018 9:04 pm

Only been building racing engines for thirty years, I am sure that pales in comparison to most on here.

When the original poster ask his question in this forum(Speedtalk) I assumed we were discussing a race engine or at least something performance oriented.

I have built numerous piston guided wet sump circle track engines with side clearances from .240" - .300". I observed no difference in oil consumption compared to engines of the same configuration, application and ring package and having more conventional side clearance(.015"-.020").

I still say the radial clearance of the rod bearing dictates the total oil flow from the rod bearing/crank interface. Assuming you have not done something ridiculous like standard bearings on a .010" undersize journal.
And therein lies some of the problem with interpretation of questions around here. The way this threads question was phrased implied it was a generalized question.. not specific to a race only motor. We get bikes boats volkswagons race engines tractor motors and everything in between here. Sure most are interested in improving performance in some way shape or form but most are far from race only applications. Otherwise it should be called racetalk.. not speedtalk. The varying degrees of speed and performance improvement is very subjective.

And let's not forget not every engine has low tension oil rings crank scrapers and vacuum pumps to allow a one size fits all approach either. Also good to remember that nascar didn't invent half the stuff they use.. they only pushed envelopes using HUGE resources with extensive r&d budgets to make some of those power saving tricks live for 500-600 miles. Parts and machining have improved but the margins and durability reserves are not huge to where one motor lasts for years. Take some of those tricks in stand alone fashion and try to use them on pure street motors, many of which are lower rpm daily drivers, and you will most certainly have negative side affects related to their implementation in the wrong application. Simply won't work as effectively or nearly as long outside their intended niche, is my main point.

I have far more experience with street type performance motors and I have seen many with oil control issues related to excessive clearances.. radial side or otherwise. Making a junk motor with subpar parts live under much higher rpm and bigger cylinder pressures comes with its own sets of rules and limitations given the fact that oil control is already a major issue to begin with.

I fully agree.. i's not even about pressure.. it's more about where the oil is going when the rods pair up. Look at the piston pins wear patterns on larger side clearanced setups and it's easy to see they have been dancing all over the place. Then try to imagine where oil is forced to go when both rods pair up against one side of the crank pin fillet. Each bank of cylindrrs is offset from one another and is entirely possible that escaping oil supply might burden one cylinder more than another. So one cylinder may see twice the supply of oil than another. No scrapers/windage trays and often no baffles either, no deep short filled pans, no napier second rings, no dry sumps, no vac pumps, and surely no small end guided setups. Just old school open pans sloshing oil all over the place during repeated and prolonged acceleration and braking.

In the context of which is better?.. I'm not at all against huge side clearances and low tension oil rings working towards reduced frictional losses, and nor are the mfgrs I'd imagine, but making those things live for 100,000 miles, much less 200,000 miles, becomes the bigger obstacle to overcome. Not to mention the added cost of vac pumps, special ring packages, piston guided rods and whatnot makes them unrealistic for most but all the more hardcore hot street machines or racecars. If it really was that easy?.. why don't we see it utilized far more often? After all.. it's a monkey see monkey do kinda world we live in.
Last edited by groberts101 on Fri Apr 06, 2018 10:28 pm, edited 1 time in total.

ptuomov
Guru
Guru
Posts: 2042
Joined: Fri Aug 07, 2009 3:52 am

Re: One more time, rod side clearance

Post by ptuomov » Fri Apr 06, 2018 10:27 pm

While I am thinking about this without much practical experience, I am just wondering if it makes sense to make the rod cap a little narrower in engines that have a problem with too much oil on the bore walls and rod cap a little wider in engines that have a problem with too little oil on the bore walls. By my logic, the rod big end gap doesn't have to be the same for the rod big end side and the big end gap side, it's a choice...
[b]Paradigms often shift without the clutch[/b] -- [url]https://www.youtube.com/watch?v=cxn-LxwsrnU[/url]

Truckedup
Guru
Guru
Posts: 1653
Joined: Mon Jan 21, 2013 2:41 pm

Re: One more time, rod side clearance

Post by Truckedup » Sat Apr 07, 2018 7:01 am

Charliesauto wrote:
Fri Apr 06, 2018 9:04 pm

When the original poster ask his question in this forum(Speedtalk) I assumed we were discussing a race engine or at least something performance oriented.
OP here, yes, performance engine, usually motorcycle in my case but the question was in general....... One poster gave a detailed story of oil usage with gas engine trucks being affected by oil ring design..That's a big variable I hadn't though about
Motorcycle land speed racing... wearing animal hides and clinging to vibrating oily machines propelled by fire

Warp Speed
Guru
Guru
Posts: 2569
Joined: Wed Jun 25, 2008 1:46 pm
Location: NC

Re: One more time, rod side clearance

Post by Warp Speed » Sat Apr 07, 2018 7:48 am

groberts101 wrote:
Fri Apr 06, 2018 3:57 pm
SupStk wrote:
Fri Apr 06, 2018 2:18 pm
Common sense seems to dictate, diametrical clearances will have more effect on oil flow than side clearance. Unless the side clearance is extremely tight.
Right. But nothing is completely set in stone, there aren't many absolutes, and stuff just plain wears out. So the words little or more certainly don't mean nothing. Anything at all no matter how small or seemingly immeasurable is still.. something. Now maybe it doesn't always matter in all applications or parts combos.. but it's still something.

And as Larry already eluded to some applications and combinations of parts might differ from others which were used as the yardstick for which some are basing their desicions and opinions on. Also consider that what was once marginal at controlling oil when new, especially at higher rpms for which it wss never originally designed, can become much less able to effectively do the job when stuff just plain wears out and gets tasked beyond its abilities.

Everyone gets caught up on oil pressure differences but what about oil shedding and cylinder to cylinder distribution of that escaping oil volume? Do the paired rods not gather up on common crank pins to change how much and where that accumulated clearance is aimed at any given time?

If rod side clearances had absolutely no affect whatsoever on oil control then everyone and their cousins would be cutting rods to mimic racers in the quest for reduced friction and it would also be built in from the factories as a win win. Less material, lighter weights, fewer tolerances with less concerns for quality control, no downsides whatsoever. That is not the reality and the first few junk motors that you toss together with less than ideal parts having massive amounts of rod side clearances will usually culminate towards excessive chamber contamination on some cylinders over others. That balancing of various effects is largely the reason we blueprint everything in the first place for improved consistency.

So yes.. imo, rod side clearances change the oil shedding distribution characteristics in a less than desirable fashion for some cylinders compared to others. So I'll continue to worry about it and blueprint accordingly with less regard towards frictional losses in trade for tighter combustion consistency with regard to cylinder to cylinder oil control.
That would be your "imo", while in fact, unless huge rod bearing clearances are being used, side clearance has no effect on oil flow. Have tested it more than a few times.
Which may have been the case in Larry's example.....

groberts101
Guru
Guru
Posts: 1879
Joined: Sat Mar 08, 2008 3:08 pm
Location: Minneapolis

Re: One more time, rod side clearance

Post by groberts101 » Sat Apr 07, 2018 1:20 pm

Warp Speed wrote:
Sat Apr 07, 2018 7:48 am
groberts101 wrote:
Fri Apr 06, 2018 3:57 pm
SupStk wrote:
Fri Apr 06, 2018 2:18 pm
Common sense seems to dictate, diametrical clearances will have more effect on oil flow than side clearance. Unless the side clearance is extremely tight.
Right. But nothing is completely set in stone, there aren't many absolutes, and stuff just plain wears out. So the words little or more certainly don't mean nothing. Anything at all no matter how small or seemingly immeasurable is still.. something. Now maybe it doesn't always matter in all applications or parts combos.. but it's still something.

And as Larry already eluded to some applications and combinations of parts might differ from others which were used as the yardstick for which some are basing their desicions and opinions on. Also consider that what was once marginal at controlling oil when new, especially at higher rpms for which it wss never originally designed, can become much less able to effectively do the job when stuff just plain wears out and gets tasked beyond its abilities.

Everyone gets caught up on oil pressure differences but what about oil shedding and cylinder to cylinder distribution of that escaping oil volume? Do the paired rods not gather up on common crank pins to change how much and where that accumulated clearance is aimed at any given time?

If rod side clearances had absolutely no affect whatsoever on oil control then everyone and their cousins would be cutting rods to mimic racers in the quest for reduced friction and it would also be built in from the factories as a win win. Less material, lighter weights, fewer tolerances with less concerns for quality control, no downsides whatsoever. That is not the reality and the first few junk motors that you toss together with less than ideal parts having massive amounts of rod side clearances will usually culminate towards excessive chamber contamination on some cylinders over others. That balancing of various effects is largely the reason we blueprint everything in the first place for improved consistency.

So yes.. imo, rod side clearances change the oil shedding distribution characteristics in a less than desirable fashion for some cylinders compared to others. So I'll continue to worry about it and blueprint accordingly with less regard towards frictional losses in trade for tighter combustion consistency with regard to cylinder to cylinder oil control.
That would be your "imo", while in fact, unless huge rod bearing clearances are being used, side clearance has no effect on oil flow. Have tested it more than a few times.
Which may have been the case in Larry's example.....
Lol.. so predictable. The thread title didn't end with.. "on a nascar motor".

It's based on my personal experiences as well as many others I've talked with and personally witnessed the teardowns. So, I guess when you start putting wetsumped non vac assisted oem panned nascar motors in your daily driver and testing those effects in day to day traffic?.. then maybe we can have an apples to apples discussion. Until then.. my own testing and experience easily trumps yours and I'll stick with what my own eyes have seen. And to be clear.. I never once said it changes the total volume of leaked oil.. only WHERE that same volume of oil is being directed. Big difference there.

Also seems a little odd you'd test a narrower rod width deal without some type of pin guided setup to even take full advantage of their potential for reduced parasitic losses? And also without some form of extra windage control? Simply looking at the piston pins wear patterns on a non-guided setup will easily clue you in to the fact that the rods gather together and pair up more than a few times over the life of the motor.

Warp Speed
Guru
Guru
Posts: 2569
Joined: Wed Jun 25, 2008 1:46 pm
Location: NC

Re: One more time, rod side clearance

Post by Warp Speed » Sat Apr 07, 2018 1:37 pm

groberts101 wrote:
Sat Apr 07, 2018 1:20 pm
Warp Speed wrote:
Sat Apr 07, 2018 7:48 am
groberts101 wrote:
Fri Apr 06, 2018 3:57 pm


Right. But nothing is completely set in stone, there aren't many absolutes, and stuff just plain wears out. So the words little or more certainly don't mean nothing. Anything at all no matter how small or seemingly immeasurable is still.. something. Now maybe it doesn't always matter in all applications or parts combos.. but it's still something.

And as Larry already eluded to some applications and combinations of parts might differ from others which were used as the yardstick for which some are basing their desicions and opinions on. Also consider that what was once marginal at controlling oil when new, especially at higher rpms for which it wss never originally designed, can become much less able to effectively do the job when stuff just plain wears out and gets tasked beyond its abilities.

Everyone gets caught up on oil pressure differences but what about oil shedding and cylinder to cylinder distribution of that escaping oil volume? Do the paired rods not gather up on common crank pins to change how much and where that accumulated clearance is aimed at any given time?

If rod side clearances had absolutely no affect whatsoever on oil control then everyone and their cousins would be cutting rods to mimic racers in the quest for reduced friction and it would also be built in from the factories as a win win. Less material, lighter weights, fewer tolerances with less concerns for quality control, no downsides whatsoever. That is not the reality and the first few junk motors that you toss together with less than ideal parts having massive amounts of rod side clearances will usually culminate towards excessive chamber contamination on some cylinders over others. That balancing of various effects is largely the reason we blueprint everything in the first place for improved consistency.

So yes.. imo, rod side clearances change the oil shedding distribution characteristics in a less than desirable fashion for some cylinders compared to others. So I'll continue to worry about it and blueprint accordingly with less regard towards frictional losses in trade for tighter combustion consistency with regard to cylinder to cylinder oil control.
That would be your "imo", while in fact, unless huge rod bearing clearances are being used, side clearance has no effect on oil flow. Have tested it more than a few times.
Which may have been the case in Larry's example.....
Lol.. so predictable. The thread title didn't end with.. "on a nascar motor".

It's based on my personal experiences as well as many others I've talked with and personally witnessed the teardowns. So, I guess when you start putting wetsumped non vac assisted oem panned nascar motors in your daily driver and testing those effects in day to day traffic?.. then maybe we can have an apples to apples discussion. Until then.. my own testing and experience easily trumps yours and I'll stick with what my own eyes have seen. And to be clear.. I never once said it changes the total volume of leaked oil.. only WHERE that same volume of oil is being directed. Big difference there.

Also seems a little odd you'd test a narrower rod width deal without some type of pin guided setup to even take full advantage of their potential for reduced parasitic losses? And also without some form of extra windage control? Simply looking at the piston pins wear patterns on a non-guided setup will easily clue you in to the fact that the rods gather together and pair up more than a few times over the life of the motor.
Even more predictable!
Your opinions are based on theory and small data sample with many noise elements.
Mine are based on facts and data gathered from scientific testing.
And unless you live in a different universe or something, the laws remain the same, not just "cup engines"....

Warp Speed
Guru
Guru
Posts: 2569
Joined: Wed Jun 25, 2008 1:46 pm
Location: NC

Re: One more time, rod side clearance

Post by Warp Speed » Sat Apr 07, 2018 1:38 pm

MadBill wrote:
Fri Apr 06, 2018 8:34 pm
One situation in which more side clearance could result in more oil outflow would be if the radial clearances were large, such that the tight side clearances were effectively doing the metering... :-k
This, otherwise, side clearance does not determine flow from rod bearings.

Post Reply