One more time, rod side clearance

[peejay]

How does even .020" of side clearance matter when there is .001" or so of radial clearance in the bearing? That's going to determine how much oil is flowing into and out of the bearing. It's the point of most restriction.

[user-30257]

How does even .020" of side clearance matter when there is .001" or so of radial clearance in the bearing? That's going to determine how much oil is flowing into and out of the bearing. It's the point of most restriction.

Because the internet GURUS are always right, and they try to refute any real world or scientifically approached data with some BS, they heard. BUT MY SISTER'S BOYFRIENDS UNCLE DID, AND HE SAID IT LEAKED LIKE CRAZY. SO YOU MISTER ARE A MORON. MY SISTER'S BOYFRIENDS UNCLE WORKS AT AUTOZONE AND KNOWS HIS STUFF.

[groberts101]

I have a question related to another comment you made elsewhere around here. Do you guys now run wide rod side gaps without some form of guides to keep them away from one another? How does that work?

The rods are guided side to side by the piston in the bore. The rod small end has tight side clearance to the piston pin bosses. Typically .004-.006.

I figured as much since everything is custom made(no shelf parts per se) to work together as supporting components. Pistons are strutted with very narrow open section widths between those much shorter pins/bosses to avoid the need for any additional spacers right off the drawing board.

Small semi-relevant tangent here, but while also on the optimised piston design subject.. I have spoken to several builders and a few racers through the years who have stated that trying to force a full round or non-boxed/non-strutted piston design into a pin guided setup can cause severe pin flexing issues because of those typically wider spacer widths needed to work with longer pin lengths and their inherently wider outboard boss locations. I have held in hand a damaged piston and seen a few pic's here and there that indicate the added spacers do absolutely nothing in regards to the longer pins overall stability(in sharp contrast to your/nascar's typically used much narrower boss piston designs) and clearances tend to move around during pin flex which causes oil flow to be temporarily pinched during heavier compression and tension loads. Which apparently potentially leads to pin boss and spacer galling over longer term or heavier usage. In fact, many years ago(about 30 years now, which goes to show this isn't something new by any stretch) one offshore powerboat racer in Cali told me to stay clear of such mod's unless I intended to run much thicker pins to reduce pin flex. And even then, I'd likely close up the ring lands and create other issues, iirc specifically reducing ring rotation, due to the much heavier mass of yesteryears off-shelf piston designs. Seemed somewhat counterproductive to add more weight while hunting for reduction of frictional losses so I stayed clear as advised.

So, finally I arrive at my question here. Is this still a problem today(running thicker spacers on much wider pins/bosses) or have the metallurgy and machining tolerances changed enough to combat and counteract some of the negatives created by using spacers on much longer pin widths having considerably wider outboard pin boss locations?

Back to the threads title subject. The little bit I have talked with others and read about in regards to oil flow allocation or maybe better to say.. "distribution paths", and the thing I can at least imagine occurring differently on such a piston guided setup is that the rods are somewhat equally separated away from adjacent components(other paired rod and common crank pin cheeks/fillets) in such a manner that the escaping oil flow is somewhat more equal and linear from a distribution standpoint. This allows the escaping oil volume to be shared more equally amongst the cylinders/pistons located directly above. In direct comparison to an engine with really wide side gaps but having no guiding mechanism.. thereby allowing those rod pairs to gather up and change up some of the escaping oil flows distribution equality and linear flow paths. Maybe more of that same volume of escaping oil ends up lopsided/on one side of the piston/bore? And ^THIS^ "distribution problem" is exactly what I was trying to get at in my long winded posts above.

Thanks for the last reply and also in advance if you have the time to share some of your hard earned knowledge,

Greg

[groberts101]

How does even .020" of side clearance matter when there is .001" or so of radial clearance in the bearing? That's going to determine how much oil is flowing into and out of the bearing. It's the point of most restriction.

Because the internet GURUS are always right, and they try to refute any real world or scientifically approached data with some BS, they heard. BUT MY SISTER'S BOYFRIENDS UNCLE DID, AND HE SAID IT LEAKED LIKE CRAZY. SO YOU MISTER ARE A MORON. MY SISTER'S BOYFRIENDS UNCLE WORKS AT AUTOZONE AND KNOWS HIS STUFF.

I wish more people would start reporting your combative and inflammatory posts as i will surely start doing. Right abouuttt.. NOW....

And speaking of internet guru's?.. How's your post count coming along with all your recent "forum contributions"? Guru pot.. meet guru kettle.

[Warp Speed]

I have a question related to another comment you made elsewhere around here. Do you guys now run wide rod side gaps without some form of guides to keep them away from one another? How does that work?

The rods are guided side to side by the piston in the bore. The rod small end has tight side clearance to the piston pin bosses. Typically .004-.006.

I figured as much since everything is custom made(no shelf parts per se) to work together as supporting components. Pistons are strutted with very narrow open section widths between those much shorter pins/bosses to avoid the need for any additional spacers right off the drawing board.

Small semi-relevant tangent here, but while also on the optimised piston design subject.. I have spoken to several builders and a few racers through the years who have stated that trying to force a full round or non-boxed/non-strutted piston design into a pin guided setup can cause severe pin flexing issues because of those typically wider spacer widths needed to work with longer pin lengths and their inherently wider outboard boss locations. I have held in hand a damaged piston and seen a few pic's here and there that indicate the added spacers do absolutely nothing in regards to the longer pins overall stability(in sharp contrast to your/nascar's typically used much narrower boss piston designs) and clearances tend to move around during pin flex which causes oil flow to be temporarily pinched during heavier compression and tension loads. Which apparently potentially leads to pin boss and spacer galling over longer term or heavier usage. In fact, many years ago(about 30 years now, which goes to show this isn't something new by any stretch) one offshore powerboat racer in Cali told me to stay clear of such mod's unless I intended to run much thicker pins to reduce pin flex. And even then, I'd likely close up the ring lands and create other issues, iirc specifically reducing ring rotation, due to the much heavier mass of yesteryears off-shelf piston designs. Seemed somewhat counterproductive to add more weight while hunting for reduction of frictional losses so I stayed clear as advised.

So, finally I arrive at my question here. Is this still a problem today(running thicker spacers on much wider pins/bosses) or have the metallurgy and machining tolerances changed enough to combat and counteract some of the negatives created by using spacers on much longer pin widths having considerably wider outboard pin boss locations?

Back to the threads title subject. The little bit I have talked with others and read about in regards to oil flow allocation or maybe better to say.. "distribution paths", and the thing I can at least imagine occurring differently on such a piston guided setup is that the rods are somewhat equally separated away from adjacent components(other paired rod and common crank pin cheeks/fillets) in such a manner that the escaping oil flow is somewhat more equal and linear from a distribution standpoint. This allows the escaping oil volume to be shared more equally amongst the cylinders/pistons located directly above. In direct comparison to an engine with really wide side gaps but having no guiding mechanism.. thereby allowing those rod pairs to gather up and change up some of the escaping oil flows distribution equality and linear flow paths. Maybe more of that same volume of escaping oil ends up lopsided/on one side of the piston/bore? And ^THIS^ "distribution problem" is exactly what I was trying to get at in my long winded posts above.

Thanks for the last reply and also in advance if you have the time to share some of your hard earned knowledge,

Greg

We ran spacers for years with no problems back in the day. But of course you don't get the piston/pin support you would with a tighter rod box, so we were only getting the partial advantage of a piston guided set up. As I said, this never caused a problem, and didnt magnify the problem of too thin of a wrist pin. If the pin is too thin, it's just too thin!
I would never suggest running really wide big end gaps without being piston guided, as something needs to lateraly stabilize the rod.
To your splash direction theory, there is a little to this, but most oil getting released by the rod bearing is into the cylinder area no matter what, and is initially contained to those cylinders by the main caps and block web area. Just think what is constantly pouring from the mains...
Main bearing clearance has a bigger effect on oil control than the rod bearings. Where is the pressure feed and groove area (highest pressure/bleed area) in a main bearing, or the system for that matter?
Right at the bulkhead beneath the cam and cylinders!

[Warp Speed]

How does even .020" of side clearance matter when there is .001" or so of radial clearance in the bearing? That's going to determine how much oil is flowing into and out of the bearing. It's the point of most restriction.

Because the internet GURUS are always right, and they try to refute any real world or scientifically approached data with some BS, they heard. BUT MY SISTER'S BOYFRIENDS UNCLE DID, AND HE SAID IT LEAKED LIKE CRAZY. SO YOU MISTER ARE A MORON. MY SISTER'S BOYFRIENDS UNCLE WORKS AT AUTOZONE AND KNOWS HIS STUFF.

I wish more people would start reporting your combative and inflammatory posts as i will surely start doing. Right abouuttt.. NOW....

And speaking of internet guru's?.. How's your post count coming along with all your recent "forum contributions"? Guru pot.. meet guru kettle.

Dont be so dramatic!
This are just machines we are talking about!
"Combative and inflammatory"?
How was your reply really any different?

[groberts101]

Dont be so dramatic!
This are just machines we are talking about!
"Combative and inflammatory"?
How was your reply really any different?

No doubt you most definitely caught me on that one. It was more a cumulative thing, not necessarily aimed at that specific post. That headguy doesn't spend any time trying to actually contribute anything positive towards the conversation. And whether we like trust or agree with the info he gives or not is irrelevant since it just adds to experience and viewpoints, just comes in shoots his mouth off craps on people and runs off like this place is some sort of personal punching bag for stress relief. Just kinda funny he talks about internet gurus and yet appears to be one and the same himself.

Anywho.. thank you very much for your time and detailed response. Read bunches of your posts through the years here and elsewhere. Always looking to refine my understanding of all things physics and engine related and you've definitely offered some valuable info.

[pcnsd]

Dont be so dramatic!
This are just machines we are talking about!
"Combative and inflammatory"?
How was your reply really any different?

No doubt you most definitely caught me on that one. It was more a cumulative thing, not necessarily aimed at that specific post. That headguy doesn't spend any time trying to actually contribute anything positive towards the conversation. And whether we like trust or agree with the info he gives or not is irrelevant since it just adds to experience and viewpoints, just comes in shoots his mouth off craps on people and runs off like this place is some sort of personal punching bag for stress relief. Just kinda funny he talks about internet gurus and yet appears to be one and the same himself.

Anywho.. thank you very much for your time and detailed response. Read bunches of your posts through the years here and elsewhere. Always looking to refine my understanding of all things physics and engine related and you've definitely offered some valuable info.

You are not alone in your umbrage and I too have a list of statesmen I look to. I believe others work by the same methods and apply the same standards.

[Walter R. Malik]

To me ... just because someone's reply is filled with sarcasm and may push someone else' feelings to get injured ... does not make it malicious.

Take it for what it is worth and move on. Don't feed the trolls ...

[Newold1]

I obviously am grateful for Warp Speed's contributions, experience and conversations here on Speedtalk and I am not trying to question his rod side clearance information on the Nascar engines he is privy to. I am however still conflicted on the idea or belief that opening rod side clearances on more conventional V-8 engines as were being discussed would not create an increased oil consumption and other oiling conditions.

My points about Nascar engines such as the GM R07 family are truly different animals and they obviously have some very well designed, engineered and tested components that are configured and used to make oil control and horsepower loss from oil splash, throw off and windage a much reduced problem in these engines. The oil control in these engines is a incredible testament to how oil control and power robbing losses from windage when improved can really make the high 10,000 rpm horsepower levels possible and how these engines can run for over 500 miles without issues!

In the attached images it becomes obvious that the design and components of these Nascar engines are so different from conventional parts of standard V-8 engines that saying wide rod side clearances in conventional V-8 engines are not an issue since wide side clearances in the Nascar piston controlled rods do not result in any oil control or volume issues. From what I can glean the almost complete separation of the oil spill and drain back on the rotating assembly in these Nascar engines , the very small knife edged narrow crankshaft counter weights, reduced rod surface areas and size and journal sizes combine to free up a lot of horsepower and a lot less oil being thrown back onto the cylinder walls. With the full external valve train oiling drain back and camshaft oiling being taken back to a dry sump oiling sump in separate passages that only empty into the sump without splashing down on the rotating assembly oil control and placement is so different from a conventional V-8 that comparing the two from increased rod side clearance oil issues standpoint does seem like a stretch to me. When you look at and study these engines you can see they are very different and it's really not possible to compare a thoroughbred to a field plow horse when it comes to comparing these oiling questions and issues. JMHO

[Truckedup]

There are other engines besides V-8's how about rod side clearance on a inline engine with only one rod per crank journal?

[Warp Speed]

I obviously am grateful for Warp Speed's contributions, experience and conversations here on Speedtalk and I am not trying to question his rod side clearance information on the Nascar engines he is privy to. I am however still conflicted on the idea or belief that opening rod side clearances on more conventional V-8 engines as were being discussed would not create an increased oil consumption and other oiling conditions.

My points about Nascar engines such as the GM R07 family are truly different animals and they obviously have some very well designed, engineered and tested components that are configured and used to make oil control and horsepower loss from oil splash, throw off and windage a much reduced problem in these engines. The oil control in these engines is a incredible testament to how oil control and power robbing losses from windage when improved can really make the high 10,000 rpm horsepower levels possible and how these engines can run for over 500 miles without issues!

In the attached images it becomes obvious that the design and components of these Nascar engines are so different from conventional parts of standard V-8 engines that saying wide rod side clearances in conventional V-8 engines are not an issue since wide side clearances in the Nascar piston controlled rods do not result in any oil control or volume issues. From what I can glean the almost complete separation of the oil spill and drain back on the rotating assembly in these Nascar engines , the very small knife edged narrow crankshaft counter weights, reduced rod surface areas and size and journal sizes combine to free up a lot of horsepower and a lot less oil being thrown back onto the cylinder walls. With the full external valve train oiling drain back and camshaft oiling being taken back to a dry sump oiling sump in separate passages that only empty into the sump without splashing down on the rotating assembly oil control and placement is so different from a conventional V-8 that comparing the two from increased rod side clearance oil issues standpoint does seem like a stretch to me. When you look at and study these engines you can see they are very different and it's really not possible to compare a thoroughbred to a field plow horse when it comes to comparing these oiling questions and issues. JMHO

Parts change, but like so many other things that people claim "don't apply because its a Cup engine", the physics remain.
When testing wider rod side clearances, and no increase in oil flow is recorded, where does this extra oil you speak of come from?!?
Does it just magically appear?!?
Oil control is EVERYTHING in high performance engines, hence the reason this has been tested so thoroughly!
With a 2.00 rod journal running .002 clearance, how tight would the side clearance need to be to become the restriction to flow?

[ptuomov]

Even if the rod side clearance doesn’t impact the oil flow from rod bearings, it can impact oil pressure if it impacts the oil distribution in the crankcase. If the oil doesn’t return as quickly or if oil gets more aerated when side clearances are large, then wet sump oil system oil pressure may go down. This reduction in oil pressure may be confused with greater oil flow, when in reality it’s just the pump compressing more air. Just a thought.

[swampbuggy]

??????

[Kevin Johnson]

Jay, if the bearing witness marks on this journal are from (a) piston guided rod(s), is it your opinion that the oil holes are not optimally located? Would you accept a crankshaft like this or have the drillings adjusted in a new one?

Thanks.

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