Here's a rod side clearance question for the guru's

[RW TECH]

SIDE CLEARANCE DOES NOT REGULATE OIL FLOW, DIAMERTRICAL CLEARANCE DOES.

Maybe we are missing the boat here or maybe after 26 years of building and racing, I am missing the boat here.

The question at hand that I am discussing is weather rods in an engine with .030 side clearence disperses out more oil during reciprocating rotation that an engine with rod side clearences of .020.

If I understand you correctly, you are saying that weather the side clearence is .030 or .020 or even greater or less in differential (regardless of the difference in side clearence), it has no effect on how much oil is released from that reciprocating assembly during rotation. Is this what your saying or is this the point your trying to get across?

That's exactly what I'm saying. Otherwise, rod side clearance would be a critical factor for controlling oil flow from the rod bearings and the tolerance spread for that gap would be a lot tighter (as in the case with rod bearing clearances).

[BLACK BART]

The math I posted is just to compare the square inch area for the two clearances nothing else. I'm not sure what rod journal size a hemi uses, so I arbitrarily chose a common 2.100" small block chevy size to use in the example.

The point I'm trying to make is that the smaller clearance will control the oil flow, what ever that may be.

Viscosity, pressure, and temperature will further influence the flow, but that was not the subject. The clearances were what was being discussed and that was what my examples were intended to explain. All else being equal, the clearances can be compared apples to apples. CJ

[Rick360]

Maybe we are missing the boat here or maybe after 26 years of building and racing, I am missing the boat here.

Some take longer than others, but the important thing is to finally get it.

Rick

[Strange Magic]

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[Speedbump]

In defense of Strange Magic and others (me), what he said is exactly the way it was taught back in the day when I learned. Then, nobody questioned the guru and at a casual, logical glance, it seemed to make sense. The larger the gap, the more oil and that was that. Old truths die hard. Now that I've heard the other explanation, it also makes sense, more sense. What I've learned over the years is to question everything. Can make one unpopular at times but there are very few absolute truths in this business and this forum does a good job at proving that.....like that thing about using a glaze breaker, duct tape and 600 grit paper...I woulda laughed you right out of the shop for that one, but a reputable guy talks about it and now I have to start thinking again.

[RW TECH]

In defense of Strange Magic and others (me), what he said is exactly the way it was taught back in the day when I learned. Then, nobody questioned the guru and at a casual, logical glance, it seemed to make sense. The larger the gap, the more oil and that was that. Old truths die hard.

Experts thought the earth was flat for hundreds of years. They drew maps to that effect, and they warned would-be sailors to be careful of how far they travel.

This is a matter of an old theory vs. a new one. Theories are exactly that - theories. They can be disproved and new theories are born that sometimes become facts once the theory is solidly proven.

Fast forward to today with the rod side clearance matter. Piston-guided rods were used for a long time in other applications besides NASCAR, where this practice is now commonly used along with 0.8mm rings on 1 & 2 and 2mm low-tension oil rings.

Crank case vacuum CANNOT overcome inertia forces that would fling all this excess oil on to the bore walls, if the excess of oil actually existed.

[Strange Magic]

where this practice is now commonly used along with 0.8mm rings

It is not commonly used in any aspect of drag racing. The majority, not all but most all, of your Fuel Teams, Pro Stock teams and comp eliminator, super stock and high output bracket super comp and super gas engines do not use this technology, nor do your top big cubic inch street and strip engine builders. This 572 inch aluminum block Mopar engine in this discussion is not a nascar engine and should never be mistaken for one.

If you tried to run nascar clearences in this type of engine (572) you would weld parts together.

[k-star]

The amount of oil leaving the rod is determined by the bearing to rod journal clearance not the side clearance.

The amount of oil leaving the rod is determined by the bearing to rod journal clearence and the connecting rod side clearence.

Hence the words "leaving the rod".

Mathematical area calculations without factoring pressures are not a true indication of what is really going on.

Ok i'll ask again.

What has your research shown to be the difference between .020 and .030 side clearence as it relates to the amount of oil thrown on the cylinders???

How did this additional oil affect the engine??? What were the negatives??

Keith

Keith

[RW TECH]

where this practice is now commonly used along with 0.8mm rings

It is not commonly used in any aspect of drag racing. The majority, not all but most all, of your Fuel Teams, Pro Stock teams and comp eliminator, super stock and high output bracket super comp and super gas engines do not use this technology, nor do your top big cubic inch street and strip engine builders. This 572 inch aluminum block Mopar engine in this discussion is not a nascar engine and should never be mistaken for one.

If you tried to run nascar clearences in this type of engine (572) you would weld parts together.

The subject clearances are rod side clearances, which are in excess of .100" on a NASCAR engine. This won't weld together on a 572.

[ed nix]

Frends, I can't say how much oil is thrown off a journal that lands on the
cyl. walls . What I can tell you is what the diference in bearing clearance has on leakage at the rod and mains. Some of you might have see the demo this old fellow with mellings oik pumps had.

He took a 4 cyl.engine and put a clear plastic pan on it ,he had an electric
motor that drove the oil pump, it had a preasure gage and a control valve
to adjust the oil preasure. The best I remember #! rod had .oo1 clearence #2 -.002 #3-.003 #4- .004 SO you could see the diference in
leakage. Let me tell you there was a world of diference in #1 ROD AND
3&4 WITH THE SIDE CLEARENCE BEING THE SAME. From what I seen
with my own eyes it apears to me that bearing clearence is the main
factor in oil sling off. His demo had alot of outher useful info. If any of you would like to hear about them let me know. Ed,

[540 RAT]

Frends, I can't say how much oil is thrown off a journal that lands on the
cyl. walls . What I can tell you is what the diference in bearing clearance has on leakage at the rod and mains. Some of you might have see the demo this old fellow with mellings oik pumps had.

He took a 4 cyl.engine and put a clear plastic pan on it ,he had an electric
motor that drove the oil pump, it had a preasure gage and a control valve
to adjust the oil preasure. The best I remember #! rod had .oo1 clearence #2 -.002 #3-.003 #4- .004 SO you could see the diference in
leakage. Let me tell you there was a world of diference in #1 ROD AND
3&4 WITH THE SIDE CLEARENCE BEING THE SAME. From what I seen
with my own eyes it apears to me that bearing clearence is the main
factor in oil sling off. His demo had alot of outher useful info. If any of you would like to hear about them let me know. Ed,

By all means, let's hear about the other useful info.

[Piledriver]

Keep in mind that if the rod BE side play gets too big, you probably need to look at piston guided rods to keep the bearing true on the crank and not kill the edges.