Con-rod oiling holes

[coater87]

 Hello,

 I have done a quick clean up of the con rods and found something odd I think. In reading the Haynes manual, only the drive side rod should have a hole for cylinder oiling. It looks as though one rod in this engine was replaced at one time, and now BOTH have that oiling hole.

 Is this a problem? I guess my concerne here is that the T/S rod having free oil flow will steal pressure from the drive side- and maybe starving that cylinder wall. Am I correct to worry, or am I way off track?

 Thanks,
Lee

[RichardL]

I agree. Pressure will be stolen and the left side will be short-changed versus original design intent. I say, plug the hole in the timing-side rod. Be sure hole in drive-side rod faces the flywheel (i.e., faces to the right).

Richard L.

[A10Boy]

I think you are thinking too much
Compare the oil loss from that tiny hole, to the loss from the sides of the big end bearing shells, its minuscule compared to that. Don't worry go ahead and use it as it is.

[RichardL]

A10Boy,

I think we must agree to disagree. If there is enough pressure at the left side to squirt to the sidewall of the cylinder, then there would seem to be excellent opportunity for pressure loss with an additional hole on the right. Are you so certain that you are willing to risk giving Lee information that could kill his engine? I am not that certain, but I know my advice will do no harm. I apologize if this sounds argumentative, because I respect your knowldge in so many other posts and hope to still benefit from your help when I need it myself.

Richard L.

[olev]

Be sure hole in drive-side rod faces the flywheel (i.e., faces to the right).

Richard, Are you sure, I heard the hole faces the other way.
cheers

[Josh Cox]

Olev,

I'm pretty sure Richard is correct, the conrod with the oil hole is the Lefthand conrod and the oil hole faces to the inside, towards the flywheel/crank centre.

[RichardL]

Thank you, Josh. I did find myself sprinting for the books. Haynes says explicitly that the hole goes toward the flywheel.  Bacon shows a section through the rods and crank with the oil hole shown in the section and pointing toward the flywheel. I would copy the Bacon drawing and share it, but it is from a copywritten book.

On  another aspect of this hole, after a lot of previous discussion, rather than arguing further, I started just accepting that the hole has a serious purpose in lubricating the left cylinder wall. I really can't understand why the left side should need such lubrication more than the right side. On re-reading Haynes and Bacon, both state that the hole is for promoting oil flow to the far end of the crank. This makes much better sense to me in terms of explainable engineering. I have also wondered if the hole prevented bubbles in the oil from pocketing on the left end of the crankshaft and, thus, holding back oil flow.

Gotta go.

Richard L.

[RichardL]

Just saw this..

If you look at page 30 of the Haynes manual, you will see a little speck at the base of the left rod, I assume, representing the hole.

Richard L.

[Pollock]

i will be no help here at all but...I am amased every time I look at rods and think how much benefit is by this hole...don't it make more sense that oil splash fromt he crank does more to oil than anything.  And why only one hole one rod?what oils the other side? Splash?
Anyhow...
Good thread.
Pollock

[bsa-bill]

BSA put it there after having problems with the left hand pot overheating.
Think about the cooling effect of the barrels, so the overheating would be on the inside of the bore away from the air cooling

I read this somewhere ( despite my antique look I was'nt there at the time ).

Al the best - Bill

[RichardL]

I think this little hole has become one of my favorite topics (buyer beware ). I have read and re-read my books and each emphasizes the need for the hole in order to avoid oil starvation to the left big end. I believe that, absent this hole, pressure bleeds off at the right-side big end. Then, if the right-side is slightly looser, even less pressure would get to the left side. With the hole, the pressure should be uniform over the length of the sludge trap. So why point the hole in one direction versus another, I think it is just so that the oil spurting from it has the least affect on anything, hitting the flywheel and shedding off. Nevertheles, Haynes says that pointing to the flywheel would "avoid problems in the future" (loosely quoted). What problems, I can only guess. (Why stop guessing now? Back to work. )

Richard L.

[RichardL]

Bill,

My post was just after yours. Your point is interesting as a possible reason for splashing toward the center, however, I failed to mention that neither MAP nor SRM have the hole in the billet rods they sell. MAP said, "don't need it."  I was not that confident that they were correct with respect to equalization of pressure, so I drilled my own hole in my left-side billet rod (the drilling setup is shown under a different topic).  I guess, if MAP was completely correct, no additional cooling or pressure equalization is necessary. As I said, I opted for the engineering explantion I could understand.

Richard L.

[Josh Cox]

Having only just pulled my engine down, the LH conrod did not have the big end with the hole in the LH upper, it was in the RH bottom, as such my sludge trap was completely blocked and the LH big end looked like shite.

[chaterlea25]

Hi Lee,
To block the hole in the righthand rod just fit the bearing shell without a hole in that position!
Thats if I remember correctly that not all the shells have holes in them
I believe the hole is there to, (as others have said) to promote oil flow,
Regards
John O R

[coater87]

 Guys,

 thank you for all the advice here. After a good read, I have decided to plug the hole on the T/S rod. I would flip the bearings but they each have the same hole ( these are glaciers, so maybe from a a65?).

 Now what do you think would be the best way to plug this hole without weakening the rod?

 Lee