Connecting rod bleed holes

kommando · May 17, 2022

Onder said:
Seems to me is all you are doing is losing OP to the rods.

And reducing the bearing surface area on the top shell which carries the highest load as the combustion pressure pushes the piston down. Hence why I fit 2 lowers and block off the hole.

marshg246 · May 17, 2022

1973x75 said:
Just what I wanted to hear. I spent the afternoon researching this, and came to the conclusion that its not worth swapping them back. Expert opinions think those bleed holes are redundant.

The good news is we're still (more or less) on the original topic. The bad news is that we're over 40 posts in and going in circles! The OP heard what he wanted to hear on post 13! My vote is shut er down

Schwany · May 17, 2022

marshg246 said:
The good news is we're still (more or less) on the original topic. The bad news is that we're over 40 posts in and going in circles! The OP heard what he wanted to hear on post 13! My vote is shut er down

That on topic part is miraculous. The going in circles part is normal for the internet.

Triton Thrasher · May 17, 2022

worntorn said:
What oil do you recommend for a Norton engine with flipped Conrod holes?

Glen

Shell oil.

dobba99 · May 17, 2022

When i rebuilt the engine in Mitzi (my Mk 3) and had the crankshaft apart i found on inspecting the used shells that the white metal layer around the bleed holes was worn away, not much, but evidently a wear pattern. I also noticed that where the crank cheeks bolt up to the flywheel also had evidence that oil leaks from there as well. The stain pattern showed where the oil was going. Not surprised at finding that as it is face to face (i.e. no gasket) I didn't want the oil wedge compromised in any way so fitted the new shells to block the holes. With the amount of oil getting flung out of the crank, cylinder lubrication is well taken care of anyway. Using Mobil 1 10w60 oil

worntorn · May 17, 2022

Triton Thrasher said:
Shell oil.

Shell didn't do well in testing.
That was Aeroshell as I recall.
It turned to smoke with very little pressure.

But I keep forgetting we are in Reverse World.
It could be ok.

comnoz · May 17, 2022

I am still running con rods with no hole -but I did add small crescent cuts to the sides of the rod like is done on many auto engines. About 22 degrees for and aft of straight up.
The sides of the rod are pretty well lined up with the cam lobes so I figured a little oil directed in their direction couldn't hurt.
I have tried to observe the oil from the rod hole using high speed cameras and my spintron but there was so much oil flying everywhere it was hard to see what was going on. Jim

PS, I am still sticking with Royal Purple HPS 20-50 or Mobile One V-twin oil.
The only bad thing with the Royal Purple is the smell. It has a nasty odor when the engine burns a little. There is something different in the additives. But it has outlived every other oil I have tried.

Torontonian · May 17, 2022

MexicoMike said:
If the service manual says to orient the OEM rods in a specific way, orient them that way. If they are aftermarket rods that have alternate instructions, do it that way! If they were installed contrary to instructions, bite the bullet, disassemble and install them correctly.

Carrillo instructions don't mention shell(s) orientation at all. They have no drillings /machined holes in them for piston or cylinder wall lubrication. The only drilling is the underside of the small ends. My feeling is it's unimportant and so I assembled them reversed . I'll take my chances on this subject when this 2nd. new MK 111 motor is to be put into use in the near future ( winter ) .

comnoz · May 17, 2022

kommando said:
And reducing the bearing surface area on the top shell which carries the highest load as the combustion pressure pushes the piston down. Hence why I fit 2 lowers and block off the hole.

I like fitting two lowers but,
While the longest duration of load is on the top shell- from combustion. The peak load is on the lower shell as the piston reverses direction at TDC on the exhaust stroke when the RPM is high.

kommando · May 18, 2022

comnoz said:
I like fitting two lowers but,
While the longest duration of load is on the top shell- from combustion. The peak load is on the lower shell as the piston reverses direction at TDC on the exhaust stroke when the RPM is high.

You best tell the German performance engine builders to fit the best performing splutter hearing to top and bottom instead of just top then. A splutter hearing is 5 times the cost of a normal shell bearing so only fitted for good reason.

Mart UK · May 18, 2022

comnoz said:
PS, I am still sticking with Royal Purple HPS 20-50 or Mobile One V-twin oil.
The only bad thing with the Royal Purple is the smell. It has a nasty odor when the engine burns a little. There is something different in the additives. But it has outlived every other oil I have tried.

Some put a cup of Castrol R in the fuel tank every fill. Nice smell. Don't add it to the oil though. Not yet tried it myself.

Fast Eddie · May 18, 2022

Mart UK said:
Some put a cup of Castrol R in the fuel tank every fill. Nice smell. Don't add it to the oil though. Not yet tried it myself.

A cup !? Don’t think that’s a good idea.

More like a teaspoon, perhaps two.

Works well in the lawnmower too !

gortnipper · May 18, 2022

Fast Eddie said:
A cup !? Don’t think that’s a good idea.

More like a teaspoon, perhaps two.

Works well in the lawnmower too !

Mart UK · May 18, 2022

Fast Eddie said:
A cup !? Don’t think that’s a good idea.

More like a teaspoon, perhaps two.

Works well in the lawnmower too !

Yep, definitely a cup. Maybe, bigger than a Roadster tank.
Edit: just remembered where I got this from, Dave Mitchell, when he did an owners review of his BSA Goldstar on the classic motorcycles YouTube channel. No personal experience.

Fast Eddie · May 18, 2022

Mart UK said:
Yep, definitely a cup. Maybe, bigger than a Roadster tank.

Rather you than me. Definitely a bad idea in a four stroke engine IMO.

Over time you’d be building up a greater (and undetermined) ratio of oil to petrol, that oil would replace petrol when being mixed with air, thus weakening the mixture.

But worse, R is bad for gumming things up (race engines were stripped and cleaned regularly back then, and oil changed every meeting) carb internals would most likely suffer, and definately valves / guides, potentially leading to sticking valves.

Back in the day of self mix two strokes, THEY had a (small) cup of oil per tank… you sure your adviser isn’t thinking of two strokes….?

However… we digress…

Fast Eddie · May 18, 2022

1973x75 said:
Connecting rod bleed holes should be facing outwards. I just finished a rebuild, but I have them facing inwards. Can I leave it as is or do I need to open it up again? How critical is it? I’ve read that some rods (Carrillo?) don’t even have the holes.

We are all curious as to what you have decided !

Or are you still undecided ?

Or are you undecided as to whether or not you’re still undecided ??

Fast Eddie · May 18, 2022

Mart UK said:
Yep, definitely a cup. Maybe, bigger than a Roadster tank.
Edit: just remembered where I got this from, Dave Mitchell, when he did an owners review of his BSA Goldstar on the classic motorcycles YouTube channel. No personal experience.

Maybe he meant egg cup ?

mdt-son · May 18, 2022

Fast Eddie said:
Well, I’ve often thought that as part of oils job is to cool, wouldn’t it be better for these oil holes to aim to the centre of the barrel, which is hotter?

I don’t have an answer to my own question, but as pointed out by others, many after market rods don’t even have the holes, and they run fine.

I think it’s alway interesting to note that irrespective of holes or not, EXACTLY the same amount of oil passes past the shells and ends up as splash / mist. Which is what lubricates and cools the rest of the bottom end.

I had a long conversation with Pete Lovell about these holes and he had no strong opinions either way, having built many, many engines with and without, and not seen any differences in wear / life / etc.

So, if engines run well with the holes, and equally well without them, I can’t personally think of a practical down side to having them, but facing the opposite way.

Holes are there to lubricate the thrust side of the barrel. Stick a piece of wire thru the oiling hole from the inside heading outward and look at it's angle of spray. I think you will find the spray is directed to the rear of the barrel ( : the major thrust side).

- Knut

Triton Thrasher · May 18, 2022

mdt-son said:
Holes are there to lubricate the thrust side of the barrel. Stick a piece of wire thru the oiling hole from the inside heading outward and look at it's angle of spray. I think you will find the spray is directed to the front of the barrel ( : the major thrust side).

- Knut

The back of the bore is the “major thrust side.”

mdt-son · May 18, 2022

Triton Thrasher said:
The back of the bore is the “major thrust side.”

You are right. I misread an illustration.

Connecting rod bleed holes

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