The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: coater87 on 15.08. 2009 17:18

Title: Con-rod oiling holes
Post by: coater87 on 15.08. 2009 17:18
 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
Title: Re: Con-rod oiling holes
Post by: RichardL on 15.08. 2009 17:58
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.
Title: Re: Con-rod oiling holes
Post by: A10Boy on 15.08. 2009 22:16
I think you are thinking too much *smile*
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.
Title: Re: Con-rod oiling holes
Post by: RichardL on 15.08. 2009 22:36
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.
Title: Re: Con-rod oiling holes
Post by: olev on 16.08. 2009 02:10

Quote
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
Title: Re: Con-rod oiling holes
Post by: Josh Cox on 16.08. 2009 02:34
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.

Title: Re: Con-rod oiling holes
Post by: RichardL on 16.08. 2009 02:51
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.
Title: Re: Con-rod oiling holes
Post by: RichardL on 16.08. 2009 02:54
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.
Title: Re: Con-rod oiling holes
Post by: Pollock on 16.08. 2009 15:36
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
Title: Re: Con-rod oiling holes
Post by: bsa-bill on 16.08. 2009 16:04
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
Title: Re: Con-rod oiling holes
Post by: RichardL on 16.08. 2009 16:08
I think this little hole has become one of my favorite topics (buyer beware *smile*). 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. *sad2*)

Richard L.
Title: Re: Con-rod oiling holes
Post by: RichardL on 16.08. 2009 16:17
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.
Title: Re: Con-rod oiling holes
Post by: Josh Cox on 16.08. 2009 21:45
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.
Title: Re: Con-rod oiling holes
Post by: chaterlea25 on 16.08. 2009 21:52
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 *conf* *conf*
I believe the hole is there to, (as others have said) to promote oil flow,
Regards
John O R
Title: Re: Con-rod oiling holes
Post by: coater87 on 17.08. 2009 10:44
 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
Title: Re: Con-rod oiling holes
Post by: RichardL on 17.08. 2009 12:05
Lee,

The hole should be 3/64" or #56 (drill) or very close thereabouts. A piece of stainless wire or part of broken drill bit that is a snug or slight press fit could be epoxied into the hole. Otherwise, maybe just some JB Weld or whatever your favorite high-quality (not "five minute") epoxy, alone, would do the trick.

Richard L.
Title: Re: Con-rod oiling holes
Post by: RichardL on 17.08. 2009 12:57
Sorry, one more idea. Maybe, tap to #0-80 thread and permanent Loctite a set screw into the hole (assuming you could source the screw).
Title: Re: Con-rod oiling holes
Post by: trevinoz on 17.08. 2009 22:10
Just my two bob's worth, the rods are fitted with the match numbers facing the camshaft.
As to the drilling in the rod, I am pretty sure that the late A65s had both rods drilled so it probably doesn't matter if both are drilled in an A7/10.
Trev.
Title: Re: Con-rod oiling holes
Post by: A10Boy on 04.06. 2010 09:57
That pretty much comes back to my view.

Richard, I think I need to say that I would never ever give advice which would risk someones engine. My view was that as the rods came out of a running engine, I would prefer to use them as they were rather than try to glue bits of wire in there, or un-necessarily go and buy replacements.

This place is great for people to ask questions and others give their opinions, but its upto the asker to decide what he prefers. I have found this forum a great help.  *smiley4*

Lee, perhaps you could update us on what you did and hows the bike going ?

Title: Re: Con-rod oiling holes
Post by: RichardL on 04.06. 2010 11:55
Andy,

I think you're right. At the least, I should have put it like, "A fool, such as I, might plug the hole with something, but I am in no way suggesting others should try it."

Thank you for putting this straight.

Richard L.
Title: Re: Con-rod oiling holes
Post by: A10Boy on 04.06. 2010 14:57
That was not a criticism. I'm sure everyone here acts with best intentions.

It would be interesting to hear what Lee did and how his bike is going.

Cheers
Title: Re: Con-rod oiling holes
Post by: RichardL on 04.06. 2010 15:53
No problem, we're good.
Title: Re: Con-rod oiling holes
Post by: beezalex on 04.06. 2010 21:41
The only thing that makes sense to me is the idea of cylinder wall lubrication.  I've seen this in many automotive engines in one form or another.  I think that oil being slung is the primary source of oiling for the cylinder walls.  The timing side has a oil coming from the timing side bearing, but the drive side does not.  The rod bearings only produce about 3cc of oil/s from leakage (@ 4krpm) while a 1 mm orifice on the con rod supplied by a 5 mm hole at 60 psi supplies about 10 times as much.  At low rpm, the bearings leak even less, so maybe that's where the problem lies.  I do know that my A65 race bike has no problems running without drillings.  Besides, that's just a spot where cracks can propagate from.

I've had a bunch of people try to tell me it's for flow equalization, but nobody could explain exactly how this works.  Doesn't make sense to me.
Title: Re: Con-rod oiling holes
Post by: RichardL on 04.06. 2010 23:03
So, how "dry" is that sump. The flywheel runs pretty close to the bottom of the crankcase, and, as I see it, the hole squirts at the side of the flywheel and never has a shot at the cylinder wall. If the flywheel runs in a puddle at the bottom of the crankcase, the spritz from the hole becomes insignificant. Regarding the timing-side bearing, how would that be contributing to throwing oil at the right cyclinder wall other than contributing to the puddle at the bottom? I see it as an oozer not a sprayer.

I'm not making a big arguement for the cause here, it's just fun trying to read the minds of dead people, like some of you will be doing with me some day and asking "What drove him  to write so many G.D. B.S. posts?"
Title: Re: Con-rod oiling holes
Post by: MG on 05.06. 2010 08:57
Quote
I'm not making a big arguement for the cause here, it's just fun trying to read the minds of dead people,...

Totally agree, Richard, so let me add my 2p worth  *smile*:

During the last weeks I've been working on my Matchy basketcase and had a very close look at the yearly engine lubrication mods on the AMC twins (and there were many of them!)
Obviously oil starvation of the lhs cylinder was a big issue for them, as there had been several different attempts to get oil up there, even by having an oil route through a drilling in the cylinder spigot (to be omitted just half a year later due to massive over-oiling of the lhs pot). They ended up with a drilling through the inlet camshaft tunnel (behind the barrels) in order to have oil spill on the lhs flywheel, thus being flung up to the cylinder wall.

This led me to belive that the lhs conrod oil hole must be there for exactly that purpose, being on the lhs and facing the flywheel.
Mr. Hopwood also bothered to design a trough for the camshaft, which is shaped so that surplus oil will be flung towards the crankshaft, thus oiling the cylinders, so I suppose considerations on reducing the cylinder wall/piston sliding friction had been an issue with BSA as well.

As the return oil pump is of much greater capacity than the feed pump, I would say the sump IS dry. Have a look at the oil returning to the oil tank, you will see it is full of air bubbles for this very reason.

Sun is shining, so I'll go for a quick spin now and enjoy the results of Mr. Hopwood's efforts.  *smiley4*

Cheers, Markus
Title: Re: Con-rod oiling holes
Post by: RichardL on 05.06. 2010 17:28
Mr. Hopwood also bothered to design a trough for the camshaft, which is shaped so that surplus oil will be flung towards the crankshaft, thus oiling the cylinders,

Markus,

So, output from the conrod hole, again, seems to me to be insignificant compared to trough overflow. Like a baby to his mother, I'm clinging to the engineering concept for this hole that I think I understand. That is, pressure and flow to both journals is better balanced by promoting more flow to the end of the path, rather than reducing pressure at the left end via the outlet at the right journal.

So, for those of you who know I'm wrong, allow me to agree with you in advance, without actually giving up my illusion, yet. For those of you who agree with me, we are probably about to be spanked. For those of you with professional training in treating obsessions, HELP!

Richard L.
Title: Re: Con-rod oiling holes
Post by: MG on 05.06. 2010 19:32
Quote
That is, pressure and flow to both journals is better balanced by promoting more flow to the end of the path, rather than reducing pressure at the left end via the outlet at the right journal.

I'm absolutely not questioning that, I would also think that this had been the main reason to add the hole. I was just trying to give an explanation why it should be facing the flywheel on the lhs.

However, as we all know, opinions are like a**holes. Everybody's got one.  *roll*


Cheers, Markus
Title: Re: Con-rod oiling holes
Post by: beezalex on 07.06. 2010 14:52
This is an interesting subject and I think it's definitely worth contemplating.  I certainly can't claim to know what was going through the BSA engineers' minds when they came up with this, but I do have a pretty firm background in mechanical design and experience with BSA twins so I'm trying work the problem backward on the assumption that there was a logical reason for the addition of the hole. 

Richard asked about the timing side journal:  oil from the timing side journal travels up the counterweight and can the be flung toward the cylinder wall.  Now, I'm going to backpedal a bit on what I said earlier with regards to slung oil lubricating the cylinder walls.  I think only the couterweight will be any good at slinging oil into the bores.  It turns out that the flywheel is no good at getting oil on the cylinder walls bacause the spray comes off the flywheel at a tangent and with the large OD of the flywheel, very little, if any gets in the bores. 

When the pistons are at TDC, however, the oil hole is clear of the flywheel and this turns out to also be the crankshaft position when the oil hole lines up with the bearing feed hole in the crankshaft...and yes, at 50-60 PSI a 1 mm orifice will make a good jet. 

As for the "equalization of flow" thing...the sludge trap basically forms a reservoir at static pressure that supplies the big end bearings.  I don't see how there can be any difference in pressure between the two journals unless the trap is plugged.  All adding a significant hole anywhere in the system does is lower the overall pressure...thus REDUCING the flow from the journals.
Title: Re: Con-rod oiling holes
Post by: MikeN on 07.06. 2010 15:09
It turns out that the flywheel is no good at getting oil on the cylinder walls bacause the spray comes off the flywheel at a tangent and with the large OD of the flywheel, very little, if any gets in the bores. 

What makes you say that oil comes off the flywheel at a tangent? I would of thought centrifugal force would fling it off the flywheel radially.
MN
Title: Re: Con-rod oiling holes
Post by: beezalex on 07.06. 2010 15:16
It turns out that the flywheel is no good at getting oil on the cylinder walls bacause the spray comes off the flywheel at a tangent and with the large OD of the flywheel, very little, if any gets in the bores. 

What makes you say that oil comes off the flywheel at a tangent? I would of thought centrifugal force would fling it off the flywheel radially.
MN

All particles leaving a round, rotating object depart at a tangent...that's physics.  Ever watch rain water coming off a tire without a mudguard?  F1 cars or bicyles in the rain?
Title: Re: Con-rod oiling holes
Post by: A10Boy on 07.06. 2010 16:22
Quote
and this turns out to also be the crankshaft position when the oil hole lines up with the bearing feed hole in the crankshaft

It isnt actually, the big end oil holes are at 90 degrees to the throw of the crank so the oil holes line up just past half way up the up stroke and just before half way down the down stroke.
Title: Re: Con-rod oiling holes
Post by: MikeN on 07.06. 2010 16:39
It turns out that the flywheel is no good at getting oil on the cylinder walls bacause the spray comes off the flywheel at a tangent and with the large OD of the flywheel, very little, if any gets in the bores. 

What makes you say that oil comes off the flywheel at a tangent? I would of thought centrifugal force would fling it off the flywheel radially.
MN

All particles leaving a round, rotating object depart at a tangent...that's physics.  Ever watch rain water coming off a tire without a mudguard?  F1 cars or bicyles in the rain?
If you want to see a particle leaving a rotating object watch this. Its funny and a good example of physics in action
http://www.youtube.com/watch?v=iRasoZMirRc&feature=player_embedded
Mike
Title: Re: Con-rod oiling holes
Post by: bsa-bill on 07.06. 2010 16:43
I read an article that was a history of the A7/A10 development, it stated they had trouble with the drive side cylinder overheating and modified the left hand rod by adding the much mentioned/maligned hole ( that's maligned not misaligned).
OK all I need now is to locate the said history - see the credibility of it and be recognised as the Smart **** that  know I am *roll*

Oh if it was that easy, I can't remember where I read it, and have trolled search engines in vain.
So it is I believe up to all of us to do whatever we think is correct, I  follow BSAs thinking whatever it was and stick to the "hole fires at the cylinder wall theory.
It is one of those subjects that if ever solved would diminish our enjoyment of our hobby, leave us with a little less to discuss - up there with the meaning of life and the oil thread, if someone discovered beyond doubt the best oil for us to use in our A's what would be left to discover

PS It's 47 in case it had escaped your notice
Title: Re: Con-rod oiling holes
Post by: beezalex on 07.06. 2010 17:01
It isnt actually, the big end oil holes are at 90 degrees to the throw of the crank so the oil holes line up just past half way up the up stroke and just before half way down the down stroke.
Damn...you're right...I really stepped in that one....so squirting at the flywheel again, we are.
Title: Re: Con-rod oiling holes
Post by: RichardL on 07.06. 2010 17:16
As for the "equalization of flow" thing...the sludge trap basically forms a reservoir at static pressure that supplies the big end bearings.  I don't see how there can be any difference in pressure between the two journals unless the trap is plugged.  All adding a significant hole anywhere in the system does is lower the overall pressure...thus REDUCING the flow from the journals.

If one looks at ductwork and piping design, one will notice that after one or more tap-offs of air or liquid, respectively, the engineers will reduce the cross-section of the duct or pipe to maintain pressure at the more distant tap-offs. Now, does that really explain why reducing pressure at the far end of the sludge trap via the infamaous hole will promote greater flow to the left side journal? Hmmm, I'm still dancing around that one.

Richard L.
Title: Re: Con-rod oiling holes
Post by: MG on 07.06. 2010 19:33
Gents, you got me thinking about the whole flow rate issue. This is the physical explanation I can come up with:


Watch out guys, switching on smart idiot mode now!


Bernoulli tells us: p + rho/2 * C^2 = const., where p is pressure, rho is the fluid's viscosity (which we assume being constant) and C is the fluid's velocity.
As both big ends are exposed to the same surrounding pressure p inside the crankcase, you can derive from Bernoulli's principle, that the fluid's velocity must be the same at both big ends, regardless of their cross-sectional area. We are neglecting line loss here, as the sludge trap is not very long this should be insignificant enough.

The volumetric flow Q is defined as
Q = A * C.
C is the same for both big ends, like stated before.
So with an increase in the cross-sectional area A, the flow rate MUST increase as well.

So YES, the with the drilling oil flow to the lhs big end WILL increase.


In case the oil pump is not able to cope with the higher flow rate (at low rpm for instance), this will lead to a reduction of volumetric flow at the rhs big end due to the principle of continuity accordingly:

Q_oil_pump = Q_big_end1 + Q_big_end2

***smart idiot mode off***


Jeez, now I really need a cold Goesser to clear my mind...   *beer*


Cheers!
Title: Re: Con-rod oiling holes
Post by: MG on 07.06. 2010 19:56
To make that a bit more ostensive:

Quote
As for the "equalization of flow" thing...the sludge trap basically forms a reservoir at static pressure that supplies the big end bearings.

Now let's use a plastic cup to act as the sludge trap. Punch two holes of the same diameter into the bottom and close them off with your finger. Fill the cup with water. What you have now is a "reservoir of (hydro)static pressure". This is the same situation as with the crankshaft, with two openings ending up in an area of constant and alike pressure (atmospheric pressure here).
Take your finger off the hole and watch the flow from the holes.
Now make one hole significantly larger than the other one and repeat the procedure.
You can also count the seconds it takes until the cup is empty in both cases and you will see the increase in the overall flow rate when increasing the cross-sectional area of one opening.
(Q_cup=Q_hole1+Q_hole2)

Contrary to the flow rate of the oil pump at constant rpm, Q_cup is variable here.


Looks like the Goesser slowly is doing it's job...  *smile*

Title: Re: Con-rod oiling holes
Post by: beezalex on 07.06. 2010 21:14
Yes, but the extra flow through the orifice doesn't help the bearing at all.  The hole might as well be on the side of the sludge trap...none of that oil enters the journal.
Title: Re: Con-rod oiling holes
Post by: RichardL on 07.06. 2010 22:11
After so much pallaber, I need to correct myself and re-evaluate my thinking. On my merry little brain ride, I kept envisioning an end-feed tube as the reservoir. Nay, nay, foolish self, the reservoir is limited, I believe, to the circumferential area around the sludge trap (for cranks with sludge traps) Therefore, there is no "tap-off" as I was saying.

The feed holes in the sludge trap are equidistant from their respective rod journals. So, it is reaonable to assume that, without the ding-dang hole, the journals should get the same amount of oil. OMG! Now what?

Maybe the hole came into being before the sludge trap and the "tap-off" logic applied.  Then, the hole could have  lingered on past its need, but we seem to have statistical evidence of more heat failures on the left in sludge-trap bikes (Oh, that's going to be the name of my bike "The Sludge Trap Express", or maybe not).   

Sooooo, if the flywheel can't really spray the cylindar wall, maybe the purpose is just to promote more droplets/mist floating around in the crankcase for better lubrication of both cyclinders . That would help explain a hole in each rod for the A65.

To the extent that I have forgotten any part of this discussion that took place in a past life of my own, please forgive.

Oh, hear me Oija Board! Conjur the spirits of Mr. Hopwood and Mr. Pike to answer our  questions and put us out of our misery!

Richard L.
Title: Re: Con-rod oiling holes
Post by: MG on 08.06. 2010 10:03
Quote
Oh, hear me Oija Board! Conjur the spirits of Mr. Hopwood and Mr. Pike to answer our  questions and put us out of our misery!

Amen!  *smile*


Hadn't the A65 oil pump been of greater capacity in order to supply two drilled rods?
Title: Re: Con-rod oiling holes
Post by: groily on 08.06. 2010 11:32
But don't SRM often install their own (presumably higher-capacity) oil pump along with their rods with no holes at all? Or would that only be with the end-feed conversion?
It's all Greek to me . . .
So glad Markus I'm not the only person here who struggles regularly with AMC year-on-year oiling mods - other whole forums exist for the unravelling of those arcane mysteries and to keep us from mis-matching parts with terminal consequences. At least no issues over holes in rods, and equal oil distribution to both big end journals via the centre main bearing . . . .
Sounds so perfick - but weirdly enough BSA twins seem to work for rather longer between radical surgery despite their timing-side centric way of shoving the slime around.
What did Triumph have, on their plain bush engines? Did Mr Turner feel the need for an 'ole on the far end? If, that is, his piston pump actually had the oomph to get the oil that far anyway after all the exertion of pushing out the tit on the tell-tale plunger?
Title: Re: Con-rod oiling holes
Post by: beezalex on 08.06. 2010 14:06
A65's didn't start with larger oil pumps...only the later ones got bigger capacity...but they need it: Higher RPM (Bearing oil consumption goes up) and larger bearings I think are the major reason.  BTW, SRM A65 oil pumps are the same capacity as the later model stock pumps.
Title: Re: Con-rod oiling holes
Post by: MG on 08.06. 2010 19:08
Quote
So glad Markus I'm not the only person here who struggles regularly with AMC year-on-year oiling mods

Well, if you haven't got enough problems, you gotta go out and buy some.  *smile*

Some of the decisions the AMC engineers made are absolutely unintelligible to me, like omitting the pressure release valve in some years. I mean, we all know about the oil-tightness of our old girls, even when oil pressure does not exceed levels of 150 psi.
I'm rebuilding the engine with '59 crankcases and updated these to the latest specs (retro-fitted the release valve, drilling through the inlet camshaft tunnel to oil the lhs cylinder, etc.)

Actually I have incorporated everything that makes sense to me, time will tell how good my decisions were...


Recently I read somewhere (can't remember where unfortunately) that Bert Hopwood had designed his A7/A10 engine within only 10 days, including making all necessary drawings for manufacturing.
Incredible achievement, regarding how well it performed and for how long a time this concept did proove it's quality.

Hats off to Mr. Hopwood!  *respect*

Markus
Title: Re: Con-rod oiling holes
Post by: Stu55Flash on 08.06. 2010 20:39
Hi not stripped my engine yet, so don't know from first hand but not mentioned on here so far:


Service sheet 202 says that on models after ZA10-4712 for A10 and A7 from AA7-101 the crankcase is modified to supply oil to the camshaft trough and directed to the cylinder walls from here.

Also in the Haynes manual on page 26 its says that after 1951 the left hand con rod of all engines has a special drilling and it is therefore not possible to interchange the con rods. If they are interchanged the left hand big end bearing will be insufficiently lubricated.

So is there possibly an issue with pressure at the left hand big end if oil pressure is lost on the right hand side. To test this is there any difference between the left and right journals when measured?

Great discussion thread!

Stu

Title: Re: Con-rod oiling holes
Post by: MikeN on 09.06. 2010 21:38
Quote
So glad Markus I'm not the only person here who struggles regularly with AMC year-on-year oiling mods

Recently I read somewhere (can't remember where unfortunately) that Bert Hopwood had designed his A7/A10 engine within only 10 days, including making all necessary drawings for manufacturing.
Incredible achievement, regarding how well it performed and for how long a time this concept did proove it's quality.

Hats off to Mr. Hopwood!  *respect*

Markus


Markus,
  The above isnt quite correct,
 Im looking at the transcript of an interview between a journalist from "the motorcyle" magazine and BSA's Mr H Hopwood,Chief designer (Motor Cycles). he says that he was "in" on the design of the BSA Vertical twins but it was Mr H Perkins, Assistant Chief Designer who laid down the A7 engine and it was, in Mr hopwoods words, "Mr Perkins baby".
With support coming from Mr, D W Munro of the Technical department.
  They discuss the original A7 and although there is no mention of the con-rod hole ( I dont think the early ones had them. the rods were made from nickel steel), it does mention that the oil pump passes 126.6 pints per hour and the return pump passes 177 pph at 5000 rpm which may be of interest.
MN
Title: Re: Con-rod oiling holes
Post by: MG on 09.06. 2010 21:48
OK, so credit to all of these smart guys.  wink2