Four cylinder engine noise

[R.White]

Hi Craig. One of the differences between your engine and mine is the oil feed. This is a C engine which has it's oil delivery from the pump via an external copper pipe to the check valve and gauge take off point at the rear of the engine.  That's how the blockage formed at the front.  

 

Plastigage  gave a reading of 0.0035" on N0.1 rod bearing which is a bit too much for a 1.560" journal.  Ideally, it would be between 0.001" and 0.002".  I removed 0.001" from each shim and confirmed a new clearance of 0.0015.  I cleaned up and re assembled with engineers blue.  Any high spots were then removed by careful scraping and a final check made before oiling and reassembling the bearing.

 

No.2  rod bearing was o.k. but someone had fitted the cap (not the shell) the wrong way round.  The oil hole next to the dipper needs to face the camshaft.  I checked No.1 main and again found the crank to be perfect but there was slightly more clearance than would be desirable;  this was set to 0.001" as per spec.

 

I am hoping the knock will go away now that a good oil supply has been restored.  If it doesn't, then, as the piston has been eliminated, I will be at a loss to know what to do.

 

Ray.

Edited September 14, 2015 by R.White (see edit history)

[cahartley]

Thanks for clearing that up!

Based on the clearance on #1 I'm guessing it wasn't much of a knock?

There was an oil feed problem on mine that caused #3 to spit babbitt all over the crankcase and two pistons got scored........   ........but despite the insane looseness with what was left the engine knocked only at higher rpm.

When I dropped the pan I couldn't believe it....... 

I had no choice but to re-babbitt the shells.

Luckily all the rod journals were LESS than .001" out of round on an original crankshaft and there was NO damage to the cylinder walls.......WHEW....... 

[R.White]

I have to say that from what I have seen, Dodge Brothers were producing a car that may not have been the cheapest but it was very well made from darn good materials and deserved the success that it achieved.  We may sneer at some of it's design features with the benefit of hind sight but if one compares the Dodge with other makes around at the time, they are no better or worse than the average and in many cases equal to the best.  I am particularly impressed with the adoption of bearing inserts or shells. This practice didn't become the norm until the 'thirties.  I have endured a number of old cars where the rods and even crank cases are directly babbitted; this may have been a cheaper option for the manufacturers at the time, but further down the line, repairs can prove very expensive.

 

Ray.

[R.White]

While I removing the cylinder head I realised that everything was not quite as it should be.  The central 3/8" stud had been replaced with one of 7/16". I made the mistake of assuming that the problem which had led to this change had been resolved; after all, the head gasket was not leaking.  Unfortunately, while pulling down the head onto a new gasket, I got that sinking feeling when I realised that the central head stud was just pulling out!  It failed at 40 ft lb.  

 

One of the things that make owning an old car a love/hate relationship is having to put right the errors made by previous owners.  When I have had this problem before on other cars, I have tapped a larger hole and used a stepped stud.  If the hole has already been enlarged I may have to try a Helicoil insert.  I wonder if I should wait and see if there is a leak first?...there is a large 'land' in the centre of the head so with only 50 psi perhaps I might get away with it?

 

Ray.

 

[R.White]

Just thought I would give an update.

 

In my last post I described how the central stud had pulled out of the block as I was tightening down the head.  I discovered that the original 3/8" stud had in fact been replaced with a metric M12 .  The end that threaded into the block had been turned down and tapped to 3/8", while the M12 thread protruding through the head obviously has a metric (larger) nut which I disliked.  Fortunately, the 3/8" thread on the stud was in good condition.

 

I then had a "lightbulb" moment! .  I tapped out the block to M12, cleaned the threads with Loctite cleaner and with the aid of Loctite 278 (oil tolerant high strength)  put the stud in the other way up!      Once the Loctite had cured, the head could then be taken down with confidence, with the added cosmetic benefit of all the nuts being the correct 3/8"size.

 

On the down side, I am sorry to say that the knock is still there and no better.  When I took the car out the other day, the "clack, clack, clack" was quite pronounced.  It is really objectionable under load and as previously established is only eliminated when No.1 cylinder is shorted out.

 

It may be a long shot and not really logical but I have purchased new valve guides and springs with a keeper set and plan on renewing the worn parts soon.

 

Having eliminated so many of the more obvious potential causes, I am now looking at investigating the possibility of early detonation.   If the strobe lamp shows the spark is occurring in slightly different places for No.1 and No. 4 then I may be on the track of a solution.  Distributor or camshaft faults may be to blame.

 

Ray.

Edited September 14, 2015 by R.White (see edit history)

[robert b]

Ray after following this thread there is one thing that has not been suggested to check which will happen on these engines after long usage is the shell fit to the rod and crush  clearance of the shell . These shells being of bronze have tendency to move in the rod and will sound like a bearing knock as you describe , if you examine the edge of the shell where the shims and spacer place pressure on the shell you will see wear marks at this point . The shell needs at least 0.002 to 0.003 " inch above the edge  to be able to get a good crush in the rod, you may also see bright marks on the back of the shell which is a good indication that the shell has been moving in the rod. 

 

Possible solution ,

 

1 Best - replace with new shells ,

 

2 Surface the rod and cap end to give crush on the shell, 

 

3 last resort is to back the shell with a shim which will lift it up in the rod but also close the clearance on the sides of the bearing near the shims.

 

 

No 3 will work but you will need to scrape the bearing to get side clearance and you will need more crush clearance to hold the shell and shin tight in the rod ,  I wood only do this as a last resort to " get home " measure in the case of failure on a tour .

 

Will give more info if required  , regards Bob

Edited September 14, 2015 by robert b (see edit history)

[R.White]

Thank you Bob.  I appreciate what you are saying.  I did not know about the 0.002 - 0.003 required for "crush" and can see your point exactly.  From what I remember, the edges were absolutely level but on the other hand, there was no evidence on the back of the shells to indicate that they had been moving about as you describe. They must be just at their limit.  The only tapping that I could replicate with the rods was a lateral movement but this went when I took up the bearing.

 

I am not convinced that the bottom end is where the knock is coming from.  As I have mentioned, when I have had the engine running, I have listened with a stethoscope type instrument and also put my ear next to the sump (pan) and heard nothing, but then the noise is worst under load which is difficult to replicate when stationary.

 

The noise seems to be coming from the head.

[Ron Lawson]

Ray Have you removed number 1 piston from the bore during your diagnosis and repairs I am wondering if you have piston slap or a worn little end in the piston    Ron 

[Spinneyhill]

Looking in a book from 1940... You will have looked at many of these things when you had the piston out.

 

Small end problem - wear on one or both sides in piston or in rod or on pin, loose clamp, sideways movement, gudgeon pin out of centre.

Cracked piston. Checked, OK.

Loose piston (too much clearance in the cylinder, cylinder worn tapered).

Slotted side of piston installed wrong way.

Bent or twisted con. rod.

Piston or ring hitting ledge at end of ring travel top or bottom.

Vibration damper loose.

 

Connecting rod noises are loudest on deceleration. Main bearing knocks are loudest under load.

Excessive crankshaft end play is indicated by an intermittent rap or knock sharper than a worn main bearing.

 

With your stethoscope did you listen against the cylinders or against the water jacket? Just wondering about transfer of sound by the open areas in the block.

[R.White]

Ray Have you removed number 1 piston from the bore during your diagnosis and repairs I am wondering if you have piston slap or a worn little end in the piston    Ron 

 

Hello Ron.  I removed No.1 piston from the bore and can confirm that there is absolutely no wear to either bore or piston. The bore measures 3 7/8" in all directions which is standard and there is no ridge at the top. As the block has definitely not been sleeved and the pistons are modern replacements with "standard" on them it indicates that this block has done minimal mileage.  These pistons do not have the old design of a clamped gudgeon pin but have a modern "floating" type with the bearing in the rod and retained by circlips at each end.  This little end is a nice fit and has no play in it.  The pistons appear to be quite recent and are in excellent condition.  The rings are all in good condition with no evidence of wear.  As the engine doesn't smoke or burn oil I felt it unnecessary to risk breaking a ring by gapping it in the bore.  I would say with confidence that the problem is not with the piston in No.1 cylinder. 

 

Ray.

[R.White]

Looking in a book from 1940... You will have looked at many of these things when you had the piston out.

 

Small end problem - wear on one or both sides in piston or in rod or on pin, loose clamp, sideways movement, gudgeon pin out of centre.

Cracked piston. Checked, OK.

Loose piston (too much clearance in the cylinder, cylinder worn tapered).

Slotted side of piston installed wrong way.

Bent or twisted con. rod.

Piston or ring hitting ledge at end of ring travel top or bottom.

Vibration damper loose.

 

Connecting rod noises are loudest on deceleration. Main bearing knocks are loudest under load.

Excessive crankshaft end play is indicated by an intermittent rap or knock sharper than a worn main bearing.

 

With your stethoscope did you listen against the cylinders or against the water jacket? Just wondering about transfer of sound by the open areas in the block.

 

Thanks for your input Spinneyhill.  I have listened for the noise all over the engine and believe it is coming from the head.  As you will remember, I could find no evidence of fouling or marks on the underside of the head and the piston tops likewise.  I shall be investigating early detonation.  I will also be renewing the worn valve guides and springs at the same time.

 

Ray.

Edited September 15, 2015 by R.White (see edit history)

[robert b]

Ray another thing to check is the rod alignment , only a small bend on such a long rod can cause the piston under load to strike the cylinder along the pin axis ,this noise will not show up until an engine has " run in " as every thing is tight . A  rod aligning jig is necessary to detect even a small amount of misalignment , you may be able to see some light wear on the piston on the top and bottom on the edge of the piston on the pin sides as an indication of possible bent rod. The noise is rather like a clatter or like a piston slap . Ray are these pistons of solid skirt or split skirt ? regards Bob

Edited September 15, 2015 by robert b (see edit history)

[R.White]

Thanks again Robert.  I found some small dents in the cylinder wall which I assumed were old damage.  Perhaps the rod is bent.  I don't have a rod aligning jig but there is an engine specialist just down the road from me.  Perhaps if I took the piston and rod into them they could check it out?  If the rod is bent at least I will have found the cause.

Try as I might, I can't remember now if the pistons had split skirts or not. Does it make a difference? 

 

Today I took the car out for a drive.  If I retard the timing to the point where performance is adversely affected, the clacking sound virtually disappears.  If I advance the timing with the hand lever to restore performance, the more it is advanced, the louder the sound.

 

Back in the garage,  I directed my strobe light onto the highlighted line on the flywheel through the "window" provided.  Worryingly, the mark on the flywheel moves about and won't stay steady despite the engine ticking over quite smoothly.  There is a bit of wear in the rotor but no worse than other cars I have had but they didn't do this.  Could there be a problem with the centrifugal weights sticking, or weak springs in the distributor?

 

Ray.

 

 

Edited September 15, 2015 by R.White (see edit history)

[R.White]

Today I went down to our local engine workshop.  I asked if they had a means of checking the alignment of a con rod and piston.  They said no they hadn't .  With them, if there was any doubt they just changed it. Con rods now are generally short and stubby compared with these so probably don't get bent or twisted as much.

 

I have an idea that if I separated the piston from the rod I would be able to see if the rod was bent or not.  I do have a con rod straightening tool but have never needed it thus far.

I would ideally like to establish that the rod is straight.   I could also provide a little "crush" for the bearing while the piston and rod is out.  That would eliminate two possible causes for the knock.

 

 If it's badly worn, I could turn up a new distributor shaft if they are not available for the 6 volt distributor cars; maybe have it run in a bronze bush if need be.  That, with new springs for the centrifugal weights, would probably stabilise the timing.  As it is, the dwell angle is all over the place. I can't see how that alone would cause a knock - just on one cylinder; only under load and with the ignition advanced... unless someone knows differently and could 'pipe up' before I get in too far.

 

I am not quite sure where to go from here?  I now have the new valve guides, springs and keeper set so I could be getting on with that while I decide what to do.

 

Ray.

[Spinneyhill]

Ref the distributor, my DC timing flopped around like that. The shaft was hard chromed and ground and a new bush fitted so the shaft always rotates in the same place. Timing stable. Xclnt. I cleaned up the weights etc. and put them back with no other changes.

 

Where to next? Ref the list from my book. It says split skirt pistons must be in the right direction. If you have the sump off, shine a light up and look at the piston skirts. Should be an easy check. Ref the bent rod, at the same time maybe you can look at the gaps each side at the small ends. Maybe there is enough to see. But the real test is whether the pin and crank are parallel. You could make up a jig if you have a lathe: two shafts, one each bearing size, inserted and measure the separation at each end. Longer shaft s-> greater difference if bent. A twist would show up too. Surely if the rod were bent you would see wear on one side of the piston at the top and at the bottom 180 degrees around?

 

I can't recall whether you checked any main bearing clearances yet? Main bearing knocks are loudest under load.

Edited September 16, 2015 by Spinneyhill (see edit history)

[Machinist_Bill]

Ray,

Not knowing your car number I see that engines after A875-380 used timing chains. You stated when using a timing light the mark was not steady. This is an indication of a loose timing chain at an idle. Just another 2 cents in the pile of advice!

Bill

[R.White]

Ref the distributor, my DC timing flopped around like that. The shaft was hard chromed and ground and a new bush fitted so the shaft always rotates in the same place. Timing stable. Xclnt. I cleaned up the weights etc. and put them back with no other changes.

 

Where to next? Ref the list from my book. It says split skirt pistons must be in the right direction. If you have the sump off, shine a light up and look at the piston skirts. Should be an easy check. Ref the bent rod, at the same time maybe you can look at the gaps each side at the small ends. Maybe there is enough to see. But the real test is whether the pin and crank are parallel. You could make up a jig if you have a lathe: two shafts, one each bearing size, inserted and measure the separation at each end. Longer shaft s-> greater difference if bent. A twist would show up too. Surely if the rod were bent you would see wear on one side of the piston at the top and at the bottom 180 degrees around?

 

I can't recall whether you checked any main bearing clearances yet? Main bearing knocks are loudest under load.

 

As my meter is not giving a consistent reading for the dwell angle and the strobe variation is consistent with this, I plan on stripping the distributor.  The shaft may well be worn. Hard chrome would be best but not really needed for the low miles that I do.  The chances are that there is wear in the housing and it will require a bush.  I can do these things on my lathe.

 

You will recall that I have had the piston and rod out of No.1 and found no marks on them.  I can't remember the pistons having split skirts.  Everything seemed in good condition but perhaps I missed something. Maybe the minor indentations on the cylinder wall are not old damage after all and are instead the result of a bent con rod?  Sideways thrust perhaps would also be the reason for the excessive lateral movement of the rod on the crankshaft which I thought was the result of oil starvation.  I thought a dry bearing  was the reason for the knock but perhaps I was mistaken.  I can see me stripping the engine again in order to eliminate rod twist or bend; there can't be much else to cause the knock.  I can make up a couple of mandrels and do the checks on my lathe; no problem.  I have a surface plate, a dial gauge and suitable callipers for the job.

 

I would rule out pre ignition because the knock begins as soon as the engine is started and it would need to get hot enough for incandescence  to occur.  It would also cause noticeable damage in no time.  I am also having doubts about detonation because although the noise gets much louder the more the timing is advanced as one would expect, the piston didn't show signs of scuffing and the slight damage to the cylinder wall was only on one side.  With detonation the boss of the piston expands and comes into contact on both sides.  Some engines, especially low output ones, run for many thousands of miles with detonation and it does little harm but I am keeping my options open with this idea being the cause of the knock.  

 

I am not expecting trouble with the main bearings but I did remove the front main bearing cap to examine for interest and found it, like the other crankshaft journals that I mic'd to be in perfect condition.  

 

 

 

Edited September 17, 2015 by R.White (see edit history)

[R.White]

Ray,

Not knowing your car number I see that engines after A875-380 used timing chains. You stated when using a timing light the mark was not steady. This is an indication of a loose timing chain at an idle. Just another 2 cents in the pile of advice!

Bill

 

Sorry, Bill,  but my engine has no timing chain.    It does, however have a gear wheel that drives the distributor/water pump shaft.  It would seem that other owners have also complained about the amount of back lash to be found with this gear.  In my case, a replacement shaft with a new key way made a difference but the final improvement that I made was one of those "light bulb" moments.  I placed a couple of well lubricated washers between the pulley and the end water pump packing nut.  Not tight, mind, because I didn't want the impeller drawn in but just enough to take up the end play.  This quietened down the gears as they became better meshed.  

 

I still have wear in the distributor to sort out but it's one more job ticked off the list!

 

Ray.

[Ron Lawson]

Ray, I really hope that you find the cause of the knock There is nothing worse than doing checks and repairs on all of the obvious and still have the problem Good luck my friend  Ron

[MikeC5]

I hope a distributor rebuild fixes things Ray but I'm wondering why would erratic timing only cause this noise to occur on number 1 cylinder?  Could it be that the replacement piston has a shorter skirt and is thus more probe to piston slap? 

Edited September 17, 2015 by MikeC5 (see edit history)

[R.White]

Good to hear from you Mike.  I don't think the erratic timing is causing the noise.  There was a possibility that detonation could have been occurring in one cylinder if something else was causing it like a worn cam lobe for example but without stable timing I am unable to pin it down by testing No.1 compared with No.4  with the strobe.  Oil starvation at could easily have caused a cam lobe to wear but from what I could see, this was not obvious.

I hope this answers your question.

 

All the pistons are the same and all quite recent with the little ends converted to modern fully floating type gudgeon pins with circlips .  I am confident that it is not piston slap as  there is no wear in the bores which measure 3 7/8" in all directions ( standard) the block has not been sleeved and the pistons are standard.

 

At the moment, options for the knock include detonation and/or bent con rod.  I have eliminated pre ignition.

 

With detonation there is an increase in the sound corresponding to an advance of ignition timing - this concurs. The noise increases under load - this also concurs and the knock emanates from the top of the engine.

 

On the other hand, the piston crown would show pitting and it is perfect. There is often damage to the ring lands - they are fine.  

There is usually some indication of the piston coming into contact with both sides of the cylinder wall at the piston boss area but in this case there are only marks on one side.  The marks are small indentations - scuffing is more characteristic of detonation.

Running  hot - it runs too cold if anything.

 

If the con rod is bent there should be marks on the piston - I saw none but perhaps I missed something.

The small indentations on one side of the bore which I originally took to be old damage would concur with a bent rod allowing the piston to hit the bore.

The excessive lateral movement of the big end bearing on the crank pin that I took to be wear due to oil starvation could possibly be caused by lateral forces associated with a bent rod.

 

Whatever the cause of the knock, I still have a lot of work to do.

Edited September 17, 2015 by R.White (see edit history)

[MikeC5]

Hi Ray,  I missed that you had replaced all pistons.  The next time you have the head off it's pretty easy to stick a dial indicator (w/ magnetic base) on top of the block and measure valve lift.  That would answer the cam lobe wear question.  If you get the rod out of there I would expect a good machine shop could set it up on a milling machine table or similar and indicate it to see if little and big ends are mis-aligned.  I would bring a good rod too for comparison. 

[R.White]

Sorry if I have not been clear, Mike.  I didn't replace the pistons - they had been replaced by a previous owner. The difficulty here is finding a shop that will even look at a small job.  As I mentioned I went to our local engine specialists "Manx Engines' and they fobbed me off claiming they hadn't got any thing to check con rods. Yeah!

 

I will be able to check for bend or twist with a couple of mandrels which I can turn in my lathe.  As I say, I have a surface plate and callipers so should be able to see if there is any bend or twist in the rod.

 

I will do as you suggest with valve lift measurement.

 

Thanks

 

Ray. 

[R.White]

 

The damage to sidewall of cylinder.  Because it was rusty and I could see no corresponding marks on the piston I took it to be old damage.

 

The photo makes it look worse than it actually is.  I would have thought the rings should just slide over the dents.

 

Edited September 18, 2015 by R.White (see edit history)

[robert b]

Ray from the pic it appears that there is wear on one side of the cylinder than the other along the pin axis , as the rings on these engines come right to the top of the bore one would expect even wear all the around the top of the bore, by this pic I would say that the rod has a bend to the front of the engine, check the piston at the top rear and lower front for scuff marks .Bob

Edited September 18, 2015 by robert b (see edit history)

[R.White]

I think you have possibly answered the question with your reply, Bob. 

 

Now I feel confident in finding a bent rod and being on the way to a resolution.

 

Many thanks.

 

Ray.

[Spinneyhill]

Would there be a bit of blow-by at the damage? Might that gradually erode the cylinder wall and gum up the rings? You will need to use good oil to keep it clean.

[cahartley]

The difficulty here is finding a shop that will even look at a small job.  As I mentioned I went to our local engine specialists "Manx Engines' and they fobbed me off claiming they hadn't got any thing to check con rods. Yeah!

 

I will be able to check for bend or twist with a couple of mandrels which I can turn in my lathe.  As I say, I have a surface plate and callipers so should be able to see if there is any bend or twist in the rod.

 

I will do as you suggest with valve lift measurement.

 

Thanks

 

Ray. 

 

WOW........I thought Brits had more class than THAT....... 

Manx has the nerve to call themselves Manx Engines? And they can't even check con rod alignment?....... 

Must be nice to be so successful they can chase away customers.

Regardless.......I like your "git 'er dun" attitude and, yes, you do have the equipment to check it yourself.

I did things myself too because someone sluffed me off.......  .......screw 'em....... 

[R.White]

Would there be a bit of blow-by at the damage? Might that gradually erode the cylinder wall and gum up the rings? You will need to use good oil to keep it clean.

 

I hadn't considered that, Spinneyhill.    As it happens, I am using straight 30 mineral and change it far more frequently than normal. I can't face a rebore.

[R.White]

WOW........I thought Brits had more class than THAT....... 

Manx has the nerve to call themselves Manx Engines? And they can't even check con rod alignment?....... 

Must be nice to be so successful they can chase away customers.

Regardless.......I like your "git 'er dun" attitude and, yes, you do have the equipment to check it yourself.

I did things myself too because someone sluffed me off.......  .......screw 'em....... 

 

Please don't get me started.  It breaks my heart when I think what GB has come to.  We have lost so many independent engineering shops that you wouldn't recognise what was once "The workshop of the world". Honestly, I could cry.  

I was looking at some statistics that showed the Brits are now less than half as productive as the Americans and you know how much capacity has been lost across the States.  

 

If you want anything made now it's cheaper to have it manufactured in China! 

 

 

 

Ray. 

[Spinneyhill]

You are not the only ones Ray. I remember wholesale engineering shop closures (both machine and steel fabrication shops) in the late '80s and again 10 years later. The model engineering (home workshop) fraternity were thrilled coz they gorged themselves on cheap good quality lathes, milling machines and so on that were far larger than they should been able to afford.

 

If you use it like that I suggest you use a CI-4 10W-30 and change it as frequently, at least initially, to get the engine cleaned up; it will include some good anti-oxidant (anti-corrosive) additives. It looks like red rust in some of those scores in the bore.

 

Are the other pistons the same as that one? I am wondering if that piston has broken not so long ago and been replaced, while leaving the others as they were. That might be when it bent the rod, if that is what you find. Just speculating a bit here...

[R.White]

I must say that the photo gave me quite a shock.  Where did the brown colour came from?; it didn't actually look half as bad as in daylight.  I think the camera may have picked up the colour from some residual dirty water that came out of the head as I was lifting it.  The dents also look much worse than I remember them to be.  Anyway, I can confirm that the only rust that I noticed was in the dent.  The pistons are all the same and look relatively new.  Nice pistons, with fully floating gudgeon pins. 

 

I don't have any history only that the car was originally in Australia.  My theory, for what it's worth, is that there was a problem with one of the original pistons.  They would, I understand, have had clamped gudgeon pins and it was quite common, apparently, for the retaining bolt to come loose allowing the pin to move about and it may have been this that caused the  damage that we see today.  I expect that the rod was bent then. 

 

I have been gradually cleaning the engine with oil changes and it is now coming out much cleaner.  I thoroughly cleaned the pan which had some muck in it but most worrying was the gritty feel of it.  I replaced the oil seals and gaskets.  I also cleaned up the front of the engine when I took off the timing cover.  The distributor housing is a good replacement and is also clean.  The oil pump is excellent and produces max pressure.  Now that the oil gallery is clear - you will remember that I cleaned out what looked like small brush bristles from the end of the line - and also the oil "pockets" have been cleaned out, I am hoping to keep the engine clean.  On an engine which has no oil filter, I would have thought a detergent oil which holds particles in suspension would not be ideal.  Without a filter to clean out the dirt, I imagine the detergent agents in a modern formula oil, would search out any muck that might otherwise have stayed put.  I don't know. I'm no expert on anything let alone oil technology.

 

Ray.

[Spinneyhill]

At 06:10 this morning I woke up thinking of your engine. Harrumph! Anyway, I was thinking that the dirt in the oil way may be because of low grade non-detergent oil, infrequently changed. It deposits the fine dirt everywhere when it stops and it is not picked up on next startup. A little more is deposited each shut-down. Eventually small places because too small for oil to pass. The grit would also settle out of a detergent oil. Only fine particles are carried. The metal bits that might score bearings etc. settle out too. If you use a 10W-30 or -40 you will clean it out and get lubrication at the bearings, timing gear, valves much sooner than with a thick 30 wt at startup, so establishing the oil film of good lubrication. On startup it is running on whatever was left after most of the oil drained away - leaving a few specs of dirt behind.

 

Did you also clean out the oil ways to the main bearings? They may be similarly compromised.

 

Remember that the books all say that main bearing noises increase on load, which I think was the initial problem.

 

Ref oil expertise, please read Richard Widman's paper on choosing the oil for his Corvair. There is some good info there reduced to understandable terms even I can understand, mostly. You can find it referred to on Richard's posts on these fora. I refer you to p. 18, item 10 in that paper.

Edited September 19, 2015 by Spinneyhill (see edit history)

[R.White]

Spinneyhill.  This engine has kept me awake at night.  At least you managed to get some sleep!  I have taken note of your sound advise on choice of oil.  Thanks.

 

To everyone who has contributed to this thread may I say a big thank you.

 

I believe the knock which has been so illusive is due to a bent con rod and thanks must go to Robert B in Australia who has vast experience of these cars.  I will be working on a fix with this in mind.

 

 As to dirt in the pan.  Dust from the Australian outback gets everywhere!

 

For the benefit of anyone unfamiliar with these cars, the oil supply arrangements leave much to be desired but are typical of the 1920s.  One of the things about these primitive engines is that non of their bearings are pressure fed. The oil pressure gauge reads just 4 psi and is only a guide to the output of the pump and not an indication of the oil received by the bearings.  From the pump in the pan, the oil is sent along a single tube with small holes in it and  simply squirted out hopefully landing in "pockets" cast in the block.  The main bearings are thus drip fed from these pockets.  The con rod big end bearings collect oil by scooping it out of troughs formed in a sheet metal tray located in the pan.

 

On my engine, the oil tube was blocked at the end of the line with what  looked like small pieces of brush bristles.  Where I went wrong was thinking that a dry bearing was the cause of the knock.  My lack of experience meant that I failed to notice a particular wear pattern in the bore that is indicative of a bent con rod.  Lets hope I can raise my game and effect a lasting repair.

Ray.

Edited September 19, 2015 by R.White (see edit history)

[Spinneyhill]

We look forward to the video of a smooth, quiet DB! Hope this resolves the situation.

[MikeC5]

Are you going to get a replacement rod or try to straighten this one?  Can they be straightened I wonder...

[R.White]

Hi Mike.  It depends how bad it is.  My Dad would probably have straightened a slightly bent rod - in fact I found his rod straightening tool amongst his affects. To assess the extent of the damage I guess he would have used the calibrating equipment at James Walkers where he worked.  Unfortunately, my methods will not be as sophisticated. The rod may be bent or indeed twisted.  What the risk is of a breakage further down the road I don't know.

 

Perhaps I would be better advised to replace the rod if it is bent.  I would still have to go through the checking process to ensure that a replacement rod was straight wouldn't I?

 

To be frank, I hadn't considered looking for a replacement until now.      

 

With the holiday season ending I will hopefully have some time to myself.

 

Ray.

[fiddlerbill]

I had a "knock" coming from the front of my head on a recent rebuild. The wood dowel method seemed to indicate it was coming from the front of the head. I discovered that it was in fact simply coming from the back of the fan shaft. When I ran the engine without the fan belt on, the "knock" stopped. It would be nice if your problem was so simple.

Good luck

[R.White]

Thanks for your good wishes, Bil.

 

Knocks can sometimes be something silly.

 

I once had a knock coming from a BMW motorbike engine.  It had many so called "experts" baffled.  Fortunately, my engineer Dad (who had probably forgotten more about machinery, especially engines, than most people will ever learn) located the fault.  The barrel nuts had loosened and it was lifting off the crankcase. My answer would have been to just tighten up the nuts but the old man realised that the studs had stretched the threads in the aluminium casing so my answer would have failed. Rather than just re fitting the studs with Loctite, we  were able to fit HT bolts up through the crankcase from inside with locking nuts holding down the barrel on the outside.  It was a proper job but I couldn't have done it by myself.

 

Ray.

Edited September 28, 2015 by R.White (see edit history)