R.White

'26 engine knock

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R.White    54

Not so much a new topic but a return to something that I thought was sorted but most definitely is not. .

 

Avid 4 cylinder car readers will recall that I was experiencing a distinct tapping sound coming from my engine.  This regular knock was coming from No.1 cylinder on the firing stroke.  Investigation revealed historic damage to the bore which also turned out to be a cracked so I had a liner fitted.  The engine was treated to a rebore and new + 0.040"  pistons installed.  I also replaced the valves guides and springs at the same time. Unfortunately, despite assurances from the engine repair guy that the noise would have been from a piston ring hitting the damaged bore,  on restarting the reassembled engine the noise is still there!  The tapping sound is most noticeable at tick over but if I short out the sparking plug on No.1 cylinder, it disappears.  I have checked the connecting rod big end bearings and the white metal looks to be in good condition and has an even clearance (with Plastigauge) of 0.0015") which I would have thought would be correct.  I guess there is a solution to the problem but I am not sure what to do now.:(

 

Ray.

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R.White    54

The gudgeon pins that came with the new pistons are a perfect fit to the little end of the rods.  The bushing in the rod shows no signs of wear.   The set up is of the modern fully floating type with cir clip retaining clips.  The engineer was also happy with the fit. 

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Bloo    83

Assuming there is no problem with the small end (I was also wondering about that), you could try tightening the big end a little.

 

I have used plastigage on almost everything I have ever worked on, but was reading the other day on the VCCA, and discovered that the 4 cylinder Chevy enthusiasts do not trust plastigage, and speak of tapping the big end sideways with a tiny hammer to check for clearance. They also turn the engine by hand to make sure the bearing being adjusted is not dragging to much.  Apparently .0015 on those engines is on the high end of acceptable, and might make noise.

 

Those Chevrolet engines are splash oilers. Is your Dodge splash oiled? Here are a couple of threads:

 

http://vcca.org/forum/ubbthreads.php/topics/306467/Re:_Adjusting_tightness_of_'30

http://vcca.org/forum/ubbthreads.php/topics/243425/Connector_rod_clearance

 

There are others over there as well. Another thing I have seen recommended is to turn the crank 90 degrees and recheck in case the crankshaft is a little less than round. This is to make sure it doesn't tighten up. Good luck.

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R.White    54

I haven't read those threads yet but I thank you for them.  Yes, the 4 cylinder Dodge Brothers engine is splash fed.  I made sure the bearing cap was on the right way so that the oil gets scooped up.  I too have always used plastigauge and never had reason to doubt it - but you are right in looking for an out of round journal.  I am surprised that 0.0015 is seen as a big clearance given that it is not pressure fed.  I can of course take up the bearing clearance a bit more and see if  that cures the knock.  It might be worth mentioning that the other bearings are adjusted the same and remain quiet.

If there is a slight out of round wear pattern on the journal, how much is considered to be too much?

 

As to lateral movement; this is a problem that I first noticed on this engine and which I was convinced was causing the knock because there was a large amount of free play.  I took up the clearance on this bearing cap by tinning the edges with soft solder.  The melting point of solder is slightly below that of the babbitt metal and given there is not much loading in that area I considered it safe. I was frustrated that my efforts had come to nothing.

 

For the record, I have eliminated the possibility of a plug fouling a valve by fitting shorter reach plugs.  I have also eliminated the possibility of wear between the valve spring retainer and pin by renewing everything.  The camshaft looks like a replacement considering the negligible wear.  I wondered if I should be setting the timing as per standard if an improved camshaft has been fitted?  I read somewhere that a different cam profile was fitted to some Australian cars (which this is).   Perhaps I should play around with the timing to see if it helps...or am I just clutching at straws?

 

Ray.

 

      

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cahartley    223

There is no point fiddling with the timing as you can do that from the steering column.

Did you happen to have the rods checked for straightness?

You can do that at home, with a helper to man the crank, by turning the engine over and watching to see if the rod walks back and forth on the piston pin between the up and down strokes.

I really wish you'd get a break!....... :(

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R.White    54
35 minutes ago, cahartley said:

There is no point fiddling with the timing as you can do that from the steering column.

Did you happen to have the rods checked for straightness?

You can do that at home, with a helper to man the crank, by turning the engine over and watching to see if the rod walks back and forth on the piston pin between the up and down strokes.

I really wish you'd get a break!....... :(

 

I only wondered if the distributor could be a whole tooth out?  Yeah, I'm clutching at straws!:(

 

I checked the con rods for straightness when I had them out.  The engineer says he also checked.   They all look central to the  wrist pins when I look up at them! 

 

I was surprised to read that the Chevy 4 could knock at 0.0015" big end clearance.  

 

I have a theory that No.1 cylinder suffered a serious trauma sometime in the past and this noise may be related to that time, I wonder if the crank pin has been knocked about enough to cause the knock. During the rebore they found a small piece of piston ring embedded in the cylinder wall!  I couldn't feel anything but an indentation - which I believed the rings were just passing over.  It is of little consolation to be proved right.<_<

 

It looks like I made a mistake by adjusting the bearing with the piston at the bottom rather than the top. I will have another go at it.

 

 

P8260053.JPG

Edited by R.White (see edit history)
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Bloo    83

I sort of doubt it has anything to do with the timing. Nearly all of my experience is with force fed engines, but as I understand it splash oilers need to run tighter than force fed engines. I think that rod tap-sideways test had more to do with checking the bearing clearance than the side clearance. I think their goal (on those Chevrolets anyway) is to run them as tight as they possibly can without binding, and they don't really quite believe what the plastigage is telling them. Any out of round would prevent getting the bearings very tight, as they would bind as you turned them. I don't know how much is too much.

 

If it were mine, I think I would shim that bearing as tight as I could get it without binding, and see if it still makes noise. Even if it still does, that is a huge clue.

 

It is so hard to tell about engine noises. All engines should behave about the same under the typical tests (cracking the throttle to listen for a rattle, disconnecting a spark plug and so on). In my experience they don't always. Usually, however, a small end (gudgeon pin) noise is a double knock. Usually it will change but not go away when you disconnect a spark plug. A rod knock should get quieter or go away. It is often hard to tell the difference between a small rod knock and some relatively harmless piston slap. What kind of pistons did you use and how much clearance?

 

I would also wonder about the closest main bearing. How tight is it?

 

I don't see how it could be anything to do with the camshaft. A noise there shouldn't change no matter what you do.

 

Edited by Bloo
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cahartley    223

Having, within the last few days, got my 1932 Chevrolet Confederate engine running I can tell you da bois at the Vintage Chevrolet Collectors Association warn that .002" clearance on a  194 six banger which has 2" rod journals WILL knock!

My Dodge had more than that before I checked the shims and it didn't knock.

Both have nearly identical rod oiling systems.

Go figure........ <_<

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R.White    54

Go figure indeed.  I was always under the impression that engines that relied on splash feed should have sufficient clearance for the oil to just flow in and out under gravity and that the introduction of pressure fed systems meant that closer tolerances could be achieved safely.  There is a certain logic  to it and that the reason we can go for closer tolerances now is that if synthetic oil is used it is not just better but thinner than the old straight oils.  I am always prepared to accept that I may have got it wrong but none of the other big end bearings are tighter than 0.002"... and they don't knock.  Why just this one?

 

Ray.

 

Bloo.  The main bearings have been a nightmare.  In a previous post I related how I couldn't get them closer than 0.003" without binding.  As I say, I think this crankshaft has suffered trauma at some time. 

 

That it runs at all is probably something of a miracle.:huh:

 

Ray.

Edited by R.White (see edit history)

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robert b    25

Ray how much crush is there on the bearing shells, you need at least 00.4" on each shell or they will walk in the rod and sound like a bigend knock ,and disappear when shorted plug on that cylinder , just a thought bob, bearing clearance is 0.001 on a round crank ,that is a light drag on a dry journal .

Edited by robert b (see edit history)

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R.White    54

Hi Bob.  On my engine the shells are trapped by the shims so cannot move around.  They are dead flush with the bearing cap and are quite a tight fit so need to be prised out.  There are also notches on the back which locate them.  As I see it, the shells cannot move in the rod when the bearings are bolted up.  I will look at it again, though, because thinking about it that might just be what is causing the knock if all the other bearings are quiet at 0.002".

 

Ray.

Edited by R.White (see edit history)

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Spinneyhill    250
On 8/14/2017 at 9:55 AM, R.White said:

Bloo.  The main bearings have been a nightmare.  In a previous post I related how I couldn't get them closer than 0.003" without binding.  As I say, I think this crankshaft has suffered trauma at some time.

 

Is it possible the shaft is bent? I think we canvassed this before.

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cahartley    223

Referring to my '29-'32 Chevrolet Service Manual which states "The dial indicator should not vary over .002"" when checking a  crankshaft.

This for a 294 straight 6, 3 main bearing, engine.

Interesting they use the word should.

The Dodge crankshaft is somewhat  more stout so I think it would have taken a catastrophic event to bend it....... :blink:

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Bloo    83
5 hours ago, Spinneyhill said:
On 8/13/2017 at 2:55 PM, R.White said:

Bloo.  The main bearings have been a nightmare.  In a previous post I related how I couldn't get them closer than 0.003" without binding.  As I say, I think this crankshaft has suffered trauma at some time.

 

Is it possible the shaft is bent? I think we canvassed this before.

 

I was wondering that too. .003 seems a bit loose.

 

7 hours ago, R.White said:

I will look at it again, though, because thinking about it that might just be what is causing the knock if all the other bearings are quiet at 0.002".

 

I brought up those Chevrolet threads because I was wondering if its possible #1 isn't really as tight as the others, even though it seems so.

 

On 8/13/2017 at 2:55 PM, R.White said:

Go figure indeed.  I was always under the impression that engines that relied on splash feed should have sufficient clearance for the oil to just flow in and out under gravity and that the introduction of pressure fed systems meant that closer tolerances could be achieved safely.

 

Actually I think that works the other way. The splash oiled engines needed to be tighter. I have heard many stories over the years about clearances in these old engines being set to the modern "rule of thumb" and winding up noisy. In pressure fed engines with a lot of miles it isn't uncommon for the bearings to talk a little before the oil pressure comes up. Splashers do need fairly thin oil to ensure flow, especially cold.

 

Edited by Bloo
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cahartley    223

There's a reason many new car manufacturers are using 0W20 oil.

Much the same reason I use 5W30 in my Model T and 10W30 in the two Chevs ('32 and '59).

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R.White    54
7 hours ago, cahartley said:

Referring to my '29-'32 Chevrolet Service Manual which states "The dial indicator should not vary over .002"" when checking a  crankshaft.

This for a 294 straight 6, 3 main bearing, engine.

Interesting they use the word should.

The Dodge crankshaft is somewhat  more stout so I think it would have taken a catastrophic event to bend it....... :blink:

 

I think this crank must have a slight bend in it because I found it impossible to fit the main bearings tighter than 0.003" without it binding.  I thought I was doing the right thing in taking up the slack because it had been running with 0.005" clearance. Previously, the engine ran fine with no mains problems but since adjusting them there is a noticeable increase in vibration.   It sometimes feels as if I am going backwards!:wacko:

 

 

Edited by R.White (see edit history)
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MikeC5    55

Hi Ray, I do know that for Model T engines, when new babbit is poured the bearings are set up very tight.  A friend of mine had his engine rebuilt by a long-time Model T specialist who was close enough that we could deliver the engine to him.  He showed us a completed short block he had on stand and let us try to turn it over with a long breaker bar.  It took considerable force to get it moving.  Instructions for starting it the first time required towing the car since it was too tight to crank by hand (our only other choice).  After running for several minutes it did loosen up enough to hand crank.  I think I would try tightening up the clearance on the offending rod big and and see if it changes things.  If it helps I might be tempted to tighten up the others too.  

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Bloo    83

I remember reading on some period publication, probably Dyke's Encyclopedia or maybe Audel's, about a machine used to "burn in" newly cast babbit bearings. The machine would spin the fresh engine with an electric motor until it spun freely. Sounds risky. I would want it to turn freely, if only barely.

 

 

 

 

Edited by Bloo
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R.White    54

Hi Mike.  I haven't had the crank reground so no new babbitt metal.  I should have ignored the "professional" advice who said it was O.K.  and had the crank reground with new babbitt metal poured.

 

The way things are going I will have to get it done anyway.:wacko:

 

Ray.

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R.White    54

Today I confronted  (politely) the engineer who  worked on my engine.  I told him how it was still making a knocking noise.  He said he was sorry to learn that - but it would seem he is too busy to do anything about it for at least six months and then it would cost me the best part of $2000 (or the £ equivalent) to regrind the crank and re babbitt the bearings.  

 

There is about as much chance of this guy fixing my engine as a one legged man winning an ass kicking contest.:rolleyes:

 

Ray.

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Spinneyhill    250

It is a real bummer when (judgement) advice you take from "experts" turns out to be poor. Drip fed bad news seems to be worse than when it all comes at once. I feel for you.

 

I am going through something similar. My radiator was blocked. i took it to a local shop and he was confident could clear it without taking the top tank off. He could not. So he took the top tank off. But then it leaked when he put it back on. And his franchise couldn't supply a new tapered core but offered a short one for a huge amount of money, even though I told him it is the frontice-piece of the car. So I took if for a "second opinion" - he couldn't agree fast enough. I asked at car club and took it to the place recommended. This fellow has been doing radiators for 30 years, the other fellow for just a year! The second man may be able to fix it... we'll see. It depends on how much damage the first man has done trying to solder the top on.

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R.White    54

OMG Spinneyhill!.:( 

 

If only our Dodge Brother Robert B wasn't so far away...

 

My engineer chap came highly recommended from other old car guys.  Yes, he is a skilled machinist and what he does is good work but that doesn't make him a good mechanic, does it?

 

Ray.

 

 

 

 

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cahartley    223

Ray, did you ever mic the rod journal yourself?

Have you tried shimming the rod bearing the old school way?

Set the bearing tight enough that you can tap it back and forth with a light hammer.

Unless the rod journals are in bad shape it seems logical the mains wouldn't be either.

After all the work you have gone through and shorting #1 stops the ticking I'm as stumped as you are....... :unsure:

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