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Four cylinder engine noise


R.White
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Since getting my '26  Dodge Brothers engine running, I have had a strange knocking sound. So, having got to the point that I can no longer tolerate it, I thought I would investigate.  Before stripping down the engine I thought I would run the problem past my friends here on the forum.  I know you guys like to delve into the oily bits so I am hoping to pick up some advice and suggestions (polite ones, please!)

 

1) The engine was presumably rebuilt; it has done 90,000 mies. I have measured even compressions @50 psi on all 4 cylinders which I believe is correct.  The engine does not smoke or burn oil.  I have sealed any exhaust leaks with a replacement manifold and new gaskets.

 

2) The noise is a regular high pitched knock/tap like a loose tappet.  I have set the tappets cold at 0.008 and 0.010.  and the noise doesn't seem to be coming from them. It seems to be emanating from the top of the engine.  However, the exhaust valve on No.1 cylinder does have a rather loose spring (when not under tension, of course) but only if I move it from side to side which it isn't supposed to do with the engine running, and doesn't from what I can see.

 

3) The sound is, in my opinion, too high pitched to be a con rod big end bearing or main bearing.

 It is most noticeable when under load or when the throttle is blipped at tick over.  A big end bearing problem would, I believe, be more likely to show itself more on the over - run, rather than under load (but not always)  and I have placed my ear next to the oil pan and all is quiet. That presumably also rules out main bearings which I assume would be a deeper rumble. Before re assembly, I could check the bearings with Plastigauge.

 

4) If I remove the cylinder head, I can check the valves, seats and guides  and perhaps look for any signs of the pistons slapping the cylinder walls - although in my experience piston slap tends to sound louder when the engine is cold. This noise remains at the same volume even when the engine is hot.  Perhaps the head has been skimmed too much and a valve or piston crown is touching the head somewhere? It may be that new pistons/ rings have been fitted without de burring ridges at the top of the cylinders?

 

If there is too much wear (oval) I will need to get a rebore and new pistons but I am hopeful that won't be necessary.

 

5) If I remove the pistons and con rods I might find a broken ring or a sloppy little end bearing?

 

6) Less likely, perhaps is too much camshaft end float or some other camshaft fault.

 

These are some of the ideas that I have been mulling over.  Perhaps you guys could make other suggestions?

 

Any help would be appreciated. 

 

Ray.

 

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When my Studebaker engine was overhauled, we reused the old pistons. It now has a gudgeon rattle. May that be your noise? I think it changes as the engine warms up but the engine hasn't run for 20 years so I can't remember very well.

 

I have a mechanics stethoscope for listening to engine noises. A simple version is a long screwdriver against your ear and touching the engine. You may be able to locate the source using such a device. Mind the fan though!

Edited by Spinneyhill (see edit history)
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Thanks Bill.  Are you asking if the valves rotate? That's something I haven't checked.  What will it tell me if they don't?  Will that cause a knock?

 

"cam to valve stem hammer"?  Do you mean tappets /  valve lifter?  The valve lifters all rotate freely.

 

I suppose a bent valve stem may cause the valve head to "click" if it doesn't sit down straight. When I first got the car going, I found that the valve clearances were almost non existant.  I assume a previous tinkerer thought they could quiet the engine but it obviously didn't work because the knock was still there with no clearances.  I have set the tappets cold but make allowances for expansion.

 

Thanks, Spinnyhill.  I meant gudgeon pin when I said "sloppy little end bearing"  I just couldn't remember that word "gudgeon" :ph34r: .  I have had this before with my Austin.  A previous owner left me with all sorts of problems to sort out!  

 

Ray.

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With the engine running and making the noise ground each spark plug, one at a time, and see what happens.

If the noise persists it's likely your problem does not lie with the rod bearings at least.

Does the tapping happen at a frequency commensurate with the speed of the engine>

Edited by cahartley (see edit history)
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With the engine running and making the noise ground each spark plug, one at a time, and see what happens.

If the noise persists it's likely your problem does not lie with the rod bearings at least.

Does the tapping happen at a frequency commensurate with the speed of the engine>

Good advise.  I have done this and the noise persists. I think we have eliminated the crankshaft but my confused assessment is that each tap/knock coincides with each firing stroke.   I once had a similar problem where someone had previously fitted new standard pistons to a very worn engine which should have been rebored.  The difference here is that there is no loss of power or smoke from the exhaust and it doesn't use much oil.  I'm pretty sure I will be tearing down the engine; I just need to get as many suggestions as I can first.  

 

I have had several experienced mechanics/ old car owners listen to the engine and they all agree it doesn't sound too bad on tick over.  The clatter really shows up under load or if you blip the throttle.  Good old Dodge has got everyone guessing!!

 

The other thing I did was make sure that the plugs don't have too long a reach.  That would be too easy.  ;)

 

Ray.  

 

 

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I agree with Bill that it most likely valve train related.  Maybe even timing gears?  Mine were making a noticeable clattering sound due to what appeared to be excess backlash.  I was able to adjust the gear spacing (water pump drive to cam gear) by leaving out the gasket and using gasket maker on the pump housing to block.  I hope you don't have to pull the engine since it looks to be quite a job.  Pistons, cam, valves, valve guides can be services in-situ so I would think pulling the engine is a last resort (especially if bottom end is not suspect).

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Yes Mike. I don't really fancy doing more than is really necessary and my logic is that if the engine has perfect compressions and doesn't smoke or burn oil, it shouldn't need a rebore. The only way to be sure, of course, is to remove the head and inspect/measure the bores. I am hopeful all will be well but if the noise is from a broken ring it could have scored the bore. I have seen an engine that was making a regular "tap tap tap" where someone had fitted new rings but should have use a "step" top ring to avoid the ridge. I haven't seen any step rings in years so they are probably obsolete.

I have improved the water pump/distributor drive by replacing the driven gear and taken up excessive back lash by fitting a new shaft and key ways. There is still a slight rumble from the gears at idle speed but nothing objectionable.

When you visited, we were in agreement that there was a regular noise coming from the exhaust manifold. That has been sorted with a period correct replacement in good condition courtesy of Ron Lawson in OZ. This noise is similar but if the valve gear is the cause, I am not sure how to fix it if tappet clearances make no difference. These engines apparently suffer from camshaft problems so in Australia someone has re profiled them to prevent exhaust valves being burned out.

Ray.

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Just for the heck of it Ray have you checked your oil pressure? It almost sounds like the valve train is dry. I would use a new gauge to see what you have.

No Bill, I haven't done that. I have been relying on the original gauge which shows good pressure. Interestingly, there is a possibility that the oil could be starved because the gauge only shows that the pump is working unlike a pressure fed engine where the supply pressure is shown. I will check that the supply pipe is not blocked. I should probably have done that as a matter of course anyway.

Edited by R.White (see edit history)
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Another source of an actual "knock" would be a loose piston pin but I think that's rather unlikely.

Have you tried listening around the engine with some kind of a wood stick or anything that will touch the engine and reach your ear lobe to localize the knock?

If it happens once per revolution it could be a loose key somewhere but you're describing twice per revolution....... ?

On many of those old engines there is an adjustment on the timing cover to take up cam shaft end play.

If it was happening ONCE per revolution the only other thing that occurs to me at the moment is a gear tooth.

Are you absolutely positive it IS coming from the engine and not farther down the line?

Some of those noises transmit in ways that make diagnosis very difficult........  :wacko:

Edited by cahartley (see edit history)
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Thanks for that suggestion of a chipped gear tooth. It is something else I can look for.

The sound I am getting is sequential with each pulse of the engine (twice per revolution.) I think it's true to say that with these old, slow revving, four cylinder engines you can almost feel the individual combustions on tick over. I have tried using a wooden 'stethoscope', I have also tried a length of 3/4" copper pipe with a plastic funnel pushed onto the end like an old fashioned ear trumpet. (Yea, like Beethoven, Ha ha.) There is no doubt the knock is coming from the top of the engine; from the head in fact.

Apparently, the camshaft end play should be set by "spreading" a plug. So far, I have not found it and the various published diagrams don't show it. On some engines it is governed by a spring.

Ray.

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Take a piece of chalk and mark the front pulley. Then use a timing light and see if knock is at same place every revolution. You may have to move your chalk mark a few times to coordinate it with where you can get light close to it. Once established where the knock is check to see if it is a specific location in the firing order, such as when number one fires, etc. 

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It's possible a lifter or two might be badly out of adjustment which would issue a click rather than a knock.......?

You could remove the side covers, stick a feeler gauge between the lifters and valve stems to see if there's any change.

I like doing all the non-destructive things first........  :P

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It's possible a lifter or two might be badly out of adjustment which would issue a click rather than a knock.......?

You could remove the side covers, stick a feeler gauge between the lifters and valve stems to see if there's any change.

I like doing all the non-destructive things first........  :P

I have adjusted the tappets which I think is what you mean. Returning to my original post No.2 I had a question about a loose spring but the noise doesn't seem to be coming from there. I agree it's best to look for the simple (or silly) things first but it looks like a tear down is on the cards. Not without expense, of course, even a gasket set is pricy and I have to add shipping and duty to the cost of parts bought in the States. On the other hand, if I can silence the knock, it will pay dividends and better still, make driving the Dodge more enjoyable - which is what it's all about.

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Take a piece of chalk and mark the front pulley. Then use a timing light and see if knock is at same place every revolution. You may have to move your chalk mark a few times to coordinate it with where you can get light close to it. Once established where the knock is check to see if it is a specific location in the firing order, such as when number one fires, etc.

That is another excellent suggestion and one that I will act on. I really appreciate you giving me the benefit of your not inconsiderable experience. Thank You nearchoclatetown.

Ray.

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Is it possible for for you take a video while it's running?

I'll be happy to host it for you....... :)

A pic is worth a 1000 words but a video is worth 10,000........ :D

That would be a first for me. Let's see how I get on with the old technology. Many thanks for your kind offer.

All you guys are very helpful.

Thanks,

Ray.

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Try the stethoscope method of finding the general area were the noise is coming from.

A wrist pin  will be a lighter noise and it can make twice in one revolution.

Valve train noises if (it is only one cylinder) would be slower.

Thanks for the suggestion. I have used the 'stethoscope' method (post 12.) The noise seems to be coming from the head.

Ray.

Edited by R.White (see edit history)
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You can put your other car along side and hook the timing light to the 12 volt battery

Then most timing lights have a impulse clamp around the number 1 plug

Then run it and do like Doug wrote

Visual and audio to determine which cylinder is making noise

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To further explain

I use a timing light on each cylinder with valve cover off

On modern engines the light will flash and stop the movement of the valve train

If noise is at the same time. I would check for a colasped lifter

Same theory on older engines

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Thanks for the explanation. I didn't realise you could use the 12 volt battery in a modern to operate a timing light on a six volt system in an other. I hope the extra amps with 6 volts won't damage the timing light - the manufacturers do say it's for 12 volts.

I should be able to try out the plan at the week end.

BTW, I hadn't considered a faulty lifter. They all seem to be working O.K. but there is a loose valve spring on No.1 exhaust, (when not under tension) as I have mentioned. I will check out it's keeper/ collets or whatever it has to be sure nothing is missing.

Many thanks.

Ray.

Edited by R.White (see edit history)
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Hello Jack. I'm thinking what you are thinking... and I'm thinking that you may well be right!

I intend to replace all the valve springs anyway. When I first found that I could get the spring on No.1 exhaust to move from side to side and make a click sound I convinced myself that I had found the problem. I showed it to my neighbour (who is also an 'old car' guy) but he put doubts in my mind - and that's what led to me posting this thread.

I will let you know how I get on.

Many thanks,

Ray.

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These would be solid lifters, not hydraulic, so they wouldn't collapse. The lifter could however, be too worn out, OR, it could be a worn cam lobe.

Yes, that is correct. These old type lifters have a tendency to wear on their sides. The ones on my engine seem fine. The camshaft lobes could have worn through the case hardening but rather than knock, I believe they would produce insufficient lift and cause exhaust valves to burn.

I believe excessive camshaft end float would make a knock.

I am presently tinkering with Geoff's timing light/marked pulley idea

Ray.

Edited by R.White (see edit history)
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Just recently, I pulled the intake valve out of a 1916 engine, the valve needed replacement, I notice the pin that goes thru the valve end was worn and bent, This can contribute to spring being looser, Hopefully you can isolate the noise to a particular cylinder and pull spring out and measure and check for tension, I am not sure what measurement is ? Or what spring tension should be.

Maybe someone out there knows, my local engine machine shop has a tester for spring compression.

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Just recently, I pulled the intake valve out of a 1916 engine, the valve needed replacement, I notice the pin that goes thru the valve end was worn and bent, This can contribute to spring being looser, Hopefully you can isolate the noise to a particular cylinder and pull spring out and measure and check for tension, I am not sure what measurement is ? Or what spring tension should be.

Maybe someone out there knows, my local engine machine shop has a tester for spring compression.

This crossed my mind. Keeper pins like this are supplied by Myers. As are valves and springs.

According to the book of information, it looks like you can replace the valve spring without removing the head; but it must be a tricky little job! You must first need to ensure the valve is at rest then using some sort of strap as a pivot for a lever/screwdriver, compress the spring. Then, while you remove the pin from the valve and lift valve up enough with your other hand you can pull out the spring with your third hand. :blink: 

How hard can it be? :huh: 

Fortunately, I have a side valve spring compressor so it shouldn't be too difficult.  :rolleyes: 

Ray.

Edited by R.White (see edit history)
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then using some sort of strap as a pivot for a lever/screwdriver, compress the spring. Then, while you remove the pin from the valve and lift valve up enough with your other hand you can pull out the spring with your third hand. :blink: 

How hard can it be? :huh: 

Fortunately, I have a side valve spring compressor so it shouldn't be too difficult.  :rolleyes: 

Ray.

Hopefully your compressor does the trick. When I was playing with valves recently I made a wedge to push into the spring just above the bottom and used a lever to compress the spring. My wedge was actually filed from one leg of a piece of 50 mm angle with a similar piece up the other way bolted to the back to give the right location to lever against one edge of the side opening. I drilled and filed a slot in the wedge to fit around the valve stem.

 

It is a right royal pain getting in there, leaning over the mud guard, going over or under the steering column and under the manifold (all on the RHS). Get some soft flooring to kneel on!

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I may have got this bit wrong so please correct me if I have.

 

The slightly loose valve spring may be down to a bent retaining pin (as a previous post stated) so I assume the easiest thing to do would be to replace the pin.  However, I am now sure that the knock I am hearing is not coming from the No.1 exhaust valve spring.  Using a large screwdriver, I increased tension on the valve spring with the engine running by prying it from the top but it made no difference to the noise at all.  Using a feeler gauge in the tappets (engine still running) I detected no change in the knock.  Using the stethoscope type method, the noise could not be detected from the valve gear however, it could be heard more clearly from the head.

 

I have also been listening to the tapping noise while using a strobe lamp connected to No.1 lead.  I now have a white mark on the pulley which I believe on this engine (looking at the manual) runs at crankshaft speed.  The  knock and the light perfectly coincides with the line at each rotation... it follows that there is just one tap per crankshaft revolution. The tap coincides with No.1 cylinder at the point of combustion.  Am I right to presume from this there could be a problem with No 1 piston.?

 

I suppose this test can eliminate the No.1 exhaust valve theory as it (and the inlet valve) would be closed for combustion in this cylinder? 

 

Ray.

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I had a guy bring me an engine ticking after he had done an at home tune up.

I was looking at his old spark plugs and saw that one had an electrode missing.

When I pulled the head I found the missing electrode, I picked it out of the top of the piston and the noise was gone.

Could there be something has fallen into a spark plug hole? This would make the tick each time the piston comes up regardless of compression or exhaust stroke.

 know these old flat heads can be prone to dirt and such around the spark plugs.

Edited by JACK M (see edit history)
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