Classic cars forum & vehicle restoration.

Ray White · Joined: 02 Dec 2014 Posts: 7133 Location: Derby

I have been investigating a tapping sound coming from the engine of my 1926 Dodge Brothers. Unlike normal wear showing up on the over run, this is louder when under load.

It is a basic side valve design of 3.5 litres with a splash fed set up. I managed to isolate the knock to No.1 cylinder on the firing stroke.

The con rods have been converted to shell bearings and I am getting a reading of 0.0025 which is for a 1.5" journal is a bit big but it is nothing compared with the side ways movement. I can get a noticeable tapping sound by moving the big end just with my hand. I have tried my best to test the little end with the piston still in the block but it seems to be fine.

The ends are fitted with shims for adjustment. What should I do about the side to side and is it responsible for the knock?

Uncle Alec · Joined: 14 Jan 2008 Posts: 734 Location: Manchester

I don't know how relevant this is, but when I convert Riley RM rods to shells, they often lose the white metal side faces.
I did a set once without making any allowance for this loss, and there was about ¼" side float, The engine did knock; I guess that even a microscopic bias to one side would on the power stroke throw the rod into side-face contact with the crank.
I removed the rods and mig-welded three blobs of weld at 120° to each rod big end, then filed them until they took up all bar a few thou side float.
Cured.

Ray White · Joined: 02 Dec 2014 Posts: 7133 Location: Derby

Thanks Alec. I must admit to not thinking of doing that but if it works... Razz

I had been thinking along the lines of adding more white metal somehow but if it just rubs off the sides your suggestion makes perfect sense.

This has been going round in my head all day. One idea I had was to pin brass shims to the edge but I wouldn't like to say how successful it would be? Probably wouldn't last long Crying or Very sad

Uncle Alec · Joined: 14 Jan 2008 Posts: 734 Location: Manchester

The blobs are under no load whatsoever, so as long as they stop the rod traversing the pin fore-and-aft they are doing the job.
The biggie is to use only the minimum amount of weld so that there is no significant heat build-up that would distort the conrod big end, hence the mig-welding.

Ray White · Joined: 02 Dec 2014 Posts: 7133 Location: Derby

Having taken up the loose bearing, the problem seems to have sorted itself out. The clearance is now 0.0015" and nearer to the 0.001" as specified and the lateral movement much reduced.

Hopefully, when I have checked the other bearings the engine will sound less like a bag of nails. Fortunately, the journal is in perfect condition.

Thanks for the helpful idea. It may well come in useful in the future.

roverdriver · Posted: Sat Jun 13, 2015 10:24 am Post subject:

Shell bearings as well as shims, sounds quite odd. White metal with shims was the norm, and when wear required the removal of shims, it was usual to blue and scrape the whitemetal of the bearing to a uniform round, unless of course, the wear had created sufficient even space on the metal to make it perfectly round with the shim(s) removed.

I was tempted to convert a Model A engine to shells at one stage, but after some investigation and thought opted to go original with cast white metal. I hand-scraped them to fit by myself, having never done such work before. I managed 200,000 miles in that car before selling it on, and bearings were still in very good condition. I do believe that shells should only be used on a pressure-fed crankshaft for several reasons.

I am glad that removing shims solved your problem Ray, I just hope that there is enough metal on the shells for the bearing to continue in good service.
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Dane- roverdriver but not a Viking.

Ray White · Joined: 02 Dec 2014 Posts: 7133 Location: Derby

The shells have quite a thick layer of white metal if the depth of the diagonal oil trough is anything to go by. I have never heard of retaining the shims with a shell conversion but if the cap fits... Embarassed

Ashley · Joined: 02 Jan 2008 Posts: 1426 Location: Near Stroud, Glos

TBH I don't think it's a good idea to convert and engine without an oil filter, preferably full flow to shells. This is because they are less able to cope with dirt than white metal.

Ray White · Joined: 02 Dec 2014 Posts: 7133 Location: Derby

Rusty · Posted: Sun Jun 14, 2015 5:00 am Post subject:

I hate to suggest a bad thought, but the original pistons in the Dodge 4 engines have the gudgeon pin held into the piston by a grub screw and I have seen these fall out and let the pin move sideways contacting the cylinder wall. I don't know if they would make that kind of noise but it may be a thought ! The gudgeon bushing is located in the end of the connecting rod and the pin itself is held rigidly in the piston by this grub screw.

Goodluck

Ray White · Joined: 02 Dec 2014 Posts: 7133 Location: Derby

I don't think I have that problem, thanks for the tip anyway.

Interestingly, that is what seems to have happened at some time in the past. When I noticed some dents in the cylinder wall I though that I had found the problem but the pistons have been replaced with modern ones with a gudgeon pin located by cir clips.

The No.1 big end bearing seemed to loose it's lateral movement after being taken up but this was misleading. The pin had a high spot that I had missed and was pinching at that point. I found that the lateral movement was still present and could be seen if the rod was gently levered. I have relieved the high spot and all seems well.

I plan on using the mig weld blobs idea which will hopefully stop the knocking especially as the oil blockage has been cleared.

We live in hope!