Over the past few months, I have helped a few club members with engine knocks. This is not something that I'm that familiar with. Of the last four engines, I could say that there was a definitely a smoking gun found, after the engine was disassembled, but I tried to listen with a stethoscope and shorting spark plugs, listening to any changes in the sound. I made a diagnosis of each knock, prior to removing the engine, I was wrong on each. Turns out that each engine had a bad bearing, but also had other factors that could have added to the sound.
The first engine had only a slight knock, under certain conditions, like acceleration. I tried the shorting out plugs, but since the knock was not present during idle, I think this test didn't do anything. I listened to the block at different spots, but the engine made so much back ground noise, this didn't produce any results either. Turns out #2 rob bearing was bad.
The second engine was first thought to be an ignition knock. Again it was not present at all times. Both the shorting and listening didn't provide any information. This engine had a bad center main bearing.
The third engine had a LOUD knock that was present all the time. Shorting the plugs didn't give and ideas. Listening definitely indicated that the knock was from the back of the engine. This turned out to be a broken flywheel bolt.
The last engine knocked while driving or at higher RPM while standing still. The shorting test seemed to indicate that the knock was in the center of the engine. Shorting out #2 & #3 seemed to quiet it down. The listening seemed definite that the knock was center engine. Center Main!. Turns out that the center main was just fine, the problem was the #4 rod. Wrong again.
So, either I do not have enough experience in listening to engine knocks or the best method to find a knock is just open up the engine and look. Mike
When you were shorting plugs where was the timing lever?
The timer level was adjusted for a good idle. Maybe 1/4 down. Mike
In the future when shorting plugs advance the spark all the way. If the car can run on both battery and mag try both when testing.
The rod is lead Babbitt, and shows no signs of being tinned.
Mike, bad sounds are hard to diagnosis sometimes, but you done what any good mechanic would do, you found the problem, and fixed it!
Herm, you mentioned that there are no signs of tining. Not being that familiar with Babbitt, what would tinning look like. Would it be similar to how solder looks after it is laid down? Mike
Good catch Mike, my rod knocked until it broke and went through the 1912 block last year.
I believe he is talking about the bearing surface of the rod itself. There appears to be no evidence of tinning on the rod. Tinning will make the babbit "stick" to the rod surface.
Like soldering, if you tin the surfaces to be connected, the solder will flow and adhere much better.
Mike, some Guys that try to pour, do not tin at all. So all that holds the Babbitt is the wedge effect from the sides making a crimped effect, that will peel out of the rod as the Babbitt moves to and from the bearing backing surface, from the action of the crank.
When watching U-Tube videos, you will see many of People heating a make shift jig with a cutting torch, and I think that may what happened to the rod shown. There are no signs of the tin now, but if it was at the time, and a cutting torch, or large torch was used with no way to control the heat, it would burn the tinning off in the middle of the bearing as the rod shows, as that is where most of the heat is concentrated, as there videos show.
Most bad rod pours come apart first as starting with the flange on the rod cracking off first, and when that happens, it will take the rest of the Babbitt with it.
When you, or any body gets a new set of rods from a vender, the way to tell if they are any good, is look at the out side flange to see if even the smallest place at where the flange lays on the rod. Does it look like water on wax, or can you see under the flange, or does it look like a continuation of the metal, an just a color difference between the two metals.
Picture one will be a bad flange Picture, of which I have many.
Picture two will be after a pour showing 100% Babbitt adhesion.
I added a few more pictures I had of this set of rods, and got carried away.
Any questions, just ask?
thanks for the picture tutorial
Herm, thanks for the pictures. I have always been fascinated with the art of pouring bearings. I worked in an electric steam power plant for years and had the opportunity to watch really large bearings being poured. I remember the men doing the work were very fussy about temperature of the bearing shell and the Babbitt. I wish I was into Model T's at that time, maybe I could have gotten some good advice.
The 10th picture in your series, the one with your thumb on the bearing, shows a nice continuous connection between the shell and bearing material is that what you are talking about being a good adhesion? And should I see this at all the interfaces between the shell/rod and the Babbitt? I appreciate the tip and I'll be paying more attention in the future when I change a rod. Thanks Mike
The 10th picture in your series, the one with your thumb on the bearing, shows a nice continuous connection between the shell and bearing material is that what you are talking about being a good adhesion? "End Quote"
Yes Mike, That one and the two above that.
There are a lot of videos on U-Tub that show how to pour bearings, I haven't seen the right way yet. The ones I have seen, have blow holes, wrinkles, seams, dirt, Babbitt puddy ect. in them.
One video shows a Brass insert being poured, and he just pours in the top of the bearing, and it goes all over, and lets it cool a little, and then takes a torch and runs around the Babbitt on top to smooth the Babbitt out. It looks better, but what he has done is push the top Babbitt away from the shell, because cold will pull Babbitt, and heat will push Babbitt away. Then Mike, he takes the bearing off the mandrel, and tries to fill the two seams at the part lines. He says him self, that it isn't sticking to the cap, but just covering up the gap.
If I get time tonight, I will try to put it on here.
And should I see this at all the interfaces between the shell/rod and the Babbitt? "End Quote"
Yes, every time!
Picture 1. shows a rod out of the set of 4 that they had tried to tin, and the bearing was to cold and left the surface all Pimply, plus it wasn't clean enough.
Picture 3 shows the loose Babbitt pried out to show what the back side of the Babbitt looks like when the out side surface looks good, but bad part lines. This was caused from the temperature of the mandrel, the shell, and both the tinning pot, and the pouring pot, if there was one. This set of rods were done shortly before we got them.
4 & 5 show the carbon spots that were not cleaned off before tinning. Guys, a Wire Brush wheel is good for nothing for cleaning shells. Nothing sticks to dirt. So all you do is polish the carbon, and it is still there. It will not tin, although it might look like it. You can take an air hose and blow the tinning off.
Picture 6. shows a clean core.
8, 9, and 10 does show what any rod or bearing should look like when the two metals blend.
11, 12, 13, and 14. Shows setting for Twist, Bend, and Off Set, in that order, and that is the way they have to be checked, also in that order.
Picture 14 also shows how far the off set was out, not uncommon.
There is not a machine in the world that will cut a rod perfect, so that is why they make alignment tooling.
So Herm, you saying that you haven't seen Mike Bender's U-tube video's?
or he's just like every one else that does babbitt work, in your opinion dosen't do it right?
No I haven't Frankie, but one thing I do know, you wouldn't know the difference!
Herm, your full of it.
He's not trying to fill the babbitt into a seam between shell and babbitt but building up the shinkage to even out the height from babbitt to shell just like doing the thrust on a T cap.
Your ears are no good either, are they Frankie.
Your 70 year old eyes are failing you Hermie babe!
first you attribute words to Herm that he did NOT type, then pick an argument with him over what you claim he wrote, but actually didn't.
Your animus toward him is legendary, so just QUIT and allow this thread to remain instructive and don't make it a personality contest between the two of you.
It reminds me of a child who used to poke animals with a stick and then complain when they got bit (for absolutely no reason of course!). That's what I see going on here, and it isn't the first time...please find another thread to find fault with and let this one remain useful. Thanks.
Scott, mmm! a retired engineer, seem to have the same problem as Herm in your old age, bad eyes!
Read his post, watch the video, and then tell me the video is what he said!