I have a 27 touring car and I ran it to fast down hill and now I have one or two rods knocking. Need help what is the next step, do I just remove some shims and what do I do if I have damaged the journals. I am not sure what is the best way to go about this is.
Get down and get under, as the song says. Pull the inspection plate off and check it out. Remember that the plate holds a good amount of oil so make sure you have something for it to pour into when you take it off.
Before you pull the plate;
With the engine running at a bit above idle short out each plug with a screw driver and see if you can find which rods want to knock.
On the recent National Tour one car started knocking badly. After the tour we brought it into the barn , pulled the inspection plate and pulled off number 1rod cap. It didn't look too bad so we took out a shim, used plasicgaga(?) to check the clearance. We got it to 0.0015 and moved on to number 2. It too need adjustment, went through the same procedure. However as we turned the crank we noticed that number 1appeared looser. After a careful inspection we realized the Babbitt had failed at the top of the bearing. This was the case on all four rods. Clearly the last Babbitt was poorly done and we replaced all four rods.
Each case has to be inspected, the is no one fixed "cure", you have to look and measure....
Mark & Tony - The use of "plastigage" can be kinda' "tricky" and from what you described Tony, your situation might have been a good example:
After you checked and adjusted #1, you say that you then "moved on to #2", but AS YOU TURNED THE CRANK, "#1 appeared looser".
Not saying that this was the situation in your case Tony, but the manner in which plastigage can fool a person is that if a crankshaft journal is out-of-round, the plastigage will "indicate" different clearances, depending upon how you've turned the crankshaft and depending on the different places on the out-of-round journal you've checked with plastigage.
All of that to say that plastigage is pretty useless with a crankshaft that has out-of-round journals,...FWIW,.....harold
When the engine has been knocking for a long time, you will find that the top of the bearing on the rod side will get the most wear. This is because the pressure is always on that side and not on the cap. When you are on compression you are pushing up on the rod and when on power you are pushing down on the rod. Secondly, if the engine has been knocking for a long time, the spot where the knock occurs will wear a flat spot on the crank. You can find this with a micrometer measuring in several directions and locations on the crankshaft. The measurement should be very close all the way around the crankshaft. Thirdly, just because the bearing is tight now and you find .0015 with the plastigauge in the spot where the crankshaft is down and you tighten up the cap, it does not mean that it is still .0015 after you turn the crankshaft part way around. And unless you have known this engine since it was rebuilt with either a new or re-turned crankshaft, you don't know whether it was already flat the last time it was adjusted.
so to make things short and sweet, measure the crankshaft whenever you tighten the bearings and if it is worn beyond limits, the adjustment won't last long before it starts to knock again.
"I have a 27 touring car and I ran it to fast down hill and now I have one or two rods knocking."
To prevent this in the future, a good "rule of thumb" is "go down the hill at the same speed you can go up it"!!!
In this way you are likely driving within the abilities of your brakes!!
It is one of the first things they teach drivers of large trucks.
Best of luck!