Hoosier, that explanation makes sense. Not knowing the engine’s history, I can’t say for sure whether the piston pin bushings have been replaced.

I dropped the front main bearing cap and found this:


Looks to me like original 1956 bearings suggesting that this engine was never overhauled. No more babbitt but bearing surface feels perfectly smooth. Just worn out I guess. I have about 30-35 psi hot oil pressure from about 2000 rpm but it’s very low at hot idle—less than 10 psi.

It appears the engine is due for a rebuild, but that won’t be in the cards for me any time soon.

Would it be worth the money to put a set of standard size bearings in at this point? I don’t push this engine hard and mostly just cruise around. If I’m not doing/risking lasting damage by continuing to do so, I might prefer to just button it back up and keep motoring until a good opportunity to rebuild.

1954 Crestline Victoria 312 4-bbl, 3-speed overdrive

Loose wrist pin bushings happen when the bushings are replaced without the proper equipment.  Sunnen makes a set of tooling for the job.  The bores in the rod are not smooth, they are rough bored.  Then Ford swedged the bushings in place, and the OD of the bushing was forced into the rough bore in the rod.  If replacement bushings are simply pressed into the rod, the bushing OD is sheared, and the fit in the rod is only temporary.  With the pounding of the wrist pin, the OD of the bushing starts to conform to the rough bore, losing its press fit.  Then it is loose and makes noise.  Sunnen tooling (I'm sure other companies have similar tooling) swedges the bushing in place, then you can hone it fit.  If peeot's engine has one bushing loose, I would suggest that the other 7 are in the same shape.

John - "The Hoosier Hurricane"

That wrist pin bushing is a strong candidate for the noise you are hearing.  A set of bearings would not hurt at this point either.  No idea on the spring.

Lorena, Texas (South of Waco)

I love that I was able to remove the oil pan without even jacking the car up. I can’t imagine that’s possible on very many cars!

I believe I have spotted the source of the knock. In
The end of the wrist pin bushing was visible outside the rod end. I was able to easily push it back into place with a screwdriver—basically no resistance.

Additionally, I found about 3-4 tablespoons of metal paste in the bottom of the otherwise-clean oil pan. There was also two pieces of a small spring I don’t recognize.

I checked the #1 rod bearing as well. She’s done.

I didn’t see any chips or cracks in any pistons or the crank, nor anything else I would expect to create a 1600-2000 rpm vibration. Could bearing slop account for it?




1954 Crestline Victoria 312 4-bbl, 3-speed overdrive

The pan will miss the steady rest on my 56 but I need to remove the sway bar. #5 needs to be near TDC to it slide off. I also installed 2 set screws at the rear of the pan for ease of reinstalling it when it was off. Good luck. 

56 Vic, B'Ville 200 MPH Club Member, So Cal.

I appreciate all the help, even if it hasn’t led to resolution yet.

I did remove the fuel pump tonight and ran the engine without it. The knock was still evident, but not any louder. Looking in the fuel pump hole, everything looked normal, if not particularly clean.

The next step is probably to drop the oil pan and look near the front of the block for anything irregular. Will the pan clear the steady rest on a ‘54 Crestline? Motor mounts are new.

1954 Crestline Victoria 312 4-bbl, 3-speed overdrive

I don't know how hard you drive your car, but if you baby it, there is the possibility that there could be some carbon build up on the top of a piston.  I had this happen on the GM 454. I would have sworn that it had a bad rod , until I used some "top engine cleaner", a product made by gm. and de carboned the eng. this can be done also by using straight water, or some have used a mix of water and brake fluid with good results. A carbon build up though is usually heard even from inside the car when driving, not just at idle. As Ted suggested it could be a cracked or broken piston skirt, it could possibly cause a balance problem with a vibration depending on if a piece has broken off, and how big of a piece. if just cracked, there is a possibility that it can go a long time before complete failure.  another possibility would be a piston that is slightly under size in the skirt area, or one that has a "collapsed ",  with out being able to hear your eng. running in person, at this point I am not sure what the noise could be.   maybe Ted, or someone with more experience with Y-blocks may have more suggestions.  sorry I was not more help---  Jim

Running the engine with the valve covers off, the knocking sounds exactly the same; only the valve train clatter is more audible. With the covers on, valve train noise is not noticeable—it’s a pretty darned quiet engine. I do not know anything about its history but nothing about it looks fresh.

As for the fuel pump, I haven’t tried removing it, but my “stethoscope” suggests the source is elsewhere.

I’m inclined to just let it be for the foreseeable future; it’s very minor and not at all evident behind the wheel above idle.

The only concern I have at this point is the vibrations at 1600-2000 rpm and the vibration of the vacuum gauge. I was thinking these might be related to the audible knock, but I’m not sure whether it merits dropping the oil pan and surveying things. Maybe if a piston (probably #1) has a broken skirt, it is causing a balance issue in the bottom end—but if that were so, wouldn’t it get worse at higher engine speeds?

1954 Crestline Victoria 312 4-bbl, 3-speed overdrive

Any idea if the last time the engine was freshened up if it was a complete rebuild with new pistons and ground crankshaft or was it a re-ring and re-bearing rebuild.  If the old pistons were reused, then a cracked skirt is a possibility.

Here’s a picture of a cracked piston from a 272 that just had a light knock.
  

Lorena, Texas (South of Waco)

Looks like he has a 3 speed with OD.