MTFCA Forum

I'm ready to scream!! The engine runs like a top except for this rattle that I get while idling or coasting. I have adjusted my rod caps and removed a dozen or so spacers. I used the 1" square news paper technique to get the proper clearance. The rattle continued. I pulled the timing cover and found no excessive cam travel. I did see my Dan McEachern brass timing gear had some extra slop so I replaced it with an oversized aluminum gear which fit much better. At the same time I replaced the generator gear. I still have the rattle. Short of an engine rebuild what am I overlooking?

The thought occurs to me to allow it to "self-trouble shoot" by continuing to drive it until whatever it is ultimately fails.

It took me years to locate an annoying rattle. Timer rod. At idle with spark moderately advance no noise. On the road with the spark advanced for normal driving rattle. I would have never found it if I had not removed the timer for cleaning.

I would be suspicious of 3 things:

slightly u/s piston to bore fit - who cares?
slightly worn piston pins - who cares?
slightly worn center main - short out #2 & 3 simultaneously and if it goes away...that's it...if it doesn't, put in ear plugs and enjoy the car

Before you tighten the rods, try having someone crank the engine slowly as you observe from underneath with the inspection plate off. If the rods move front to back to front as the engine turns over, you likely have a bent rod. This will cause the piston to be slightly cocked and the wrist pin will not be perfectly parallel with the crankshaft. So when the rod is moving upward, the pin will move in one direction, and when the rod is moving downward, it will move in the other direction. This will not be noticeable on a recently poured bearing, but as the engine wears, the thrust surface will wear until you get this knock. This problem will not cause your engine any problems until it gets so worn that the end of the wrist pin starts to score the cylinder. It is just annoying . If you decide to straighten the rods you will need to pull the head and pull the pistons out. If you do so, you should also replace the rings while it is apart.
Norm

Scott, Thank you so much for your help. Using your suggestion it appears to be the center main. Actually when I short out either 2 or 3 the noise quits. So what does one do with a noisy center main bearing?

John

I am emailing you.

"Rattle driving me crazy "...
My old man always said, "that's not a drive, it's a short putt" !!

Or, you could just throw up your hands ans confess it is a Model T after all, not a bloody Packard and all Model T's seem to rattle some, or squeak or make any one of a dozen noises I can think of...sometimes you've just got to let Lizzy be Lizzy (although I do routinely go around an tighten every nut and bolt on her just to make sure it isn't something important).