Technical Looking for some help with a nasty noise

The car is a 1948 Chrysler Windsor


So tonight after 3 months apart I finally started the Chrysler.... And once it started I was greeted with a bad tapping noise. (I'm uploading a video to YouTube right now and will post a link once uploaded)

Before taking everything apart there was no tapping. I had the radiator off, fan off, replaced the water pump with a new one from Napa. Took the head off and sandblasted/painted it. New water distribution tube. All new fuel lines, new brake lines, new brakes, new wiring (in parts that needed it) everything is working ok except this noise problem.


When the car is shifted into reverse the noise stops, then barely comes back when shifted into drive (3/4 gear) and I can hear it clear as day when driving down the road. Once shifted back into neutral it's there again.

Also when idling the oil pressure says just under 40 ... I don't know what it was before but I saw in a video that when driving it home the first time the oil pressure was just over 40 while cruising around 30.

 

Here is the BEFORE video, the carb wasn't leaking either then and now the carb is soaked....??? I didn't touch the carb on this rebuild. I only took off the intake manifold because I thought a wire connector dropped into it ( nothing was in there)

 

And as of tonight here is the sound...

 

You tapped on the water pump? is that where the sound is coming from?

 

I am not familiar with that engine, but my first thought based on what you did is fan bolts contacting the water pump, or other contact. Remove the belt and run it for a short time, see if it does it, and rotate fan,generator by hand to feel for contact.

 

Sorry I was pointing on the water pump to show where to point the flashlight.

 

Marvel mystery oil, sometime these motors have sticky lifters,,,,,

 

You say it goes away when put into reverse? So is the noise coming from the engine, or the bellhousing area? If it goes away when put into reverse, I would suspect it's something in the clutch, flywheel area. Maybe the starter bendix is hanging up on the flywheel.

 

Or maybe it's a rocker arm ....

 

last time i heard a noise like that i found a nut the customer dropped/forgot embedded in the top of the piston.

 

did you have the head cut when it was off?

 

Pull the plugs and get a scope and look into all the cylinders for something that shouldn't be in there.

 

Sounds like the fan is hitting something but it could be that you left a surgical glove inside the patient.

 

Seems unlikely it would be a rocker arm on a flathead. I'd say remove the belt and turn the fan by hand to see if there is any resistance in some spots and not others. If it's not there, pull the head back off and remove the wire connector from the piston top. Can't imagine why it would care what gear it's in if you weren't messing with the drive train. You might get an inexpensive mechanics stethoscope off ebay or someplace to localize the area of the noise. You'd be surprised what you can hear with one of those.

Reminds me of a story my dad tells about when he was working in a garage in Sioux Falls in the 30's. There was a Chevy sedan came in with a knocking rod. The old guy that was given the job was pretty close to being deaf so he grabbed a great big screw driver and put the metal end on the engine and the wood end against his ear to use as a stethoscope. He was revving the engine way up with one hand and holding the screwdriver with the other as he moved it around looking for the source of the noise that he had been told about, but could not hear. Apparently the guy was revving the engine so high with that rod knocking so loud everyone in the shop could hear it that they all stopped what they were doing and were watching and cringing. Pretty soon the rod let go and exited through the side of the engine.... right where he had his screwdriver. Pap says, "The damned thing smacked him up side the head and knocked him on his *** and he was dazed for several minutes after.", then he laughs.

 

He could just remove the belt and fire the engine up and see if the noise went away. that is what I would do.

 

I'm back.... I took off the belt and spun the fan, no noise or resistance from that. I then checked the generator and that was fine as well as the lower crank pully bolts.

I started it without the fan and at first I didn't hear anything then after giving it a little throttle it was there. I took out the spark plugs and didn't see any damage on any of them. I haven't taken the head off yet as it hasn't cooled down and I don't want to change warping it.

The car sat for 2/3 months with fresh oil and MMO in the pan... Could this of broken up and sludge and/or freed any wrecked bearing? I don't know at this point.. Just throwing out things until I can remove the head. The temp gauge reads about 130 right now

 

I was thinking it had to do with the clutch being depressed and shifting into reverse but now I'm thinking it just lowered the rpm's enough that I couldn't hear it.


It seems that the higher the rpm's are the faster and louder it is

 

Too simple..

 

Lol I've already done that... Didn't go away

 

If your fortunate enough to know an aircraft mechanic, borrow a head set and put the male plug on anything that you suspect (engine running of course) Works just like a stethoscope.

 

Wonder if it could be something as simple as a loose piece of carbon ricocheting around between the top of the piston and the head? I've heard a couple engines do this in the past and the sound was similar to that in the video. I've even seen the problem fix itself if the engine is revved and driven a bit if the carbon manages to find its way past the exhaust valve. But this was on an OHV engine and that may be asking for a lot on a flathead.

When you had the head off did you de-carbon the tops of the pistons and clean out ALL the debris from the cylinders?

 

It sounds like it is getting ready to ventilate the side of your block!
Try pulling 1 plug wire off at a time with it running to see if that makes it stop.

 

Thank you for all the replies so far ... Here is an update. I got under the car today and took off the oil pan...

Here is the movement

 

LOL fire it up and see if that's where the noise is coming from.

Sorry I just could not hold that one in.

I would have to look it up but just a guess is that it may be a little too much side play.

 

an old broom handle makes a good stethoscope when trying to pinpoint the location of noise , often an old dry fuel pump will make a lot of racket

 

Thanks Dave, but with the oil pan off I don't think I'll be needing that broom handle lol.

But that is a good tip for the future

 

Didn't look to me like you were moving those rods side to side , just for and aft. Pull the caps and have a look see. I'm guessing you don't have bad bearings. Side play won't make that knock. Don't tear that engine all apart just to reduce a little side play. Something is hitting something else to make the noise you have. While you're in there, go to the parts store for some Plasti-gage and check your rod bearing clearance. That side play has been that way since the engine was ***embled.

 

Fabber McGee.....I was only able to move them towards the front of the car and towards the rear. I don't know if its considered side to side or for and aft.

I will also get that Plasti-gage and check it next time I work on the car (probably sunday).

On the driver side, inside the block there are three maybe score marks...looks like something is rubbing the side of the block. One is towards the front third of the engine, the second is near the middle and the last is towards the rear. I know this may be hard or impossible to interpret with my terminology. Ill try and take a picture tomorrow morning once its light out again. I'll also see if I can take a video with me turning the fan to turn the crank.

 

If you could move the rod toward the sides of the car it would mean there is excessive clearance on the journal and that would be bad bearings. It would make a knocking sound then. Moving it from the front to rear of the car means the sides of the rod have a lot of clearance and that is not a knock issue. Pull the caps and you'll know right away. You probably already know this, but it doesn't hurt to remind you, pay attention to which way the caps are installed. Do not mix them from rod to rod and do not turn them around. Meaning the left side of the #1 rod cap will be going back on the left side of #1rod. If they aren't already numbered, do it now. You can get inexpensive number stamps from Harbor Freight or just use a center punch. Good luck and be sure to keep us in the loop.

 

Just to keep updates going along, while cleaning the yard up for my family reunion (tomorrow) I snuck under the Chrysler to take pictures and found some damage to the bottom of the #1 piston ... Here are some pics