My flathead started knocking.

[rjlester]

A few days ago I fired up my 1954 Meteor with an original 255 Flathead (Canada got the flathead one more year). It was parked all winter. I did start it a couple of times over the winter. No issues.

Last night on the way home from town, I slowed for an intersection and I heard a noticeable rattle coming from the engine. I had a sticky valve a couple years ago so I figured this was the same thing. Previous noisy valve went away with some seafoam in the oil and a drive down the road. Now after messing with it today, I'm not so sure. I added seafoam, drove it for about a half hour and it has not gone away.

I did a compression test, and I have compression on all 8 cylinders. They have always been a bit low, but it runs amazingly well, they were all between 75 and 90 with the throttle cracked open a little. If it was a sticky valve, wouldn't I lack compression in one cylinder?

The funny thing is, I have great oil pressure, no different than before. Stock gauge has always worked and I show over 40psi while driving, over 20 idling.

I used a broomstick to my ear and it is definitely coming from the drivers side. You can actually feel the noise (in my hands) holding the broomstick against the lower two head bolts at the bottom of cylinder 7. So, I suspect cylinder 7. The head bolts above the spark plug do not reflect the same amount of noise. Pulling the spark plug wire off all of the plugs while running makes no difference to the sound.

I can see all of the valves opening and closing through the spark plug holes. Sprayed seafoam down all of the valve stems. No change. I suspect a wrist pin. The noise is there at any RPM, just gets louder with more speed. When you come off the throttle it almost seems louder momentarily.

Any ideas? I'm stumped with having good oil pressure. Worried it's a wrist pin.

[cas3]

"If " its a wrist pin, I drove an old 68 White truck , 290 cummins, for 10 years with a wrist pin knock that started years before I got in the drivers seat. Seasonal job, but we put about 10k on every summer so I did about 100k and it never changed. It would rap pretty good when cold, but going down the road it was not noticeable.

If you keep good oil pressure I would drive it a bit and see if it changes. A wrist pin should not blow up and wreck everything.

[J Franklin]

You might need a second opinion from a good mechanic. BTW I once owned a '54 Meteor with a flathead V-8.

[pistonbroke]

If the sound is coming from the top and not the pan I wouldpull the head and see whats up. The peace of mind would be worth the price of a head gasket to me. Tim

[Kube]

I'm gonna go along with wrist pin or piston slap.
Is the noise constant with RPM? Or is it more notable when decelerating? Accelerating?

[glennpm]

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Do you have a borescope? Since you believe that #7 is the bad actor, pull the spark plug and rotate the engine to get the #7 piston at the bottom of it's stroke. This could show cylinder wall scoring if the wrist pin is moving in and out due to the broken pin.

[glennpm]

You could also drain the engine oil into an open pan. In the sun, look for metal bits glittering.

[solidaxle]

This is probably not the solution but before you get into expensive repair, check the timing. I was adjusting mine by trail and error to get the most performance without a timing light and it at one point it was so far off it knocked.

[hueyhoolihan]

Originally Posted by solidaxle

This is probably not the solution but before you get into expensive repair, check the timing. I was adjusting mine by trail and error to get the most performance without a timing light and it at one point it was so far off it knocked.

good point...

a slight knocking can occur due to a lack of octane too. usually exacerbated with in increased load on the engine. another quick and simple test. although most likely to occur in a performance, high compression engine though.

[rjlester]

Interesting thought about timing. It does have fuel in it from last fall. It knocks at idle speed too though.

Another thought, can a fuel pump rod/fuel pump issue cause a noise that loud? Should I try pulling the pump/rod and running it momentarily?

I'm prepared to pull that cylinder head in the next day or two if nothing else pans out.

[Kube]

Originally Posted by rjlester

Interesting thought about timing. It does have fuel in it from last fall. It knocks at idle speed too though.

Another thought, can a fuel pump rod/fuel pump issue cause a noise that loud? Should I try pulling the pump/rod and running it momentarily?

I'm prepared to pull that cylinder head in the next day or two if nothing else pans out.

I have, albeit rarely, had a fuel pump make a rattle. However, with a stethoscope or rod held to the pump, you WILL know right away whether or not that's the culprit.

[RalphG]

I like a piece of heater hose to use as a "stethoscope" on an engine. Re: timing, I think if it was advanced so far that it caused knock at idle then the starter likely wouldn't be able to turn the engine over. Its a pretty sure sign when the engine kicks back against the starter that the timing is a bit far advanced.

[rjlester]

Good points about the fuel pump and the timing affecting starting. Starts perfectly as it always has, so timing is fine.

I did put the broomstick on the fuel pump and there was almost no sound there in comparison to the bottom of cylinder 7.

Likely pulling the cylinder head tonight if I get some time.

[Kube]

Originally Posted by rjlester

Good points about the fuel pump and the timing affecting starting. Starts perfectly as it always has, so timing is fine.

I did put the broomstick on the fuel pump and there was almost no sound there in comparison to the bottom of cylinder 7.

Likely pulling the cylinder head tonight if I get some time.

Best of fortune to you. Please let us know what you find.

[big deuce]

Might be a good situation to try a enduroscope or borescope camera before pulling the head. I wonder if the camera would get by the valve to see the bore? Would a loose rod cap make such noise? The piston could be kissing the head.

[rjlester]

Didn't get to the cylinder head last night. I do have a borescope, but it cannot get around the corner on a flathead engine, too big of a camera I guess. Might have to invest in a newer one, they are so cheap to buy now.

I've discussed the issue on the phone with a good friend who has been into flatheads since the 50's. He also thought either something is in the combustion chamber or a rod came loose possibly.

[rjlester]

Ok guys, found the problem.

Small piece of a piston ring worked its way to the combustion chamber. In cylinder number 7 as I suspected! A minor score on the cylinder wall. So, I know I will be rebuilding it down the road, but coming up in a few weeks, I'm building a new shop so I can get work like this done! I'll be very tied up working on my shop for a long time.

Now get this, I think this ring broke back in December! In fact, over Christmas I started up all my old cars on a nice warm day to run them for a few minutes. The old meteor fired right up, but it hammered and banged so loud, I thought somebodys cat was in the belts! I shut it down immediately, restarted it and it was perfectly quiet until this week. I put over 100 miles on it in that time. Crazy!

This engine rebuild project will have to go on the back burner for now. However, I'm tempted to slap it back together so I can at least move it out of the garage and back into storage. I've rebuilt a number of engines in my day, but never seen a piston ring work its way out like that.

So what causes this, corrosion on the piston from being parked from 1965 until 2021, and it finally let loose after 5 years of driving over 18000 miles?

[petehoovie]

Originally Posted by rjlester

Ok guys, found the problem.

Small piece of a piston ring worked its way to the combustion chamber. In cylinder number 7 as I suspected! A minor score on the cylinder wall. So, I know I will be rebuilding it down the road, but coming up in a few weeks, I'm building a new shop so I can get work like this done! I'll be very tied up working on my shop for a long time.

Now get this, I think this ring broke back in December! In fact, over Christmas I started up all my old cars on a nice warm day to run them for a few minutes. The old meteor fired right up, but it hammered and banged so loud, I thought somebodys cat was in the belts! I shut it down immediately, restarted it and it was perfectly quiet until this week. I put over 100 miles on it in that time. Crazy!

This engine rebuild project will have to go on the back burner for now. However, I'm tempted to slap it back together so I can at least move it out of the garage and back into storage. I've rebuilt a number of engines in my day, but never seen a piston ring work its way out like that.

So what causes this, corrosion on the piston from being parked from 1965 until 2021, and it finally let loose after 5 years of driving over 18000 miles?

[leon bee]

That's something new for me. ^^

[Mart]

yeah, if it's important that it is able to be moved around, just putting it together is probably the best bet. I wouldn't bother changing any gaskets, just bolt it back together and keep the run time and revs to a minimum.
Mart.