MTFCA Forum

Do I need to worry about this sound?

https://photos.app.goo.gl/fvNN8DqKWsWPfNxR7

jason... What position is your spark lever in at idle? To me , it sounds like it's too for advanced at idle and you're getting some spark knock

A couple of things can sound like a big end knock, the big end it's self and the float in the cam shaft, both are easy to check. Also I see washers on the head bolts so assuming a Z head, was all the pistons checked for clearance?

Maybe an advanced spark knock? But sounds like a typical T to me. Hard to tell over a video. Did it just start the sound?

Moxie26 wrote: ↑

Thu Apr 06, 2023 6:43 pm

jason... What position is your spark lever in at idle? To me , it sounds like it's too for advanced at idle and you're getting some spark knock

Advance is maybe halfway down the quadrant.

Kerry wrote: ↑

Thu Apr 06, 2023 6:50 pm

A couple of things can sound like a big end knock, the big end it's self and the float in the cam shaft, both are easy to check. Also I see washers on the head bolts so assuming a Z head, was all the pistons checked for clearance?

I put the Z head on two years ago. I heard no knocking when I did a test fit.

Throw us some back ground.
Sudden knock? slowly developing?
Have you shorted out plugs to eliminate a loose rod?
Only a head change or other changes like a cam?
Has she run before?(after the head change)

The engine was rebuilt in 1990. Not long after, Car sat until 2020 in a shed. I have owned it for two years, put on the z head two winters ago. Overheated last August after the radiator failed so I had the head off again to clean and inspect. Some photos attached. The sound seems new to me, but I’m not really sure.

It's pretty hard to get a Model T to "detonate", "clatter" or develop "spark knock" using modern gasoline, especially at idle. Over advanced timing might do it, but I'd think it would more likley caused by a very hot exhaust valve that wasn't seating, or a spark plug electrode getting very hot, or some kind of head gasket projection getting very hot, or perhaps a timer wire shorting and firing a cylinder BTDC. A "spark knock", or any related combustion knock, will usually occur at half throttle or more with a warmed up motor, and get worse as more throttle is applied, and will go away completely at light throttle. Gasoline that has had all the ethanol stripped out out of it might suffer enough octane loss to knock in a T motor. A lot of oil getting into one of the combustion chambers can lead to knock, by causing heavy carbon deposits, raising compression, and by creating hot spots.

It sounds to me like a mechanical knock, perhaps a tight piston or a tight wrist pin.

Have you looked very carefully for any evidence of piston scuffing or scoring? Check both the upper and lower bores. The lower edge of the piston skirt in the second picture looks odd. Is that oil?

" Z " cylinder heads give more compression, and more power at ignition.... Relying on proper initial ignition settings, engine will run better with less spark advance compared to the original cylinder head. As you drive, and move the spark lever, you will find the "sweet" spot the engine will run regardless of battery or magneto ignition power... I found that changing to a 10w30 synthetic engine oil will eradicate a lot of engine sounds.

The pistons appear to be a good tight fit in the bores, which is good. However, the overheating incident last August could have led to some scuffing or light scoring of one or more pistons, which could cause a sound like that.

A Z head would certainly raise compression, but it's still very low for an engine running on 87 octane gas, and at idle or anywhere near it, the effective compression is very low due to the throttle being nearly closed and thus the intake manifold pressure and actual compression pressure being very low.

From here, it sounds to me like a mechanical issue, probably a minor one.

That is very correct.. 87 octane gas will really bog down an engine...... you need to run on 70 octane. Good luck on your fixes, and do get back to us and tell us how you solved your problem .

You might try to isolate the sound by shorting out one plug at a time. Either ground at coil terminal, or at the spark plug. If sound will diminish at one plug, might check out that cylinder.

Or other isolating means is to use a metal 'sounding rod' or a long heavy screwdriver with shank all the way thru the handle, grasp that rod with hand and thumb over one end, and rest your ear on that thumb, with the other end of the rod resting against the block, cylinder wall, or front plate. Amazing what sound you can locate with that method. Your using 'bone conduction' to help your ear magnify that odd sound.

Get a length of 7/16 steel rod about 2 ft long and drill and tap a hole in one end for a small bolt. Go to the store and get a small can of El Pato red tomato sauce. Put the sauce on your scrambled eggs, then rinse the can and drill a hole in the bottom of it for the small bolt. Using a pair of flat washers, bolt the bottom of the can to the end of the rod. You now have an amplified acoustic "telephone" to chase knocks with. The can will mask outside noise and amplify the sounds conducted up the steel rod. (Can is about 2 1/4 X 2 1/2". It has a bright yellow 1929 copyright lithograph type label with a nice color picture of a duck)

I looked at your videos again and noticed that your horn bell end is sitting directly on the head. That’s probably not what your hearing but might cause a rattling sound??

Also the fan belt is running awfully close to the large fan adjustment bolt. If it’s not rubbing it’s really close that it occasionally might hit the bolt head if the belts a little loose.

The old trick of using a screwdriver to short out each plug and see which one has the loudest sound might give you a pretty good idea what’s happening.

John kuehn wrote: ↑

Thu Apr 06, 2023 10:37 pm

I looked at your videos again and noticed that your horn bell end is sitting directly on the head. That’s probably not what your hearing but might cause a rattling sound??

Also the fan belt is running awfully close to the large fan adjustment bolt. If it’s not rubbing it’s really close that it occasionally might hit the bolt head if the belts a little loose.

The old trick of using a screwdriver to short out each plug and see which one has the loudest sound might give you a pretty good idea what’s happening.

I will try shorting out the cylinders tomorrow and see what happens. Ill check that belt too.


So, is this something I need to worry about? Can I drive it like this?

TXGOAT2 wrote: ↑

Thu Apr 06, 2023 7:42 pm

Have you looked very carefully for any evidence of piston scuffing or scoring? Check both the upper and lower bores. The lower edge of the piston skirt in the second picture looks odd. Is that oil?

Some very light lines, I couldn't catch my fingernail on any of them. Everything felt smooth mostly.

TXGOAT2 wrote: ↑

Thu Apr 06, 2023 7:57 pm

The pistons appear to be a good tight fit in the bores, which is good. However, the overheating incident last August could have led to some scuffing or light scoring of one or more pistons, which could cause a sound like that.

A Z head would certainly raise compression, but it's still very low for an engine running on 87 octane gas, and at idle or anywhere near it, the effective compression is very low due to the throttle being nearly closed and thus the intake manifold pressure and actual compression pressure being very low.

From here, it sounds to me like a mechanical issue, probably a minor one.

Do I need to worry much? Can I drive it like this?

Hi Jason,
This is one of those places were a good electronic listening device is worth it's weight in gold.The word hurt & knock should be next to each
other in the dictionary. When was the last time you heard that someone was hurt real good. I would do everything I could to find out what the
knock is because driving the car until it tells you what the knock is may be very expensive.
Craig.

I would like to hear it while revving and letting off the gas at different rpms. I also know that a chunk of carbon on top of a piston can make a knocking sound. I've known about the screwdriver trick for listening for noises but I bought a mechanics stethescope (sp) years ago. You can get one for about $10.

Sounds like a rod knock. Try shorting out the spark plugs, one-by-one, as others suggest. The sound won't necessarily go away in the problem cylinder, but it should at least change. The next step is to remove the bottom cover and inspect your connecting rods for excessive clearance or babbitt damage.

You could try running with a little less advance and see what that changes. Doing so however is usually just a neat trick to cover up a rod knock and a way to "get by" for a while. Although, too far advanced can cause a knock all its own. Worth trying it out to eliminate that possibility.

This has nothing to do with octane, or carbon build-up, or oil grade, or piston clearance me thinks.

You ask if it's okay to drive like this. Well, it's probably not ready to explode on you, but driving it won't make it get any better.

"Overheated last August after the radiator failed so I had the head off again to clean and inspect. Some photos attached. The sound seems new to me, but I’m not really sure." (Etc.)


Did you try cranking the engine by hand when you had the head off? It should turn very easily with no uneven friction or drag, and most of that friction/drag should be from the clutch.

No one can tell you with certainty whether the engine is or is not safe to run by listening to a recording.

At best, you'll get educated guesses.

A person with substantial mechanical experience who is familiar with Model Ts could give you a much better opinion of your engine's condition if that person could examine the vehicle in person. Such an examination would consist of starting the engine cold and observing it while it warms up, then taking the vehicle out on the road for half an hour or so, then observing it some more.

Following that, an informed opinion of what might be wrong, if anything, can be offered, and an informed opinion of how serious an issue it is can be offered.

RE: "Overheated last August after the radiator failed so I had the head off again to clean and inspect. Some photos attached. The sound seems new to me, but I’m not really sure." .............

I'd want to make absolutely certain that no piston scuffing/scoring resulted from this incident.

A simple boilover isn't likely to have caused trouble, unless the aluminum pistons were fit very tightly, which they appear to be, or unless for any reason lubrication was less than ideal.

Properly adjusted ignition coils using a ECCT would solve your ignition imbalance.

Moxie26 wrote: ↑

Fri Apr 07, 2023 9:57 am

Properly adjusted ignition coils using a ECCT would solve your ignition imbalance.

Who says he has an ignition imbalance????

Just something to check that maybe causing his sound problem

I would drop the pan and check your clearance on all the rods. easy to do and would eliminate of obvious.

TRZim wrote: ↑

Fri Apr 07, 2023 12:03 pm

I would drop the pan and check your clearance on all the rods. easy to do and would eliminate of obvious.

Check for evidence of stuck/stiff wrist pins whall you are there.
Thats been an ongoing overlooked issue.

Regarding "can I keep running it?" NO, not advisable, UNTIL you know what the noise is. If it were determined to be timing gear noise, for example. OK to run. If it loose or pounded rod bearings, obviously no.

..... "Check for evidence of stuck/stiff wrist pins whall you are there.
Thats been an ongoing overlooked issue.".....


I don't see any oil holes in the piston pin bosses.

Jason

there are quite a few folks in Denver who could and likely would help you.

Make a contact, rent a UHaul trailer and make a day of it and just be done with it. Of all the folks who have heard the engine, you are the only one who has heard the real deal...recordings just don't do it unless it's about to throw a rod.

Going to Denver will result in one of two things: you'll find out everything is OK, or you'll find out what is wrong so that you can fix it and it will be OK.

No matter how well meaning the posters are here, and they are indeed well meaning, you have received enough advice, that if it were all followed with the same urgency, it would suggest you pretty much tear things down, hunting and pecking along the way.

Don't do that.

TXGOAT2 wrote: ↑

Fri Apr 07, 2023 1:46 pm

..... "Check for evidence of stuck/stiff wrist pins whall you are there.
Thats been an ongoing overlooked issue.".....


I don't see any oil holes in the piston pin bosses.

Further reason to check. Good call.

Any heat evidence on the other bosses?

Any evidence that the " Z " cylinder head was purchased and installed new?.. or, purchased used and at some time the cylinder head was decked for warpage , to raise compression?... Possibility of a valve contacting the head on opening or even piston contacting the cylinder head.???? .... May have to go as far as removing the cylinder head and replace with a original Ford cylinder head to see if the problem is fixed or continues.

JBog wrote: ↑

Thu Apr 06, 2023 7:22 pm

The engine was rebuilt in 1990. Not long after, Car sat until 2020 in a shed. I have owned it for two years, put on the z head two winters ago. Overheated last August after the radiator failed so I had the head off again to clean and inspect. Some photos attached. The sound seems new to me, but I’m not really sure.

Perhaps the sound is the reason the car sat is a shed for 30 years.
Also still haven't answered
speedytinc » Thu Apr 06, 2023 6:10 pm
Throw us some back ground.
Sudden knock? slowly developing?
.....
Has she run before?(after the head change)

Not clear your problem, but by the little description, here's a possibility. Re-install of the head & knocking noise.

When installing such a head, the procedure is to put in place with bolts loose in the block with no head gasket for line up. Bolts allow at least 1/4" rise in the head. Push the head to the left & hand crank. Watch for ony movement. Repeat this test pushing the head to the right, front & rear.
This way you confirm nothing internally will hit. You can install the head gasket.

You can paint the valve pocket/combustion chambers also. Any upset in the paint but no head movement indicates a close situation. Trim tight spots as needed.

My experience with past Z heads is the combustion chambers vary wildly.

Jason - I had the same knocking sound start on my 1919 after running the engine a few years after a rebuild. Upon inspection, I found babbitt missing on the #4 rod and cap (see photos). Although I have a three-dip pan, after removing the head, I was able to make repairs through the inspection plate. It was a tight squeeze and I had to get a little creative even with small hands, but it can be done. Been runnning well ever since.

Here are links to videos I made at the time:
https://www.youtube.com/watch?v=wHk0fWPFw0w&t=32s
https://www.youtube.com/watch?v=Af_oPY3Ag-Q
https://www.youtube.com/watch?v=ilWMhwHovoA&t=6s