Model A Tapping sound

D

ddelproop

Member
Hi all,

Here is a youtube link of 1 minute recording of our running model a engine warmed up.

https://youtu.be/26fLwNUb8ac?si=KHmsjPWfjMC1me-z

I am concerned about the tapping sound.

I want to say at the start that I measured the lifters and all are out of spec.
.016 with one at .028 (max)

I assumed the loud tapping sound is naturally associated with valve #6 which is at .028. It made some sense to me ...

However... the more I put a stethoscope to the engine the frequency of the engine tappets and lifters which are noisy... appears not to be the louder tapping sound which can be heard in the recording.

Here is what I have discovered so far.
Lifters, springs keepers and guides are modern style new in appearance. Tappets move freely
Timing gear appears to be new. I checked for loose timing gear.
Tappets are original based on appearance.

Vacuum Gauge indicates a single sticky valve but after running many tanks of MM and seafoam cleaning and backing that with inspection of valves and checking movement including endoscope inspection of cylinders.. very clean and I do not see evidence of a sticky nor burnt valve.

Good compression all cylinders all at 65PSI +/- 1 psi

The engine was clearly rebuilt at some point but not professionally.

With endoscope..
Mains have been adjusted with shims.
New castle nuts on connecting rods.
Oil pump is bright and clean.
Engine is VERY clean inside.
Crankshaft is original.

I installed new headers and gasket. Checked recently and no leaks intake.
I can find no exhaust leak so far
I do suspect head gasket leak but so far no evidence.

I have not pulled the head gasket yet but was planning to do so in a few weeks and will also inspect main bearing clearances.

The loud tapping sound is NOT present when engine is turned over by hand nor with starter. The sound is not present when engine is winding down after ignition is turned off. The sound is always present when engine is running and never changes except in frequency in lock step with rpm

The sound is also present when engine is not at idle but I am unable to determine if it is relatively louder.

Any comments.. suggestions concerns from what you hear let me know.

Dan
 
Lifters, springs keepers and guides are modern style new in appearance. Tappets move freely
Timing gear appears to be new. I checked for loose timing gear.
Tappets are original based on appearance.
Click to expand...

To me, lifters and tappets are the same thing.
First you say: "Lifters, springs keepers and guides are modern style new in appearance."
Then you say: "Tappets are original based on appearance."
So, which is it?
 
You have done your diagnostic trouble shooting homework well. I would drive it and keep monitoring the noise. What kind of oil are you using? You might want to try using a single grade 30W or 40W racing oil containing Zn additive.
 
That engine on the video sounds normal to me. I wouldn't be looking for something that isn't a problem.
 
I am no expert in model a engines and part descriptions and I thought the same as well but going by part descriptions by Synders the tappets follow the cam and that is what I was referring to not the springs ect.
Thanks
 
I fully admit. I am not 100% sure what is normal is for a Model A
The measurement of the lifters ...good or bad turned into conformation bias or better :)
Thanks for you comment
 
Update.
I just tried a head gasket leak detector tester. RELD from Amazon. Did not think it could work in model A due to non pressurized cooling but after warming up the engine the color of the liquid is changing color indicating exhaust gases in cooling fluid.

So hopefully this is it and the head gasket was on the list of repairs as there was past evidence of older leak
 
The valve tappet clearances you note are excessive and are likely the cause of the tricking noise. Set all of the clearances to 0.010" to 0.013" while the engine is at room temperature. Hopefully your engine has adjustable valve lifters, otherwise it is a pain to grind valves the original Ford way. If the engine does not have adjustable lifters, you should convert to them at this time. The lifters with the single tightening nut are the better ones.
 
Regarding using a high viscosity motor oil such as 20W50, the 20 Viscosity occurs at 0F, and the 50 Viscosity occurs at 212F. A normal Model "A" engine runs at 160F to 180F, so the oil's viscosity only gets to about 20 at operating temperature.
 
Thank you for your comment
Ya... unfortunately non-adjustable.
That is on my list as well and agree a conversion would be best.
I was told eventually the excessive tolerances would lead to accelerated wear which will also effect the engines performance as the valves no longer open up fully.

We love our model A and can be found on back roads every weekend.
What a wonderful car. So many people smile.

Have a great day!
 
The valve clearances you have set are a bit extreme. Set them cold to .010" intake and .012" exhaust and see if you have an improvement. I run SAE 40 fleet diesel (Farm&Fleet) in my older engines. This oil does not have the same EPA requirements that removed the ZDDP from automotive engine oils as far as I know. Push rod engines need this additive to prevent premature cam lobe/ lifter failures.
 
Bob Bidonde said:
The valve tappet clearances you note are excessive and are likely the cause of the tricking noise. Set all of the clearances to 0.010" to 0.013" while the engine is at room temperature. Hopefully your engine has adjustable valve lifters, otherwise it is a pain to grind valves the original Ford way. If the engine does not have adjustable lifters, you should convert to them at this time. The lifters with the single tightening nut are the better ones.
Click to expand...




Thanks!
 
Take a spark plug (copper) strap off, and start it. Does the sound go away? If not, put the strap back on, and repeat 3 more cylinders.
 
Gene F said:
Take a spark plug (copper) strap off, and start it. Does the sound go away? If not, put the strap back on, and repeat 3 more cylinders.
Click to expand...

No need to stop and start the engine so many times. I use a screw driver with an insulated handle and short each plug to earth in turn. If the problem (if there is one) is related to bearings, piston slap etc, the noise will stop when the offending cylinder is shorted out.
 
I would suggest addressing the valves at the same time you replace the head gasket. Lapping in original valves to reduce the clearances is not terribly difficult and is a lot cheaper than replacing the valves with modern.
However I would replace the valve springs with a new set. A set of 8 will be around $10.00

Where are you located?
 
Short out the plugs one at a time as Synchro suggested. Try retarding the spark to see if that changes things. Install adjustable lifters. (You can do this by dropping the pan, taking out the valves, keeping all the existing lifters up using clothes pins, and then pulling the cam. Then reverse the procedure using adjustable lifters.)

You will have to do a lot of lapping to bring the tappet clearance into spec. You could grind the valves but will end up with thin edges.

Best to do all this work, including checking the mains, with the engine out of the car and on an engine stand. That will actually save time in the long run and help to assure that things are done correctly.
 
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