1931 Pickup Engine Knock
 

I bought this 1931 and brought it back to La Vergne, Tennessee from Sioux Falls, South Dakota. It had blown exhaust manifold gaskets when I got it. I replaced with copper gaskets and no further issues there. However there is a knock. The person I got the truck from never mentioned any engine work but when I ran the vin I found a previous ad where that owner said the engine was rebuilt. Apparently this truck has gone through multiple owners in a fairly short amount of time. I have only driven the truck around the block. My previous Model A was a Tudor with a Antique Engine Builders motor with inserted bearings and this truck just seems to really vibrate compared to that car. It being new to me I have dropped the oil pan and started inspecting. I plastigaged the center main today and it looks to be within the limits. I don't see anything jumping out a me that would cause such a knock. Before dropping the pan I did run the motor without the belt and still have the knock. I can see that the #3 piston is different than the other 3. If anyone has any advice I'm all ears. Also if anyone recognizes the truck and knows the previous owner or owners please message me. Surely you wouldn't forget a motor that has so much chrome, lol. I have never seen one.

Here is a link to the engine running.
https://youtu.be/bfTi7IC2eWYhttps://uploads.tapatalk-cdn.com/202...834b681338.jpghttps://uploads.tapatalk-cdn.com/202...43ab2f3069.jpghttps://uploads.tapatalk-cdn.com/202...b6fb3b3771.jpghttps://uploads.tapatalk-cdn.com/202...98b27727af.jpghttps://uploads.tapatalk-cdn.com/202...6d886de4f8.jpghttps://uploads.tapatalk-cdn.com/202...3983913760.jpghttps://uploads.tapatalk-cdn.com/202...f8872f4c68.jpghttps://uploads.tapatalk-cdn.com/202...f2c7926317.jpghttps://uploads.tapatalk-cdn.com/202...b3c908de68.jpghttps://uploads.tapatalk-cdn.com/202...b5d982649b.jpghttps://uploads.tapatalk-cdn.com/202...e8a99fac55.jpghttps://uploads.tapatalk-cdn.com/202...6c55e411f1.jpghttps://uploads.tapatalk-cdn.com/202...050045161a.jpghttps://uploads.tapatalk-cdn.com/202...aa883845b4.jpg

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Re: 1931 Pickup Engine Knock
 

Cam shaft fore and aft movement?

Re: 1931 Pickup Engine Knock
 

Looks recently rebuilt or unused since. I don't see the piston difference. What are the valve clearances? Maybe you can contact the rebuilder.

Re: 1931 Pickup Engine Knock
 

Nice looking truck.

Re: 1931 Pickup Engine Knock
 

I'd start exactly where you did - checking the middle main bearing. That not being the cause of the noise, I'd move on and check the other mains and the big ends. Is the knock worse on initial start up, then reduce as the oil comes through. If it is like that, I lean towards a main bearing. If one of those is loose, the oil drains out of it quickly after you shut it down so the bearing is running fairly dry till the oil pump gets oil up into the gallery and it runs down to the bearing. If it is a big end, the rod is dipping oil from the word go so you won't have that delay. Check them all and while you are in there, you will see if there is anything disastrous like broken babbit.
It sure sounds like a bearing to me.

Re: 1931 Pickup Engine Knock
 

Check to see if your timing gear is loose.

Re: 1931 Pickup Engine Knock
 

What’s that gray stuff on the rear main cap?

Re: 1931 Pickup Engine Knock
 

I would check that manifold and gasket again, then try a "sounding stick" placed to your ear and along the valve chamber; timing gear cover, and finally the oil pan. Also go to the tailpipe and listen, this will tell you if it's in the valve area. Our club engine had a knock which turned out to be caused by the oversized .004 distributor/oil pump drive gear. I learned this stuff from the "old timers" in our club which suddenly, I'm now one!

Re: 1931 Pickup Engine Knock
 

Rtv.

Re: 1931 Pickup Engine Knock
 

This can be a very difficult thing to diagnose. I would lean toward the rod bearings and makn bearings aa previously stated. Those things can really cause a knock. Valves that are out of adjustment - even way off have a different sound.

Something else you should try that has not been mentioned is verify that nothing is hitting the oil pan dipper tray. Look for any shiny marks. Also, verify that you have the thrust plunger in the timing gear cover and it is in good shape with no broken spring.

Re: 1931 Pickup Engine Knock
 

I can't reach out to the engine builder because I don't know who he is. I have found previous owners on Facebook through my wife's account (I don't have one) and messaged them with no response.

#3 piston has like half moon cutouts on the body of the piston where the other 3 are flush around the base. This difference my purely be a difference in brand.

I did check to see if the dippers were hitting the pan when I dropped it and don't see any tell tell markings.

Just glancing up from the bottom it looks like the thrust spring is there but I will check more thoroughly later. I had to get my son off to school this morning.

However I did find a crack in the oil pump shaft housing. It appears the housing has already been welded previously.

This is just an update of what I have found and will continue to check things as advised. I really appreciate everyone's time and input on this.https://uploads.tapatalk-cdn.com/202...e65967c124.jpghttps://uploads.tapatalk-cdn.com/202...4a26eb558a.jpghttps://uploads.tapatalk-cdn.com/202...eaf13d07b7.jpg

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Re: 1931 Pickup Engine Knock
 

i had an engine knock that did not fit into any of the diagnoses charts. turns out that
the flywheel ring gear was not on properly as well as the crank had excessive end ply.
so the crank would move ahead and the ring gear would touch the bell housing. the noise sounded like the rods were coming out or the engine.
it took a while to figure this out

so keep looking you just never know what you will find
not much help

ou
tom

Re: 1931 Pickup Engine Knock
 

Do you know that for a fact? It looks like something else. Let’s hear what the OP has for an answer

Re: 1931 Pickup Engine Knock
 

Good afternoon...You might consider taking the head off to see if one of the pistons his hitting the head...this does happen from time to time, especially at the higher RPM's...Ernie in Arizona...

Re: 1931 Pickup Engine Knock
 

The first thing I saw was the dipper on #3 rod is backwards.
Or is that an optical illusion?

Re: 1931 Pickup Engine Knock
 

'"I found previous owners on FB and reached out to them with no response."

That's not a good sign. That and several owners in a short period of time.

Maybe to be safe you should pull the motor and send it to AER , Rich Falluca up in Skokie? Or Ora Landis over at Schwalm's??

Just a thought.

You know your way around a Model A motor I'd say. You'll find it. Keep at it let us know, this is an interesting thread......

Re: 1931 Pickup Engine Knock
 

To my untrained ear that sounds like a rod knock not a main bearing knock . Run the engine and short out the cylinders one at a time to see if the knock alters . It could be the piston pin end at a last resort take a cap off and see if you get any vertical movement there should be zero . I have the indentical truck but with the Budd steel top cab it has spectacular crank end float but no related knock and no rear main leak . My sons 31 coupe had a similar noise it turned out the timing wheel aluminium centre was loose ( original Celeron ) take the side cover off and see if the wheel has any fore and aft looeness . Keep that truck !!! they are the best looking ever .

John in Suffolk County England .

Re: 1931 Pickup Engine Knock
 

I'm a rookie here, but I think I see what Tom sees. Dipper backwards???

Re: 1931 Pickup Engine Knock
 

I don't see the backwards dipper. I see the threads on the bolt that may look like a backwards dipper.

There are all sorts of things that can cause a knock. They are listed in Les Andrews' Troubleshooting book (the blue one). It can range from a bent rod to loose bearings. Everything has to be measured and examined. It really needs the engine removed from the car and gone through in detail.

Re: 1931 Pickup Engine Knock
 

What you are pointing to is babbit. On the bottom of the crank is RTV.

All the dippers are facing the same way which is scooping towards the oil pump.

I did replace the oil pump with a good one. (Not Cracked)

Also I shorted between cylinders and no change. The engine drew down but the galloping knock/clatter didn't change.

Today I decided to put everything back together and put some miles on the truck in hopes to get more familiar with it. I haven't even put a mile on the truck since I've had it until today. I still have the same clattery/knocking sound as always. I realize Model As aren't far from tractors and this one sounds like one, lol. I honestly appreciate everyone's input. The Model A community has always been very helpful and go the extra mile for a fellow Model A'ers. For example when a friend of mine Milton called to see how the truck was going I told him I found the oil pump housing was cracked. Within 30 minutes he was at my house ready to take me to his friend's Tom's house who had some spares. Of course his friend is leaving to go out of town but he left his shop unlocked for us to get what we needed. I personally have never seen a hoard of Model A parts that big. Not to mention the Model A wrecker, Model T fire truck, and several others. We went in and got what we needed and left. My friend dropped me off back home and that was that. Mind you my friend Milton is 82 years old. Out standing group of people.

Should I ever find the cause or find a way to quiet down the old girl I will be sure to share back here.

Here is a video my 7 year old son made while we were driving. At the beginning you can here the knocking noise and periodically you can here some clatter.

https://youtu.be/qYnYgitoQq4

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