VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1929-1932 1931 Motor Rebuild Update

Hello All,

I've reached a bit of a snag. I had my car out on the road, and it drove great, no apparent problems. I put roughly 30 miles on the odometer when a dreaded noise started. I swear that it sounded like a rod knocking (it has been a few days so now I might be confusing things...). It happened just as I pulled the car into the garage, so I was able to shut the engine off fairly quickly. After some time (maybe 20 minutes) I went out and took a brass rod I have and pressed it against the block and my ear trying to see if I could hear anything, with the engine running (everything was still warm). At higher speed, around 1500 RPM (I hooked up a tach to the coil) I could hear something in the vicinity of the number 2 cylinder, with the brass rod closer to the bottom of the engine. I thought to myself, "SELF!" you've gone done screwed something up (other colorful language omitted...)!

After the holiday, I pulled the pan expecting to find something in the pan. I saw nothing out of the ordinary (no metal in the oil). I pulled the rod cap off of the number 2 cylinder and found nothing. I used green plastigage (0.001 to 0.003) and the clearance was less than 0.001 (best I can give, I don't think they make plastigage for any smaller clearance. The top and bottom bearing surface looked great! I checked the other rod bolts for torque to ensure that I hadn't missed anything (I didn't). The rod troughs had oil in them so I don't think the bearing was running dry I need to check the depth of the troughs which with research on the board I now feel confident I can do, although I do not have the gauge shown in the repair manual, the 15/64 of an inch baseline from another post gives me number with which to measure to.

At this point I am at the end of my rope!

Short of putting the pan back on and running the engine again can anybody offer any suggestions as to what might be going on? I really would appreciate it. I'm sorry to be so verbose, but I really wanted to give as much information as I could.

Thanks in advance for any help given.

Respectfully submitted,

Rusty Berg

P.S. At least it has been raining for the past 3 or 4 days (got to find a bright point somewhere eh?)

It could be a main bearing knocking or possibly a bent push rod knocking against the push rod cover. You also might want to check the main bearings while the pan is off.

In the 40 plus years I've had my 30 Coupe, I had two annoying "engine noises" one turned out to be the freeze plug behind the water pump-it loosened and was hitting the pump impeller. The second was the gas pedal rod hitting the block.
You may also want to check the fan belt, antifreeze on the belt can make a knocking noise. Also are you sure the noise wasn't a result of engine timing.
Hope this helps

Gday, I had a similar problem in my 1930 tourer and it turned out to be the clearance on a valve guide and when the engine was hot the valve would stick in the guide and then the rocker arm would hit the top of the valve which was no longer moving up and down.It would be worth checking as I never had any problems with the motor until we started using unleaded fuel here and it seems to run a bit drier and I have since been using a felt pad on the rockers and have had no further problems. Best of luck Michael.

This is not recommended for the faint of heart, but you can take the pan off and start the engine. Do not supply fuel, just let it start at the idle position. If you can hear the noise you can locate it quickly. Do not let the engine run for over 30 seconds. As soon as you shut it off feel of each throw to see if it is hotter than the other rods.

ray: you are amazing. regards,mike

All,

Thanks for the suggestions. I pulled the push rod cover, and found them all straight and true. Someone had mentioned to me that possibly the lifter bores could be out of round, and the lifter could be rattling. Any idea on what the clearance should be for bore? Also with respect to the valve guides, I had new ones pressed in last year, so I would be surprised if they were worn, that being said how could I check the clearance for any issue?

I checked the clearance on the center main (I generally get about an hour on my back before I get a twinge in my neck... so I need to do the others, but the clearance came in at 0.002. I think this might be a little bit much, but there are no shims anymore as the gentleman who did the bearings stated I would not need them, and that the bearing would be truly round without them. I will check the others and confer with him on this, however there are no flat spots in the bearing, or shiny spots, which I have been told indicates wear. Can someone confirm for me the height of the point of the dipper from the flange of the block (without gasket)? I used a straight edge and a pair of calipers, coming up with 3.6425in, but it is tricky to balance three things at once...

Ray, what you describe is truly frightening... however at work we have full face shields for machining and I think with one our two shots of liquid courage (Tennessee Variety ) I might attempt this since I really am coming up with nothing.

Thanks everyone for your help, I will keep digging, but now to take care of the twinge in my neck...

Cheers,

Rusty Berg

Rusty,
My heartfelt sympathy for you... I've had problems like this before and chased my tail for months. One rule that I have now for ALL engine noises --

In my earlier days, I tore into a couple of engines after hearing some noises.. and then with all of the pieces exposed, I'll be danged if I could tell what the heck was the problem. .003 looks a lot like .005

So -- one thought would be for you to reassemble enough so that you can start it again, and do some more (extensive) diagnostics on it. For example - you should ALWAYS know which cylinder is making the noise BEFORE you tear it apart. Again, they all look alike when they're shiny and oily... and apart.


Put the pan back on with only 4 bolts. Don't worry about the leaking that might occur.... just provide enough of an oil container so that you can run the engine at idle.

BUT, since it's already apart -- my first impression is similar to what someone else hinted at. I'm guessing that SOMETHING isn't getting enough oil on it. And I'd look very closely at the value guides. Dump tons of oil on them while the engine is running. Listen to it very carefully. Then if you're going to drive it, then add the oiler pad (as previously suggested).

Also, is your distributor shaft getting oil? Pull it and look to see how shiny it is (ie. no oil). It might be "sticking" and ready to seize up.

I'm inclined to ignore the rod caps and main caps since you think the clearances are pretty tight.

I'm a tad nervous about the wrist pins... Is there any chance that ONE of them is hitting the wall? This is the kind of thing that you should find out BEFORE you tear the engine apart. For example -- define exactly WHICH Cylinder is making the noise (by shorting the plug wires). In the meantime, look for tiny scuff marks near the top of the cylinder wall where the piston shifts from compression to expansion (ie. wrist pin shift). Don't ask me how you're going to see up there. ha ha...

Just more ramblings for you to process.... Good luck!!

Gday Rusty Berg, The noise you heard after driving 30 miles did it suddenly start without any sign of noise before? and when you restarted the motor after it had cooled was the knock audible then? If it only happens when the motor gets hot I would be looking for a clearance which must tighten up when it is hot. Michael.

When you checked the clearance on the center main did you support the crankshaft? If you didn't, your measurement would be considered suspicious.

Bill has given you some very important information in his post. Others reading this thread should also take Bills advice to heart.

I am in agreement with some of the previous commentors. I would put the pan on. Start the engine and pull each wire off one at a time. Use gloves to prevent getting zapped. If the noise goes away when one of the wires is removed you have the culprit. Either rod, wrist pin, piston, or valve train. Good Luck. h

it could be a chipped tooth on the timing gear or a missing tooth will sound like a rod knock . take the fan belt off start the engine and listen to the front of the engine with your scope . do the easy things first . hope this helps

Hello again all,

I cannot begin to express my gratitude in the help being offered by everyone on the board. I put the pan on today, filled the engine with fresh oil and started her up. To add to my insanity I could not get the engine to replicate the noise. I ran it until it got hot, for about a half an hour, and varying ranges of speed up to 2000 RPM. Oil was going everywhere!!

Now the one thing I did before starting the engine (I know I should have held off probably, but it seemed like a good idea at the time...) was to lubricate the valve guides in the head. I gave a couple good shots of oil to each one, so I wonder if that was the issue to begin with...

Since I could not get anything to come up, I am going to take the car out for a shakedown to see if anything comes up. More information to come. I think the other thing I will do is order one of the oiling pads for the top end.

Stay tuned,

Thanks again,

Rusty Berg

Gday rustyjazz1938, I am curious whether you have worked out where the noise in you engine was coming from. Regards Michael.

I would look at the front crank pully real good, a loose one will make some noise.

Michael,

Sorry it took so long to get back to you on this, but it has been a hectic past few weeks. Although I cannot confirm since my car blew a rod bearing and I had to perform another rebuild (finished just in time to get to Flint, look me up if you are in the area), but I noticed in the teardown that there was excessive endplay on the camshaft, what ended up happening is that the steel of the timing gear cut a groove into the brass of the thrust bearing. If I had to place money, I would think it would be that since the noise seemed to be coming from the distributor side of the engine and was more in time with the camshaft speed (half engine speed) than the main crank speed.

Hope this was informative,

Respectfully submitted,

Rusty Berg

P.S. I said Flint or Bust and I really meant it!