VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1933-1936 noise in engine

I'm not quite out of the woods yet with this engine. I just adjusted the valves hot, and it completely eliminated the backfiring. I proceeded to rev the engine a bit (not a lot), and it sounded great. After about a second though, I suddenly started hearing a noticeable rattle/banging in the back half of the engine. I made sure the rocker arm assembly was tight, and rechecked the valves cold. Everything there is ok. Changing the vacuum advance doesn't change anything. I pulled the push rod cover, and everything looks normal. Pulled the pan, fearing I had a problem with a connecting rod, but everything looks normal. No metal or any other evidence of damage.

Any ideas about how I should troubleshoot the noise? Should I retorque the connecting rod/bearing bolts?

Perhaps some "foreign" material got in the combustion chamber and is caught between the top of the piston and the head.
Does pulling the wire off a spark plug (one at a time) change the noise?
Push rod hitting the side cover?
Are the springs on top of the lifters installed or have they been discarded?
Wish you would have said something before pulling things apart.

Yes, my typical impatience...

I did pull plug wires off of 4, 5 and 6 one at a time, and there wasn't much difference. I also thought that a push rod might be hitting the cover, but I ran it temporarily with the cover off, and no change. Springs are installed on top of the lifters.

I was just starting to think that there might be something inside one of the cylinders. If that's the case, any tips to verify and get out any foreign material short of pulling the head? I sure wish I had a camera on the end of a tube to see inside.

To blowout combustion chamber run engine with spark plug removed. Perhaps run a wire through the hole and slide it around iside and then fish with a magnet.
If like carbon pour a solvent through the carburetor with the engine runnin g(you will not have carbon)
Could a connecting rod be hitting the oil pan trough in the pan?
Wouldn't hurt to retorque the rod bearings.
Return spring in the fuel pump broke and arm rattling around?

Will check these things and post results tomorrow.

So far...
Return spring in fuel pump OK.
Removed each plug one at a time to try to blow out any foreign material. No change in rattle on any cylinder. No obvious foreign material.
Used a stethoscope to see if I could pinpoint the source of the noise. It's louder near the back of the engine, and seemed like it was right behind push rod cover, down near the springs. But then I put the scope on the oil pan, and it hurt my ears it was so loud. Looks like I should drop the pan and see if there's any evidence that a connecting rod (or dipper?) is hitting the troughs in the pan. Tomorrow's another day.

Could "something" have fell into the throat of the carburetor and when you opened the throttle farther it got sucked into a cylinder. Or a brass screw fell out of the choke or throttle valve. Often when these small objects get caught between the top of the piston and head they imbed into the aluminum piston and are "stuck".

Randy,
I don't mean to jinx you but I know a guy with a '51 and he had a piece of the carburetor insulator liner (steel sleeve) break off and find its way into a cylinder. Rattled like hell.
I suspect the stethoscope on the pan is much louder as the pan is thin sheet metal versus the cast iron block. Is the pan louder than the sheet metal side cover?
Maybe pull all the spark plugs and fish a retrieving magnet into each while at TDC. Won't work on brass of course but it's an easy path for starters.
As always, please keep us posted.

Thanks guys. I suspect you're right that the thin metal on the pan makes it sound louder. I really don't want to pull the head unless I have to, so I'm trying to hunt down a fiberoptic borescope that I borrow. The flexible cameras that will pass through a spark plug hole are too darn expensive to buy. I'll post an update once I've had a look.

I've eliminated two possibilities on the noise problem:

1. Ran borescope down through spark plug holes and examined each cylinder carefully. They are all clean. I can't really see all of the underside of the head, but I would imagine that if something were lodged, it would be on the top of the pistons. Nothing there. All clear.

2. Took off rocker arm assembly, lifter spring cover, pulled out push rods, lifter springs and lifters on rear half of engine. No broken springs, lifters look fine, no bent push rods. Tried to fish the borescope down through the lifter holes, but couldn't get a clear view of anything.

Unless someone has another idea, I'm going to drop the pan and see if there's any place on the rods (dippers?) that looks like it might be hitting the troughs in the oil pan.

At this point I would say to drop the pan and have a look.

Let me propose a few unlikely but possible causes of the noise. Broken camshaft, broken crankshaft, (yes they can break and the engine still run depending on the jaggedness of the break), bolt or nut on flywheel hitting block or clutch housing, or bolt hitting flywheel, pressure plate problem. The crankshaft can effectively transmit noises so you think that the problem is in one place and later find it somewhere else.

FOUND IT! And boy, do I feel small.... Chipper, you were pretty close. The flywheel was loose! I actually had only two bolts in it when I was pulling the flywheel and checking possible timing problems. Didn't put the other bolts back, and the others worked themselves a little more loose. This was easy since I don't have the clutch and transmission on it yet. Tightened the bolts, and voila, noise gone!

It sure sounded like it was coming from within the engine, but as you say Chipper, noises can transmit to other places.

Will reset valves, and move on to the next step: steering reassembly.

This will make for a good chapter in your restoration book.
Did you drop the pan or find this before you got that far?

Found it before dropping the pan, though I've already had the pan off once before.

Normally a loose flywheel makes a clicking sound. But if it gets too loose then it will be louder.

Glad you found it without tearing the engine apart.

Had same problem 30 years ago with an aircooled VW engine. Loose flywheel began to make clicking sounds, did take out engine at same day, but flywheel and crankshaft was over. a expensive experience for a poor student in 1980. but at the junkyards there were hundreds of old vw engines and I could find the needed parts cheaper than expected...

Stefangermany