In the process of installing my dual carbs I spent a lot of time listening to the engine. I notice what I would classify as an internal clanking sound on the number 3 cylinder. Which of course varied with engine speed but is present to some degree at idle. I recently reset the valves so I am fairly sure it is not that as it has none of the tapping sound I associate with valve clearance issues. It is much more of a clunk. Engine runs well and has good compression so I am thinking it is a problem that is much deeper.

This is a 1.8 with a big bore (96mm x 66mm) and a mild cam. I am thinking piston wrist pin? I will go back and check the valves before doing anything but I thought I would see if someone might have suggestions on other possibilities

Any thoughts on other sources?

Are you sure it is from the engine, not the fuel pump or lose hear exhangers ?

Sounds like something fell inside your carb, then made its way thru the intake

Unfortunately I have to agree that this is a real possibility BTDT many years ago & blew up an engine. We found the hardware we had "lost" after tearing the engine down. A screw we dropped while tuning up the car found it's way down the carb and into the engine.

I would recommend not running it until you can scope it to see if anything is in the cylinder.

Get a mechanics stethoscope or use the "old school" method of holding a very long handled screwdriver up to your ear.
Touch various areas of the engine to see if you can isolate the source of the noise.

If the above responses turn out to be wrong, the first thing that comes to mind is a rod bearing.
I know that sound ALL too well! (but on other engines)

Stu

All good advice above. However I pulled an engine not that long ago because of a clanking I couldn't isolate Turned out to be an engine mount was torn. So check that too.

loose valve seat?

Something changed. Engine was doing fine till he decided to install carbs a few weeks ago. Since then he had problems tuning the carbs, I'm sure the air cleaners were left off. It's very unlikely to have sudden bearing damage out of the blue, for just installing carburetors. However, the probability is much higher to have some FOD drop in thru the carbs. I've done it myself, dropping some silly engine tin screw in the intake.

It was there before but I assumed it was just that I had one of the valves out. Still may be valve as it has gotten a little louder but engine seems ok. Will listen old school and scope it this weekend.

FOD! That brings back memories.

Sounds like you participated in those morning FOD walks as well

I bought a 914 sight unseen. PO said that it was driving last time he parked it, but that it was making a "knocking sound".

As I disassembled it I found:
1 - Missing exhaust nuts - that could cause a "knocking sound"
2 - BOTH engine mounts broken - that could cause a "knocking sound"
3 - damaged bearing surfaces on the front main and a "wobbly" #2 Rod.- that could cause a "knocking sound"

Stu

Well not in the service but I worked for the Air Force in certain capacities and when I first started I heard FOD and saw signs and had no idea what they were doing or talking about. As a result of that lack of knowledge I had to participated in a walk and listen to countless stories and instructions of what was FOD. I don't think I have to explain how memorable that was. For a while I would find all of FOD on my desk. Of course it often included items that while technically not FOD. The sources were not very likely. For example a size 1,000 (not really but they were huge) pair of women's panties! Yes I deserved it!

You know sometimes I think I have things covered and then I ask the question here and the wealth of knowledge is amazing. I thought exhaust but decided it would be louder. I am checking that in the morning. I looked at the mounts for the shifting problem so I think I am good there. I will keep you posted thanks for the input!

Check to see if you tightened down your valve adjuster jam nut. I've done that before and it makes 1 hell of a racket when they back out. Also I have run across improperly hardened adjuster screws. I would adjust the valves and days later start hearing a light knocking noise that would progressively get worse.

If it's a wrist pin bushing you can tell by pulling the plug wire off and rev the engine. If the sound goes away it's likely the bushing.

A lot of what is described here would result in a "ticking" or "tapping" sound. KNOCKING on the other had would be a rod bearing or a wrist pin I would think. A "tapping" sound can sometimes be dealt with easily. A "knocking" sound however, not so easy. I hope it's not something too nasty.
Cheers, Elliot

Did you ever find out what the problem was?

Never got a "for sure" answer. But visual inspection showed that one of the rods was contacting the case somehow. Could not find a rod with a lot of play in it but there were ome pretty worn rod nearings. I did not split the case so I don't know if it was a main bearing. I can only think that the crank was moving forward and back more than it should. What ever it was it was resulting in a lot of metal in the sump.