bmohr

Searched and can't find anything that matches my experience so I started a new thread. Note, this is my first air cooled engine so this might be normal. Anyway, i've noticed that when I WOT in my lower gears and get past 5k rpm's or so that I hear what I can only describe as a flutter/raspy type noise. To my unexperienced mind I would say "valve flutter", yet I truly don't know what that sounds like. Engine runs great, no loss of noticable power, no oil leaks. Engine does consume a small amount of oil, but nothing worth mentioning really. 1992 engine, valves adjusted 10k miles ago. Did have 2 slight missed shifts since the adjustment. 57k miles. Oh, and I replaced the dizzy belt just 5k miles ago, dizzy rotors and ignitiion coils and have no electric "leakage" occuring. Also replaced O2 sensor as mine was dead. I can note that my airflow thingy on top of the alternator split open a while ago. I gorrila taped it. Maybe this is a cause of the sound? However sound does not occur with stationary throttle bumps. Anyone had a similar issue, or is this normal? Again, the "flutter" noise only occurs past a high rpm range and is not noticable during idle, or stationary.

Rocket Rob

Any chance you can record the sound and post it? That would help.

If the car is stationary, can you recreate the noise? I would hope so. I would try having an assistant rev the motor while you try to move around the car trying to isolate it.

bmohr

no as stated it doesn't make the flutter sound while stationary..at least not up to 4-5k rpms. I'll see if I can record a sound file. Will be adjusting valves again this weekend, so i'll recheck all my tins too to see if they were loose and could have caused the noise.

sixxto

Had a similar sound, turned out to be a broken head bolt. Do a compression check.

altarchsa

Have you revved the engine while it's on stands and you're nearby/under the car? Tin usually makes noise, and it can sound heavy, like valves. Do you still have the Cat bottom heat shield on the car? It's a common source of noise.

bmohr

Yes, i've rev'd it really good while my head is in the engine bay and no noise. No Cat bottom heat shield either. Im wondering if it has anything to do with my busted/cracked/split airflow tube thingy over my alternator. I'll start with replacing that part and doing valve adjustment/oil change and see if the noise is still there. IF so, then i'll do the compression check.

bmohr

so i got the valve covers off and it seems 4 of the double sided threaded studs came out with the nuts. Is this a bad sign? lol. They are not broken, but they are the ones with space in the middle of the threads and I've had similar ones on the alternator pulley snap off. Should all these be replaced as a matter of precaution?

bmohr

okay, i adjusted the valves and noticed no broken head bolts, so that good. Although the nuts in the spark plug holes did seem corroded pretty good. The ones next to them in the valve area were obviously in better shape with the oil environment. The only valve that was tight..and i mean too tight was number one exhaust. I'm wondering if that was the culprit in the high rpm noise? And if so, did i do damage? The only other thing to note was horizontal lines by the two head bolts that face each other in the exhaust valve center area. Weird..almost looked line pencil marks. Anyway, i swapped in new plugs and i got to say the car runs strong with no valve flutter. I'm happy for now Now i got to slap in a 3 inch heat hose for the airduct to heat exchangers bit and rip out my a/c. I'm understanding now why hawk has his weekly tech post...never ends does it?