Sudden loud engine noise!!!, Help me diagnose.. but be gentle! Options

[bondo]

Ok, I've got a 914, with an unknown engine (serial is for RoW 1.7) that was rebuilt "several years ago". Just now I was shuffling cars... started it up, backed it down the driveway. I let it warm up for a couple minutes and shut it off. Then I went to move the MG so I would have toom to park the 914 next to it. The 914 was off for maybe 5 minutes. When I went to start up the 914, it immediately had a loud clack/knock. I drove it up the driveway and parked it next to the MG, and it made the noise the whole way. (about 75 feet) I shut it off, went to get the camera to record some videos. Then I started it up, and recorded these videos:

First is idling at about 1400 RPM, for 30 seconds.

Second is idling with a few blips of the throttle, also for 30 seconds.

The videos are 2.7 megs each. Thanks!

[r_towle]

sounds valve related...

take off the valve covers and check all the rockers etc..
Otherwise, it might be a dropped valve seat...

Whatever, dont run it again...its not a good sound.

You might need to take off the heads to determine what is going on...

Rich

[billswim]

Wow what a great tool that video camera turned out to be!

Sounds like valve train noise to me. Don't run it again esp under load until you pull off the valve covers and check each rocker arm and adjuster. I've seen the locknuts back off and make come off and get down the pushrod tubes and cause damage.

[J P Stein]

A big day for noises. Sounds valve related....use your own imagination. (gentle enuff?) (IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif)

(edit)
Just call me ole quick draw

[Bleyseng]

Sounds like a valve adjuster is in need of adjusting.

[bondo]

Valves.. good..

It doesn't seem to me that it could simply be "out of adjustment", because it made no such noise when I shut it down 5 minutes earlier.

So what all can make a noise like this suddenly? Dropped valve seat of course... what about a broken valve spring?

[Bleyseng]

The rocker can jump off the valve end and make that noise too. Best way is to pop off the valve covers and look....


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[ChicagoChris]

It is a dropped valve seat.

I learned the hard way. I had that happen in my 1.8. All the adjusting in the world won't fix that problem. Remove the head and take it to be fixed.

Good luck and don't run it.

Chris

[mightyohm]

Pretty tinny/clacky sounding noise, my first guess is that a valve adjuster backed out. Do valve seats make those noises when they go?

My second guess, is there a nut missing from the top of the carb somewhere??

I don't know what a valve seat dropping sounds like.

[Eric Taylor]

Have you checked the exhaust? Mine has done that on warm-up then once warm purs like a kitten, but i'm pretty sure I've got an exhaust leak and once the metal heats up and mates right it runs well and sounds good. What do you guys think? I hope I don't hvae a valve issue too.
Eric

[McMark]

Sounds remarkably like the valve head that broke off and lodged itself into the piston crown. Unfortunately my vote is for bad news. (IMG:http://www.914world.com/bbs2/html/emoticons/sad.gif)

[Eric Taylor]

What if the noise stops after a while?
Eric

[SGB]

(IMG:http://www.914world.com/bbs2/html/emoticons/wink.gif)
I'm sorry to be inclined to say thats painfull to listen to. I think it prolly is a valve seat also, It is possible that an adjuster has backed off (but that really can't happen suddenly), or the rocker assembly has backe off far enough to let a pushrod fall out of the cup (and I can tell you from experience that noise is LOUD- like beating a garbage can), but that would more typically include a recent valve or rocker reassembly gone bad.
Eric-
a welladjusted motor is alittle noiser cold, and if the valve clearances are too great a motor will be noisy until realy compleely fully warm. My motor sometime is more noisy when first startedthan other times. I think it is due to the position of the pushrod and flat spots that devellop after many many miles. the pushrods turn as the reciprocate and I think sometimes they location when turned off is sorta flatened and therefor has greater clearance than oiginallly adjusted to, Does any of that make sense or am I just too imagianitive?

[bondo]

QUOTE (McMark @ Dec 3 2005, 09:18 PM)

Sounds remarkably like the valve head that broke off and lodged itself into the piston crown. Unfortunately my vote is for bad news. (IMG:http://www.914world.com/bbs2/html/emoticons/sad.gif)

OOf.. I'm pretty sure that can't be it, because it's pretty clearly still running on all four.

Dropped valve seat seems like the most plausible explanation so far.

The funny thing is that I intend to drop the engine in the next month or two anyways, as it's going in a different 914. This literally couldn't have happened at a better time. (besides "never") (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif)

[scruz914]

If it is a problem with a valve/valve seat a compression test might help pinpoint which cylinder.

I would check the spark plug wire paths for shorting. That ticking noise also sounds like a spark from a loose or bare wire. Check your distributor rotor and cap too.
-Jeff

[Series9]

Sounds like a rod bearing to me.

Regardless, I'm pretty sure the engine will have to come apart.

[bondo]

QUOTE (914RS @ Dec 3 2005, 11:49 PM)

Sounds like a rod bearing to me.

Don't say that! (IMG:http://www.914world.com/bbs2/html/emoticons/wacko.gif)

It's definitely not just a stray spark.. it's much louder than any valve noise I've ever heard.. the sound doesn't seem as loud in the video. For reference, it has a bursch exhaust that's pretty loud. Turn up your volume until it sounds like a 914 with a louder exhaust, and you'll get an idea of what it's like. (IMG:http://www.914world.com/bbs2/html/emoticons/blink.gif)

[pfierb]

On my 73 2.0 had a similar noise....turned out to be a 10mm washer that a local "expert" Porsche shop had accidentally dropped into the manifold while changing a base gasket on one of the Webers.....they called me and said that the car had thrown a rod and for 6 to 12 thousand dollars they would rebuild the motor....I called one of the good guys in the club EJM and had the car flat bedded to his shop where he pulled the motor and found the washer embeded in a piston and cylinder head....Ed was able to clean up the gouges and reassemble...at a later date he pulled the carbs off and put the FI back runs great now....jeez but that is a long story just to tell you that something could have fallen off or thru of one of your carbs.

[Dead Air]

QUOTE (bondo @ Dec 3 2005, 05:27 PM)

First is idling at about 1400 RPM, for 30 seconds.

[QUOTE]

OUCH

[Mark Henry]

Take the cover off and adjust your valves...if one adjuster is totally out of whack start ripping her apart.
Also look for a pushrod off it's rocker.

Didn't listen to your problem...dial-up is just to slow.
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