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Clanking 3.0

Hello Porsche community. This is my first post on the site, look forward to the vast pool of knowledge. My problem started a few weeks ago and suddenly. Car is a 1974 914 with a 1980 3.0sc motor rebuilt stock in 2002 by p.o, has webber carbs and stock ignition, conversion done well. Took a long ride and stopped at a store for about 10min, came out and started, and there was a clanking(not ticking) sound coming from engine on drivers side at idle, that went away after about 15 sec. Checked oil level while it idled, was below line, but not significantly low. Proceeded home cautiously but noticed it had a completely different sound/feel below 3000 rpm's, like it was struggling for power, decent above 3000 rpm, but not the same. Valves adjustment not due for quite a while, any thoughts?

Old 11-15-2009, 07:40 AM
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If you mean "loud clicking" by clanking, Possible that a rocker nut has backed off.
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Old 11-15-2009, 07:44 AM
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No, actually it's deeper sound than clicking.
Old 11-15-2009, 08:07 AM
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drain the oil, drag a magnet thru it. If you have any metal sticking to it, then remove the oil filter and cut that open. look for shiny metal and copper. a clank sound is often mistaken for a bad rocker situation, when it is actually a rod bearing failure.
Do a compression test next- remember to cock open the throttle, disconnect the coil while doing this.
If the oil is clean of metal debris, then pull the valve covers and check valve adjustment/ rockers. if you find one valve that is extra tight, that could be your bad cylinder where the rod may have "stretched" enough to bend the valve
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Old 11-15-2009, 09:00 AM
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What exhaust system are you using?
eric
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Old 11-15-2009, 09:34 AM
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I was afraid it might be bearing failure because of proximity of sound. I'm definately not going to drive it until diagnosed. To answer the other question, it has BB 1-3/4" SS heat exchangers.
Old 11-16-2009, 07:14 AM
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Chain tensioners? does it have the upgrade.. it can sound like a chain saw.. rattling in a can.. is the sound around 1 cylinder, or by the back of the engine.. hold a long screwdriver up to your ear, jam it in there, and then hold it to the motor while its idleing and to locate where the sound is coming from. Its not a perfect science, but it will get you close.. I had a pressure fed tensioner go bad.. and it would go away at higher rpm as the tension on the chains increased.. when you slow the rpm, the chain loosens and causes the clanking sound..
I would check that for sure.
Old 11-16-2009, 08:27 AM
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It does have the tensioner upgrade. The sound is only heard at start up, it's worse when cold, but will go away after about 10 sec. When it's hot, you will hear it right when it starts for about 3 sec and go away.
Old 11-16-2009, 09:26 AM
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carrera tensioners do fail ya know. when it's doing it, put a real long screwdriver against each chain housing, close to where the tensioner is and the handle firm against your ear. works like a stethoscope.
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Old 11-16-2009, 10:26 AM
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Will give that a try, thanks.

Old 11-16-2009, 12:07 PM
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