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Loud engine "diesel" noise - valve adjust time?

When the engine is started, I notice a very loud diesel-like "smack-smack-smack" noise from the engine compartment. It persists no matter how long you run the engine for, although it does tend to "smooth out" a bit when the throttle is revved. Is this normal or a sign of a valve adjustment being needed? The engine performs okay and is pretty reliable/strong, it just concerns me because typically loud noises of this type aren't the type one associates with "normal operation", or is it for a 4cyl 914 engine?

I can maybe take a recording and post a .wav file link if the description doesn't make sense.
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Old 01-17-2008, 10:48 PM
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Try adjusting (or at least checking the adjustment of) the valves and see if the noise stops. And in the future, check the valves every 6000 miles, not when they make lots of noise. Remember, a tight valve can burn, and tight valves don't make noise...

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Old 01-18-2008, 06:19 AM
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Yea, didn't have too much choice in the matter. The car was bought from a guy in NM and driven straight to CA. Hasn't been driven too much since, probably under 50 miles in 4 or 5 months. I figure valves are the first things to check so I'll keep use light until I can adjust them.

If a valve got burnt, wouldn't there be other, much more noticeable symptoms?
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Old 01-18-2008, 07:23 PM
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There would be, once it was burnt enough. But you can get one that starts to go, and you won't get symptoms for a while...

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Old 01-18-2008, 11:02 PM
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drain the oil and look for metal flecks in it. Typically a loud knock at idle that smooths out with a little rpm is a rod bearing. Valve adj should sound like a loudish "ticking", not a knocking. If the oil looks good, then check the valves... but I would think that sounds like a rod.

We toasted a rod on a shop race car once and the knocking at idle was horrendous (14:1 CR 1300rpm idle monster roller cam V8) and then drove it around to block to the back of the shop... it ran no problem until we shut it down to tear out the engine, just had really low oil pressure. The bearing was completely gone when we got it opened up and it still ran.
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Old 01-19-2008, 01:30 PM
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What would cause a rod bearing failure on a 914 engine? Assuming that's the noise I'm hearing, how might I address the cause, rather than just the symptoms (replacing the bearing)?
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Old 01-19-2008, 06:03 PM
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Quote:
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What would cause a rod bearing failure on a 914 engine? Assuming that's the noise I'm hearing, how might I address the cause, rather than just the symptoms (replacing the bearing)?
Various things can knock them out, but two typical ones are the obvious oil starvation possibility, the other is detonation. It is possible that the car was running slightly lean as you came from New Mexico to CA (if you bought the car at a higher altitude spot in NM it may have been tuned to that altitude by turning the screw on the pressure "thingy" - I forget the tech term as it has been years since I had a stock 914, but there is a fuel pressure part that is a biggish, aluminum looking piece with a single, big screw in one end that should be epoxied into place. Often times people will remove the epoxy and richen or lean the car out with it.

If it was set mixed lean for a high altitude, and you drove it to CA, you may have had long term high engine heat and detonation and not known it, which could certainly lead to a bearing failure, or at least hurt one.

Two examples of this I know for sure - my friend lived in CO (I was in CA at the time) and I built him a stroked Ford engine for his Mustang. He tuned it with a programmed chip (so the computer couldn't fix much altitude change) and drove it to SoCal for final work and a dyno session. He burned the motor up, smoked a piston coming down. He got to the race shop and said he heard pinging, which made no sense until he told me about the chip. I told him immediately to remove it and go back to stock computer settings and the car seemed fine (would set car sideways through the first three gears of 5). Made almost 500 ft-lbs of torque on the dyno with #7 completely smoked and I didn't know it. So it is possible to hurt 'em and the car seems fine (tho' down on power even at 480-ish ft-lbs on 377 cubes)

The car I mentioned earlier with the mess up bearing was a nitrous race car. Fuel pump glitched on a pass and the car went lean on juice and knocked the bearing out instantaneously with the severe detonation.
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Old 01-19-2008, 10:34 PM
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Porsche Crest engine noise

hello , try taking a very long screw driver and while the engine is running put s yo move it around you will notice the differancethe screwdriver to your ear the handel side and place the tip end towhere you think the sound is coming from and it will amplify the noise considerable louder a you will find the noise. it is very rare to find valve adjustment to get so loose to make a considerable noise unles they were adjusted wrong to begin with. try that nd let me know. good luck dave
Old 01-20-2008, 03:02 AM
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Okay thanks for the tips guys. I suppose a lean-ish condition is possible due to denser air down here at sea level than in Santa Fe (which is where the car was originally). The car has Weber carbs on it now, so I'll read up on adjusting and then try to pin down whether it needs a bearing or a valve or what. This is sort of a long-ish term side project so I have time to work on it. I have a 911 to finish up first.
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Old 01-20-2008, 05:16 AM
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The last time I heard a noise like you're describing coming from my car, it turned out to be an exhaust leak. It didn't dissipate when the engine warmed up, though they often do. I thought it was valve noise originally, until I noticed that plugging the exhaust pipe w/a gloved hand didn't come close to killing the engine. So I tightened the nut at the exhaust manifold and all was good.
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Old 01-20-2008, 01:12 PM
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Quote:
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Okay thanks for the tips guys. I suppose a lean-ish condition is possible due to denser air down here at sea level than in Santa Fe (which is where the car was originally). The car has Weber carbs on it now, so I'll read up on adjusting and then try to pin down whether it needs a bearing or a valve or what. This is sort of a long-ish term side project so I have time to work on it. I have a 911 to finish up first.
Holy crap, Santa Fe! Here is a nice stat

Quote:
Founded in 1609, Santa Fe is the oldest capital in the United States. At an altitude of 7,000 feet, it's the highest capital city.
That is higher than Denver when my buddy burned his motor up starting somewhere in Utah.

So it is actually possible that you are just hearing severe detonation period. If you are lucky you haven't hurt it, but my money is on the fact if that car ran "right" in Santa Fe, then it is running WAY, WAY lean in the LBC and the more you run it the more you are gonna hurt it.

Understand, if you hurt a rod bearing, you aren't replacing the bearing, you are rebuilding the whole bottom end and maybe top end if enough metal has run through the rocker arms and valve guides. If you are hearing a rod bearing, things have hit the fan. But now I am hopeful that you are just hearing gnarly detonation.

Did you notice any diesel sounding noises under low rpm acceleration on your way from NM to CA?? Like say a knocking (aka pinging if you know what that sounds like) when you accelerated out of a gas station or on an on ramp to the freeway after a fill?
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Old 01-20-2008, 02:54 PM
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No, mostly it ran fine on the trip, however towards the end it didn't seem to have the power that it did earlier in the journey (which was odd, given that we were in denser air) but being sleep-deprived and just wanting to get the hell home at that point, I just pushed on at as constant of a speed as I could.

Obviously I don't WANT to have to deal with all the stuff associated with a bad bearing, but if that's the case, I'm likely to just chuck the engine entirely and find myself a 2.7/6 or something. It'd be about the same cost as rebuilding the 4 cyl, and be a lot more fun when complete.

Yes, Santa Fe was quite high.
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Old 01-21-2008, 05:04 AM
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actually the fact is was losing power with more air makes complete sense to me... you were detonating (which takes away power), overheating the cylinders and so forth so that motor was hurting. If the motor was having trouble holding a constant speed, consider yourself lucky to make it home - I am betting money that motor is a bit toasted. The only way more air works is to have more fuel to burn with it. It is FAR better to be rich than lean, so you unfortunately went the wrong way. Carburetors have no way of adjusting fuel mixture like f.i. does, so the motor running sweet at altitude was clearly tuned perfectly there and the change killed it.

Check things out, but I bet the oil has a burnt smell and the motor is hurt. Expect a six conversion in your future.
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Old 01-21-2008, 08:42 PM
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Well, unfortunate for sure but I guess it's an excuse for a six. Or an eight.

I probably won't be able to delve into the situation for a couple weeks, but I'll check things out then and post the findings. Based on what I'm hearing, I'll expect the worst.
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Old 01-23-2008, 10:49 AM
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do a leak down test on it
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Old 01-27-2008, 04:26 AM
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That's good advice too. I'll probably schedule that in a couple weeks. I hate to say it, but I'm probably going to park this car at a friend's shop for a while, given how busy I am with my other projects but it will eventually get my full attention. I've always liked the 914s for their simplicity. I got this one pretty cheap and it's in good shape for the most part, just needs some TLC (and whatever engine-related repair or upgrades come out of this).
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Old 01-27-2008, 11:54 PM
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I had a bad sound come from my engine under the same circumstances.

New engine, ****ty screws. They were the only thing available at the time, and it was 2 days to Parade

You might want to check yours. I've also had a cam follower detonate, it sounded pretty bad.

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Old 01-28-2008, 05:56 PM
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before you park it, put some fuel stabilizer in the tank and run it a bit, will save you a TON of grief later, trust me.
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Old 01-29-2008, 05:58 AM
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