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Engine rattle at startup

The 1994 454 suddenly started to tattle at startup. Rattles for maybe 2 seconds. Why???
What can I do to remedy it?
Is it fatal?

A worn timing chain is often the cause of your noise. If that is the problem it’s neither fatal nor particularly difficult to correct. Get it checked out. Remember " a stitch in time saves nine." When the chain jumps time the engine won’t run and it usually jumps at the worst possible time.

Ahh, very good. That was the only thing I had in my head…Timing. Thank you

That’s very true, but on an engine that age wear on the sleeve bearings is also a common cause.
Hopefully Rod’s guess is right and mine is wrong. His is easier to correct.

It started sudden and I just fired it up warm and no rattle.

Could it be valve clatter? Have you tried to isolate the source of the noise?

Top end. I haven’t tried to locate it. Sounds like rockers???

Valve clatter for a moment after start up is not unusual for an old engine, sometimes a lifter will bleed down under the spring pressure of an open valve while at rest. Don’t worry about worn bearings unless the engine has been starved of oil in the past.

If this were my truck I wouldn’t react immediately, I would evaluate the noise ten years from now.

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10 years? I like to know my vehicle is dependable. 10yrs of wondering if
it’s going to fail would kill me

I don’t think this has an affect on dependability, I have moved new vehicles around the lot that had valve clatter after start up but if this makes you nervous replace the engine.

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I should probably figure out what it is before I replace the engine

A wise approach.
It’s hard to tell from here, but there are enough meaningless problems that can cause this on an engine this age that unless it seems to be causing an operating problem or gets progressively worse, accepting it as just the noises of an aging engine would not be an unreasonable approach. It could simply be piston slap. If someone with an experienced ear can hear it and tell you exactly what it is, that would certainly give you more information to make a more certain decision, and it’s always a good idea, but would that change your decision?

Idk. I’d just like to know what it is. The vehicle is clean enough to keep
it rolling solid down the road. I’m the kind of person that wants
everything just so.
If I could find the right mechanic (seeing as how I have no place to work
on it) I would have everything fixed. Finding a mechanic is always an
issue. I had a good one in Fairbanks but I’m no longer in Fairbanks.
I just don’t want to drive it if it’s something that needs fixed. It’s all
I have right now…I’ve heard this same noise in other vehicles over the
If I check the timing myself and it fluctuates, does that mean the chain is
loose/wore? I mean it’s bound to be a little out of time at 167000 miles

The noise was described as a ‘rattle’ in the OP and that leaves a lot to the imagination of everyone who reads the post. My best SWAG is the timing chain because of the age of the engine and the history of General Motor’s V-8 engines developing a loose timing chain noise that I would describe as a rattle as they approach 200,000 highway miles and significantly earlier in urban driving. @badbearing might get under the truck with a bright light and look at the passenger side of the timing cover for a seeping leak indicating that the chain has worn enough to rub through the cover. Also a mechanic’s stethoscope can detect timing chain rattle even after the engine has run and the noise is no longer noticeable from the cab or even standing next to the truck. Of course several here are familiar with watching the ignition rotor while moving the crankshaft forward and back to determine the amount of play. If taken to a good shop that procedure would likely be done first. It is quite decisive and demonstrable.

A worn timing chain will not cause a timing light to fluctuate when the engine is running smoothly. It will cause the base timing to retard a few degrees but do you know what base timing was set on?

Base timing would be whatever spec’s is…no? Top end rattle for maybe 2

Hope your user name is not prophetic.

To thesamemountainbike - sleeve bearings? I have never heard the term, it is not a Willis-Knight.

I have a 94 with the 350 motor and currently about 180 thousand miles. I noticed a similar, cold start sound a few years ago which disappeared after I started driving it on the highway more often. I also changed the EGR valve and cleaned out the passages. I don’t know about your driving habits but doing nothing but city is definitely not good for these motors in my experience.

It’s commonly used where I’m from to describe the split bearings used for mains and connecting rods. They kind of look like the sleeves on expensive dress shirts, thus the name. At least I suspect that’s where the name came from. It might be from the fact that they form a sleeve around the corresponding surface.

You’re thinking of sleeve valves used in the Willys-Knight.

My first reaction to this was clattering lifters or rockers. Did you change the oil recently and put in a new filter? I understand some oil filters have a one way valve in them to keep the oil from draining down, back to the crankcase, and that keeps more up in the engine so there’s less start-up valve clatter. If you changed brands of oil filter, try changing back.