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mysterious engine rattle, *FIXED* AND SOLVED!

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xsmokey11499x

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so, the engine, im curious about is a 350. It has a new cam and topend .
im getting a Rattle only when im driving. if I let off the gas it goes away, if I step on it. it goes away.. when its in park or neutral, and I rev the engine up. I dont hear it.. if it were a rod knock. or bearing. wouldnt it do it at idle, Or in park,/neutral Revving it up? Im thinking its the valves need to be readjusted. after the cam /topend install
 
xsmokey11499x said:
so, the engine, im curious about is a 350. It has a new cam and topend .
im getting a Rattle only when im driving. if I let off the gas it goes away, if I step on it. it goes away.. when its in park or neutral, and I rev the engine up. I dont hear it.. if it were a rod knock. or bearing. wouldnt it do it at idle, Or in park,/neutral Revving it up? Im thinking its the valves need to be readjusted. after the cam /topend install
Click to expand...

That sounds like detonation. Assuming it is DON'T let it continue without fixing the cause or you'll destroy an engine fairly quiick.
 
Ussualy sounds more like a rattle or a handful of bolts in a coffee can maybe? More of a rattle than bell ringing. What's your timing at after the install? So low load steady cruise is when it does it? A sound is a very hard thing to describe. What I call a knock u call a tap someOne else calls ping

Just a new cam/lifters? Heads stay on? Hydraulic flat cam u installed? Guessing rockers are adjusted right if it's not doing at idle and just does at cruise
 
ratlover said:
Ussualy sounds more like a rattle or a handful of bolts in a coffee can maybe? More of a rattle than bell ringing. What's your timing at after the install? So low load steady cruise is when it does it? A sound is a very hard thing to describe. What I call a knock u call a tap someOne else calls ping

Just a new cam/lifters? Heads stay on? Hydraulic flat cam u installed? Guessing rockers are adjusted right if it's not doing at idle and just does at cruise
Click to expand...

heads came on, heads were done also. well the way you described a handful of bolts in a coffee can. thats probably the closest you could describe the sound.

when it makes that noise. I can either let off, and it goes away, OR give it more throttle and it goes away.
 
Detonation is BAD on a motor. If u have to drive it(like ur at work and have to get it home to fix it) u might b ok to fill it full of premium fuel, unplug and cap the vac advance and get it home to put a timing light on it. Personally I'd try not to drive it till I verified timing. Checking timing is first order of biz. Guessing ur high and when vac advance kicks at low load throws it really off.

May not b detonating at heavy throttle(vac advance, richer mix etc.) or it could be doing it a little and ur just not hearing it. B careful with driving it at all! Verify timing then report back
 
ratlover said:
Detonation is BAD on a motor. If u have to drive it(like ur at work and have to get it home to fix it) u might b ok to fill it full of premium fuel, unplug and cap the vac advance and get it home to put a timing light on it. Personally I'd try not to drive it till I verified timing. Checking timing is first order of biz. Guessing ur high and when vac advance kicks at low load throws it really off.
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Well its.not detonation. I. Can feel the rattle when my hand is on the valve cover. I pulled the covers off. And a bunch of rockers? Are loose.
 
Either nuts backed themselves off(use new nuts?), wasn't set right from start. Easy to do if u set all the valves at once and dont roll the motor over. Screw in studs?
Hydraulic cam right? How many miles after install?
 
What's ur definition of lose? They won't all be tight like can't move em tight and some will be tighter than others if it's pushing the valve down. The rocker should have a slight play if that valve is closed. Not flopping around lose though

Edit: could also b hitting the valvecovers but fairly doubtful. Might need taller ones.
 
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ratlover said:
What's ur definition of lose? They won't all be tight like can't move em tight and some will be tighter than others if it's pushing the valve down. The rocker should have a slight play if that valve is closed. Not flopping around lose though
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There are some that are flopping around a bit. More than just a little play
 
Could be your nuts are too used :haha: and loosened up. Could be it wasn't done right from start.

New nuts?
You do the install? U run all the valves at once?
 
so. I got the problem solved.. I drove it around for a week the way it was.. it progressively has gotten worse. turns out. I had a cracked flexplate.
:woot: no engine problems for me!:waytogo:
 
Haha... My dad had an 85 Silverado that did that. I was really a weird noise, sounded almost like a knock at JUST the right low rpm. We would have never guessed that was the failed part unless the seller had divulged that it was the issue! (Bought the truck as is)..
 
Highpsi said:
Haha... My dad had an 85 Silverado that did that. I was really a weird noise, sounded almost like a knock at JUST the right low rpm. We would have never guessed that was the failed part unless the seller had divulged that it was the issue! (Bought the truck as is)..
Click to expand...

mine was wierd, it only did it while under load. then it got worse. and I heard it when I started the car. the Ping.

on a side note. I checked my oil pressure, It sits at 60psi cold
 
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