Whats this sound!?!? New Motor... Video inside
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Whats this sound!?!? New Motor... Video inside

  1. #1
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    Default Whats this sound!?!? New Motor... Video inside

    I just got my 408 sbc running Saturday and Im getting this sound from it. Once its warmed up it goes away and if you give it throttle it goes away. I have good oil pressure and no misfires. We started it up on the floor and this sound wasnt there. Put it in the boat and now... Kinda baffled...







    400 sbc .40 over
    Profiler Heads
    750 edel
    rpm performer intake
    9.3 cr

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    Senior Member 74Bonneville's Avatar
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    Warms up goes away - Maybe exhaust leak

    The rattle I hear could be inside, but since it goes away with throttle and/or warm up I'm not sure what internals would do that. Lifters with too much clearance? Doesn't really sound like lifter clickity clack to me.

    Seems like it's on the right side of video, Is this what you think?

    Working as a gas station mechanic as a kid I heard a lot of strange noises, long time ago.

    No noise on start up before installed in boat, Hmm

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    Quote Originally Posted by 74Bonneville View Post
    Warms up goes away - Maybe exhaust leak

    The rattle I hear could be inside, but since it goes away with throttle and/or warm up I'm not sure what internals would do that. Lifters with too much clearance? Doesn't really sound like lifter clickity clack to me.

    Seems like it's on the right side of video, Is this what you think?

    Working as a gas station mechanic as a kid I heard a lot of strange noises, long time ago.

    No noise on start up before installed in boat, Hmm

    Yeah it could be a exhaust leak.... Buddy of mine was thinking piston slap from the short skirts. But I agree... seems to be on the upper right side.
    Last edited by chrisf695; 05-22-2013 at 07:26 AM.

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    Or Seth, either one Budweiser's Avatar
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    Quote Originally Posted by 74Bonneville View Post
    No noise on start up before installed in boat, Hmm
    What accessories were not on the engine when you test fired it?

    It sounds like it's comming from the alternator. Is the alt fan clear of brackets and bolts? With the belt off, is there any play in the alt shaft?

    Do yourself a favor and pick one of these up at the local parts store, they can be a big help sometimes.

    Automotive Stethoscope Cheep too!

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    Quote Originally Posted by Budweiser View Post
    What accessories were not on the engine when you test fired it?

    It sounds like it's comming from the alternator. Is the alt fan clear of brackets and bolts? With the belt off, is there any play in the alt shaft?

    Do yourself a favor and pick one of these up at the local parts store, they can be a big help sometimes.

    Automotive Stethoscope Cheep too!

    Ill go pick one up tonight, but I gotta agree with you... sounds like its coming from the alt... Look at the belt too, its all chewed up and uneven. The power steering isnt moving either....

    Ill take look tonight at clearance of any brackets and bolts and again ill pick up the stethoscope.

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    Senior Member GT Jets's Avatar
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    Take all the belts off and run it again.

    Also too, you sure it's not coming from the oudrive having the drive that high?

    Sure sounds like an alternator bearing or something...
    GT


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    Put a 300 on the back of it, Flywheel it and a nosecone. $15,000 later you'll have a 65 mph pile of shit......

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    Ill try without the belts tonight, but Im pretty damn sure its not coming from the drive or bell housing area. Its somewhere on the front of the motor...

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    Or Seth, either one Budweiser's Avatar
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    Quote Originally Posted by chrisf695 View Post
    The power steering isnt moving either....
    I'd guess the power steering is spinning just fine. Just a video illusion that occurs when something is spinning close to a multiple of 30, as most common cameras shoot at a rate of 30 frames per second. Some more, some a little less. 27-60 fps is the average spectrum, with 30fps being the most common.
    Last edited by Budweiser; 05-22-2013 at 12:33 PM.

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    Check your flywheel if you put a different motor in it, could be flexing on you. My 2X
    Believe Nothing you hear and 1/2 of what you see.

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    Quote Originally Posted by GT Jets View Post
    Take all the belts off and run it again.

    Also too, you sure it's not coming from the oudrive having the drive that high?

    Sure sounds like an alternator bearing or something...
    That's not high at all. Shouldn't make any noise at that level. High speed trim would be about that anyway.

    I was just gonna suggest removing the accessory drive stuff. Even the waterpump (sea pump), as you can run it for a minute or less without water. No more though.

    Next would be pull the drive and then run it. Isolate as much as you can. But one at a time.
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    If the video is anything lke the real sound, I'd have shut that thing off in 5 seconds.
    If God is your co-pilot, change seats!
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    Quote Originally Posted by steelcomp View Post
    If the video is anything lke the real sound, I'd have shut that thing off in 5 seconds.
    Now how is that going to help you find the problem. You and I have totally different troubleshooting techniques. I'd run that POS ball to the wall and see what breaks. Then you know for sure what it WAS!



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    Quote Originally Posted by gn7 View Post
    Now how is that going to help you find the problem. You and I have totally different troubleshooting techniques. I'd run that POS ball to the wall and see what breaks. Then you know for sure what it WAS!

    Almost fell out of the chair... That is funny...

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    Quote Originally Posted by Beer:30 View Post
    That's not high at all. Shouldn't make any noise at that level. High speed trim would be about that anyway.

    I was just gonna suggest removing the accessory drive stuff. Even the waterpump (sea pump), as you can run it for a minute or less without water. No more though.

    Next would be pull the drive and then run it. Isolate as much as you can. But one at a time.
    It's high if you have a bad gimball or u joints...

    Just so you know that is an Alpha.... The seawater pump is in the drive....

    Just bustin' balls...
    GT


    Quote Originally Posted by Quickjet View Post
    Put a 300 on the back of it, Flywheel it and a nosecone. $15,000 later you'll have a 65 mph pile of shit......

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