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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: shaneo on July 14, 2017, 01:38:01 am

Title: Top end rattle
Post by: shaneo on July 14, 2017, 01:38:01 am

Hi I have a 468 Chevy engine that has a top end rattle when I back off the gas and goes away when I floor it again does not make rattle when engine is idling only when driving along the Road I'm thinking to replace the Rockers and lifters but I don't know if this will solve the problem if anyone could help would be much appreciated(https://uploads.tapatalk-cdn.com/20170714/1beebafa5e474b47febe2d759034ec6a.jpg)

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Title: Re: Top end rattle
Post by: SkinnyG on July 14, 2017, 02:23:00 am

If I understand you correctly, you only get a rattle off-throttle - as in, then the engine is revving down?  That's often a timing chain noise. 

Can you make it do it, and post a video?

Title: Re: Top end rattle
Post by: shaneo on July 14, 2017, 03:50:41 am

Quote from: SkinnyG on July 14, 2017, 02:23:00 am

If I understand you correctly, you only get a rattle off-throttle - as in, then the engine is revving down?  That's often a timing chain noise. 

Can you make it do it, and post a video?

Yeah it's more like when the car is at it's desired speed and you back off a fraction that's when the engine starts rattling around 2 to 3000 revs I tried to take a video over the next couple of days thanks for the feedback

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Title: Re: Top end rattle
Post by: VileZambonie on July 14, 2017, 07:21:31 am

Sounds like it's pinging. Have you tried retarding the timing? Have you checked the timing? Are you running the correct fuel for your compression ratio?

Title: Re: Top end rattle
Post by: shaneo on July 16, 2017, 08:36:21 pm

Quote from: SkinnyG on July 14, 2017, 02:23:00 am

If I understand you correctly, you only get a rattle off-throttle - as in, then the engine is revving down?  That's often a timing chain noise. 

Can you make it do it, and post a video?

https://youtu.be/UCAHdWKjHfs

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Title: Re: Top end rattle
Post by: SkinnyG on July 16, 2017, 08:59:26 pm

That sounds more like a heat-sheild rattle, or something loose in the exhaust.  Some sort of vibratory noise. RPM/Load dependent - it's not at all a consistent rattle like valvetrain would be.

Could also be detonation as Vile suggested.  Try disconnecting and plugging the vacuum advance hose and see if it goes away.  If it goes away, it's too much timing.  If it doesn't go away, it's likely something vibrating.

Title: Re: Top end rattle
Post by: Irish_Alley on July 20, 2017, 12:51:28 am

cut your exhaust off. problem solved ;)

Title: Re: Top end rattle
Post by: frankentruck79 on July 21, 2017, 07:27:39 am

Not advisable. I did that to mine and you can't hear much of anything but ringing after a ride


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Title: Re: Top end rattle
Post by: Irish_Alley on July 21, 2017, 12:43:31 pm

But you can't hear the rattle ;)