4,000 RPM+ throttle cut noise

[Alexia]

If I cut the throttle below 4,000 RPM the engine drops down normally without making this rattling noise in the video. Above 4,000 RPM and cutting throttle it sounds like metal slamming into each other. It is a freshly built 4.7 stroker. I am being paranoid and it might just be excessive noise from the exhaust since it dumps behind the catalytic converter right now.

http://www.youtube.com/watch?v=G6sqWg0VXpM

[Cheromaniac]

It's hard to tell from the video where the noise is coming from. Might be a good idea to ask someone else to rev the engine while you use your ears to pinpoint the source.

[99OHXJ]

To me it sounds like your bouncing the rev limiter and its coming down fine.

[SilverXJ]

Sounds like normal exhaust noise. Why the hell are you reving it to 4k with no load anyhow?

[Alexia]

It's hard to tell from the video where the noise is coming from. Might be a good idea to ask someone else to rev the engine while you use your ears to pinpoint the source.

I will grab my room mate and bug him to tap the gas for me.

To me it sounds like your bouncing the rev limiter and its coming down fine.

That is just me letting off the gas abruptly.

Sounds like normal exhaust noise. Why the hell are you reving it to 4k with no load anyhow?

Because I can and I was doing some data logging on my laptop. It is not like I was holding it there.

I have a coworker opinion here that I may need to do some tuning for the higher RPM range if I wanted to race it, but otherwise is fine. I never plan to race it, but I will get it tuned anyway for my sanity. I am just paranoid since is my first full engine rebuild and not just replacing a cylinder head.

Thanks!

[Desertjr]

Sounds like mine with a magnapacks with no fiberglass packing anymore

I always thought it was an exhaust resonance(is that the right word?)? Like the exhaust vibrating or rattling...mine does it around 4500-ish.

[Alexia]

Sounds like mine with a magnapacks with no fiberglass packing anymore

I always thought it was an exhaust resonance(is that the right word?)? Like the exhaust vibrating or rattling...mine does it around 4500-ish.

Seems to be. I just never ran one of these dumping with no muffler before. After I got it driving earlier this week is was quite happy throughout the RPM range while under load.

[racing89]

Sounds like mine with a magnapacks with no fiberglass packing anymore

I always thought it was an exhaust resonance(is that the right word?)? Like the exhaust vibrating or rattling...mine does it around 4500-ish.

x2. proper term ! Its not a v-8 ya know !