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Resolved Weird sound coming from a freshly rebuilt 5.0L

  • Thread starter Thread starter karhoot
  • Start date Start date Jun 24, 2026
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karhoot

Member
Apr 23, 2026
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Jun 24, 2026
#1
  • Jun 24, 2026
  • #1
Back again with another post! Engine build has been completed. Ended up refreshing then installing a XE274HR cam, AFR heads alongside an Edelbrock Performer RPM intake. Went with Holley Terminator X standalone. Plugs (NGK BK5RE) are currently gapped at 0.045" & ignition has been upgraded with MSD 8456/8227 (TFI & coil respectively). Took the car out for a rest drive last week, kept dying above 3k (BEFORE MSD spark components installed). Car idled perfectly fine & no noises were heard.

After installing the above named MSD components, this WEIRD noise is being heard. I've already confirmed positioning of the TFI (removed all plugs, set #1 to TDC on comp stroke, then set rotor pointing toward #1 plug wire on cap)

Tried original distributor/coil, nothing.
Removed & checked plugs (see below, 1st pic is bank 1, 2nd is bank 2, each bank is in order : 1234, 5678)
I did confirm firing order following 1-3-7-2-6-5-4-8

Rerouted all of my spark plugs wires in accordance with TSB figuring it was crossfire & nothing
Below I've attached a video of the sound



Kind of lost at the moment. Have any of you ever heard this noise before?
 

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gkomo

now i can hopefully expect to receive the shaft
Aug 2, 2024
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San Diego, CA
Jun 25, 2026
#2
  • Jun 25, 2026
  • #2
I think your video/audio file link is broken.
 
K

karhoot

Member
Apr 23, 2026
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Jun 25, 2026
#3
  • Jun 25, 2026
  • #3

Here is an updated link of the noise incase the audio file above does not work.
 

nickyb

I gotta say i never painted my nuts, Never Ever
15 Year Member
Apr 3, 2009
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nevada
Jun 25, 2026
#4
  • Jun 25, 2026
  • #4
WTF? That sounds terrible, almost sounds like fuel igniting in the headers.
 
K

karhoot

Member
Apr 23, 2026
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Jun 25, 2026
#5
  • Jun 25, 2026
  • #5
nickyb said:
WTF? That sounds terrible, almost sounds like fuel igniting in the headers.
Click to expand...
It's extremely odd. My next plan is to pull the intake off, pull valve covers & start checking rocker arm clearances for the 12th time. It sounds like maybe a valve is stuck or something. I have no clue.
 
K

karhoot

Member
Apr 23, 2026
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CT
Jun 25, 2026
#6
  • Jun 25, 2026
  • #6
Well..... this may be the quickest diagnosis yet. Pulled valve covers and boom, found this. Going to start from scratch & reset all of my geometry because CLEARLY someone left something loose! Lol. Marking this resolved.
 
Reactions: slow84lx and gkomo

nickyb

I gotta say i never painted my nuts, Never Ever
15 Year Member
Apr 3, 2009
2,979
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153
nevada
Jun 25, 2026
#7
  • Jun 25, 2026
  • #7
Good deal.
 

Mac131

Active Member
Aug 9, 2024
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USA
Jun 27, 2026
#8
  • Jun 27, 2026
  • #8
karhoot said:
Well..... this may be the quickest diagnosis yet. Pulled valve covers and boom, found this. Going to start from scratch & reset all of my geometry because CLEARLY someone left something loose! Lol. Marking this resolved.
Click to expand...
That could have been bad! Glad you found it quickly.
 
Reactions: karhoot
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