Hollow sounding knock form 383

Old 01-21-2008, 07:10 PM
  #1  
edbrgolf
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Default Hollow sounding knock form 383

Well i will try to make this short I took over my brothers project truck. 1997 sonoma it has a 383 stroker kit that was purchased from speedway. He never had it running right due to five accel shorty plugs being bad.
I installed aluminum heads on the motor and noticed that #4 and 5 cyl were not firing tops of the pistons were clean like new. he drove it like this for about a month. Today my buddy heard a hollw knocking sound comming from the engine. The motor has a bad vibration so i disconnected the convertor to eliminate the trans. But dam the bad luck its comming from the motor.

Well i will be pulling the motor this weekend any ideas on what i should be looking for. The knock is slow so i dont think its a rod, and its has good oil pressure. Im thnking maby the crank any help on this matter would be greatly appreciated thanks.
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Old 01-21-2008, 07:27 PM
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bbchevy
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Default 383

The 1st thing to Look @?Make sure that you have Proper Rod to Block Clearence?I had 1 of my 1st Strokers that had a Strange Noise(KNOCK) when the Motor would get Up to temp?Sure enuff,i had 1 Connecting Rod that was just barely bumping the Block!
How long of Rods are in the Motor,and are they H-Beam or I-Beam?
I would think that the Motor is Extenaly Balanced?Do you have an Ext.Balancer and Flywheel with a weight?
Hope this HELPS?
Later
G 8)
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Old 01-21-2008, 07:48 PM
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edbrgolf
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it has 5.7 I beam rods and the rotating assy. was balanced by speedway. it came with crank, rods, pistons, and harmonic balancer. he got a fly wheel from the trans shop.
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Old 01-21-2008, 08:25 PM
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OneBadGMC
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Slow knock = rod..

Fast knock = valve train.
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Old 01-22-2008, 02:51 AM
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johnracer
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Could be block to rod clearance or even rod bolt to cam clearance with an I-beam rod.....
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Old 01-22-2008, 04:40 AM
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hink
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We have seen balance jobs done buy magazines that have not been very close and guys get there kits and the piston box still has the factory seal on the box and rods are still in there sealed plastic wrap.

And 99.9% of engines kits sold are not clearanced on bothe ends of the rods or the pin bores in the pistons, We have seen guys bring in there rotators in because bearing issues to find nothing has been clearanced.
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Old 01-22-2008, 05:33 AM
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performanceengin
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for sure need to check clearances. need minimum of .060 - .100 for crank deflexion . same on upper end.
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Old 01-22-2008, 06:57 AM
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edbrgolf
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Well I talked to my brother and he advised that the kit had the spec sheet with all the weights of the pistons and rods. the crank appeared that it may have been balanced but who knows could be the same sheet with all the kits. If no major damage is done and its just a clearance issue should iI have the everything balanced again.
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Old 01-22-2008, 08:12 AM
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hink
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Originally Posted by edbrgolf
Well I talked to my brother and he advised that the kit had the spec sheet with all the weights of the pistons and rods. the crank appeared that it may have been balanced but who knows could be the same sheet with all the kits. If no major damage is done and its just a clearance issue should iI have the everything balanced again.
I would surly go through everything to make sure is correcta far as balacing and has the proper clearance.
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