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#1
04-05-2011, 04:53 PM
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Mystery Knock
I have a 97 3.1 here that knocks just like a rod knocking. I dropped the pan and the rods didn't look bad, but showed a little wear (no brass) so I slipped in a set. Knock is still there and it gets louder (REAL loud) when you pull off the #1 plug wire. If it ain't a rod what is it? Piston wristpin? I can actually FEEL the knock with my hand on the intake but can't really hear it well; I'm a little bit on the deaf side. This little engine runs great and never gives any trouble at all, I'm even still driving it. Just knocks like crazy and sounds like it's gonna fly apart at any second. Any insight?
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'83 Pontiac Bonneville 361 SBC .150 domes 3.500" Sprint car crank Comp 260 H 3.73:1 behind 700 R4 Jensen tape deck & 6X9's 
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#3
04-06-2011, 11:08 AM
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Re: Mystery Knock
Not a stethy but I got a tire iron I use for that. Best I can say is it sounds like a hammer on the bottom of the intake. EVERYONE around here says it just has to be a rod, but I've just been there it's not a rod, least not the big end. Pulled the rod bearings out to look and they seemed fine. I slipped a set in thinking it might just tighten it up but the noise didn't change. It does hold good oil pressure by the guage. Sure gets loud when you pull off the #1 wire, though, and only on #1. I guess I'm just gonna pull it out and tear it down.
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'83 Pontiac Bonneville 361 SBC .150 domes 3.500" Sprint car crank Comp 260 H 3.73:1 behind 700 R4 Jensen tape deck & 6X9's Last edited by eric_454; 04-06-2011 at 11:12 AM. Reason: Spelling error.
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#4
04-06-2011, 06:35 PM
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Re: Mystery Knock
What about the hydraulic lifters?
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#5
04-06-2011, 07:01 PM
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Re: Mystery Knock
Well, pulled the head off after work and #1 has enough piston-to-wall clearance to drive a truck through! I'll get the pan off in the morning and knock out the assembly for a better look, but I'm pretty sure as of right now the noise was a piston slap from Hades. Looks like I'll be boring this one. I don't know how it didn't just smoke like a chimney.
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'83 Pontiac Bonneville 361 SBC .150 domes 3.500" Sprint car crank Comp 260 H 3.73:1 behind 700 R4 Jensen tape deck & 6X9's
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#7
04-07-2011, 12:12 PM
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Re: Mystery Knock
Odometer reads 144,174 miles. Pulling the pan as we speak, pretty close.
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'83 Pontiac Bonneville 361 SBC .150 domes 3.500" Sprint car crank Comp 260 H 3.73:1 behind 700 R4 Jensen tape deck & 6X9's
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#8
04-07-2011, 05:24 PM
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Re: Mystery Knock
Well, Got the #1 rod and piston out. There was a little noticable play in the wristpin to piston (enough that I'd think it would make noise) so the local engine guy got me another piston on and I'll be slammin' it back together in the morning. His used piston was about a thou bigger than mine and should take out some of that slack too. I know it's a Band-Aid but I really didn't wanna bore this little jewel anyway. If it lasts a couple three more years or till the trans quits I'll be very pleased!
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'83 Pontiac Bonneville 361 SBC .150 domes 3.500" Sprint car crank Comp 260 H 3.73:1 behind 700 R4 Jensen tape deck & 6X9's
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#9
04-13-2011, 05:58 PM
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Re: Mystery Knock
Well, it's not fixed. Got all the stuff and put it back together and the noise is STILL THERE! Resized rod w/piston, new rod bearings throughout, and it still has the same noise. Absolutely unchanged. Knocks like a rod then knocks REAL loud if you pull off #1 wire. I don't know what could possibly make a noise like that besides a rod, but it sure ain't a rod. They measured right on the money and like I said the bearings didn't even look bad to start with. Mains looked great. Didn't see anything that looked bad in there maybe the cam is broke, I dunno. I'm done with it though, not spending anymore money on it. Auction time. Thanks for the input and opinions.
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'83 Pontiac Bonneville 361 SBC .150 domes 3.500" Sprint car crank Comp 260 H 3.73:1 behind 700 R4 Jensen tape deck & 6X9's
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#10
04-13-2011, 06:25 PM
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Re: Mystery Knock
SORRY TO HEAR ERIC,
it did sound like you were on the right track any chance for a video or audio?
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Live For Today Yesterday is gone, Tomorrows are'nt promised.
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#11
04-13-2011, 06:49 PM
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Re: Mystery Knock
Eric, read this bullitin #57-61-24A
making sure you read the entire bullitin or until it gets your attention!!!!
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Live For Today Yesterday is gone, Tomorrows are'nt promised.
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