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Old 01-04-2004, 02:20 AM
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Knocking noise, HELP! Please!!

Okay, I know I have posted this before but please bare with me. I will try to explain as much as possible. It's long but please, I am in dire need of help... Here it goes:

My engine:

"383"
350 4 Bolt Main Bored .030 Over
400 Cast Iron Crank
Summit Stage II Rods & Bolts
Keith Black #111 Pistons (Hyperutectic .100 Dome)
Comp Cam 270H Camshaft
Comp Cam Double Roller Timing Chain
Edeldbrock Performer RPM Air-Gap Intake
Protorque Summit Starter
B & M Holeshot 3000 Torque Converter
Federal Mogul Crank and Rod Bearings (Rounded Edges)
Summit Piston Rings (.030 over, 1/16, 1/16, 3/16
Summit Oil Pump
Comp Cam Roller Rockers (1.6 Ratio 3/8 in.)
2 World Products S/R Torquer Cylinder Heads w/76cc
Hooker Comp Headers

Okay well thats my engine. Here is the story:

My engine build went nice and the break in went well. At about 500 miles of the break in I took my car on the freeway and got it up to 90 mph slowly and stayed steady for about 3-6 minutes. After that I slowed down gradually and got in town. When I was cruising around I started to hear a horrible knocking sound. So I pulled over and inspected my engine to find that #8 rocker nut had come completely loose and the rocker had been flopping around. Now these set of rockers were some cheap rollers I bought that kept coming loose. After I fixed the rocker the noise went away and the car was fine. After a week or so I realized the rocker nuts kept coming loose and I replaced them with some Comp Cam 1.6 Roller Rockers and nuts. Then I would say about a couple weeks after replacing them I started to hear another knocking sound. It started out low and is now louder but not very louder. It has been a couple months and it has stayed at the same loudness. It sounds like a lifter is bad but I am not sure. You can only hear the noise at 2000 rpm and above. It starts out slow and then gets faster but then steadies out to an even countinuos sound. When I let off the gas it stops even if above 2000 rpm. It sounds very clear as if coming from the top end. Last oil change I noticed no abnormal pieces of metal but I am going to check again soon. I have checked the rockers and valve train serveral times with the engine on and off to make sure everything is tight and at zero lash. There is no loss in power or problems with running my car. Even when racing which I have done maybe once or twice. The car has alot of power and goes. I have also check the timing serveral times and it is at i believe 32-34 degrees.

Conclusion:

I have had this noise for some time and it doesn't seem to affect any preformance. I have had people tell me it is the valvetrain(ie. flattened lifter, coil stacking.) and some, well actually one say it is a rod. The noise is not a loud deep noise but more of a higher pitched knocking noise. Could it be piston slap? Maybe I heard the noise before, just didn't notice it? It almost sounds if it is coming from the #8 area, which was the one that the rocker came loose on.

Please help, I am going nuts trying to figure this out. Thank you if you actually read this far and thank you for any help.
Mike

THANK YOU!

P.S. I might beable to get a sound clip of my engine running sometime soon.

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Old 01-04-2004, 05:17 AM
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This is hard to diagnose without hearing the noise.

1) I had a noise like you describe, on the #8 side of the engine but it was the fuel pump rod. The fuel pump lever was defective, but not broken. New pump and rod....problem solved.

2) had the same sort of noise on a car I bought but it had a electric fuel pump (aftermarket). I took the block off plate down and the rod was still there. Took the rod out....problem solved.

Just places to look........No gaurantees.......
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Old 01-04-2004, 07:46 AM
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ive had that before .it turned out it was spark knock in one cylinder.i unpluged the vacume advance and set it for mechanical only it runs great.so back off your timing .or unhook vaccume .and try that .let me know your results.
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Old 01-04-2004, 10:21 AM
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well about the fuel rod and pump, i am pretty sure it isnt that, the sound is coming more towards the top and i have a mechanical fuel pump so the rod hasn't been left in there. thanks for the input, every bit helps.
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Old 01-04-2004, 11:31 AM
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a buddy of mine had the same type problem except it was snapping off the whole rocker stud. eventually he had a similar noise and it ended up being a lifter. it never effected his performance so he just turned up the radio.
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