Olds 403 with POSSIBLE bottom end knock

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CamaroAdam73

Royal Smart Person
Well i built this engine over the summer, bottom end was a shortbloock. I put new main studs in it and checked everything while i was in there, it all seemed tight and i didn't see any cause for concern. Broke the cam in just fine, and did allot of test driving to get the engine tuned in correctly, no problems. I didn't really run the car at all over the winter, this month was the first month it's been fired up, when i did fire it up after it idles for a few minutes i THOUGHT i heard what sounds like a bottom end knock, i had a few friends/ other mechanics look at it and they all said it's all in my head. The cars still open header so it makes it pretty hard to determine. The sound to me sounded like it was originating from the passenger side of the engine, so i got down under the car while it was idling and cupped my hand beside the header collector where it ends, and i couldn't hear the noise i "thought" i was hearing, anymore.

Am i crazy or is something going on here?


No noises when it revs up, nothing at all.
I'm going to plum in the rest of the exhaust tomorrow so it's not so loud
Here's the clincher, i've got to drive this car from PA to SC in three weeks, so i have to get to the bottom of this now. :blam:
 

CamaroAdam73

Royal Smart Person
Arg im making myself paranoid and i can't stop thinking about this now.

Wouldn't a knock be more consistent and unmistakable?


I really hope it's just me, i'm ****ed if i have to pull this engine, i'll lose my car.
 

-83MONTESS-

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Nov 4, 2010
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In my experience a rod knock is way more evident as the rpm goes up. Since its open headers still I would find a mechanics stethoscope and start probing! I just use a long screw driver and set it to my ear. May sound hokie but it helped me.
 

pontiacgp

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Mar 31, 2006
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hhhhmmmmm...maybe that green motor oil you "saw" in the beetle wasn't green after all... :mrgreen:

bottom end knocks don't go away, they only get worse so if it's not there now it was something else and open headers can sure make you think you heard something..
 

CamaroAdam73

Royal Smart Person
GP, did i really type " i saw green motor oil" haha, english wasn't my strong point in school. But it was green :p


I guess i over reacted, i bolted up the ehxaust, ran it for about 20 minutes, no sounds what so ever. I used a homemade stethoscope and checked every inch of that block/heads/pan to make sure there's nothing going on, she's running like a champ. :D
 

pontiacgp

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Mar 31, 2006
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CamaroAdam73 said:
GP, did i really type " i saw green motor oil" haha, english wasn't my strong point in school. But it was green :p


I guess i over reacted, i bolted up the ehxaust, ran it for about 20 minutes, no sounds what so ever. I used a homemade stethoscope and checked every inch of that block/heads/pan to make sure there's nothing going on, she's running like a champ. :D

you didn't say it those words but if you didn't see it then how would you know it looked green... :mrgreen:

I put an engine together after I consumed vast amounts of rum and coke, had a nap and then dropped the engine in the car. When I fired it up with open headers I was sure it had an engine knock but I talked myself out of that and got about half a mile down to rad on the way the muffler shop when I made a u-turn hoping to get the car back to my house before the engine blew cause the knock was getting worse. It blew but I was close enough to glide into the driveway. If your engine was knocking you'd know. I still like my rum and coke but I never mix it with engines anymore..lol
 
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