Knocking sound after installing new intake

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ghsnu

ghsnu

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spedy7
Hey y'all, been awhile since I've been on here (glad to see this place is still going strong) and just ran into an problem with my truck that I'm stumped on. I just finished putting a new intake on (edelbrock performer), new weights/springs/cap/rotor/HEI bits, rebuilt the edelbrock carb, and new spark plugs and wires. Went to fire it up today after finishing it and once I got the timing right, she fired up fine, but has a loud as :censored:ing hell knock coming from what sounds like the p/s of the engine (like someone hitting a solid steel chunk with a sledge hammer). It idles pretty smooth, but the RPM will jump up and down and it staggers some when hitting the throttle. Also sounded like it was missing some when winding down. Adjusted the vacuum advance some and sounded like it may have dulled the knock a tiny bit.

I have no doubt there's probably something timing related, but I can't think of anything causing that loud a knock besides a rod knock. Wasn't doing it before I took everything apart ether.

It's a '69 C10 with a swapped in 350 from something. Neither of the heads match and one of them is the worst that GM has ever produced. I'm stuck on what it could be - my best guess would be spark knock and my dad says vacuum leak (which I wouldn't doubt with the engine having a mind of its own). Knock also increases with RPM's - which it starts sounding like a diesel.
 
Spark knock usually only happens under a load. It sounds more like a foreign object, like a bolt fell in an intake port maybe. If it was me I would bite the bullet and tear it down again to be safe. Borescope camera is another option, decent ones are getting less expensive.
 
LM7325
Spark knock usually only happens under a load. It sounds more like a foreign object, like a bolt fell in an intake port maybe. If it was me I would bite the bullet and tear it down again to be safe. Borescope camera is another option, decent ones are getting less expensive.
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Could be. I made sure to cover up the valley when the old one was off, but it's possible. I pulled one spark plug and it got smacked by something - the tip was bent down bad but luckily didn't break. All were black as night too except one. Changed to the old ones and still doing it.

Drove it to see how it does and it studders like mad under part throttle and hesitates bad when I punch it.
 
Well the plug damage would indicate something is in that cylinder. I would at least attempt to remove it before continuing to run the engine. It probably bent the intake valve before it made it into the cylinder.

Continuing to run the engine is not helping it at this point imo. Look at it as an opportunity to get a decent set of heads and let that 350 rip like it should.
 
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