I've made a few posts about a knocking sound coming from the bottom end of my Nutek 396. Here's the history of this problem:

http://web.camaross.com/forums/showthread.php?t=444059
http://web.camaross.com/forums/showthread.php?t=450783
http://web.camaross.com/forums/showthread.php?t=462667
http://web.camaross.com/forums/showthread.php?t=468293

Basically, the noise was faint when the motor was cold. When the motor would warm up to operating temp, the noise would get louder and was very consistent. After replacing header gaskets, swapping injectors, adjusting rockers, switching back to stock rockers, unplugging plug wires/injectors, etc. I think I have finally found the noise:

Click Here

The 'knicks' line up exactly with the #4 and #6 connecting rods, which is where the noise sounded like it was coming from. That is a Canton 7 Qt. oil pan, and it looks like the crank scraper needs to be clearanced a little for a 383/396.

I just wanted to verify that this is the noise I'm hearing. I can't imagine this ISN'T the noise, but just wanted to be 100% sure before I put it back together.

It looks like a few minutes with a dremel will fix the noise, and the bottom end is fine.

 

for that much crank i'm pretty sure your builder should have known to clear the block. i had clearance issues on my 383...sorry to say i'd bring it back to the builder and have them pay for everything.

 

Its looks like the block is fine, its just hitting the Canton pan... or am I missing something?

 

You're not missing anything. That picture might not be too clear, but two of the rods were knicking the pan, not the block. The cleareacing on the block looks good.

 

Might not hurt to check the said rod to make sure its OK... Is there enough metal to grind away so it'll clear?

 

i would say you have found your problem, i had to clearance my canton pan as well for my 383. I dont know why the sound would change based on temp though.

Scott

 

Back in my ford days, We had to clearence a Canton pan on a 408 I had built. I was having the same issue. Just grind the spots back, clean it up and enjoy.

 

Since it clearanced itself wouldn't the noise be gone? I know when people don't clear the pan for whatever reason it tends to make a nice dent in the pan and then the noise stops. I'd figure it'd be the same in this situation, no?

 

Both the crank scraper and rod will expand as they heat up, causing them to make more noise as temps rise.

 

My thinking on this is that the crank scraper was clearanced a little by the rods, but I think the scraper is probably bending slightly each time the rods hit, then bending back causing the rod to continue smacking it - kind of like a card in the bike spokes.

If the rods were striking the actual pan itself, what you say may be true.

 

Looks like that's it. Just cut that area back .050" or more and you should be fine.

Bret

 

All Canton Pan need to be clearanced before installed on a 383 ?

 

Yeah 9 times out of ten. I had to clearance mine as well. Just chalked it, turned it once, and then took the dremel to it. Should only take a couple of minutes.

 

Oh then I hope my engine builder already done that.

97Bowtie: I just took a video, can you hear that noise?

BTW, I had a knock retard issue before I desentisized the knock module.

 

any decent engine builder will turn the engine over by hand a couple times before they put it in the car. It only makes sense to make sure you have everything right first.