Additionally, the engine has great oil pressure, never ran hot, etc. Ran great with no issues, swapped transmissions, now the engine knocks. It has an electric fuel pump so a broken mechanical fuel pump can be ruled out.

 

correct flywheel/bolts/running true

 

Yep, best I can tell anyways. It is also the correct balance flywheel. This weekend I plan on putting the oil pan back on and cranking it with the old starter and flex plate. I’ve checked everything related to the flywheel but maybe I’ve missed something. But running it with the original flex plate, bolts, and starter will answer that.

 

Broken flex plate OR the flexplates bolts are too long hitting the block. Unbolt the convertor and see if it'll go away. Flexplate runout might also be a thing.

 

No flex plate with a clutch.

 

Did you install a pilot bushing up the crank's rear?

 

Yes, installed pilot bushing. That could have cause the noise while the transmission was installed but it knocks with the transmission out of the truck as well.

 

Check all your clearance areas in the clutch assembly, since you've got mixed parts, maybe something with the pressure plate assembly and the clutch disc sprung hub.
Maybe a counterbalance weigh on the flywheel issue with the starter nose cone is another place to look

 

All good ideas but the noise is present with the clutch, all hydraulics, and pressure plate uninstalled. I have visually confirmed that the starter engages/disengages properly so that’s not it either.

 

Engine has ran absolutely perfect. I recently pulled down the 700r4 to replace with an LS style T-56. I used a SBC clutch and flywheel with the pressure plate from the LS.

Something changed, and it wasn't inside the engine. You said it ran fine before with no noise, so chances of something going wrong inside do not outweigh what you changed on the outside for the swap.
Unless it is an absolute freak occurence.
I know its loud, but can you tell where the noise is coming from? Like front, back, or middle?

 

Something changed, and it wasn't inside the engine. You said it ran fine before with no noise, so chances of something going wrong inside do not outweigh what you changed on the outside for the swap.
Unless it is an absolute freak occurence.
I know its loud, but can you tell where the noise is coming from? Like front, back, or middle?

Definitely seems like it’s coming from the rear of the engine and bottom end. I thought it might be the thrust bearings on the crank but those checked out and were perfect.

 

what bellhousing?
what diameter clutch cover?
mechanical or hydraulic throw out bearing?

 

I am using an LS1 bellhousing, which came on the transmission, and a stock hydraulic throw out bearing. The transmission is adapted to the engine correctly, the noise is not transmission related because the knock is still present with the transmission and clutch removed from the truck, as stated previously. The knock is likely something I changed or messed up while installing the transmission but what exactly is what I am trying to figure out.

 

A repeating single knock or a quick double? Heavy more like a thud or a tick?

Trying to separate crank and piston sounds from valve train or accessories.

Bogie

 

A pretty heavy tone. Not a valve train noise or wrist pin I don’t think. And for additional context it does it hot or cold and the noise follows engine rpm

 

can you post a video?

 

I’ll work on that this weekend. The oil pan is still off and I have to re torque everything but I’ll see what I can do. Thank you everyone for the suggestions so far!

 

no way anything got dropped into the intake?

 

I’m about to pull the intake off and check that. The carburetor was acting up when all of this started. I had just done all the work for the trans swap so I assumed the noise and carb were not connected. It was an old carb and I had been wanting to get a Holley sniper efi setup so I did that and never thought about the carb again. Now I’m starting to think part of the carburetor came loose and found it’s way into an intake valve.

 

I know this is low mileage but almost sounds like a piece of carbon on top of a piston?

 

Where I was going is heavy knocks that are in time to crankshaft rotation are usually associated with the crankshaft. A single heavy knock is and indicator of a a main bearing going bad where a rapid double knock with a lighter tone is a rod bearing. Piston skirt excess clearance or cracked skirt is more ticking sound similar with wrist pins but those like the rod bearing have a rapid double cadence.

Bogie

 

Just throwing this out there - I've heard of fuel pumps/fuel pump rods making a loud knock. Is it at all possible it's coming from that area? You could use something like a wooden dowel/cut broom handle to poke around, and put your ear up to the other end to try and pinpoint where it's coming from.

Another thought is the oil pump pickup contacting the pan, but that would be more of a ticking than a knock.

So let's take a step backwards for a sec. It ran perfect before the trans swap, yet it's making this noise with the trans disconnected. I know the transmission was your main goal, but did you do ANYTHING else? Anything at all on the engine side of things? Pulled a valve cover, left the air cleaner off, anything that would've left an opening for something to fall in? What, if any, other parts did you remove or replace?

Try to listen to when and how the noise is occurring like Bogie said, that might give you a clue. Definitely post a video when you can too. It's easiest to just upload to YouTube and drop the link in here.

Whatever it is, I'm sure you'll figure it out and get it sorted. Good luck and be patient!

 

Thanks for the suggestions! It has a block off for the mechanical fuel pump and I’m running an electric pump so that’s not it. I have the oil pan off and checked the oil pump and it’s not contacting anything. If you read back you’ll see I mentioned the carburetor acting up when the noise started so I’m starting to look into issues surrounding that. The air cleaner never came off and there’s no chance something was dropped down the intake unless it came from the carburetor itself, which is what I’m afraid of now. Truthfully, I have little experience diagnosing these type of issues. I’ve put engines together several times but don’t have enough experience to really say what noise is what. With that said, does anyone think it’s a possibility that something fell off the carb and ended up on top of the piston? Could that make a “knocking” noise? Thank y’all for all the continued suggestions!

 

Maybe someone had the throttle plate removed on the carb and didn’t get the plate screws staked back into place and one fell out. They’re tiny but could easily get past a valve.

 

When you pulled the trans did the distributor contact the firewall? Take the cap off,check the rotor.If it’s ok reinstall the cap and start it up.I’ve seen this before.

 

I checked that. Valve covers hit before the distributor so there’s no way it could have hit. This is going to drive me crazy haha

 

^^^^^
Same deal with the pushed over distributor cap here once too, many years ago. It's a surprisingly loud knock.
The hollow distributor cap acts like a miniature bass drum.

 

Yeah while I had the distributor apart I tapped on the cap with a screwdriver and found that it does amplify the noise quite a bit. Today I am going to try and get it put back together and crank it up and see if the distributor was, in fact, the issue. I am hopeful because the rest of the engine looks brand new, as it should. Fingers crossed! Thank you everyone for all the suggestions!

 

Another thought is a loose or broken engine or transmission mount allowing movement that emanates a thud either from the mount or some object hitting another due to these movements.

Bogie

 

I installed an SBC and forgot to tighten the bell housing bolts that are on top right up against the firewall. It allowed enough movement that it sounded like an engine knock when you revived it up.

 

Check the flywheel and Pressure Plate bolts. If they are a little too long or don't have a lock washer under the head, they will hit the back of the block webs and you'll think the rods are falling out! Don't ask me how I know...