DeadWalker

Hello all, below (assuming everything worked) you’ll see all the information I know about the engine from the shop I purchased it from/built it as well as a video with the currently problem I noticed (if you can hear it too that is)…long story short the engine detailed below just finished getting its 120-150 mile break in period with break in oil that the mechanic I had put it in recommended, it’s going back to his shop Tuesday for an oil change and check up, it ran fine all 120-149 miles then suddenly I heard this soft thump thump thump almost like a helicopter in the distance (for my fellow vets) as soon as it came it went, and I’m just wondering if anyone knows what could have caused it or what it could be, this is my first cammed engine so I’m worried about basically every noise as I get used to it. Not listed that I added is as Edelbrock 800 AVS2 carb, that has been tuned. Thanks for any insight or help in advanced, I’ve sent the video to a few friends and fellow gear heads/builders and it’s about 50/50 if they can hear what I’m hearing. I would like to mention that during the break in period it never went over 63mph, and i followed everything the mechanic wanted me to do, no hard accelerating, no hard stops, just nice smooth granny driving not bringing rpms above 4000.

TTOP350

iTrader: (8)

Sounds like a rod knock, or broken flex plate, loose converter/flywheel bolts.

DeadWalker

First, thanks TTop for the reply, sorry im late to acknowledging it, second, for anyone following along or that was curious/cared. It went to the mechanic on Tuesday as stated, he was a little backed up on work so it just came home today...no rod knock or lifter issues, oil looked great he said, threw some new plugs at it as well and tires. Mechanic gave it the stamp of approval for mechanical there is no reason he can see that it shouldnt be able to go cross country at 8mpg if i really wanted to, so thats a huge sigh of relief. as for the sound in the video those that could hear the thump...that was my dumb a**, completely forgot i was having latch issues prior to that cruise, so i did not let the hood catch on the latch, instead i had to resting on it and held down by the hood pins, so what I/we were hearing was the hood vibrating/bouncing slightly against the latch and the air cleaner (mine has a spacer between the filter and carb so the throttle linkage wouldnt hit the filter). This was confirmed 12 hours after taking that video the mechanic just so happened to call me as i was pulling it out of the garage and had the hood up and he said he couldnt hear anything i should be worried about, and then obviously getting it to his shop and him being able to dive into it in person he confirmed no issues like stated early.

TLDR; It'll go coast to coast no issues as long as i can fund the gas, and im an idiot/need to replace my hood latch.

ULTM8Z

The frequency seems to high to be a rod knock at idle speed (in terms the rate at which the knock occurs).

Where does it sound like the noise is coming from? Under the car? In the engine compartment?

DeadWalker

It was a mix of my air cleaning bouncing off the hood, and the hood latch bouncing off the hood release at the same time due to it not fully securing before that cruise