hi i recently built a new 307-350 now ok i am doing the break in today ran it for about an hour not heating up nor nocking running like a new motor should but i checked the oil and there was metal flakes in the oil a small amount could they be from the breakin please let me know im worried please any 1 o and yes i did prime the oil pump before i did the breakin

 

You're going to get some "stuff" as the nice new sharp rings seat into the freshly honed cylinder walls. What size "flakes" are we talking about? By the way, the best way to break in an engine, (for the sake of the rings to cylinder walls seating in well), is to drive the car, not free-wheeling the engine in the garage. If you were driving the car, then never mind! Oh, and what's a 307-350?

 

307 bored out to fit standard 350 pistons

 

like sugar size flakes

 

very very small and no i was breakin it in in my garage

 

Did you do this work yourself? It is nearly impossible to get that displacement. You have to go from 3.875 to 4.00 inches. That is A LOT of material to remove. Plus, I'm pretty sure a 307 used a 3.25 stroke...

 

theres a preformance engine place here in southern texas called matsspeed and they did the adjustments for me and also helped me build the motor

 

Ok, well again just know that failure rate on those motors is in excess of 1 in 10 due to the high amount of machine work to stuff that 4 in piston in there as well as that 350 crank. If you do indeed have what they said you do, be very careful with that motor as your cylider walls are really, I mean really thin. I believe there are head/valve fitment issues with that set-up as well, but I have no experience with that. To be safe, change your oil, cut open your filter and look to see what types of particles are in that oil/filter. As 69 said, some "stuff" is normal, there will be shards from rings, maybe a little grey dust from bearings, rubber from seal install's, dust from cam etc. If you get big pieces, or you constantly have metal in your oil after multiple changings, you have an issue.

 

thank u all

 

My thoughts there exactly dj. I wasn't aware there was that much extra material in a 307. Most blocks have plenty for an .030 overbore, more than that and you want the block to be closely checked out first. But this one is way more than that even. The 307 block casting wasn't used for a 4" bore engine, so that too should tell you something. I've had a 307 in a previous Camaro, and rebuilt it using 327 heads, so there's no issue with using different heads. It's still a small block, just a little smaller (inside). I'd also be concerned about that engine running too hot (since there's so much less material between the cylinder walls and water jackets), so keep a good eye on the temp. gauge.