L31 knock after rebuild

[Hipster]

Yeah you see, the machinist in my area that I went to told me the opposite. He said the piston had to be removed in order for the rod to be resized (3 rods actually) and he told me that he had no way of removing the pistons without breaking or deforming them. I had no reason to doubt him, I'm not a machinist. He also held onto the parts for a little less than 2 months, I gave him a call and asked about it and his response was "I'll call you then, i didn't get to em yet." I understand this is his busy season but it was pretty unprofessional and frankly the guy was a dick so I went and picked them up, in the same box they were dropped off in. Only machinist in my general area (way out in the sticks and I can't drive anywhere without a truck) so I wasn't about to go back to him with the crank for work as well. From everything I read and what others told me on forums I didn't think one ten thousandths would've presented an issue anyways.

As far as pressing the pins into the rods I froze the wrist pins And I put the rods in the oven. That part went seemingly well. Nothing bound up on any of them, all were centered. Seemed ok but theirs a reason I'm asking questions on here. Not an expert. The rods I bought were scat by the way, again they all mic'd out good and we're round. I have a rod vise and torqued everything when I checked it. I've heard good things about them along with eagle products. I've also heard both brands are junk. At the end of the day it came down to cost so I took my chances. All 8 bearings I got .002 clearance. I don't think the noise is a rod anyways , it doesn't act like a rod knock nor does it quite sound like one. It does but its got a different note to it, more of dull sound. Not quite as high pitched. It's too constant and the sound doesn't change at all when unplugging spark plugs wires, when the engine is under load, when load is taken off, or between hot and cold. Theirs no difference any time. It is the same noise under any conditions. Just gets faster as rpm rises up until maybe 1800-2000? Not sure exactly, I'm pretty sure the exhaust is just drowning out the noise at that point.

And this block I'm using didn't "need" a rebuild. The truck had a rotted frame and no title. It did in fact run great before it was torn down. Was just a project for "***** and giggles". At the time I had a 4.3 truck I wanted to swap a v8 into, I was in no rush and I was 17 at the time and wanted to "build" it, as a teenager i was only concerned with making power, loud exhaust and doing burnouts. I just had to ****** it. That was the original plan for it until I was rear ended by a kid I went to highschool with. I was at a dead stop and he was driving 60-65 no brakes on his phone. Driving an f150 too, go figure. So much for that engine swap. This block was just in better shape and so I decided to use it. Far less miles on it. Cylinders weren't as far out and in better shape, bearing bores we're all still round. Plus it had been hot tanked already and sat covered with a bag and wrapped in plastic wrap under a moving blanket so it was already clean. Even if it needed work I was still ahead of using the other one. My logic anyways

They have to have the fixturing to do the pistons. Just kind of sounds like he didn't want to mess with just a couple of pieces.

 

[mr_josh]

As was said, take the accessory drive belt off and see if there’s a change. If you pull the fuel pump fuse and crank the motor can you hear it then? And if so, can you hear it with the spark plugs pulled (i.e. with no compression)?

I would even make sure to turn the motor over with the distributor cap off and listen / look for weirdness there (even though you said it sounded “deep”, sounds can get telegraphed through a block in weird ways).

 

[kenh]

Rod bearing will knock when the engine is in a "float" mode. Not coasting or providing power. You will hear them knock as you progress through that float mode. Main bearings will have a deep tone knock. I'd guess from your description, it's the rear main as it has too much clearance.

Ken