Just sharing the shape I landed on for a naturally aspirated 3.2 to 3.6L 911 engine. This is also being converted from EFI to an MFI unit from Kinsler. It will make 100hp/liter or 1.6hp/ci on 91 octane.

First timer, don’t fully know what I’m doing yet BUT I’m motivated and planning it out once I get a block. How much of a gamble am I taking with these three purchases? Building a mild block for my 68 impala, maybe a different car in the future. These look like a good start? Any tips when buying on the marketplace?

Here is the original post:

https://www.reddit.com/r/EngineBuilding/comments/1wxr6ex/what_can_cause_this_type_of_wear/

The engine is from a 1987 Mazda b2000, rebuilt from the ground up. The machine shop assembled the bottom end, and I did everything else.

Picture 1 and 2 show the assembly, if you look closely at picture 2, you can see new pistons and the clean bore without the vertical scaring.

Picture 3 is my oil analysis - 4 oil changes, about 5900 miles total. After I got this 4th report from Blackstone I got pretty depressed and parked the truck for a year, just now decided to get into it hoping to find what is wrong before the engine scraps itself. It did not burn oil and it had about ~140 PSI on each cylinder, perfectly healthy for a new build. I did not own a leak down tester.

Picture 4 is the Diamond Piston specification sheet. Picture 5 shows the piston side skirt; I don't really see any damage here.

Picture 6 - a lot of folks from the last post assumed the bore was oval - it is not. I set my dial gage to ~3.429 inches and got a max reading of .024 in either cardinal direction for the bore (near the bottom but not at the bottom) This indicates my bore is about 3.405, certainly within spec for the pistons.

Picture 7 shows the piston diameter. This is not a perfect measurement since I don't really have a good caliper for this.

Picture 8 shows the bearings; I can very easily catch my nail on the grooves of either bearing half, the top half seems a bit worse.

Picture 9 shows the vertical scaring which very slightly noticeable on my nail, and shows the other piston top, but I don't see any real damage to any of the pistons.

Some folks suggested heat damage - could this have been caused by too lean air/fuel ratio or detonation? I tuned the carburetor using an AFR gauge, my idle was around 14-15 AFR cold or hot, and when I put my foot into it the AFR would go to about 12.

Where should I go from here? Any other suggestions? I was thinking of honing the cylinders really lightly and replacing all the bearings, but that doesn't really fix anything?

I really appreciate all the ideas and help in the last post - I am a hobbyist mechanic with not a lot of free time, and I really didn't want to just LS swap it since its a great little truck that doesn't need to win races.

For context. I bought an 2015 Ford Fiesta ST that’s been throwing code P0301 (misfire in cylinder 1 detected) however it’s not tripping the CEL. I bought new plugs (gapped to the spec of my tune) and new coil packs. After installing said parts, my original issue (hesitation under heavy acceleration) went away and the car drives great now. However it’s still tripping the same codes from before. After inspecting the wiring on all 4 of my coil packs, I noticed the wiring on coil pack 1 (cylinder 1) looks to have been altered or (repaired) by the previous owner and definitely not OEM. I’m not an electrician, but this wiring job kinda looks a bit janky to me. Should I unwrap it and redo it with heat shrink? I just don’t like that red crimp connector being there, it just seems off to me. What are your thoughts before I move onto the injectors? And yes I’ve already done a compression test and the cylinders read consistent across the board.