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Discussion and questions related to the course Practical Engine Building
What's up guys.
I received an engine for rebuild today and things don't look so good. It is a 5efe engine that's running a 4efte turbo setup on a ep71 starlet. The engine had been rebuilt 500kms (.5 over) ago and suffered a headgasket failure due to a water leak that had developed on a long drive. Upon pulling the head out things look worse than just a mere headgasket failure. The cylinder walls have light score marks, I'm not able to feel it with my finger nail however can visually see them. Things get worse when I take a video using my phone with the flash on. I notice that only on the front side of the cylinder, across all 4, have a shiny patch on them. The rest of the cylinders look okay by the eye.
I will be taking the block to the machinist on Monday. Just thought it'd be good to discuss this with fellow members and get to know if someone has experienced this or might be experiencing this?
What do you guys think is the problem? What could have gone wrong? You think the block would be use able without going for 1.0mm overbore? Could a light hone and a set of new rings solve the issue?
I will try to post the video on the following post
Here's the video.
Hmmm, not impressed by the debris left on top of the piston, especially as it may have been contributing to one of the issues.
The vertical markings on the bore are most likely due to debris being trapped between the piston and cylinder wall, possibly embedded into the piston itself. There will also be a possiblility of debris causing rings to stick. There are two common reasons for this, either or both could apply - the engine has been run unfiltered, and/or a lack of cleaniness during assembly. That last part includes manifolds, pipe-work, charge cooler, etc - anything in the engine from intake to cylinder.
The shiny patches are most likely the result of high piston skirt loading. If so, checking the piston-bore clearances, and the corresponding part of the piston skirt and opposite side of the piston top land for significant scuffing, should clarify that. While I was at it, I'd check the engine was actually oversize with the correct pistons - at best those look second hand, but that may be down to the issues that had the customer bringing it in.
I may be quite wrong, though - anyone else?
In addition to what’s already been said, looking at the polishing or shiny patches I’d suggest getting the Bower’s down the bore to measure ovality, it could’ve been over bored without a torque plate causing the bore to deform when the head is torqued down.
Its also worth checking the ring gaps as vertical scoring can occur when the gap closes up and ends butt up.
It does look very second hand for 500km even considering an overheat.
Car ran filterless in African dusty road conditions
Con bearing #4 was shot to the cooper layers
Took the block to the machine shop and they resleeved it and now it's back to 74mm bores, I have a set of OEM 4efte pistons I plan to use for lower compression ratio
Let's see how this one goes.