I've built a handfull, including twice parking the car amongst a pile of parts on Friday night, doing a short block swap, cam and head(s), exhaust carb, dizzy and tuning....commissioning/run-in on Sunday, and drive 40 miles to work Monday.
Nowadays, and LIM feels like a big day out on a weekend, and work is only 10 miles away.
If I knew how, I would try it, but I'm afraid I do not know all the extra things, like talking clearances to someone, machining language lingo, and all the specialty tools needed and so on. I have got a 1500 sq ft basement to do many projects, just no skills in that area,,,oil changes, some brake work, but I dont do that anymore, u get old and lazy after awhile...mercy.
Today may be your last day on the planet, take a silent moment, you know what I mean....
I'll be doing a Ford 3.8 in a couple of weeks, but when you figure in all costs (such as running around to the manchine shop and parts shipping charges), it's probably cheaper just to get a good reman. Still, if you do it yourself, you know exactly what's in it.
Having worked in the marine and automotive racing industry, not to mention my current job in aviation, I've done plenty of overhauls and "rebuilds".
The work itself is not all that hard. Especially if you contract a competent machine shop to complete the critical items.
However, when dealing with used parts, there are nearly always "issues". Including metal fatigue, corrosion, wear, cracks, distortion, bending and so on.
When I overhauled my aircraft engine, I chose to install all sorts of new parts. Even though it was not required. This ensures a good service life from the engine without risk of installing a used part that might not have much life left in it. If I had the funds, I would have purchased a brand new engine.
Aluminum, for example, has a fatigue limit. It is capable of just so many fatigue cycles and then failure results. We can perform all sorts of non destructive testing on aluminum parts, get a clean bill of health, and still have a part that will fail in short order.
Those that "rebuild" or "overhaul" engines need to have detailed knowledge about the particular engine. Armed with that, the results can be spectacularly good.
It is kind of sad, the only engine I've ever had completely apart, was a briggs and stratton in class in high school. It ran quite well with a couple pulls too once I got it back together. I did rings and clutch springs on my 2T dirt bike as well, but that's it. I agree with Trav too, that engines are getting harder to rebuild properly and with the price of remans or even junkyard engines, doing a common engine yourself may not really pay off.
07 Focus ZXW, 5spd manual, 130km MM F1 5W20 06 CRV, 5 spd auto AWD, 230km