I burned up my slant build a few weekends ago... I thought I'd post pics for everyone's amusement, and maybe to commiserate a bit. Either way, everyone loves pics of someone else's broken stuff.

I built a hydro cam slant six a few years ago (there's a couple threads on this board about it) and it was great! Went with a slight overbore, basic home port job, super six, Dutra duels, comp cam grind (terrible experience). I was extremely pleased with the build in terms of cost/effort and fun - most folks I encountered were shocked at how well the slant ran with some basic work.

I added a 100hp nitrous shot, which was a hoot!

The motor met it's end on an extended high speed run, however. I knew the carb tune was a little on the lean side, but I didn't think it was too dangerous. In normal scenarios, it was fine. But, with an extra push, it was very not fine.

After ~30,000 miles of happy street duty, it met it's end like this: Nitrous shot to get up to high speed, and extended WOT running to maintain it. The carb tune was marginal in normal scenarios was apparently dangerously lean on the top for an extended period of running. No detonation/pre-ignition was heard or felt, but it was clearly there.

Only me to blame for this one; I've successfully run forced induction and nitrous cars before, I got careless with this one. I love playing with Holley's and Weber's, but was lazy tuning the stock carter on this one. And I guess I have to admit that I figure it was just an over-engineered slant, after all!

So, on to the destruction! A 100hp nitrous shot was used to get up to triple digit speed, and then it was maintained for several miles before all power was lost and a tow home ensued. My telling of the story is thus:

• N20 shot applied (as has been done dozens of times before)
  High speed maintained via N/A operation only (no additional uses of nitrous, speed was maintained via normal operation only)
  After a few minutes of this, overheating started, and power was lost
  Tow home. (buddy picked me up, used my trailer to get home)

I know the nitrous shot was ok, it was tuned using an 02 sensor, and numerous plug readings. I think it started the process of getting hot. Sustained high speed running prevented things from cooling off, until it reached a critical point, and the lean cylinders let loose. The #6 piston has a hole in it, and I think the molten aluminum was sucked into the intake by a stuck #6 intake valve, causing all other cylinders to lose compression. It looks like the #1 piston got so hot it pinched the rings, scoring the cylinder bore. The other 4 cylinders looked fine. (confirms normal plug readings, 3 and 4 good, 2 and 5 ok,, 1 and 6 a little lean).

I'm convinced that a richer tune (and maybe trying to even out the mixture between cylinders) and colder spark plugs would have prevented this. 100% tuning error.

So, after writing the next great american novel, here's the pics!









All in all, a learning experience, and a chance to try out a different build. First time I've actually destroyed an engine... live and learn.

Nice pics. Doesn't look too bad - main parts should be salvagable. #1 tends to run hottest on Slants due to cooling configuration.

Lou

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