Discussion in 'Builds and Fabricators Forum' started by Johns1967CJ5, Jan 12, 2019.
This isn't the one that was in the truck. This is the original
One step forward three steps back
What would cause this damage in 4 of 6 pistons ???
Detonation? Lean mixture or advanced timing?
Sucking in water while fording with the rpms high?
Water to ice to crack to shrapnel. Damhik
Ethanol blends are apparently suspected of causing Low Speed Pre-Ignition. It seems the phenomenon is noy completely understood yet. Most papers on it are focused on turbo engines, and say the issue happens at low speed and high loads. Curiously some say the solution is to increase pressure, not decrease it as we may assume. I guess this is what is unique about this latest way to ruin engines with detonation.
Consider that most turbo engines run a low static CR (8:1, 9:1) and the problem happens at low speeds (low boost so essentially normally aspirated), high loads (lugging up a hill) and it may seem plausible that our engines are operating exactly in that environment. But nobody would bother to write a research paper on ethanol's effect on 50 yr old Jeep engines.
And some say LSPI is caused by changes to the motor oil detergent package.
Direct Injection Piston Damage? Check Your Oil - Hot Rod Engine Tech
Broken top rings. I don't know what caused them to break. I pulled an old Ford flathead V8 down that had this same issue. That one I believe was caused from rust in the cylinder walls from sitting, then starting it up and putting it into service. Did this engine sit for some time before running it again?
Yes it did
It's that time-saver he has, shown in the same photo.
John, I'm glad you are going original, the Super-Hurricane has enough power to get the truck around and even pass some folks on the highway. It does respond pretty well to a little boost in compression ratio though so you might think about shaving a head a little. Not too much of course or you shroud valves.
I'd also suggest you get out a die-grinder and sensitive scale, you can do a nice job of balancing your rods and pistons yourself and save a ton of money over having a shop do it. It's not like you are going to be winding your motor way out but careful balance work sure does make the low end sweet!
Got all the parts cleaned up and painted, valve areas are pitted pretty good, going to work on that tomorrow and lap the valves
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