88ci Shovelhead goes kapow...?

Question

I had an engine built on S&S big bore cases, stock flywheels and conn rods, JIM's shafts, KB pistons and CCI 3 5/8 cylinders, JIM's lifters, Andrews B cam etc, etc..

I had just over 500 miles on it when...there I was...cruising down the hiway...tick, tick, tick for about 2 seconds but loud enough to hear over the road noise and pipes. Then the rear cylinder exploded. There was bits of piston and cylinder and hot oil all over me, my ride and the road.

Any guesses? It looks like either the cylinder had a fault and exploded and the piston followed suit when it went rattling around nuts or the piston let go and took everything with it.

I had been doing oil changes with high quality after the first run, 25 miles and at each 100 mile marker after that.

Either way...cases are damaged in teh spigots, rods bent and I'm missing a cylinder....$$$$$$$

Answer 1

I have heard tales of CCI cylinder walls separating from the casting causing siezure and broken rods.
I suppose this could be the extreem of the cylinder dropping?

Answer 2

Ouch!!!! I would expect a fault in the casting of the cylinder.
If you can/did find all/most of the parts f the cylinder and piston, a good autopsy should give a good idea as to the cause of failure. A piston failure normally is not so severe, the rod and wrist pin runs up and down in the cylinder until you can stop. A few odd cases where the skirt of the piston goes away, and the crown turns sideways, and hits the head full force. Normal happening here is that the head splits, or breaks the head bolts, or pull the studs out of the case. A cylinder shattering is rare, unless it has a casting fault. How much of the piston did you find? do you see scuff or gallded lines on the skirt pieces? Where is the rod bent? All of these things when analized can give a good idea as to what went wrong first. If you have a digital camera, make pictures of all the remains and E-mail them t me. Be glads to have a look.
As you might guess, I have seen several of these in the last 50 odd years I have been into this stuff.

Tomcotexas

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Answer 3

Changing oil every 100 miles??? Talk about overkill! At least you can rule out bad oil...Take a look at the connecting rod, is it broken in half? Does it rotate smoothly on the crankshaft or seem to be binding? Are either of the valves broken off? Without looking at the carnage, I'd first suspect a broken connecting rod or if a valve is broken off, it broke and dropped into the cylinder and when the piston tried to compress it, things hit the fan. I suspect either of the two for two reasons; more power put through factory connecting rods or the souped up valve train, too much lift with too little clearance between it and the piston. If anything, I'd suspect the latter as the culprit.

Answer 4

Sounds like your engine threw a rod.
Who did the work? A shop or yourself?
If it was a shop - bust their bals, it should be warrantied!
It's possible the rod caps weren't torqued, or locktite wasn't used.
Bent rods? Oh....maybe that cylinder dropped a valve. That would cause the ticking and eventually bend the rod if it dropped into the cylinder far enough.

Answer 5

Sounds like it all began when a valve dropped.When the piston came up things had to go somewhere. In this case it seems it decided to go through the jug.