The Stovebolt Site Forums The Shop Area Engine Shop 261, bent rod?

http://www.pbase.com/dennygraham/image/161524394

Ok, heared a bunch of guesses as to how the rod got bent. So
I'm gonna open it up to the masses and see what else might
pop up.

No contact at top of piston and no loose objects in the cylinder.

One guess, probably the only one that makes any sense is
hydraulic lock, possibly from water getting into the
cylinder thru an open valve. This was a problem with
radial or inverted aircraft engines due to oil or fuel draining
into the lower or inverted cylinders.

Any other guesses?
dg

Bent many a rod in the old flathead Ford V8's as they were prone to cracking and filling cylinders with coolant. When they wouldn't turn over the first thing done was to hook a chain on them and drag them off. Many times once they turned over and started they ran terrible---a sure sign of a bent rod. Often if revved high the bent rod would go bye-bye.

I had a one time issue with the bolts coming loose on the rocker arm supports. Driving home the engine started to stumble and cough through the carb. Later inspection found an exhaust valve that was not opening(the rocker arm never touched it) the pressure on every other rotation was almost enough to stop a truck still in motion. When the intake opened, not a lot but some, it would vent through the intake. Then the next time around, a new charge would fire and be trapped. Was harder to find than you might think. If it had gone on when I was driving faster, well I think I might have seen the same thing.

That's almost got to be a hydraulic lock situation, combined with an effort to tow-start the engine. Be sure and check that cylinder for cracks, either with dye penetrant or magnaflux- - - -the cylinder walls are usually weaker than the rods, particularly on a 261 since the rods have a heavier cross-section and a bigger wrist pin.
Jerry

When this rod bent Evan, it turned over 1/2 revolution and
stopped dead. Rod would not clear ether side of the block.

Intake valve on this engine is stuck open Steve, if any thing
it would have been a free running No.1 cylinder.

My first thought Jerry, that is, that it had to do damage to the
cylinder wall and or the block where it locked up or possibly
to the web. But short of burning out the block and
Magnafluxing it, it appears solid. I ran a stone hone thru
the cylinder to clean it up and it appears good. Again, just a
visual but I've a friend that says he's got a Magnaflux
setup. Will check it out when I get it cleaned up. Was a
little worried that the crank could have been bent also but
it turns freely, which is a good sign.
Hydraulic lock is about the only thing that it could possibly be.
When I didn't see any visual sign of a hole in the block I
picked up a new rod. Now I have to find a standard piston.
Shouldn't be to hard as lots of guys have had them over
bored.
Only problem is most of the guys don't get the old parts
back from the machine shop, who just toss the old pistons in
the scrap barrel.
Got the bore gauge out but it was to late to set up so I'll
check it out tomorrow and see just how much wears there is.
No ridge to speak of, just appears to be a little carbon ring
in there.

dg

Wow, Denny, that rod REALLY bent. I guess my old flathead rods would be more accurately described as bowed.

Denny, i have 6 used 261 pistons. I will check tomorrow to make sure they are standard. You can have them for the postage. Mtneermike

a new charge would fire and be trapped

It's trapped in the same way that a normal fill is trapped, except it contributes nothing to the crank motion.
The piston goes down no matter what. If both valves are closed you have... a modern drop-some-cylinders engine.

PM'ed you Mike, don't want to buy, sell or trade anything like that here. You know how it's moderated.
Thanks

dg

My guess would be it fired on the compression stroke before tdc.
Maybe a cross fire, number 4 cylinder and number 1 fired at the same time. I would think number 4 fired in order and at the same time a spark jump to number 1 . Jbennett

Think I'm goin' with Jerry's guess, hydro-lock and they tried
pushing it. Big truck like a 6000 series would have a lot of
weight behind it for plenty of traction and in a low gear it
could put a lot of load on the rod if the cylinder had just a
few ounces of water in it.

dg

Cylinder combustion pressure doesn't bend rods.

A bench vice and a 3 foot long pipe wouldn't bend a rod like that!
I can hear "Grampaw" now. "We'll break her loose or break her apart!" "Now get behind the wheel and hang on."

I reconditioned a connecting rod once for an 855 cubic inch Cummins engine that had enough twist in the I beam section that the wrist pin bushing boring job went all the way through the bronze facing and took out part of the steel backing. Now a Cummins rod is 12" on center between the wrist pin and the rod journal, the wrist pin is a 2" diameter piece of solid, hardened steel, and each rod weighs about 15 pounds! I'm guessing that one got twisted by an overdose of starting fluid and a little bit of water in a cylinder.
Jerry