Broken rod bolt

General engine tech -- Drag Racing to Circle Track

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1972ho
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Broken rod bolt

Post by 1972ho » Wed Oct 04, 2017 10:24 am

Just to double check with you expert this looks to me like the capscrew rod bolt and caused this to fail.
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redliner
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Re: Broken rod bolt

Post by redliner » Wed Oct 04, 2017 10:45 am

What rods... what bolts?

David Redszus
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Re: Broken rod bolt

Post by David Redszus » Wed Oct 04, 2017 10:48 am

Remove the other rod bolts.
Measure the necked down diameter of the bolt.
Compare to new rod bolts or mfg specs.

If any are undersize, they are on the way to failure.

1972ho
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Re: Broken rod bolt

Post by 1972ho » Wed Oct 04, 2017 10:54 am

ARP bolts and eagle rod.

Frankshaft
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Re: Broken rod bolt

Post by Frankshaft » Wed Oct 04, 2017 11:13 am

Notice how the rod is blue? That means the bearing went away first. Cause and effect. The bearing going away caused the rod bolt to break, its that simple. Fix your oiling issue, and learn to read the signs that I am near certain the engine was screaming to you, and you would avoid those results. Sorry for your loss, but it wasn't what you think it was.

statsystems
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Re: Broken rod bolt

Post by statsystems » Wed Oct 04, 2017 11:48 am

Frank shaft nailed it.

Fix your oiling issues.

bigmike
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Re: Broken rod bolt

Post by bigmike » Wed Oct 04, 2017 11:53 am

Looks to me like bearing went away 1st.

1972ho
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Re: Broken rod bolt

Post by 1972ho » Wed Oct 04, 2017 11:55 am

I had no running oil issue and I could hear no rod knocking are any unusual engine noise.Ive been running this engine for years and has had the same oil pressure at idle and down track that’s why I was thinking the bolt broke first and bearing journal area darkened I’ll know more when I take the rest of them off.

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Re: Broken rod bolt

Post by racear2865 » Wed Oct 04, 2017 12:54 pm

In occurrences that Ive seen in the past, when a rod bolt turns loose, it will be instantaneous failure. The rod WILL NOT have time to turn blue. Per above conversation, the blue came first.
reed

Mark O'Neal
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Re: Broken rod bolt

Post by Mark O'Neal » Wed Oct 04, 2017 1:26 pm

1972ho wrote:
Wed Oct 04, 2017 11:55 am
I had no running oil issue and I could hear no rod knocking are any unusual engine noise.Ive been running this engine for years and has had the same oil pressure at idle and down track that’s why I was thinking the bolt broke first and bearing journal area darkened I’ll know more when I take the rest of them off.

It grabbed the bearing.

When you figure out why it did that, you'll have the cause of the apocalypse.

piston guy
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Re: Broken rod bolt

Post by piston guy » Wed Oct 04, 2017 1:59 pm

When a rod bolt breaks the bearing is in perfect condition though a bit wadded up. Like most everybody said it lost the bearing first. As David suggested , the rod bolts "could" be stretching and losing tension and in turn spinning the bearing. A high volume oil pump could have masked the problem at the gauge.

Krooser
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Re: Broken rod bolt

Post by Krooser » Wed Oct 04, 2017 4:22 pm

My SBM looked the same way... blued bearing broke the rod and took out two more rods and four pistons... previous driver used HEAVY weight oil with an STP type additive... didn't warm up the engine on a cool September night... alky engine... three laps KABANG!!!
Last place in the B-main is better than anyplace in the grandstands...

racear2865
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Re: Broken rod bolt

Post by racear2865 » Wed Oct 04, 2017 5:05 pm

Krooser wrote:
Wed Oct 04, 2017 4:22 pm
My SBM looked the same way... blued bearing broke the rod and took out two more rods and four pistons... previous driver used HEAVY weight oil with an STP type additive... didn't warm up the engine on a cool September night... alky engine... three laps KABANG!!!
Do u think the oil was thick enough.reed

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Re: Broken rod bolt

Post by Cubic_Cleveland » Wed Oct 04, 2017 7:45 pm

Too add to the spun bearing theory, this is a Toyota 5L rod that broke a bolt. Zero heat discolouration..
IMG_3190.jpg
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statsystems
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Re: Broken rod bolt

Post by statsystems » Wed Oct 04, 2017 7:50 pm

Cubic_Cleveland wrote:
Wed Oct 04, 2017 7:45 pm
Too add to the spun bearing theory, this is a Toyota 5L rod that broke a bolt. Zero heat discolouration..
IMG_3190.jpg
Did the bolt fail first or did the rod break?

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