Broken rod bolt

General engine tech -- Drag Racing to Circle Track

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joe 90
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Re: Broken rod bolt

Post by joe 90 » Fri Oct 13, 2017 6:41 pm

1972ho wrote:
Fri Oct 13, 2017 9:48 am
Tuffxf yes 4MA cleveland crank 3.513 stroked.

I'm sure that's not right?

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Re: Broken rod bolt

Post by 1972ho » Sat Oct 14, 2017 11:35 am

What’s not right about it.Joe90

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Re: Broken rod bolt

Post by joe 90 » Sat Oct 14, 2017 5:27 pm

Stock stroke is 3.5 inch.
For a stock 4MA crank.

Unless it's been offset ground in which case the stroke might be 3.7 and use SBC rods.

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Re: Broken rod bolt

Post by 1972ho » Mon Oct 16, 2017 4:27 pm

This is #4 main and it was not starved for oil,the reason that I I’m still trying to tie this down to the rod bolt is because this engine is not a just built engine it’s been running and racing for over 10 years with no oil problems.So it’s kind of hard for me to have to except the oil problem,and there are no other things to be done to the block to improve the oil system.The only change that I made was installing a windage tray and a different manufacturer head gasket.It will be hard to do a rebuild thinking there is a oil system problem.
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Re: Broken rod bolt

Post by 1972ho » Mon Oct 16, 2017 4:35 pm

https://m.facebook.com/groups/263768747 ... _tn__=EH-R. Not my cleveland but this one looks oil starved and the rod bolt did not break everything is just blue and black.

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Re: Broken rod bolt

Post by joe 90 » Mon Oct 16, 2017 4:47 pm

How about some pics of what's left of the big end bearing.

Maybe ALL of them?
All the mains too?


Detonation can kill bearings too, specially if it's got forged pistons, that's only because with stock pistons, you'll break them first and it'll smoke........then you'll know you got it wrong.

To me, that main looks like it's had a hard life.

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Re: Broken rod bolt

Post by statsystems » Mon Oct 16, 2017 5:21 pm

1972ho wrote:
Mon Oct 16, 2017 4:27 pm
This is #4 main and it was not starved for oil,the reason that I I’m still trying to tie this down to the rod bolt is because this engine is not a just built engine it’s been running and racing for over 10 years with no oil problems.So it’s kind of hard for me to have to except the oil problem,and there are no other things to be done to the block to improve the oil system.The only change that I made was installing a windage tray and a different manufacturer head gasket.It will be hard to do a rebuild thinking there is a oil system problem.
The mains will get oil when the rods don't. You have an oil issue.

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Re: Broken rod bolt

Post by tuffxf » Mon Oct 16, 2017 6:09 pm

Rods can fail and mains can still look fine.
When you had it apart last did you change main bearings ?
Cheers

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Re: Broken rod bolt

Post by 1972ho » Mon Oct 16, 2017 7:33 pm

Yep rods,camshaft bearing and mains replaced oil changed and was still clean with no change in color up until the rod broke.

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Re: Broken rod bolt

Post by KnightEngines » Mon Oct 16, 2017 8:49 pm

That main is wiped, it's just not completely destroyed.

You had an oil issue, killed the rod bearing & it hammered the bolt till it failed.
Wiped main bearing + blue rod = spun rod bearing due to oil supply issue.

End of story, you can look at that bolt as hard as you like but you'd be better off spending your time looking for the cause of the oiling issue with that rod. Pull #4 rod & check the bearing, it feeds off the same main as #7, if it's ok that tells you something, if it's shot that also tells you something.

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Re: Broken rod bolt

Post by BigBro74 » Mon Oct 16, 2017 9:15 pm

1972ho wrote:
Mon Oct 16, 2017 7:33 pm
Yep rods,camshaft bearing and mains replaced oil changed and was still clean with no change in color up until the rod broke.
Did you happen to use a different method to tighten the rod bolts on the freshen up? i.e. stretched this time instead of torque last time?

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Re: Broken rod bolt

Post by tuffxf » Mon Oct 16, 2017 9:39 pm

Just as tk said,
I would want to know what your bearing clearances were last time and whether you had full groove mains or not.
When it was rebuilt, what were the clearances, were the mains full or half or 3/4 groove.
You have an oiling issue whether you want to hear it or not.
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Re: Broken rod bolt

Post by 1972ho » Tue Oct 17, 2017 2:03 pm

The mains are 1/2 groove with .0027 clearance,Here’s a pic of the #3 rod bearing and thrust bearing.
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Re: Broken rod bolt

Post by joe 90 » Tue Oct 17, 2017 5:03 pm

Those mains don't look good to me.

Maybe they've run dry for a while?

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Re: Broken rod bolt

Post by tuffxf » Tue Oct 17, 2017 6:00 pm

G,day,
Last time for me :D
What style of mains last time, full groove, 3/4 or half?
What big end clearance?
How is the oiling system set up?
what lifters?
How high do you turn it on the shift and across the stripe?
Internal or external balance, 28 or 50 oz?
Clevelands will shit 2 and 7 every time before the rest with a stock crank if not set up right depending on how high your turning them.
Paul

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