Not high tech, but need experienced advice

Tech questions that don't fit above forums

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Chargermal
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Not high tech, but need experienced advice

Post by Chargermal » Thu Feb 02, 2012 2:33 am

Three weeks ago I broke my Cast Eagle crank -

Chrysler LA 318/392 stroker - Mild solid cam - peak HP at 5500, peak RPM 6200, internally balanced, SFI balancer and flex plate, 12.4 AF, 28 deg total timing,

You get the picture - took it to a Cummins Diesel engineer and he diagnosed a serious crank flaw in the rod journal..a a stress riser in the middle of the hole thru the journal and also a poor casting grain.

Here's my question -

318 blocks don't grow on trees in Australia - and the #4 main cap was also cracked. :( ..although no other visible damage.

I can get ProGram replacement caps - but I'm worried about other possible damage.

So - How "failsafe" is a mag and sonic check for detecting flaws?

( It will be tough for me financially to get a new block and machine it up like the current one which was torqueplate bored, align honed, squared and decked, tapped notched and was virgin bore. )

I'd like to hear what others think - assuming any testing comes back with a clean sheet?

Cheers and thx in advance for your opinions.
1971 VALIANT CHARGER - (by Chrysler Australia Limited)
Gen 3 6.1 HEMI, carb induction

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dfree383
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Re: Not high tech, but need experienced advice

Post by dfree383 » Thu Feb 02, 2012 3:02 am

Inspect it first, if its useable, go with the caps.

Old Grey

Re: Not high tech, but need experienced advice

Post by Old Grey » Thu Feb 02, 2012 4:09 pm

Chargermal wrote:So - How "failsafe" is a mag and sonic check for detecting flaws?
Are you going full ultra violet inspection - which would be difficult - , or localised magnetic powder testing - more likely -.

Magnetic powder
It depends on the operator, but even then it's not that difficult. It involves using an electro-magnet with 2 poles, placing it either side of the suspected crack, turn it on, and puff/sprinkle metal power over the area. Cracks show up very well, longitudinally to the poles, and that means that it has to be done a second time at right angles to the other on the same area. The right angle test will be difficult on the mains, but cracks don't usually go that way, just look at the direction of your main cap crack. They should also check the webbing under the main. Also, the block has to be spotlessly dry, no oil.

We Magnetic powder every CI head we do on the face, and if anything, it finds too many cracks - some don't leak -. We don't do the rocker cover area, because it rarely cracks there, so we have been caught out in this area once or twice - until we work out what heads are prone to cracking there - and then we test all of those in that area.

What I'm say is that it depends on the operator

Ultra violet inspection
It's harder to miss stuff with this one.

Some photos would be good.

Chargermal
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Re: Not high tech, but need experienced advice

Post by Chargermal » Fri Feb 03, 2012 1:48 am

Thanks for the description.

Sounds like there's no guarantees and i really don't want to be picking up pieces of engine after another rebuild - I think I'm looking at a fresh block.

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Re: Not high tech, but need experienced advice

Post by RL » Fri Feb 03, 2012 3:55 am

Our customer snapped a crank in his sports sedan, I'm sure he reused the factory 010 Chev block again.

I would say that the cap acted like a fuse, and saved the block. If it was me, I would crack test it and use it if it passed.

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Re: Not high tech, but need experienced advice

Post by rce4csh » Fri Feb 03, 2012 9:26 am

If you have a way to get things really clean, then a through dye penetrant test along with a real good look with mag particle (powder) will be good enough. Wet mag (liquid flourescent) is a pretty tough interpretation in these areas. Do not forget to do a pressure check prior to any of this. BTW, Mag or Dye penetrant test the block with the caps on and the hardware fully tensioned (torqued). In this case, substituting another cap for this test is preferrable to not having one there at all. The load induced into the block by having the caps is place is helpful to more readily find cracks and the like when using either of these two methods. Following a check with caps on, some additional testing with the caps off in the bolt hole area is recommended. Dye pentrant kits can be easily found on ebay and the like for cheap! Look for the ones with expired date codes. They will still do their job, they just fall out of specs for critical aerospace and power plant kind of work (tight specification sort of thing).

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Re: Not high tech, but need experienced advice

Post by enigma57 » Mon Feb 06, 2012 1:59 am

I concur. Did NDT work in the '70s whilst in the service. Visual inspection, then dye penetrant inspection, followed by dry method mag particle inspection is the way to go in my view.

Bear in mind that dye penetrant will only reveal discontinuities open to the surface. Mag particle will reveal discontinuities open to the surface and to a very shallow depth, depending upon amperage used and surface smoothness, contours and shape of the part(s) being tested.

The only way to get a look deeper beneath the surface would involve radiographing the part(s) in question.

Ultrasonic inspection won't tell you much in this instance. It can be used for testing metal thickness, % of bond in brazed or silver soldered pieces, etc.

Angle beam shear wave (ultrasonic) inspection came out about the time I mustered out and returned to civilian life. Frankly, I wasn't impressed with it, as it provided no permanent record as when reading a radiograph. You could use it to identify a possible problem area in objects having fairly uniform surfaces and if you found something, check it out in greater detail by radiography. Beyond that, I saw little use for it, at least in our testing environment working on the subs.

As noted, priour to testing you must have the test surfaces clean to bare metal and thoroughly degreased. We used acetone as a final cleaning method back in the '70s (wiped on with a lint free cloth and allowed to air dry). There may be other cleaning methods that will work for you. Just read over the dye penetrant manufacturer's instructions regarding cleaner and application of dye penetrant and developer. And of course, follow safety precautions.

Also...... We did some side work on our street rod projects in our spare time. When testing flywheels and other cast iron parts, we found it best to test them priour to resurfacing, as the resurfacing process can actually mask some defects open to the surface. Then test them again following final surfacing. I would suggest testing a cast nodular iron crankshaft or main cap or machined areas of a cast iron cylinder block in the same way.

You will see indications of porosity (roundish indications) when doing your dye penetrant testing. If very large, take note...... But pay particular attention to linear discontinuities, as these can indicate cracks.

Best regards,

Harry

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Re: Not high tech, but need experienced advice

Post by Chargermal » Mon Feb 06, 2012 4:06 am

I would like to thank you all for the interest and comprehensive replies. :notworthy:

To be frank, I've come to the conclusion that the risk doesn't justify the extent to which I'd have to go, and even then internal flaws may still be present as a result of the stresses on the caps and cradle when the crank let go.

I think I'll be going down the path of a fresh block . 8)

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Re: Not high tech, but need experienced advice

Post by moper » Mon Feb 06, 2012 9:40 pm

Mal, I think for your peace of mind that's the way to go... Sorry Mate.

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Re: Not high tech, but need experienced advice

Post by enigma57 » Tue Feb 07, 2012 6:58 am

Roger that, moper! A picture is worth a thousand words...... Gives a better comprehension of the carnage.

Sorry to hear of the mishap with your Eagle stroker crank, Chargermal. Visited your homepage. Outstanding car. Well thought out and executed engine combo.

Best regards,

Harry

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Re: Not high tech, but need experienced advice

Post by Chargermal » Tue Feb 07, 2012 2:46 pm

Thanks Harry...I can't take any credit for te engine build - but it MPHd at 111 in a 3650lb car with factory heads so it OK for what it was.

I just hope no-one gets sucked in to buying eagle cast cranks after reading this post.

I'll reply to your IM later today

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Re: Not high tech, but need experienced advice

Post by enigma57 » Tue Feb 07, 2012 5:19 pm

I agree. They might be OK for a mild street build...... If you luck out and get a straight, properly machined crankshaft having no casting flaws of consequence. But with offshore manufacturers having sketchy quality control...... You're rolling the dice.

For serious performance builds, I would stick with a high quality forged rotating assembly as a foundation.

Found this today whilst looking into Eagle cast cranks......

http://www.forabodiesonly.com/mopar/sho ... hp?t=62612

Best regards,

Harry

P.S. >>>> Regarding castings...... Last year, the original alternator on my '88 Buick daily driver finally crapped out. No complaints...... It lasted 23 years.

So off to the local auto parts store for a replacement....... They had 3 levels (and prices) to pick from (all sourced from Mexico)......

* New, both body casting and internals with limited lifetime warranty
* Rebuilt, using original GM body casting and all new internals with limited lifetime warranty
* Rebuilt, using original GM body casting and some new internals (as needed) with 1 year limited warranty

This car is a keeper, so initially I went with their 'top of the line' all new unit. There was a problem with the body casting, though. The material was so soft and had such a coarse grain structure that I couldn't even tension the serpentine drive belt without the casting breaking at the mounting ear.

Returned it and went with their 'middle of the line' (and slightly less expensive) version having all new internals in a used original GM body casting. One look at the difference in casting quality and I knew I had made the right choice. So far, this unit has performed flawlessly.

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Re: Not high tech, but need experienced advice

Post by Schurkey » Tue Apr 24, 2012 11:07 pm

Buy and machine a new block. Send the bill to Eagle. It's their fault, and they should pay.


(Good luck!)

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Re: Not high tech, but need experienced advice

Post by ZIGGY » Thu Apr 26, 2012 8:56 am

enigma57 wrote:* New, both body casting and internals with limited lifetime warranty
* Rebuilt, using original GM body casting and all new internals with limited lifetime warranty
* Rebuilt, using original GM body casting and some new internals (as needed) with 1 year limited warranty
You made the best choice, but they all have a high percentage of shit, to put it crudely. I own a substantial auto repair
business and aftermarket part quality from the chain parts stores is a constant problem.

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Re: Not high tech, but need experienced advice

Post by enigma57 » Thu Apr 26, 2012 2:34 pm

That has been my experience in recent years as well, Ziggy. Had I not been in a situation of needing to get the Buick on the road again over the weekend, I would have driven my wife's car down to Houston the following Monday to see if the old armature rewinding shop on N. Shepherd in the Heights is still in business. Always had great luck with their stuff over the years (rebuilt generators, alternators and starter motors).

I am planning on making a run down there before long and will swing by to see if they are still around.

Best regards,

Harry

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