<VV> Broken Crank!

Tue May 4 15:18:01 EDT 2010

 Kind of a loosy goosy question, but GM claims that nitriding increases surface fatigue resistance (where cracks start) by something like 5 times that of an unnitrided crank, if memory serves me. And yes, a regrind removes it, but only at the journals. The question is, where do these cracks originate? I don't believe that balancing hole was the starting point, it simply was in the path. 

So, yes, it helps. On the other hand, ANYTHING one can do to reduce crank flex, like a GOOD harmonic damper, a case where the mains are KNOWN to be in line, etc., will only do good things in this direction. 

John Roberts

-----Original Message-----
From: shortle <shortle556 at earthlink.net>
To: jvhroberts at aol.com; dnoneal at bellsouth.net; virtualvairs at corvair.org; BobHelt at aol.com; N2VZD at aol.com
Sent: Tue, May 4, 2010 1:58 pm
Subject: Re: <VV> Broken Crank!

And do the nitrided cranks break (when used in a stock application- the way GM intended)? And having 1 of these cranks "undersized" removes this special stuff?
Timothy Shortle in Durango Colorado

-----Original Message----- 
From: jvhroberts at aol.com 
Sent: May 4, 2010 11:42 AM 
To: shortle556 at earthlink.net, dnoneal at bellsouth.net, virtualvairs at corvair.org, BobHelt at aol.com, N2VZD at aol.com 
Subject: Re: Broken Crank! 

To the best of my knowledge, and someone can correct me if I am wrong, ALL 140s had nitrided cranks. At least during the 65-66 years. 

John Roberts

-----Original Message-----
From: shortle <shortle556 at earthlink.net>
To: jvhroberts at aol.com; dnoneal at bellsouth.net; virtualvairs at corvair.org; BobHelt at aol.com; N2VZD at aol.com
Sent: Tue, May 4, 2010 12:10 pm
Subject: Re: <VV> Broken Crank!

Did ALL the 140's have the nitrated cranks? Or just the Corsas?
Timothy Shortle in (beautiful) Durango Colorado

-----Original Message----- 
From: jvhroberts at aol.com 
Sent: May 4, 2010 7:14 AM 
To: dnoneal at bellsouth.net, shortle556 at earthlink.net, virtualvairs at corvair.org, BobHelt at aol.com, N2VZD at aol.com 
Subject: Re: Broken Crank! 

8409 is for all long stroke 164 cranks. There are, however, two flavors of this crankshaft. There's the 110 and lower version, and then there's the 140 and 180 cranks, which are nitrided. These have an ampersand (&) stamped on the end of the crank nose next to the flywheel flange. The & cranks are FAR more fatigue resistant than their lesser brethren. 

John Roberts

-----Original Message-----
From: David O'Neal <dnoneal at bellsouth.net>
To: 'shortle' <shortle556 at earthlink.net>; virtualvairs at corvair.org; BobHelt at aol.com; N2VZD at aol.com
Sent: Tue, May 4, 2010 9:10 am
Subject: Re: <VV> Broken Crank!

The engine number is T0625RH and the crank is marked 8409.  According to the

Junkyard Primer this is a long stroke crank. Do all the 164 engines have

this crank?

I haven't gotten down to the bearings yet, but there were no loose bolts on

the converter, no abnormal looking wear on the parts, and no unusual

vibrations in the car before this happened.  I am not very experienced with

Corvair engines though and I may be missing something.

Good question about that last bearing - if the engine has been rebuilt and

the wrong one placed there then it could be the cause.  Will check that

next.

Thanks for the questions and input.

David O'Neal

-----Original Message-----

From: shortle [mailto:shortle556 at earthlink.net] 

Sent: Monday, May 03, 2010 12:19 PM

To: David O'Neal; virtualvairs at corvair.org; BobHelt at aol.com

Subject: Re: <VV> Broken Crank!

What are the crankshaft numbers and the engine numbers please? Timothy

Shortle in Durango Colorado

-----Original Message-----

>From: David O'Neal <dnoneal at bellsouth.net>

>Sent: May 3, 2010 11:50 AM

>To: virtualvairs at corvair.org, BobHelt at aol.com

>Subject: Re: <VV> Broken Crank!

>

> 

>Sorry for the lack of the vital details.

> 

>This is a '65 Coupe 110 PG with a harmonic damper!  I think the mileage 

>is fairly low, <120k (speedo broke at 74k).  When I removed the engine 

>I could tell it has been removed before.  The car sat for 10+ years in 

>a driveway before I got it - but it turned over easily and I carefully 

>lubed it up, tuned it up, and cleaned it out (gas tank, carbs, etc.) 

>before cranking it. I expected to find something internal, such as a 

>dropped valve seat, but the only thing I found was a dead coil and very 

>old wires, etc.  I fixed the oil leaks, reworked the brakes and it ran 

>very good until this happened.  Total mileage I put on it is <500miles.  

>It did a tiny bit of visible smoke at start up but you can see the 

>blow-by carbon inside the block (don't know if this amount is normal)- 

>it probably got a re-ring job in the past.

> 

>David O'Neal

> 

>

> 

> 

>----- Original Message -----

>From: BobHelt at aol.com 

>To: dnoneal at comcast.net ; virtualvairs at corvair.org 

>Sent: Monday, May 03, 2010 10:07 AM

>Subject: Re: <VV> Broken Crank!

>

>In a message dated 5/3/2010 6:03:36 A.M. US Mountain Standard Time, 

>dnoneal at comcast.net writes:

>

>Finally got into the engine and see what I found.

>

>Notice the large hole milled out by Uncle Chevy to balance the crank.  

>There is an even larger hole on the other end.  Those holes are large 

>enough to put your index finger in.

>

>This engine still ran after the break.

>

>David O'Neal

>

>

>David,

>Please give us some details....Engine hp? MT or PG?  Harmonic damper or 

>not? Mileage? Car use..racing? Thanks,

>Regards,

>Bob Helt

> _______________________________________________

>This message was sent by the VirtualVairs mailing list, all copyrights are

the property

>of the writer, please attribute properly. For help,

mailto:vv-help at corvair.org

>This list sponsored by the Corvair Society of America,

http://www.corvair.org/

>Post messages to: VirtualVairs at corvair.org

>Change your options: http://www.vv.corvair.org/mailman/options/virtualvairs

> _______________________________________________

 _______________________________________________

This message was sent by the VirtualVairs mailing list, all copyrights are the 

property

of the writer, please attribute properly. For help, mailto:vv-help at corvair.org

This list sponsored by the Corvair Society of America, http://www.corvair.org/

Post messages to: VirtualVairs at corvair.org

Change your options: http://www.vv.corvair.org/mailman/options/virtualvairs 

 _______________________________________________