Pelican Parts
Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   Pelican Parts Forums > Porsche Forums > 911 Engine Rebuilding Forum


Reply
 
LinkBack Thread Tools Rate Thread
Author
Thread Post New Thread    Reply
Registered
 
Tim L's Avatar
 
Join Date: Jul 2001
Location: Hamden, CT, USA
Posts: 446
Broken 3.2 crank need some advice

I'm getting ready to rebuild my 84 3.2 again. It has about 10,000 miles since the last rebuild. First I'm looking for a good used crank if anyone has one. I was going to remove the heads with the cam housing together, what is the procedure? Since the miles are low I was just going to replace the bearings and put it back together does this sound ok.

Thanks

Tim

Old 06-03-2004, 10:13 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #1 (permalink)
Registered
 
KobaltBlau's Avatar
 
Join Date: Mar 2004
Location: City of Seattle, WA
Posts: 3,374
Depends on what caused your failure. If you have shrapnel everywhere you might have bigger problems elsewhere.

Tell us more about how/why the crank broke, and whether this is the only problem you know of.
__________________
Andy
Old 06-03-2004, 10:21 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #2 (permalink)
Registered
 
KobaltBlau's Avatar
 
Join Date: Mar 2004
Location: City of Seattle, WA
Posts: 3,374
Oh, and hi, Tim. Thanks for selling me that bar. I'm sorry to hear about your engine woes.
__________________
Andy
Old 06-03-2004, 10:25 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #3 (permalink)
Licensed User
 
Shuie's Avatar
 
Join Date: Feb 2003
Location: ....down Highway 61
Posts: 6,505
What happened after 10k miles to necessitate another rebuild? A broken crank sounds a little severe. Are you sure all it needs is new bearings?

Oh yeah, EBS has the 3.2 cranks .

Good luck!
Old 06-03-2004, 10:27 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #4 (permalink)
Registered
 
Tim L's Avatar
 
Join Date: Jul 2001
Location: Hamden, CT, USA
Posts: 446
I rebuilt the motor because of a spun #6 bearing. I had the crank ground and hard chromed back to standard on that one journal. There was no metal in the case or in the filter. I heard it go and shut the motor down, although I didn’t know what the problem was at the time. I’m talking best case if everything checks out.

Thanks

Tim
Old 06-03-2004, 10:49 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #5 (permalink)
Registered
 
Join Date: May 2002
Location: St Louis
Posts: 4,211
I would love to see a picture. How about a description of the break?
Old 06-03-2004, 01:05 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #6 (permalink)
 
Try not, Do or Do not
 
Henry Schmidt's Avatar
 
Join Date: Apr 2004
Location: Fallbrook, Ca. 92028
Posts: 14,041
Garage
3.2 crank woes, not too uncommon

Hi, sorry to here about your bearing failure. It is hard to say what failed but it's a pretty good guess that if all was well during the assembly process that your problem is/was contamination. It is critical that all parts / specs are checked completely after major crank repair and you are now learning why a std/std 3.2 crank is so valuable. We do a conversion on these cranks that can sometimes bring them back to life but in general it's best to seek out the std/std replacement.
__________________
Henry Schmidt
SUPERTEC PERFORMANCE
Ph: 760-728-3062
Email: supertec1@earthlink.net
Old 06-03-2004, 02:41 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #7 (permalink)
Registered
 
Tim L's Avatar
 
Join Date: Jul 2001
Location: Hamden, CT, USA
Posts: 446
I finally had time to tear the motor down last night. I don’t think JB weld is going to work.
Old 06-16-2004, 05:15 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #8 (permalink)
Try not, Do or Do not
 
Henry Schmidt's Avatar
 
Join Date: Apr 2004
Location: Fallbrook, Ca. 92028
Posts: 14,041
Garage
Magnaflux, Magnaflux Magnaflux

Magnaflux
If this crank was installed 10k miles ago, there is little or no chance this crank was not cracked before installation. I have seen more and more cracked 3.2/3.3 cranks lately. Cracked cranks in the smaller sizes is almost unheard of. Don't get me wrong you must always magnaflux for cracks, but early cranks rarely crack.
Now why are 3.2 and 3.3 cranks cracking. Remembering that I am not an engineer, I would say that twisting loads created by horrible rod angularity is the culprit. We are also seeing cracks in cranks that have spun bearings. Often when a rod bearing losses lubrication you see great amounts of heat. this heat warps the crank. Crank shops repair the crank and during the repair process they have to straighten them. This is an interesting process. The crank grinder will locate the crank in centers and measure for the high spot, then with all the technology available to engine builders today, he takes a big hammer and a V shaped chisel and then just beat the hell out of it. The hope is the crank gets straight and does not crack. If this crank was repair because of a spun bearing, it is likely that it was pounded straight.
__________________
Henry Schmidt
SUPERTEC PERFORMANCE
Ph: 760-728-3062
Email: supertec1@earthlink.net

Last edited by Henry Schmidt; 06-19-2004 at 06:58 AM..
Old 06-16-2004, 06:31 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #9 (permalink)
Senior Member
 
Doug Zielke's Avatar
 
Join Date: Jan 2001
Location: Left Coast, Canada
Posts: 4,572
Tim,
Now *that* is some real fine destruction!
If I was handing out prizes for the best images of the Mechanical
Mayhem Files, this would surely be a winner.
Thanks for sharing!
__________________
'81 SC Coupe "Blue Bomber"
"Keep your eyes on the road, and your hands upon the wheel."- J.D.M.
Old 06-16-2004, 06:42 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #10 (permalink)
Registered
 
Tim L's Avatar
 
Join Date: Jul 2001
Location: Hamden, CT, USA
Posts: 446
Before the repair I had it magnafluxed and checked for straightness. The shop that repaired it also magnafluxed it. The crank was ground then hard chromed and ground to standard. Something in this process compromised the integrity of the crank, I think.?

Tim
__________________
Tim Lynn
84 911 Carrera
PCA E Stock #278
Old 06-16-2004, 06:59 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #11 (permalink)
Licensed User
 
Shuie's Avatar
 
Join Date: Feb 2003
Location: ....down Highway 61
Posts: 6,505
Ive got no experience building engines and even less of a clue what happened to the crank, but doesn't hard chrome cause hydrogen-embrittlement in steel?
Old 06-16-2004, 09:01 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #12 (permalink)
Registered
 
Join Date: Mar 2004
Location: So. Ca.
Posts: 521
It is quite possible that in the process of grinding for hard chroming the operator removed some of the radius in the Rod Journal, hence the stress raiser forming and beach type apperance from the crank pin out.
Old 06-17-2004, 06:28 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #13 (permalink)
Try not, Do or Do not
 
Henry Schmidt's Avatar
 
Join Date: Apr 2004
Location: Fallbrook, Ca. 92028
Posts: 14,041
Garage
Most likely the crank grinder missed the crack. Think horses not zebras.
People are human and mistakes happen. We could go on ad nauseam trying to analyze this failure but a damaged crank got repaired and failed shortly there after. Most likely the crank grinder missed the crack.

For those of us who insist on overanalyzing everything there's a 12 step group for you. OAA

PS: we have cranks
__________________
Henry Schmidt
SUPERTEC PERFORMANCE
Ph: 760-728-3062
Email: supertec1@earthlink.net

Last edited by Henry Schmidt; 06-18-2004 at 08:17 AM..
Old 06-17-2004, 06:49 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #14 (permalink)
Registered
 
Join Date: Mar 2004
Location: So. Ca.
Posts: 521
It was a response to

"Something in this process compromised the integrity of the crank"
Old 06-17-2004, 01:55 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #15 (permalink)
Irrationally exuberant
 
ChrisBennet's Avatar
 
Join Date: Aug 2001
Location: Nashua, NH USA
Posts: 8,164
Garage
I've heard of people checking cranks by "ringing" them. Does this test work or is it just a quick test to tell if a crank is bad (but not if it is necessarily good)?
-Chris
__________________
'80 911 Nogaro blue Phoenix!
'07 BMW 328i 245K miles!
http://members.rennlist.org/messinwith911s/
Old 06-19-2004, 03:19 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #16 (permalink)
Try not, Do or Do not
 
Henry Schmidt's Avatar
 
Join Date: Apr 2004
Location: Fallbrook, Ca. 92028
Posts: 14,041
Garage
Quote:
Originally posted by ChrisBennet
I've heard of people checking cranks by "ringing" them. Does this test work or is it just a quick test to tell if a crank is bad (but not if it is necessarily good)?
-Chris
This question shows good insight. You answered your own question.
Ringing a crank is a good way to tell if it's bad but it doesn't tell you that it's good.

To paraphrase my favorite lawyer:
"If it doesn't ring, don't use the thing."
__________________
Henry Schmidt
SUPERTEC PERFORMANCE
Ph: 760-728-3062
Email: supertec1@earthlink.net

Last edited by Henry Schmidt; 06-19-2004 at 07:02 AM..
Old 06-19-2004, 05:25 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #17 (permalink)
Registered
 
Join Date: May 2004
Location: New Orleans
Posts: 38
Re: Magnetic particle examination – crankshafts

Although common to the automotive engine rebuilding industry, the commercial engine (truck & marine diesel) rebuilding community has for many years employed a different technique to check for cracks in crankshafts and other rotating components. The most widely used process is fluorescent dye penetrant testing. The reasons for this are as follows:

1). Dye penetrant does not require that a magnetic field be introduced into the part. Do you want your crankshaft acting like a magnetic drain plug?

2). We are talking “in service cracks” and as such, are ALWAYS open to the surface. Some proponents of “Magnaflux” will tell you that dye penetrant will not locate sub-surface discontinuities. My answer to that line is that a sub-surface flaw is not likely to cause a failure. I’m sure the good Dr. Porsche & Co. subjected the cranks to non-destructive testing at many stages of the manufacturing process. Gross sub-surface flaws would have been weeded out during that process. Porsche may have employed magnetic particle examination on the final product, but also, would have subjected the crank to a proper degaussing. I suspect that most machine shops do not have the proper equipment, nor do they have the expertise to properly degauss a crank. “Pass it through the coil and call it a done deal”. Going back to surface and sub-surface; as cracks are surface breaking they will respond nicely to dye penetrant. Pay particular attention to the radius on either side of the journal, and the oil passages. I prefer the fluorescent type, but a non-fluorescent type will work just fine. One word of caution; dye penetrant will not tolerate dirt, grease or other contaminates. The part needs to be clean. Magnaflux Corp. makes a handy kit that is available from most commercial supply houses.
Old 06-21-2004, 07:54 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #18 (permalink)
 
Registered
 
350HP930's Avatar
 
Join Date: Jun 2003
Location: St Petersburg, FL
Posts: 3,814
Re: Magnaflux, Magnaflux Magnaflux

Quote:
Originally posted by Henry Schmidt
Crank shops repair the crank and during the repair process they have to straighten them. This is an interesting process. The crank grinder will locate the crank in centers and measure for the high spot, then with all the technology available to engine builders today, he takes a big hammer and a V shaped chisel and then just beat the hell out of it. The hope is the crank gets straight and does not crack. If this crank was repair because of a spun bearing, it is likely that it was pounded straight.
Every machine shop that grinds and straightens cranks that I know of uses a crank bending press.

If your crank grinder uses a chisel I suggest finding another machine shop.

Old 06-21-2004, 08:01 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #20 (permalink)
Reply


 


All times are GMT -8. The time now is 12:53 PM.


 
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2025, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2025 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website -    DMCA Registered Agent Contact Page
 

DTO Garage Plus vBulletin Plugins by Drive Thru Online, Inc.