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-   -   Bad crank shaft (http://forums.pelicanparts.com/911-engine-rebuilding-forum/981572-bad-crank-shaft.html)

frankoporsche 12-22-2017 06:06 PM

Bad crank shaft
 
But any how I always wanted to learn to how rebuilt Porsche engine ..So I brought the Wayne Dempsey books and it is the one of best porsche I ever read ...
So I did the complete engine tear down and did the crank journal inspection it looking good , I sent off my crank shaft to Machine shop to have check dim. and Mag and micro polish ..
got it back today and I double check the machine work ,the D1 and D2 are good within spec, but the D3 is under size s/b 30.980-30.993 and I am getting 30.862 and the D6 pulley s/b 29.960-29.993 my reading 29.849 way under the spec.

Normally the D3 shaft should be good .they hardly wear
How can this happen?? man this suck
not sure about going for over size bearing and have the crank turn down...any thought?

frankoporsche 12-22-2017 09:38 PM

Quote:

Originally Posted by frankoporsche (Post 9858724)
But any how I always wanted to learn to how rebuilt Porsche engine ..So I brought the Wayne Dempsey books and it is the one of best porsche I ever read ...
So I did the complete engine tear down and did the crank journal inspection it looking good , I sent off my crank shaft to Machine shop to have check dim. and Mag and micro polish ..
got it back today and I double check the machine work ,the D1 and D2 are good within spec, but the D3 is under size s/b 30.980-30.993 and I am getting 30.862 and the D6 pulley s/b 29.960-29.993 my reading 29.849 way under the spec.

Normally the D3 shaft should be good .they hardly wear
How can this happen?? man this suck
not sure about going for over size bearing and have the crank turn down...any thought?

There is a ring mark on the middle front D#6 of the crank shaft..has any one seem those line B4 ?
I can catch the line with my finger nail
http://forums.pelicanparts.com/uploa...1514007519.jpg

DRACO A5OG 12-22-2017 10:56 PM

Well, you have couple of options here.

Send it back to the machine shop and and have them grind down the rest to match the thinner one and go with thicker bearings

or

Get two sets of bearings and mix to match. Mine were a bit off so I took the thicker bearings and matched them with the thinner journals ( I uses Standard bearings )

As far as the deformation on the snout. I would no worry about as the sealing of the #8 bearing is more important. So that gouge was not there before you sent it to the shop?

frankoporsche 12-23-2017 12:06 AM

Quote:

Originally Posted by DRACO A5OG (Post 9858916)
Well, you have couple of options here.

Send it back to the machine shop and and have them grind down the rest to match the thinner one and go with thicker bearings

or

Get two sets of bearings and mix to match. Mine were a bit off so I took the thicker bearings and matched them with the thinner journals ( I uses Standard bearings )

As far as the deformation on the snout. I would no worry about as the sealing of the #8 bearing is more important. So that gouge was not there before you sent it to the shop?

yes the gouge was not there B4....
what is the real reason for standard size bearing is better or the rules of thumb over thicker bearing (+.25mm) for undersize journal?
question: if the crank shaft has being .130mm smaller than standard will is effect my oil pressure from the beginning before I torn down the motor?

DRACO A5OG 12-23-2017 11:51 AM

Oh my goodness, you may need to find another machine shop as the one you used is very neglectful.

I used Standard Size because even with 180,000 miles on the Crank Clock and even my Snout damaged. My measurements were still within minimum Porsche Specifications so that is why I chose the standard size. When I micro measured each bearing, I found all of them where a it off, so I matched them. I placed the thicker ones where the journals are more worn than others. I don't think it matters much but I felt much better knowing the wear would be more evenly distributed.

I got this idea when I was waiting for my crank shaft results. A builder, got three sets +.25, Standard & -.25 and mixed and matched. A bit extreme but the engine was used for racing and expected a tear down in short order.

The Rule of Thumb, the thing is if you go too thick, oil pressure will be affected badly where oil may not get in between the bearing and journals. SO please be careful here on your choice.

If 0.130MM is within in spec of wear, use standard, if it is more than standard spec, I would consider finding a better machine shop, and grind it down to accommodate the thicker bearings to do it correctly.

frankoporsche 12-23-2017 12:51 PM

Quote:

Originally Posted by DRACO A5OG (Post 9859394)
Oh my goodness, you may need to find another machine shop as the one you used is very neglectful.

I used Standard Size because even with 180,000 miles on the Crank Clock and even my Snout damaged. My measurements were still within minimum Porsche Specifications so that is why I chose the standard size. When I micro measured each bearing, I found all of them where a it off, so I matched them. I placed the thicker ones where the journals are more worn than others. I don't think it matters much but I felt much better knowing the wear would be more evenly distributed.

I got this idea when I was waiting for my crank shaft results. A builder, got three sets +.25, Standard & -.25 and mixed and matched. A bit extreme but the engine was used for racing and expected a tear down in short order.

The Rule of Thumb, the thing is if you go too thick, oil pressure will be affected badly where oil may not get in between the bearing and journals. SO please be careful here on your choice.

If 0.130MM is within in spec of wear, use standard, if it is more than standard spec, I would consider finding a better machine shop, and grind it down to accommodate the thicker bearings to do it correctly.

The person who own the shop ,he does know about Porsche crank spec ..other person in the shop may have did the work...
The shaft wear limit is .012mm per spec and mine is plus .108mm too small...
The only thing I can do is to ask the shop owner find me another crank shaft . if he take the blame.... other wise I am screwed .
like you mention take to other shop to accommodate to new thicker bearing
Thank you for helping out..

frankoporsche 12-23-2017 01:26 PM

Bearing Brands
 
I heard stories about certain brands are bad
what is a good common brands for main and rod bearing to get?

Flat6pac 12-23-2017 03:18 PM

By the time you finish buying bearings, if you can find them, a different crank could be less expensive.
Bruce

DRACO A5OG 12-23-2017 05:34 PM

Porsche mic-ed bearings, EBS has them as well ask for Don.

The bearings available on after market shops do not mic the bearings so you would need to do so to insure they are within acceptable specs.

I got the YELLOW Goetz brand.

Here is my 3.4L Build journey http://forums.pelicanparts.com/911-engine-rebuilding-forum/948857-part-trois-3-4l-build-journey.html

frankoporsche 12-24-2017 10:42 AM

Quote:

Originally Posted by DRACO A5OG (Post 9859728)
Porsche mic-ed bearings, EBS has them as well ask for Don.

The bearings available on after market shops do not mic the bearings so you would need to do so to insure they are within acceptable specs.

I got the YELLOW Goetz brand.

Here is my 3.4L Build journey http://forums.pelicanparts.com/911-engine-rebuilding-forum/948857-part-trois-3-4l-build-journey.html

The really help
Thank you very much....

boosted79 12-24-2017 04:04 PM

Take the crank back to the shop and take your mic. Have him measure the journals with his mic and compare to the measurements with your mic. Put a speedi-sleeve on the snout or you'll most likely have a seal leak.

frankoporsche 12-24-2017 10:05 PM

Quote:

Originally Posted by boosted79 (Post 9860534)
Take the crank back to the shop and take your mic. Have him measure the journals with his mic and compare to the measurements with your mic. Put a speedi-sleeve on the snout or you'll most likely have a seal leak.

yes I am going to take the crank back to the shop and have them mic and I am positively my measurement is correct, ...I also did check the shaft dim. before I sent it off to the shop..I alway check and double check my work and others..I dont like playing guessing games

The owner said his mechanic check to verify the crank is standard size is good , just before they micro polish .....

frankoporsche 12-26-2017 09:26 AM

Quote:

Originally Posted by Flat6pac (Post 9859613)
By the time you finish buying bearings, if you can find them, a different crank could be less expensive.
Bruce

I have agreed

frankoporsche 12-27-2017 11:43 PM

. Everything now moving forward...Thank you everyone help.

boosted79 12-29-2017 07:29 AM

What did you end up doing?

frankoporsche 12-29-2017 09:32 AM

Quote:

Originally Posted by boosted79 (Post 9865108)
What did you end up doing?

Replacing the crank

cmcfaul 01-05-2018 02:01 PM

oversized bearings are expensive. Much better to just replace the crank with a standard one.

Chris

frankoporsche 01-05-2018 05:55 PM

Quote:

Originally Posted by cmcfaul (Post 9873848)
oversized bearings are expensive. Much better to just replace the crank with a standard one.

Chris

I did replaced to standard crank...thanks

MBAtarga 01-17-2018 07:59 PM

Quote:

Originally Posted by frankoporsche (Post 9858875)

I know you've replaced the crank that was out of spec, but your original from the machine shop doesn't look like it's been micro-polished to me. Shouldn't that be almost a mirror finish?

Trackrash 01-18-2018 04:35 PM

The factory manual gives a spec for the finish of the crank. Without spitting hairs or going into great detail suffice it to say that you don't want a mirror finish on your crank. The microscopic groves in the crank will aid in the oiling of the bearings.


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