 Case inspection, align bore or not |
|
|
|
Porsche, and the Porsche crest are registered trademarks of Dr. Ing. h.c. F. Porsche AG.
This site is not affiliated with Porsche in any way. Its only purpose is to provide an online forum for car enthusiasts. All other trademarks are property of their respective owners. |
|
|
| 930cabman |
 Oct 16 2022, 05:52 PM
Post
#1
|
|
Advanced Member  Group: Members Posts: 3,130 Joined: 12-November 20 From: Buffalo Member No.: 24,877 Region Association: North East States 
 |
Recently I had my local good guy machinist make a steel inspection shaft to pickup the main bearing bores leaving a thou or so clearance. Seems to make sense, similar to installing the crank with new bearings and making sure the crank spins smoothly (easy). The next part of the plan would involve fabricating another gauge to pickup the cylinder mounting surfaces. Sure this can all be done with indicators, but I am trying another tack with this process. Thoughts?
I also use Plastigage to check actual (after crush) clearances Working a 2.7 911 cases I have found the main bearing bores become elongated due to many heat/loading cycles. This is very common to this magnesium case and keeps guys like Ollies in business. Is this elongation also common to our VW/914 cases TIA |
   |
 
|
  |
Replies
| r_towle |
Oct 16 2022, 09:03 PM
Post
#2
|
|
Custom Member Group: Members Posts: 24,585 Joined: 9-January 03 From: Taxachusetts Member No.: 124 Region Association: North East States
|
First, find the bearings you can actually purchase.
|
|
|
|
| 930cabman |
Oct 17 2022, 04:52 AM
Post
#3
|
|
Advanced Member Group: Members Posts: 3,130 Joined: 12-November 20 From: Buffalo Member No.: 24,877 Region Association: North East States
|
QUOTE(r_towle @ Oct 16 2022, 09:03 PM)  First, find the bearings you can actually purchase. Got Silverline on the shelf |
|
|
|
| barefoot |
Oct 17 2022, 06:56 AM
Post
#4
|
|
Senior Member Group: Members Posts: 1,279 Joined: 19-March 13 From: Charleston SC Member No.: 15,673 Region Association: South East States
|
QUOTE(930cabman @ Oct 17 2022, 06:52 AM) QUOTE(r_towle @ Oct 16 2022, 09:03 PM) First, find the bearings you can actually purchase. Got Silverline on the shelf Now, see if the main brgs. are a tight fit in the case, if so line boring probably not needed |
|
|
|
| 930cabman |
Oct 17 2022, 10:03 AM
Post
#5
|
|
Advanced Member Group: Members Posts: 3,130 Joined: 12-November 20 From: Buffalo Member No.: 24,877 Region Association: North East States
|
QUOTE(barefoot @ Oct 17 2022, 06:56 AM) QUOTE(930cabman @ Oct 17 2022, 06:52 AM) QUOTE(r_towle @ Oct 16 2022, 09:03 PM) First, find the bearings you can actually purchase. Got Silverline on the shelf Now, see if the main brgs. are a tight fit in the case, if so line boring probably not needed The testing gauge fits very good, turns by hand with a thou or so clearance at all four case bores |
|
|
|
| Superhawk996 |
Oct 17 2022, 02:01 PM
Post
#6
|
|
914 Guru Group: Members Posts: 5,875 Joined: 25-August 18 From: Woods of N. Idaho Member No.: 22,428 Region Association: Galt's Gulch
|
QUOTE(930cabman @ Oct 17 2022, 12:03 PM) QUOTE(barefoot @ Oct 17 2022, 06:56 AM) QUOTE(930cabman @ Oct 17 2022, 06:52 AM) QUOTE(r_towle @ Oct 16 2022, 09:03 PM) First, find the bearings you can actually purchase. Got Silverline on the shelf Now, see if the main brgs. are a tight fit in the case, if so line boring probably not needed The testing gauge fits very good, turns by hand with a thou or so clearance at all four case bores FYI - your looking for elongation of the bearing saddles. The middle saddle is particularly prone to be hammered out by crank whip. A test bar that crosses all three with 0.001” clearance really isn’t going to tell you what you you need to know. Measure with bore gauge is best. 2nd choice would be telescoping bore gauge (snap gauge) and measured with a micrometer. Should be same diameter across two axis perpendicular to each other. |
 |
|
| 930cabman |
Oct 18 2022, 07:45 AM
Post
#7
|
|
Advanced Member Group: Members Posts: 3,130 Joined: 12-November 20 From: Buffalo Member No.: 24,877 Region Association: North East States
|
QUOTE(Superhawk996 @ Oct 17 2022, 02:01 PM) QUOTE(930cabman @ Oct 17 2022, 12:03 PM) QUOTE(barefoot @ Oct 17 2022, 06:56 AM) QUOTE(930cabman @ Oct 17 2022, 06:52 AM) QUOTE(r_towle @ Oct 16 2022, 09:03 PM) First, find the bearings you can actually purchase. Got Silverline on the shelf Now, see if the main brgs. are a tight fit in the case, if so line boring probably not needed The testing gauge fits very good, turns by hand with a thou or so clearance at all four case bores FYI - your looking for elongation of the bearing saddles. The middle saddle is particularly prone to be hammered out by crank whip. A test bar that crosses all three with 0.001” clearance really isn’t going to tell you what you you need to know. Measure with bore gauge is best. 2nd choice would be telescoping bore gauge (snap gauge) and measured with a micrometer. Should be same diameter across two axis perpendicular to each other. A bore gauge is probably best and will give the size and roundness of the bores, but will not result in knowing of the alignment of the bores. this gauge is new to me, prussian blue will provide additional information. So far I am pleased with the results. Anyone have an extra 78mm stroker crank laying around? My 2056 has given great results (including 30+ mpg highway), but taking a different tack this one. |
|
|
|
Posts in this topic
930cabman Case inspection Oct 16 2022, 05:52 PM
Montreal914 :popcorn: Oct 16 2022, 08:06 PM
Superhawk996 More info use as you see fit.
Align boring is u... Oct 18 2022, 08:37 AM Superhawk996 Regarding crush: the other post you posted to is ... Oct 18 2022, 11:49 AM
930cabman thank you for the information from King Bearings, ... Oct 18 2022, 12:58 PM |
1 User(s) are reading this topic (1 Guests and 0 Anonymous Users)
0 Members:
|
Lo-Fi Version | Time is now: 1st June 2024 - 10:32 AM |
Invision Power Board
v9.1.4 © 2024 IPS, Inc.