rear main problem - Pontiac GTO Forum
User Tag List

 
LinkBack Thread Tools Display Modes
post #1 of 8 (permalink) Old 08-31-2018, 05:35 PM Thread Starter
 
Join Date: Jul 2014
Location: new york
Posts: 29
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
rear main problem

I have a 1969 428 4 bolt main at engine builder for the last 12 months. Everything in motor has been replaced. All forged. heads are KRE. motor was stroked. It finally went on dyno and rear main from tin Indian leaked. Took it apart and a BOP one pc. was used. Went back on dyno and it leaked. Now he said he has ordered a Best gasket rope seal. it needs to come apart for the third time. Besides having 10K in the build its still leaking oil. I'm not convinced the rope seal is going to do it. crank, block, assembler??
army6741 is offline  
Sponsored Links
Advertisement
 
post #2 of 8 (permalink) Old 08-31-2018, 05:50 PM
 
PontiacJim's Avatar
 
Join Date: Dec 2012
Location: Gastonia, NC - Born & raised in Connecticut - 31 years
Posts: 3,563
Mentioned: 1 Post(s)
Tagged: 1 Thread(s)
Quoted: 367 Post(s)
Garage
Quote:
Originally Posted by army6741 View Post
I have a 1969 428 4 bolt main at engine builder for the last 12 months. Everything in motor has been replaced. All forged. heads are KRE. motor was stroked. It finally went on dyno and rear main from tin Indian leaked. Took it apart and a BOP one pc. was used. Went back on dyno and it leaked. Now he said he has ordered a Best gasket rope seal. it needs to come apart for the third time. Besides having 10K in the build its still leaking oil. I'm not convinced the rope seal is going to do it. crank, block, assembler??
Could be all of the above. Sometimes those BOP seals just don't seem to do the job. From what I have read, it can be related to the serrations found on the crank that the seal rides on, the recess in the seal is not correct, align boring the block without checking the main seal groove. Read this info about this on this forum with pictures: https://firstgenfirebird.org/forums/...&Number=299538
PontiacJim is offline  
post #3 of 8 (permalink) Old 09-05-2018, 04:12 PM
64-67 Expert
 
geeteeohguy's Avatar
 
Join Date: Feb 2008
Location: Fresno, California
Posts: 8,491
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 102 Post(s)
What Jim said. I'll add, that the 421-428-455 engines with the large journal crank have more sealing issues due to imperfections at the rear main. The Best Gasket square rope type seal is the preferred seal for these engines as it tolerates looser tolerances. Good luck.
geeteeohguy is offline  
 
post #4 of 8 (permalink) Old 09-05-2018, 11:26 PM
Super Moderator
 
BearGFR's Avatar
 
Join Date: Aug 2008
Location: Springtown, TX
Posts: 5,737
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 122 Post(s)
Garage
There's more to properly fitting one of the BOP 1-piece seals than meets the eye, and unfortunately the instructions that come with them don't cover it all yet either. I made a video about how to do it.


Bear

BearGFR
Springtown, TEXAS
BearGFR is offline  
post #5 of 8 (permalink) Old 09-14-2018, 05:48 PM Thread Starter
 
Join Date: Jul 2014
Location: new york
Posts: 29
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
third seal failed. He thinks seal cavity out of round and out of alignment with centerline of crank??
army6741 is offline  
post #6 of 8 (permalink) Old 09-14-2018, 06:29 PM
 
PontiacJim's Avatar
 
Join Date: Dec 2012
Location: Gastonia, NC - Born & raised in Connecticut - 31 years
Posts: 3,563
Mentioned: 1 Post(s)
Tagged: 1 Thread(s)
Quoted: 367 Post(s)
Garage
Quote:
Originally Posted by army6741 View Post
third seal failed. He thinks seal cavity out of round and out of alignment with centerline of crank??
Did you read the link I posted and did you let your machinist read it?
PontiacJim is offline  
post #7 of 8 (permalink) Old 09-14-2018, 08:25 PM Thread Starter
 
Join Date: Jul 2014
Location: new york
Posts: 29
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Yes I did Jim. that was his message today. I will be going there Monday to discuss the problem. He has been doing this for thirty years. will discuss the article with him. thanks to Bear also.
army6741 is offline  
post #8 of 8 (permalink) Old 09-14-2018, 09:41 PM
 
PontiacJim's Avatar
 
Join Date: Dec 2012
Location: Gastonia, NC - Born & raised in Connecticut - 31 years
Posts: 3,563
Mentioned: 1 Post(s)
Tagged: 1 Thread(s)
Quoted: 367 Post(s)
Garage
Quote:
Originally Posted by army6741 View Post
Yes I did Jim. that was his message today. I will be going there Monday to discuss the problem. He has been doing this for thirty years. will discuss the article with him. thanks to Bear also.
OK, good. Wanted to make sure because I thought there was some info that might shed some light on your situation.

I also know the main cap crush is important and this may also effect the seal. Here is what I found on the web: "The main bores must be inspected after the block is cleaned. You check for straightness and diameter size. The straightness is brought in by properly clipping the main caps, and then a skilled hone operator must hone the main bores carefully. We find that the housing bore size should be kept to the middle or to the minimum to maintain good bearing crush. NEVER PAST THE MIDDLE. Loose housing bores are the main culprit behind spun bearings. On a 3.250 main bore, (421/428/455) the factory says; 3.4380" - 3.4390". We use 3.4380" - 3.4385"."

Again, am sure your machinist knows this and probably has done this, but check out the BOP seal and installation on page 56 of this article: http://www.nitemareperformance.com/i...Blueprint1.pdf

And this might be a long shot, but if the rear main is moving around at all, it could be off just enough to create a problem. Check out page 53 with regards to the longer dowel pins used to locate the main caps more securely: http://www.nitemareperformance.com/i...Blueprint1.pdf

Eventually your machinist will get it. I'm sure he is pretty frustrated trying to figure it out.
PontiacJim is offline  
Sponsored Links
Advertisement
 
Reply

  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, Lemans & GTO Complete Engine Compartment Discussion

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Pontiac GTO Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Similar Threads
Thread Thread Starter Forum Replies Last Post
Rear Main Seal?? Pontiac 350 Kip Page 1964-1974 Tempest, LeMans & GTO Technical and Electrical Wiring 3 10-31-2009 03:51 PM
Rear main seal replacement tv66 1964-1974 Tempest, LeMans & GTO Technical and Electrical Wiring 10 10-04-2009 08:17 AM
68 Gto Rear Main Seal Leak khinton 1964-1974 Tempest, Lemans & GTO General Discussion 16 03-14-2009 06:01 PM
Rear main seal 66 GTO Kentucky_GTO 1964-1974 Tempest, LeMans & GTO Technical and Electrical Wiring 5 04-26-2008 07:07 PM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome