Loose Wrist Pin In Rod - Team Camaro Tech
Team Camaro Tech join team camaro
Camaro Parts at SS396.com     
GROUND UP & SS396.com         
Official Sponsor of Team Camaro

Auto Insurance

Registered users (free) do not see these large ads

Engine General Engine Discussion.

Thread Tools Display Modes
Old Apr 22nd, 13, 05:13 PM
69-er 69-er is offline
Gold Lifetime Member

Join Date: Oct 1999
Location: Alamogordo, NM, USA
Posts: 895
Default Loose Wrist Pin In Rod

What would cause a wrist pin to come loose in the rod? The engine developed a knock and upon tear down I found that the wrist pin had moved back against the cylinder wall and gouged two grooves in it. It's a factory 68 Firebird 400 with the exception of 9.5 pistons and a mild cam. The engine has 1,000 miles on it since a complete rebuild.

A little background:

There have been two sets of pistons installed recently. The first set was during the first rebuild, 7,000 miles ago. The second set was after the engine overheated and the engine rebuilt again. The overheating caused piston and cylinder scuffing on two cylinders. The majority of the damage was with the same cylinder as the loose pin. The adjacent cylinder also had a little bit less scuffing.

I'm thinking the overheating had something to do with it. I'm wondering if the machine shop should have detected a little bit less force required to remove the damaged piston. I'm sure if the overheating did in fact cause the loose pin, it should have been noticed then.

At this time, the pin is loose enough to be pushed out with light tapping.

Any ideas? Thanks!
Attached Thumbnails
Click image for larger version

Name:	IMG_5205.jpg
Views:	55
Size:	55.3 KB
ID:	33321   Click image for larger version

Name:	IMG_5208 small.jpg
Views:	55
Size:	118.0 KB
ID:	33322  
Current Project:
66 Chevy C10 Resto-Mod
Next In Line: 69 Z/28 Resto-Mod
Reply With Quote Quick reply to this message
Sponsored Links
Old Apr 22nd, 13, 07:12 PM
Everett#2390's Avatar
Everett#2390 Everett#2390 is offline

<Jake-68's rule
Join Date: Sep 2000
Location: Va Beach VA
Posts: 28,611
Default Re: Loose Wrist Pin In Rod

Shops, as I remember, use a stove to heat the small rod end to cherry red, then insert the rod while hot, into the piston and press the pin in place using a small hydraulic press. If the tech wasn't watching the pressure gauge, he/she would never know the 'force' used to press the pin in place.

My thought is the Pontiac block, same cylinder on both rebuilds, or a faulty piston rod, as in overheated and has taken a different dimension since then, hence the looseness.

Maybe the professional engine builders will diverge their knowledge.
Give a man a rescued dog for the health of both their souls.
'With age comes wisdom, but then wisdom ages you even more.' Other Stuff
Reply With Quote Quick reply to this message
Old Apr 22nd, 13, 09:00 PM
69Z28's Avatar
69Z28 69Z28 is offline
Gold Lifetime Member

Join Date: Oct 2000
Location: Delaware
Posts: 2,289
Default Re: Loose Wrist Pin In Rod

Yeah as Everette said. I was reading the How to rebuild Chevy engine book today and there was something in it about rods getting damaged at the wrist pin if the engine was to overheat. It can happen according to the book, maybe from before the last engine build?
"MY Z"
06A 1969 Camaro Z28
X33D80 69 B 711 Black Stripes
Console w/tach and gauges.
Reply With Quote Quick reply to this message
Sponsored Links
Gear in this thread - Powered by O'Reilly Auto Parts
Team Camaro Tech > First Generation Camaro Info and Tech - 1967- 1969 "Where it all started" > Engine      Current Topic: Loose Wrist Pin In Rod
Quick Reply

Register Now

In order to be able to post messages on the Team Camaro Tech forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.
Confirm Password:
Email Address
Please enter a valid email address.
NOTE we receive a lot of registrations with bad email addresses. IF you do not receive your confirmation email you will not be able to post. contact support and we will try and help.
Be sure you enter a valid email address and check your spam folder as well.

Email Address:
First Name
Rather than just Hot69, gotta real name?
One last thing to do to slow down the spammers
Enter the first letter of this word: Camaro


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

Thread Tools
Display Modes

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

Forum Jump

All times are GMT -7. The time now is 08:03 AM.

Camaros.net - 2009 AutoForums.com