Bent Push-Rod on Chevy SB 350! - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Engine
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 11-29-2004, 04:54 PM
32Hoopie's Avatar
Registered User
 
Last photo:
Join Date: Aug 2004
Location: Ventura County, CA
Age: 54
Posts: 10
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Question Bent Push-Rod on Chevy SB 350!

I have now bent one pushrod and broke another. #8 cylinder first, repaired it, ran for a month, then bent one on the other side #5. Also broke a Rocker Stud. Any ideas on what might cause this type of failure? Motor has about 1k miles on it.

Specs: Chevy SB 350 .030+, TRW Pistons #L2403-030, CompCam(mild) #270H, Roller Rockers w/Guides, Stock heads - #3890462 1.94/1.5, Edelbrock EPS intake w/600 carb.

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 11-29-2004, 05:03 PM
NXS's Avatar
NXS NXS is offline
wind & fire = guides to power
 
Last photo:
Join Date: Nov 2004
Location: Oklahoma
Posts: 1,534
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
I would check for binding between the pushrods and guide plates first.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 11-29-2004, 05:11 PM
BOBCRMAN@aol.com's Avatar
Member
 
Last photo:
Join Date: May 2002
Location: Holly, michigan
Posts: 8,129
Wiki Edits: 0

Thanks: 25
Thanked 267 Times in 250 Posts
You are making contact in the valve train somewhere. Check the top of the valveguide/seal for contact with the inner portion of the valve retainer. Usually on the exhaust side. Check for coil bind, also common if you are using rotators and the wrong head/spring combo. Check rocker arm geometry. also clearance from rocker to stud at full lift (.060 min)
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 11-29-2004, 05:13 PM
32Hoopie's Avatar
Registered User
 
Last photo:
Join Date: Aug 2004
Location: Ventura County, CA
Age: 54
Posts: 10
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
I did check the guides and they all seem to allow the pushrod plenty of freedom. What I don't understand is how do you break a Rocker-arm stud? Actually broke 2 of them...
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 11-29-2004, 05:18 PM
NXS's Avatar
NXS NXS is offline
wind & fire = guides to power
 
Last photo:
Join Date: Nov 2004
Location: Oklahoma
Posts: 1,534
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
Quote:
also clearance from rocker to stud at full lift (.060 min)
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 11-29-2004, 09:41 PM
sbchevfreak's Avatar
Licenced Automotive Technician
 
Last photo:
Join Date: Feb 2004
Location: Land of big Easter eggs, Alberta
Age: 34
Posts: 1,604
Wiki Edits: 0

Thanks: 8
Thanked 9 Times in 9 Posts
Over revving.
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 11-30-2004, 06:43 AM
Member
 
Last photo:
Join Date: Aug 2003
Location: Detroit, MI
Posts: 139
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Is your cam lift too high for the valve spring to compress? Did you use a different ratio rocker arm?

The push rod is the "fuse" to the valve system.

Check to see if your valve springs can be compressed enough. If the valve can only be depressed so far and the push rod wants to push more than somethings going to give.
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 12-03-2004, 05:09 PM
32Hoopie's Avatar
Registered User
 
Last photo:
Join Date: Aug 2004
Location: Ventura County, CA
Age: 54
Posts: 10
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Thanks for the thought. I don't know a lot about this motor (inherited), but I do know the cam is a little bit wild and the heads are stock. I'll keep looking...
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 12-03-2004, 06:59 PM
GoneNova/406's Avatar
Member
 
Join Date: Aug 2003
Location: columbus,ohio
Age: 58
Posts: 1,163
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
about two yrs ago i had a problem with using old head bolts and ended up replacing a head gasket and bought new bolts but when i put it back together i use a cheaper smaller timing chain and gear on it because i new i was going to be back in it in the very near future for something else and would use a better part then.soon i started bending 1 push rod at a time in the same aerea on the same side.i replaced them and started looking for the culprit and took the front cover off a cople of times in the valve covers constantly and soon i found it but almost by mistake.when i look behind the timing cover i didn't see the first two times that the timing chain was broke on one side(inside)but you really had to look hard to see it.i would drive it and be ok til i would get on the free way and stick my foot in it a little.or jump on it moving away from a lite.the chain never completely broke.
Reply With Quote Quick reply to this message
  #10 (permalink)  
Old 12-06-2004, 09:22 AM
32Hoopie's Avatar
Registered User
 
Last photo:
Join Date: Aug 2004
Location: Ventura County, CA
Age: 54
Posts: 10
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
That is really interesting, cuz I had talked that same scenario over with a neighbor and we kind of dismissed it as too far fetched. Getting to the timing cover on this hot rod is a real task, since I have almost no clearance between the pump and radiator, but it sounds like a worth while task. What's also odd is that the last time it broke we were just sitting at a stop light and Bam and then silence. We drive this car pretty mild so over-revving is not an issue, even at 65+ it's only turning about 2200 rpms, thanks to the 3.08s in the rear. Thanks again for the info...we keep looking...
Reply With Quote Quick reply to this message
  #11 (permalink)  
Old 08-07-2010, 02:56 PM
Registered User
 
Join Date: Aug 2010
Location: Kentucky
Posts: 4
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
brian storming

have you had any problems with the spark plug, missing a peace or bent? It kinda sounds like bad valve guide or bent valve steam. maby with the rocker arms off you can push the valve down to see if it moves freely.
Reply With Quote Quick reply to this message
  #12 (permalink)  
Old 08-07-2010, 09:30 PM
Registered User
 
Last photo:
Join Date: Jan 2007
Location: canada
Posts: 564
Wiki Edits: 0

Thanks: 0
Thanked 3 Times in 3 Posts
look at the date of this posting. thread died in late 06
Reply With Quote Quick reply to this message
  #13 (permalink)  
Old 08-08-2010, 08:46 AM
32Hoopie's Avatar
Registered User
 
Last photo:
Join Date: Aug 2004
Location: Ventura County, CA
Age: 54
Posts: 10
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
The final diagnosis was just weak Rocker Stud Bolts. I replaced all of them with some new ARP big dogs and everything has worked like a champ.
Reply With Quote Quick reply to this message

Recent Engine posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
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:

Log-in

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.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

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



All times are GMT -6. The time now is 11:48 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.