broken rocker stud #8 exhaust vortec heads - 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 03-07-2011, 12:41 AM
psbaker75's Avatar
Registered User
 
Join Date: Mar 2011
Location: riverside, ca
Posts: 60
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
broken rocker stud #8 exhaust vortec heads

Ok, here's the info sb 350 with 062 vortec heads, press in studs, stock self-aligning rockers, summit valve spring kit pn 174001 (to allow more lift w/o head mods), comp thumpr cam pn 12-600-4. Had trouble w/ the timing due to a bad vac canister and stuck mechanical advance on the GM hei dizzy, so I squared that all up and started noticing a whining noise. Pulled out the stethoscope and started listening, when I heard a noise that sounded like rocker chatter, so I pulled the valve cover on the left bank only to find that #8 cyl was shut down. Exhaust rocker was laying on the head and the intake pushrod on the same cyl was broken in 3 pieces. I'm bringing it to the machine shop in the morning to have the stud replaced, but I want to prevent something similar from happening in the future. I have a new set of comp high energy pushrod coming, but does anyone have any insight into what the probable cause was in the first place? I really don't want to put a band aid on a broken leg.

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 03-07-2011, 03:06 AM
DoubleVision's Avatar
Not Considered a Senior Member
 
Last photo:
Join Date: Oct 2002
Location: Heart Of Dixie
Age: 40
Posts: 10,658
Wiki Edits: 0

Thanks: 15
Thanked 60 Times in 57 Posts
Did you have the valve guides clearanced for the use of a higher lift cam?
Did you check for interferance when you assembled the valve train and go over the valve train geometry?
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 03-07-2011, 06:29 AM
Registered User
 
Last photo:
Join Date: Dec 2010
Location: williamston sc
Posts: 319
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Sounds like you need to replace all the studs with screw in type.Stronger push rods are only going to shift the problem to the studs and or rocker arms.
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 03-07-2011, 11:20 AM
F-BIRD'88's Avatar
Yada Yada Yada
 
Last photo:
Join Date: Oct 2005
Location: Ontario, Canada
Posts: 9,284
Wiki Edits: 0

Thanks: 5
Thanked 399 Times in 393 Posts
You replaced the valve springs but did not address the issue of retainer to valve guide boss clearance at full valve lift.
Get the valve guide boss/seal combo cutter and arbor and fix it.
(shorten the guide boss, reduce diameter for aftermarket type seals)
Stock GM rockers may bind with more than .480" lift.
Lengthen the rocker arm slot or get long slot type.
You crashed the valve train. It takes a lot of force to break a rocker arm stud and bend a push rod. I bet you have at least 1 bent valve too now.

If you didn't want to do the vortec head valvetrain mods for high lift you should have stuck to a .450" lift rule cam.
EG: a Isky #201278 or #201288 will give the same rough racey idle of a thumpr cam without the high valve lift. Both have .450" lift.
Need better than stock vortec springs for max performance.
More torque and power than thumprs easier install, same radical rough racey idle. Lots of duration and overlap (106LSA) , Need a high stall converter for best results. Needs the distributor advance curve modified for best results.Degree them in to verify valve tming, best when slightly advanced (3 to 6deg advanced from straight up) 100 to 103 degree intake C/L.

This is the easy goof proof way of putting the "thumpy idle" in a vortec motor.
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 03-07-2011, 01:27 PM
cobalt327's Avatar
WFO
 
Last wiki edit: Intake manifold
Last journal entry: 1980 Malibu Wagon
Last photo:
Join Date: Mar 2009
Location: Atlanta
Age: 60
Posts: 5,037
Wiki Edits: 1616

Thanks: 128
Thanked 598 Times in 547 Posts
Quote:
Originally Posted by psbaker75
does anyone have any insight into what the probable cause was in the first place?
The installed height being too short, or insufficient retainer to guide boss clearance at full lift are two things that could be the cause.

What leads you to believe those springs will allow more lift before the retainer to guide boss clearance is an issue? I don't recall seeing anything on that- not saying there isn't anything on it, just that I haven't seen it. A link would be appreciated.

Otherwise, cutting down the boss would be the best move at this point- along w/CAREFULLY inspecting the remaining valves/retainers/seals/etc. to be sure nothing else was damaged and just hasn't broken yet.

Here's a list of some areas of the valve train that need to be verified. This is a general guide, and is not all-inclusive. There is no substitute for physically measuring everything.
  • Springs for installed height
  • Coil bind
  • Retainer to seal/valve guide boss at full lift
  • Retainer to rocker
  • Trunnion to stud boss
  • Piston-to-valve clearance (both before and after TDC on overlap)
  • Push rod to guide slot in head (if used)
  • Can use EITHER self aligning rockers OR pushrod guide slots in head OR guide plates, not two or more of these at the same time
  • ”Rails” of self aligning rockers (if used) to retainer
  • Rocker to valve tip (by adjusting guide plates if used)
  • Rocker slot to stud (if using stamped/cast rockers w/pivot balls)
  • Proper geometry (push rod length)
  • Rocker/polyloc to valve cover or baffle
  • Camshaft endplay
  • Distributor shaft and gear endplay
  • Distributor gear material compatible with cam material
  • Hydraulic lifter preload or solid lifter lash setting
  • Timing set phasing
  • Cam gear to crank gear alignment
  • Cam gear end play if roller cam
  • If using the SBC OEM roller lifters and retainers (aka dogbones), lobe lift must be kept below 0.354” so the lifters don’t lose contact w/the retainers
  • Cam lobe to connecting rod on strokers
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 03-07-2011, 09:35 PM
psbaker75's Avatar
Registered User
 
Join Date: Mar 2011
Location: riverside, ca
Posts: 60
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Thanks for all the great feedback. First, the increased lift clearance info for the springs came from summit tech support, they recommended the springs stating "they will increase lift range to .480 with no head mods." I took it at face value (my mistake) after all of my research suggested I should machine the valve guides. I just ordered the valve guide cutter and arbor (comp cams pn 4726 and 4732) and also picked up the spring seat cutter pn 4718 so I'm going to cut down the valve guides, but I want to double check my info. Does .25" sound correct? Anyone have any input on how far down I should take them? Also, I'm only running single springs now, so should I hold off on cutting in the spring seat inside diameter or just go ahead and do it now since I have the heads off? Any negative impact from doing it now with the singles on it? It seems like every pic I could find of people who have modded their guides also modded the seats. Also, even though I'm only running stock 1.5 stamped rockers, should I open up the pushrod holes to allow for 1.6 later down the road or just wait and see if I ever decide to go that route before making that change?
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 03-07-2011, 10:09 PM
F-BIRD'88's Avatar
Yada Yada Yada
 
Last photo:
Join Date: Oct 2005
Location: Ontario, Canada
Posts: 9,284
Wiki Edits: 0

Thanks: 5
Thanked 399 Times in 393 Posts
You do not need to ask anyone how much to shorten the guide boss height.
on your vortec heads.
All you need to do is cut one guide boss for the new seals diameter and mock it up with a seal, valve, retainer and locks and measure between the new seal and the retainer. You need a minimum of the gross valve lift+.060" extra. make sure the seal is all the way down on the guide top.

now take it back apart and cut the guide boss shorter, with the seal dimater cutter to get the required additional clearance and re-mock it back up and double check. Now do the other 15 the same height as the first. A straight edge across the guide tops will show you the way. Not that hard to do. Do the other head the same way. Do one first, get it right check and then do all the rest the same.

When I do my 305HO heads for high lift and aftermarket seals, but stock diameter spring seats I routinely shorten the guide top by .200" for .550" lift stock GM retainers and locks and valves and aftermarket seals.

When we did my vortec heads we cut the spring seats for the 1.44" medium dual springs like the Comp 987's even thou I am running stock diameter isky racing springs right now. They run fine on the now larger spring seats.
I don;t remember exactly how much we shortended the guide boss top height but it was a good bit.

If you are going to do the larger spring seats, do the pressed in studs to screw in studs and guide plates conversion too.

When you install the new screwin studs put some RTV sealer on all the exhaust rocker stud threads. They hit water in the vortec heads. Don't forget to re-torque them after the heads are installed and after checking the push rod and guide plate slot. Sometimes minor adjustment of the pushrod guide plate position is nessessary. You will only have to do this once.

If you want to enlarge the push rod pass thru hole in the cylinder heads for 1.6 rockers make the hole longer towards the rocker stud, not wider. elongate the hole with a 5/16" rat tail file in a drill by about .030-.040". Thats all you need to do.

Use moderate cutting speed and something ( oil, auto trans fluid, cutting fluid, WD 40, Beer to lube and cool while cutting. Don't rush.
It can all be done on the bench with a decent electric drill.
High drill speed will overheat and dull the cutters.

Last edited by F-BIRD'88; 03-07-2011 at 10:30 PM.
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 03-08-2011, 10:41 AM
psbaker75's Avatar
Registered User
 
Join Date: Mar 2011
Location: riverside, ca
Posts: 60
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Ok, good info on the cutdown procedure, thanks. I checked the retainer to seal clearance when I got the head back and it came in at .438 on the valve that had the broken stud... well below my cam exhaust lift of .465. Once bitten, twice shy. I'm glad the cutter and arbor will be here tomorrow, so I will cut and re-check until I get it right. With my work schedule being what it is this week, I should have her up and running by Friday afternoon. I'll post some project pics as I'm going along so that maybe my experience with this can help someone else down the line.
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 03-08-2011, 05:36 PM
cobalt327's Avatar
WFO
 
Last wiki edit: Intake manifold
Last journal entry: 1980 Malibu Wagon
Last photo:
Join Date: Mar 2009
Location: Atlanta
Age: 60
Posts: 5,037
Wiki Edits: 1616

Thanks: 128
Thanked 598 Times in 547 Posts
Quote:
Originally Posted by psbaker75
I checked the retainer to seal clearance when I got the head back and it came in at .438 on the valve that had the broken stud... well below my cam exhaust lift of .465. Once bitten, twice shy. I'm glad the cutter and arbor will be here tomorrow, so I will cut and re-check until I get it right.
Good job

Now, be sure to check that none of the other pressed in studs have started to "pull" from the head. The time to catch them is NOW, before reassembling the heads and having problems down the road. Then roll the cleaned pushrods on a piece of glass, etc. to check them for straightness.

If it's in your budget, it would be a good investment to go w/screw in studs.
Reply With Quote Quick reply to this message
  #10 (permalink)  
Old 03-08-2011, 06:31 PM
psbaker75's Avatar
Registered User
 
Join Date: Mar 2011
Location: riverside, ca
Posts: 60
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
I'm replacing all of the pushrod just to be safe, and I will definitely check the other studs. I really wish I could just replace them all right now, but me and the wife got a little one on the way in May so money is real tight right now. I'm planning on some bottom end work in the next several months, so when I do that, I will definitely budget for the screw ins.
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:
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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Broken rocker stud, why two breaks? RAW Engine 20 07-17-2011 07:33 PM
Broken Rocker Arm Stud, Help to Remove RAW Engine 10 02-15-2006 03:23 PM
pontiac 389 broken rocker stud tree_entz Engine 4 06-08-2004 01:29 PM
broken rocker stud removal smokin 69 Engine 4 10-30-2003 07:11 PM
348 Chevy broken rocker arm stud NAIRB Engine 1 12-16-2002 05:56 PM


All times are GMT -6. The time now is 10:52 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.