Drop in Z28 springs needs many shims? - 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 06-16-2010, 06:58 PM
Member
 
Last photo:
Join Date: Oct 2004
Location: IL
Age: 47
Posts: 238
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Drop in Z28 springs needs many shims?

I went to do my first valve spring upgrade today on my 882 sbc heads. My new springs are rated at 110lbs at 1.710" and 305lbs at .500 lift.I bought the proper valve spring height micrometer but when I went to do my first valve I found that I needed four .060" shims and one .030" shim to get to the installed 1.710 valve height. Is this right to need so many shims?

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 06-16-2010, 07:57 PM
BOBCRMAN@aol.com's Avatar
Member
 
Last photo:
Join Date: May 2002
Location: Holly, michigan
Posts: 8,131
Wiki Edits: 0

Thanks: 25
Thanked 267 Times in 250 Posts
Sounds like you are not using the mic. correctly.

Most spring mics, when used on 1.25 retainers, require the use of a shim under the stock retainer. Otherwise the small retainer falls to the inner step on the mic.

The heads will probably need extra shims in the exhaust spring pockets if you remove the rotators (recommended) and use conventional retainers.

Try mic, then a shim, then retainer, then locks. Determine height then subtract thickness of the top shim. This will give you true spring installed height.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 06-16-2010, 08:16 PM
406 bug's Avatar
9.82 @ 139mph
 
Last wiki edit: Finding vacuum leaks Last photo:
Join Date: Nov 2007
Location: phoenix, arizona
Posts: 582
Wiki Edits: 1

Thanks: 0
Thanked 1 Time in 1 Post
If you are using the same retainer why not obtain and compare the spec height of your old spring with the new one to see if your shim pack is "in the ball park".
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 06-16-2010, 08:57 PM
OLNOLAN's Avatar
Registered User
 
Last photo:
Join Date: Apr 2009
Location: Louisiana
Posts: 1,046
Wiki Edits: 0

Thanks: 371
Thanked 98 Times in 81 Posts
Exhaust Valve Rotators

Hey Man, If your are eliminating a valve rotator, shims are not the best way to do it. On big blocks the rotator is .300", you need to replace them with a cupped spring locater seat. That much shim is going to make your springs start doing a dance, which is not good. You may want to look into this more on your small block heads. I personally have never come across a small block head with them, but I have used Comp rotator eliminators on more than one big block w/781 heads. olnolan
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 06-17-2010, 03:49 AM
cobalt327's Avatar
WFO
 
Last wiki edit: Intake manifold
Last journal entry: 1980 Malibu Wagon
Last photo:
Join Date: Mar 2009
Location: Atlanta
Age: 59
Posts: 5,037
Wiki Edits: 1616

Thanks: 128
Thanked 597 Times in 546 Posts
On stock SBC heads w/rotators, the installed height is lessened by the added thickness of the rotator, so there shouldn't be a need for a bunch of shims to make up for the rotator's thickness.

I use a snap gage (just haven't been able to justify the cost a spring height mic ), so I can't speak to the need for a shim under the retainer, but it sounds plausible- and this would throw the measurement off by the amount of the step that's on the retainer. I don't have a stock retainer in my hand, but the step isn't very large, maybe 0.080" at a WAG?

But there's no earthly way that you should need over 1/4"(!!!) of shims to obtain a 1.710" installed spring height unless there are other extenuating circumstances.

Are the valves, retainers and locks stock-spec parts?
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 06-17-2010, 04:42 AM
Member
 
Last photo:
Join Date: Oct 2004
Location: IL
Age: 47
Posts: 238
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Yes , just stock style stuff. Last night I reviewed how to use the mic in the Competition Products catolog. Seems that I'm doing it right. I also noticed that the more expensive drop in springs have an installed height of 1.850".If I had got these springs I would only need a shim or two. I'm going to measure the mic today, maybe it should have been a reject . If it's ok I'll stop at the machine shop on the way home for a little hands on class.
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 06-17-2010, 04:48 AM
Member
 
Last photo:
Join Date: Oct 2004
Location: IL
Age: 47
Posts: 238
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
"Most spring mics, when used on 1.25 retainers, require the use of a shim under the stock retainer. Otherwise the small retainer falls to the inner step on the mic."
Yes this is what is happening! But the instructions say to simply put the mic in place of the spring. Nothing about putting a shim under the retainer and subtracting it.
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 06-17-2010, 05:30 AM
cobalt327's Avatar
WFO
 
Last wiki edit: Intake manifold
Last journal entry: 1980 Malibu Wagon
Last photo:
Join Date: Mar 2009
Location: Atlanta
Age: 59
Posts: 5,037
Wiki Edits: 1616

Thanks: 128
Thanked 597 Times in 546 Posts
Just to recap, what you're measuring is the distance between the retainer- where the outer spring actually contacts it- to the spring seat on the head itself. This can be measured fairly closely w/a machinist's rule or a caliper's depth function- at least close enough to see that the height mic is accurate or not.

Often, it's just a matter of learning to read an individual tool, so be sure of what you think you're seeing IS what you're seeing! lol

Longer than stock springs will have an effect on the installed height, and are commonly used on performance heads and cases where additional spring installed height is needed. You should check the overall length of the valve and compare it to a stock length spring of 4.910".

The retainer design and even the locks can alter the installed height.

Last edited by cobalt327; 06-17-2010 at 05:35 AM.
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 06-17-2010, 06:11 AM
Member
 
Last photo:
Join Date: Oct 2004
Location: IL
Age: 47
Posts: 238
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Well, I just measured the mic, Bobcrman hit the nail on the head. Crazy, the sbc retainer fits perfect in the second step of the valve spring mic but that throws the measurment off 1/8" .

Whats the benifet of keeping the rotator cups off?

Last edited by upstand2; 06-17-2010 at 06:18 AM.
Reply With Quote Quick reply to this message
  #10 (permalink)  
Old 06-17-2010, 06:19 AM
cobalt327's Avatar
WFO
 
Last wiki edit: Intake manifold
Last journal entry: 1980 Malibu Wagon
Last photo:
Join Date: Mar 2009
Location: Atlanta
Age: 59
Posts: 5,037
Wiki Edits: 1616

Thanks: 128
Thanked 597 Times in 546 Posts
Quote:
Originally Posted by upstand2
Well, I just measured the mic, Bobcrman hit the nail on the head. Crazy, the sbc retainer fits perfect in the second step of the valve spring mic but that throws the measurment off 1/8" .
OK, so you have accounted for 0.125" of the 0.270" that you measured earlier. Any idea where the other 0.145" is or went?
Quote:
I needed four .060" shims and one .030" shim to get to the installed 1.710 valve height
Reply With Quote Quick reply to this message
  #11 (permalink)  
Old 06-17-2010, 06:34 AM
F-BIRD'88's Avatar
Yada Yada Yada
 
Last photo:
Join Date: Oct 2005
Location: Ontario, Canada
Posts: 9,153
Wiki Edits: 0

Thanks: 5
Thanked 380 Times in 374 Posts
Once you get the height mic figured out you'll find that the smog heads have a deeper exhaust spring seat than the intakes. When eliminating the rotators use a .105" stack of shims to compensate. 60+30+15

The oil shield is .030"
comp cams #4753 shim set
Reply With Quote Quick reply to this message
  #12 (permalink)  
Old 06-17-2010, 07:22 AM
BOBCRMAN@aol.com's Avatar
Member
 
Last photo:
Join Date: May 2002
Location: Holly, michigan
Posts: 8,131
Wiki Edits: 0

Thanks: 25
Thanked 267 Times in 250 Posts
The reason to eliminate the rotators is. They are quite heavy. They are also known to come apart at high rpm.

Any lightening of the valve train is a plus. Also the shields are usually eliminated with lifts over .470. They too have been known to break and cause problems.

Good luck.
Reply With Quote Quick reply to this message
  #13 (permalink)  
Old 06-17-2010, 07:23 AM
Member
 
Last photo:
Join Date: Oct 2004
Location: IL
Age: 47
Posts: 238
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Quote:
Originally Posted by cobalt327
OK, so you have accounted for 0.125" of the 0.270" that you measured earlier. Any idea where the other 0.145" is or went?
I think F-bird covered the missing .115"( my first valve was the exhaust).
I'll still need an additional .010" shim to get it at the recomended height. I do have the Comp #4753 shim set.Thanks alot everyone!
Reply With Quote Quick reply to this message
  #14 (permalink)  
Old 06-17-2010, 01:41 PM
Silverback's Avatar
Boost Retard
 
Last photo:
Join Date: Mar 2007
Location: DC Metro
Posts: 377
Wiki Edits: 0

Thanks: 1
Thanked 2 Times in 2 Posts
When you guys get rid of the rotators and shields, do you bother to install the o-ring below the keeper groove?
Reply With Quote Quick reply to this message
  #15 (permalink)  
Old 06-17-2010, 04:43 PM
BOBCRMAN@aol.com's Avatar
Member
 
Last photo:
Join Date: May 2002
Location: Holly, michigan
Posts: 8,131
Wiki Edits: 0

Thanks: 25
Thanked 267 Times in 250 Posts
NO, as a matter of fact. Once I change a head to high performance status, (no rotators and plain retainers, no shields). I use rubber umbrellas as a minimum (customer with tight pockets). The rubber O-ring is very ineffective after the metal shield is removed. Most budget springs clear the small universal rubber umbrella seals.

If the head is a later model that can handle "positive" seals. I use the Blue type seal on the intakes and an umbrella on the exhaust.

GM quit using the O-rings in the 90's. Most of the aftermkt valves are now single groove.
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


Similar Threads
Thread Thread Starter Forum Replies Last Post
V8 Convertible Beetle Leaf Springs??? zbhover Suspension - Brakes - Steering 1 01-26-2009 09:44 PM
Question with Valve Springs Diameter Houman SS '70 Engine 6 03-17-2008 11:31 AM
vortec drop in beehive spring help Mustangsaly Engine 4 11-12-2007 06:00 PM
Z28 springs gods_flame03 Engine 3 08-06-2007 10:57 PM
valve springs seats or shims??? 69elcaminoss Engine 3 03-27-2004 09:22 PM


All times are GMT -6. The time now is 03:21 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.