L27 heads - Rockers on 3/8 bolts - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


Performance, Brainstorming & Tuning Talk about modifications, or anything else associated with performance enhancements. Have a new idea for performance/reliability? Post it here. No idea is stupid! (please use Detailing and Appearance for cosmetic ideas)

Reply
 
 
 
Thread Tools Search this Thread
Old 03-29-2010, 04:15 PM   #1
Senior Member
True Car Nut
Thread Starter
 
xtremerevolution's Avatar
 
Join Date: Jun 2007
Location: New Lenox, IL
Posts: 2,478
Thanks: 0
Thanked 0 Times in 0 Posts
xtremerevolution is on a distinguished road
Default L27 heads - Rockers on 3/8 bolts

So I have a bit of a problem. I've been dealing with a guy here on the Bonneville Forum regarding the purchase of an engine for parts. I was going to drive up to Philips, Wisconsin, from New Lenox, IL (a ~400 mile drive) to pull the parts off of the engine myself. Instead, he needed to scrap the block so he pulled the parts off for me.

I needed the heads in particular for my 95 L27 as I have a burned valve and figured it would be cheaper and easier to get these heads with 85k miles on them, which I was told are from a 93 or 94 Park Avenue or Lesabre (I forget which), than it would be to have my 214k mile heads rebuilt by a machine shop.

I went and picked up the heads on Saturday, brought them home, and today I started cleaning them. I noticed while cleaning them that the factory rocker arms weren't roller rockers as they were on the later year heads. This also meant that the rocker arms use 3/8" bolts instead of the 5/16" bolts that my heads use.

This is a bit of a problem for me because I have Yella Terra 1.9 ratio roller rockers, which I need to transfer over to the new heads. I need to know if, aside from the thread size in the heads, if there is ANY difference between the 3/8" bolt heads and the 5/16" bolt heads.

If there isn't a difference, I'd appreciate it if anyone could tell me what my options are. I could obviously drill out the rocker bracket and the rocker arms to fit 3/8" bolts and find some allen head 3/8" bolts, but I need a second opinion. It would be 1/8" of a difference to drill out.

Any advice would be appreciated. If I bought these heads, I'd like to try to make them work, as I spent a good deal of money on them and the rest of the parts off that engine, and another $80 in gas to pick them up.

Last edited by xtremerevolution; 03-29-2010 at 04:21 PM.
xtremerevolution is offline   Reply With Quote
Old 03-29-2010, 05:48 PM   #2
Senior Member
True Car Nut
Thread Starter
 
xtremerevolution's Avatar
 
Join Date: Jun 2007
Location: New Lenox, IL
Posts: 2,478
Thanks: 0
Thanked 0 Times in 0 Posts
xtremerevolution is on a distinguished road
Default

Well since nobody'* replied so far, I figure I'll give you all an update. I found studs that would work at lowes. The head of the studs fits perfectly inside the roller rocker arm, so all I have left to do is drill out the rocker seats and the rocker arms themselves and they *should* fit. This is of course, assuming that aside from the thread size in these heads, everything is 100% identical.
xtremerevolution is offline   Reply With Quote
Old 03-29-2010, 06:00 PM   #3
Retired Senior Admin

Expert Gearhead
 
Danthurs's Avatar
 
Join Date: May 2006
Location: Sheboygan Wisconsin
Posts: 29,661
Thanks: 0
Thanked 16 Times in 13 Posts
Danthurs is a name known to allDanthurs is a name known to allDanthurs is a name known to allDanthurs is a name known to allDanthurs is a name known to allDanthurs is a name known to all
Default

Some times you need to give a little time for a reply. Many of us work. Try asking Billboost, he might have a answer.
Danthurs is offline   Reply With Quote
Old 03-29-2010, 09:28 PM   #4
Senior Member
True Car Nut
 
Purplehazeir's Avatar
 
Join Date: Sep 2008
Location: Arlington, WA
Posts: 7,979
Thanks: 0
Thanked 1 Time in 1 Post
Purplehazeir is on a distinguished road
Default

Before you do any drilling and or threading, definitely ask Bill his thoughts. Sometimes removing just 1/8" of material is enough to cause a failure point!
Purplehazeir is offline   Reply With Quote
Old 03-30-2010, 12:12 AM   #5
Senior Member
True Car Nut
Thread Starter
 
xtremerevolution's Avatar
 
Join Date: Jun 2007
Location: New Lenox, IL
Posts: 2,478
Thanks: 0
Thanked 0 Times in 0 Posts
xtremerevolution is on a distinguished road
Default

Quote:
Originally Posted by Purplehazeir View Post
Before you do any drilling and or threading, definitely ask Bill his thoughts. Sometimes removing just 1/8" of material is enough to cause a failure point!
I know, but its either this or I find new heads and I've wasted all this money.

At this point, I don't think drilling 1/8" into the material will cause a failure point, as I'm only drilling into the rocker arm pivot mount, not the arm itself. Therefore, I'm not weakening the parts that experience the most stress. The pivot mount never moves. Here are some photos that should help.

Roller rocker with factory bolt:
Name:  IMG_4165.jpg
Views: 15
Size:  38.5 KB

Pivot mount I need to drill 1/8" larger (its that part in the middle):
Name:  IMG_4168.jpg
Views: 15
Size:  34.0 KB

Rocker base I also need to drill 1/8" larger. Comparison of 3/8" bolt and 5/16" bolt:


3/8" bolt on top of the rocker base:
Name:  IMG_4172.jpg
Views: 16
Size:  42.2 KB

Comparison of rocker, base, and both bolts:
Name:  IMG_4170.jpg
Views: 13
Size:  53.0 KB

Last edited by xtremerevolution; 03-30-2010 at 12:20 AM.
xtremerevolution is offline   Reply With Quote
Old 03-30-2010, 03:24 AM   #6
Senior Member
Posts like a 4 Banger
 
2000bonny's Avatar
 
Join Date: Jan 2010
Posts: 114
Thanks: 0
Thanked 0 Times in 0 Posts
2000bonny is on a distinguished road
Default

I'm sorry for that. I did pull that motor from a 94 buick lesabre. I'm not sure why the studs aren't what you wanted. The door tag says 02/94. I have that wrote on the paper tag I had put on the engine alone with the 85,000 miles. Please accept my apology as I'm not sure on all the internal parts that may or may not cross over.
thanks
craig
2000bonny is offline   Reply With Quote
Old 03-30-2010, 08:44 AM   #7
DINOSAURUS BOOSTUS

Expert Gearhead
 
BillBoost37's Avatar
 
Join Date: Mar 2005
Location: Enfield, CT
Posts: 41,391
Thanks: 0
Thanked 0 Times in 0 Posts
BillBoost37 is a glorious beacon of lightBillBoost37 is a glorious beacon of lightBillBoost37 is a glorious beacon of lightBillBoost37 is a glorious beacon of lightBillBoost37 is a glorious beacon of lightBillBoost37 is a glorious beacon of light
Default

Sorry..I don't have much info other that what we can search/find.
BillBoost37 is offline   Reply With Quote
Old 03-30-2010, 09:55 AM   #8
Retired Senior Admin

Expert Gearhead
 
Danthurs's Avatar
 
Join Date: May 2006
Location: Sheboygan Wisconsin
Posts: 29,661
Thanks: 0
Thanked 16 Times in 13 Posts
Danthurs is a name known to allDanthurs is a name known to allDanthurs is a name known to allDanthurs is a name known to allDanthurs is a name known to allDanthurs is a name known to all
Default

It may be only 1/8" But how can you be sure you have that dead center. We've see HS roller rockers with bad wear because the pedistals were not perfect. Will you have the same problem here? You may be better adding a helicoil in the head and use the proper rocker bolt.
Danthurs is offline   Reply With Quote
Old 03-30-2010, 12:09 PM   #9
Senior Member
True Car Nut
Thread Starter
 
xtremerevolution's Avatar
 
Join Date: Jun 2007
Location: New Lenox, IL
Posts: 2,478
Thanks: 0
Thanked 0 Times in 0 Posts
xtremerevolution is on a distinguished road
Default

Quote:
Originally Posted by Danthurs View Post
It may be only 1/8" But how can you be sure you have that dead center. We've see HS roller rockers with bad wear because the pedistals were not perfect. Will you have the same problem here? You may be better adding a helicoil in the head and use the proper rocker bolt.
I would have a machine shop do the drilling, and I'm not quite sure if I want to mess with a helicoil. I'm wondering how secure those things really are when I really need those things to stay put permanently. Where can I get a helicoil kit?

Last edited by xtremerevolution; 03-30-2010 at 12:11 PM.
xtremerevolution is offline   Reply With Quote
Old 03-30-2010, 12:14 PM   #10
Senior Member
True Car Nut
Thread Starter
 
xtremerevolution's Avatar
 
Join Date: Jun 2007
Location: New Lenox, IL
Posts: 2,478
Thanks: 0
Thanked 0 Times in 0 Posts
xtremerevolution is on a distinguished road
Default

Quote:
Originally Posted by 2000bonny View Post
I'm sorry for that. I did pull that motor from a 94 buick lesabre. I'm not sure why the studs aren't what you wanted. The door tag says 02/94. I have that wrote on the paper tag I had put on the engine alone with the 85,000 miles. Please accept my apology as I'm not sure on all the internal parts that may or may not cross over.
thanks
craig
I'll be damned. I wonder if the engine you had was a completely different design for some strange reason.

I can't just tap out the threads in the block, as they are bigger than the bolts I need for the roller rockers. My option is now to either have the rockers professionally drilled, or to get a heli coil kit.
xtremerevolution is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
are 3.8 L. heads interchangable with 4.3 L. heads? Hay Bay Woody General GM Chat 1 06-21-2010 06:32 PM
Series 1 roller rockers vs Series 2 roller rockers xtremerevolution Performance, Brainstorming & Tuning 7 06-04-2010 07:52 PM
L27 rockers on LN3 question about guide plate. mAsalicio Performance, Brainstorming & Tuning 4 05-28-2007 01:41 PM
INTENSE S3 Heads and 1.8:1 Roller Rockers = Rogue Performance, Brainstorming & Tuning 14 03-23-2006 06:14 PM
L27 heads on a LN3? OLBlueEyesBonne Performance, Brainstorming & Tuning 6 03-08-2005 07:29 PM


Tags
3/8, 5/16, bolts, heads, rocker bolts, rockers, valvetrain

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not 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 Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 02:17 PM.


We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.