changing amount of advance on GM HEI - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



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

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 09-19-2004, 04:28 PM
cool rockin daddy's Avatar
Member
 
Join Date: Aug 2003
Location: wherever cool cars are
Posts: 1,533
Wiki Edits: 0

Thanks: 0
Thanked 4 Times in 4 Posts
Cool changing amount of advance on GM HEI

Hey guys, does anybody know approximately how much to shorten the slots on the advance mechanism to reduce the amount of mechanical advance on the HEI? Can you use epoxy or something similar to that to actually shorten the slots or does it need to be brazed or welded. Thanks.

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 09-19-2004, 05:42 PM
Hotrodders.com Moderator
 

Last journal entry: PICTURE TEST
Join Date: Jan 2004
Location: york pa
Age: 57
Posts: 2,783
Wiki Edits: 0

Thanks: 0
Thanked 2 Times in 2 Posts
slot

If you make the slot .100 shorter you should get about 10 degrees at the crank. I guess you could use jb weld or something but i always weld mine close.

Keith
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 09-19-2004, 05:43 PM
1BAD80's Avatar
The Smell of Nitro in the morn
 
Last wiki edit: How to adjust valves
Join Date: Jun 2001
Location: Mich
Posts: 2,408
Wiki Edits: 2

Thanks: 0
Thanked 3 Times in 2 Posts
Why ?
If you want to adjust it pick up a new adjustable vacuum advance unit so you can dial it in correctly not to much $ for it.
__________________
Luv the smell of NITRO in the morning.
Reply With Quote Quick reply to this message
 
  #4 (permalink)  
Old 09-19-2004, 05:56 PM
1BAD80's Avatar
The Smell of Nitro in the morn
 
Last wiki edit: How to adjust valves
Join Date: Jun 2001
Location: Mich
Posts: 2,408
Wiki Edits: 2

Thanks: 0
Thanked 3 Times in 2 Posts
I would get the new vac advance first before you do anything else. You can adjust it out.
__________________
Luv the smell of NITRO in the morning.
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 09-19-2004, 06:05 PM
killerformula's Avatar
Hotrodders.com Moderator
 
Last wiki edit: Carburetor
Last journal entry: Clean up
Join Date: Oct 2003
Location: Northeast
Age: 39
Posts: 3,519
Wiki Edits: 3

Thanks: 30
Thanked 39 Times in 26 Posts
There should be no vacuum advance for a WOT take off, that's all mechanical. Your vacuum signal at WOT is nil. Initial and mechanical advance are only ever responsable for about 36-38 degrees, anything beyond that is vacuum. If you're pinging at 46 degrees you don't need to mess with your mechanical, just take off part of the partial throttle vacuum with the canister like george is talking about.

K
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 09-19-2004, 10:10 PM
cool rockin daddy's Avatar
Member
 
Join Date: Aug 2003
Location: wherever cool cars are
Posts: 1,533
Wiki Edits: 0

Thanks: 0
Thanked 4 Times in 4 Posts
Cool

Jmark hit the nail on the head. Need more initial advance but mechanical advance is too much. Braze, weld, epoxy, or what is best way to permantly shorten the slots in the mechanism?
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 09-19-2004, 10:14 PM
killerformula's Avatar
Hotrodders.com Moderator
 
Last wiki edit: Carburetor
Last journal entry: Clean up
Join Date: Oct 2003
Location: Northeast
Age: 39
Posts: 3,519
Wiki Edits: 3

Thanks: 30
Thanked 39 Times in 26 Posts
IF you're tuned for max vacuum at idle, or close thereto, then you're fine on initial timing. If Jmark wants more timing on takeoff he can use lighter springs!

K
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 09-19-2004, 11:42 PM
GoneNova/406's Avatar
Member
 
Join Date: Aug 2003
Location: columbus,ohio
Age: 64
Posts: 1,161
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
why don't you simply adv. the cam 4* if you want more take off.
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 09-20-2004, 09:36 AM
GoneNova/406's Avatar
Member
 
Join Date: Aug 2003
Location: columbus,ohio
Age: 64
Posts: 1,161
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
jegs has an msd curve kit that has 3 sets of springs and 5 bushins for $10.00.they will also have a diagram with it thatshows you how to use the springs as a set or how to mix them up just as they will with the bushings.there are so many combinations at all different rpm's that you should be able to make something work.i got one with the distributor i bought from them so it should come with the curve kit to.this kit is better than mr. gasket and some of the others.
Reply With Quote Quick reply to this message
  #10 (permalink)  
Old 09-20-2004, 11:47 AM
1BAD80's Avatar
The Smell of Nitro in the morn
 
Last wiki edit: How to adjust valves
Join Date: Jun 2001
Location: Mich
Posts: 2,408
Wiki Edits: 2

Thanks: 0
Thanked 3 Times in 2 Posts
You must be careful when advancing cams.
CompCams has 4* advance machined into them to allow for ware.
So at straight up its 4* advanced, it depends on the cam manuf.
__________________
Luv the smell of NITRO in the morning.
Reply With Quote Quick reply to this message
  #11 (permalink)  
Old 09-20-2004, 07:22 PM
johnsongrass1's Avatar
Race it, Don't rice it!
 
Join Date: Jul 2002
Location: Columbia, Mo
Age: 43
Posts: 7,086
Wiki Edits: 0

Thanks: 114
Thanked 748 Times in 614 Posts
Quote:
it took off great from a stop, but pinged bad as I got further into it.
Quote:
There should be no vacuum advance for a WOT take off, that's all mechanical.
I think jmark meant after the car got rolling and the vacuum came up from the reduced load. A sure bet it's the vacuum advancing too much. It goes away after you hammer into it again.
Reply With Quote Quick reply to this message
  #12 (permalink)  
Old 09-20-2004, 10:16 PM
cool rockin daddy's Avatar
Member
 
Join Date: Aug 2003
Location: wherever cool cars are
Posts: 1,533
Wiki Edits: 0

Thanks: 0
Thanked 4 Times in 4 Posts
Cool

you guys completely over analyzed the question! I want to run more initial advance to get a better mixture burn at lower speeds, better economy, and generally follow the recommendations for my Speed Demon carb. Instead ot telling me the best way to modify my distributor, which is what I asked for, a discussion on advancing the cam ensues! When the thread didn't talk about cams it addressed using springs to change the rate of the advance, not the amount of advance. I am grateful for the replies, they just didn't address the question!!!!
Reply With Quote Quick reply to this message
  #13 (permalink)  
Old 09-21-2004, 06:42 AM
Hotrodders.com Moderator
 

Last journal entry: PICTURE TEST
Join Date: Jan 2004
Location: york pa
Age: 57
Posts: 2,783
Wiki Edits: 0

Thanks: 0
Thanked 2 Times in 2 Posts
uh.....

I answered the question!!!!!! read my post......

Keith
Reply With Quote Quick reply to this message
  #14 (permalink)  
Old 09-21-2004, 06:16 PM
cool rockin daddy's Avatar
Member
 
Join Date: Aug 2003
Location: wherever cool cars are
Posts: 1,533
Wiki Edits: 0

Thanks: 0
Thanked 4 Times in 4 Posts
Cool

My humblest apologies Keith. You did answer it and I thank you for staying on the subject thread.
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:
Insurance
Please select your insurance company (Optional)

Log-in



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 01:24 PM.


Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.