vacuum advance - 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 04-30-2011, 06:56 AM
Registered User
 
Last photo:
Join Date: Nov 2010
Location: southern Virginia
Age: 61
Posts: 88
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
vacuum advance

I have a 355 engine w/hei that the timing is advancing to much when the vacuum hose is reconnected after setting the timing. Anyone use an adjustable vacuum advance? If so which one (accel, summit, etc.) and does it do the job?

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 04-30-2011, 07:15 AM
cool rockin daddy's Avatar
1.21 giga-watts???!!!!
 
Join Date: Aug 2003
Location: wherever cool cars are
Posts: 1,535
Wiki Edits: 0

Thanks: 0
Thanked 3 Times in 3 Posts
Put "HEI tuning" in search box for this forum. bottom right hand side of page. Many answers to your query.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 04-30-2011, 09:03 AM
sqzbox's Avatar
My pipes are my music
 
Last photo:
Join Date: Sep 2009
Location: indiana
Age: 64
Posts: 2,938
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
Quote:
Originally Posted by rwa1015
I have a 355 engine w/hei that the timing is advancing to much when the vacuum hose is reconnected after setting the timing. Anyone use an adjustable vacuum advance? If so which one (accel, summit, etc.) and does it do the job?
It sounds to me like you have the vacuum hose hooked up to a full time vacuum port. You need to try and find the metered port and hook up to it and see if you get the results your looking for before you invest in an adjustable vacuum can. If you don't have a vacuum gauge, you can find the metered port by capping off the port you have your hose hooked to now and un-cap another port on the carb. that doesn't affect the idle speed when you take the cap off. That will be the metered port. The adjustable can doesn't control how much advance you get at idle but, it does control how soon the advance comes in.
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 04-30-2011, 09:08 AM
cool rockin daddy's Avatar
1.21 giga-watts???!!!!
 
Join Date: Aug 2003
Location: wherever cool cars are
Posts: 1,535
Wiki Edits: 0

Thanks: 0
Thanked 3 Times in 3 Posts
Really suggest you read the article "HEI tuning" before you make the mistake of running ported vacuum.
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 04-30-2011, 09:25 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 rwa1015
I have a 355 engine w/hei that the timing is advancing to much when the vacuum hose is reconnected after setting the timing. Anyone use an adjustable vacuum advance? If so which one (accel, summit, etc.) and does it do the job?
If the tip-in point is acceptable and all you need to do is limit the total amount the vacuum advance adds in, use a vacuum advance limiter plate like the Crane #99619-1, #99619 Instructions. Or you can make one.

On a performance SBC engine, 10-12 degrees added by the vacuum advance works out about right. This is providing the mechanical advance curve is correct.
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 04-30-2011, 04:22 PM
sqzbox's Avatar
My pipes are my music
 
Last photo:
Join Date: Sep 2009
Location: indiana
Age: 64
Posts: 2,938
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
Quote:
Originally Posted by cool rockin daddy
Really suggest you read the article "HEI tuning" before you make the mistake of running ported vacuum.
I try the best with what I've got and there's a whole lotta info missing other than it's a 355. Running full time vacuum advance is not chiseled in stone and depending on how and what you drive has a lot to do with it.
That ported vacuum port wasn't put on carbs to run the heater controls.
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 04-30-2011, 10:23 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: 59
Posts: 5,037
Wiki Edits: 1616

Thanks: 128
Thanked 597 Times in 546 Posts
I have found that a stock engine (i.e. high vacuum) might not run any better w/the vacuum advance hooked to manifold vacuum. The bigger the cam duration/overlap is, the more the engine seems to 'like' manifold vac., IMO.
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 05-01-2011, 06:27 AM
Registered User
 
Last photo:
Join Date: Nov 2010
Location: southern Virginia
Age: 61
Posts: 88
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
This engine is 355cid with a GM(crane) solid lifter cam (459/485), 492 heads, GM winters alum intake and Holley 750 cfm w/vacuum secondaries with the pistons I have and heads resurfaced make for about 10.5 to 1 compression ratio. to get 38* total timing(3000rpm) I end up setting the initial timing at 23*(800to1000rpm) with the vacuum advance disconnected, when I reconnect the vacuum hose the timing goes to 38* at idle(800 to 1000rpm) I would like about 8* to 10* advance not 15* I know the initial timing is higher than I would like but around 20* should be acceptable (I hope)
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 05-01-2011, 07:07 AM
sqzbox's Avatar
My pipes are my music
 
Last photo:
Join Date: Sep 2009
Location: indiana
Age: 64
Posts: 2,938
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
OIC now, that's a race engine! I can see using full time vacuum now. OR, you could go with a full mechanical centrifugal advance dist. and eliminate the vacuum advance all together.
Reply With Quote Quick reply to this message
  #10 (permalink)  
Old 05-01-2011, 07:25 AM
Registered User
 
Last photo:
Join Date: Nov 2010
Location: southern Virginia
Age: 61
Posts: 88
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
No its a 1970 LT1/ Z28 engine in a 1985 S10 Blazer 4x2, not a daily driver but a not a race car either, just for fun!
Reply With Quote Quick reply to this message
  #11 (permalink)  
Old 05-01-2011, 07:34 AM
sqzbox's Avatar
My pipes are my music
 
Last photo:
Join Date: Sep 2009
Location: indiana
Age: 64
Posts: 2,938
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
Quote:
Originally Posted by rwa1015
No its a 1970 LT1/ Z28 engine in a 1985 S10 Blazer 4x2, not a daily driver but a not a race car either, just for fun!
Don't make any difference. Once you changed the cam everything changes.
That's why your having a problem getting the advance set up the way you want it over the way it was. I had a friend with a 70 Z LT1 and it was awesome to drive. I can imagine what it's like in your S-10 blazer. Probably scare me!
Reply With Quote Quick reply to this message
  #12 (permalink)  
Old 05-01-2011, 08:32 AM
Registered User
 
Last photo:
Join Date: Nov 2010
Location: southern Virginia
Age: 61
Posts: 88
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Thanks to everyone for the input, the crane kit or making something to limit the travel of the vacuum advance rod is probably my best bet since I don't want to completely remove it just have less vacuum advance.
Reply With Quote Quick reply to this message
  #13 (permalink)  
Old 05-01-2011, 10:03 AM
Custom10's Avatar
my KARMA ran over my DOGMA
 

Last journal entry: SS
Last photo:
Join Date: May 2009
Location: Saskatchewan, Canada
Age: 49
Posts: 1,095
Wiki Edits: 0

Thanks: 14
Thanked 24 Times in 22 Posts
For complete adjustment and setting this kit is available:

http://www.summitracing.com/parts/CRN-99600-1/

Its good quaility stuff

It includes the limiter plate cobalt mentioned as well as an adjustable can which will allow you to fine tune the vacuum advance rate as compared to engine vac be it ported or manifold.

It has some mechanical/centrifugal advance curve springs too which may come in handy.
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
Opinions on ported of full vacuum for vacuum advance ? y2k600f4 Engine 15 10-07-2011 09:38 PM
Timing... vacuum or no vacuum advance? 454ChevelleMalibu Engine 18 04-25-2010 09:37 PM
Vacuum advance western star Engine 14 11-30-2009 10:28 PM
ok to use same vacuum line for vacuum advance and tranny vacuum modulator? brian400ex Engine 4 02-19-2003 02:25 PM
computer advance or vacuum advance?? 1984camaroZ28 Engine 1 10-12-2002 02:57 PM


All times are GMT -6. The time now is 06:10 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.