Club Cobra Keith Craft Motorsports  

Go Back   Club Cobra > Engine Building, Tuning, and Induction > Small Block Talk

MMG Superformance
Nevada Classics
MMG Superformance
Main Menu
Module Jump:
Nevada Classics
Nevada Classics
MMG Superformance
MMG Superformance
Advertise at CC
Banner Ad Rates
Keith Craft Racing
Keith Craft Racing
MMG Superformance
November 2024
S M T W T F S
          1 2
3 4 5 6 7 8 9
10 11 12 13 14 15 16
17 18 19 20 21 22 23
24 25 26 27 28 29 30

Kirkham Motorsports

Reply
 
LinkBack Thread Tools Rate Thread Display Modes
  #1 (permalink)  
Old 05-23-2004, 02:46 PM
CC Member
Visit my Photo Gallery

 
Join Date: Feb 2004
Cobra Make, Engine:
Posts: 563
Not Ranked     
Default vacuum advance or not?

..........

Last edited by rob frink; 12-28-2010 at 07:35 AM..
Reply With Quote
  #2 (permalink)  
Old 05-23-2004, 05:45 PM
Shade Tree Mechanic
Visit my Photo Gallery

 
Join Date: Oct 2000
Location: La Plata, MD
Cobra Make, Engine: - Unique - 302 - 4 spd. -
Posts: 680
Not Ranked     
Default

Rob,

I agree that 5 degrees is a little light for static timing. If you need the additional advance to get the car to idle correctly, you'll have to adjust the mechanical/centrifugal advance limit to offset the difference.

As it stands now, your getting 27 degrees of centrifugal advance. I wouldn't suggest going more than 15 degrees static advance. Going too far can cause some starting problems, unless your ignition box has a retard feature during start up.

Vacuum advance is usually connected to a port above the throttle plates and provides some lead time with slight throttle opening when slowly starting off and at part throttle conditions while crusing down the road. Under full throttle conditions where low or no vacuum is present, vacuum advance is not in the picture. Also, with total mechanical advance comming in at probably under 3000 RPM with your motor, I wouldn't think you would benefit from any vacuum advance.

Now, if you were to connect the vacuum advance to manifold vacuum, you would see vacuum advance at idle. And you could adjust it for say an additional 10 degrees of advance. The one problem I see would be when you step on the gas..... vacuum goes away and the additional advance goes with it.... possible off throttle stumble.

I'm not clear if your dizzy has or doesn't have a vacuum advance on it. If it does, try hooking it up to manifold vacuum and see how it performs. Trying it is a lot easier than pulling the dizzy and adjusting the mechanical limits. Who knows???? it might work...
__________________
- Jim Harding -
- Capital Area Cobra Club -
- Just another day in Cobra Paradise -
Reply With Quote
  #3 (permalink)  
Old 05-24-2004, 01:56 PM
CC Member
Visit my Photo Gallery

 
Join Date: Feb 2004
Cobra Make, Engine:
Posts: 563
Not Ranked     
Default

..........

Last edited by rob frink; 12-28-2010 at 07:35 AM..
Reply With Quote
  #4 (permalink)  
Old 05-24-2004, 02:03 PM
Mr.Fixit's Avatar
CC Member
Visit my Photo Gallery

 
Join Date: Mar 2002
Location: so cal, Cal
Cobra Make, Engine: I used to fix them for a living
Posts: 2,563
Not Ranked     
Default

No vac advance.

Try starting with 14-15 initial, and another 20 centrifugal, bringing total to 34 degrees.
__________________
In a fit of 16 year old genius, I looked down through the carb while cranking it to see if fuel was flowing, and it was. Flowing straight up in a vapor cloud, around my head, on fire.
Reply With Quote
  #5 (permalink)  
Old 05-24-2004, 02:10 PM
CC Member
Visit my Photo Gallery

 
Join Date: Nov 2002
Location: North Florida, USA
Cobra Make, Engine: FFR4067, 393W
Posts: 95
Not Ranked     
Default

I have a 393 with Duraspark, Speed Demon 750DP, Mallory HyfireVI and vac advance. Here's the way mine runs best:
20 degrees at idle, 36 at 3000RPM, 46 with the vac advance hooked up at 3K. The Crane recurve kit works well.
I ran without vac advance for a while, but the mileage was killin' me. The vac advance adds about 25% to my mileage.
Too much vac advance causes a high-RPM/light-throttle misfire.

HTH, Ed
__________________
We used to own the government, now the government owns us. Where'd we go wrong?
Reply With Quote
Reply


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 On
Pingbacks are On
Refbacks are On



All times are GMT -7. The time now is 01:11 PM.


Powered by vBulletin® Version 3.8.0
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Search Engine Friendly URLs by vBSEO 3.6.0
The representations expressed are the representations and opinions of the clubcobra.com forum members and do not necessarily reflect the opinions and viewpoints of the site owners, moderators, Shelby American, any other replica manufacturer, Ford Motor Company. This website has been planned and developed by clubcobra.com and its forum members and should not be construed as being endorsed by Ford Motor Company, or Shelby American or any other manufacturer unless expressly noted by that entity. "Cobra" and the Cobra logo are registered trademarks for Ford Motor Co., Inc. clubcobra.com forum members agree not to post any copyrighted material unless the copyrighted material is owned by you. Although we do not and cannot review the messages posted and are not responsible for the content of any of these messages, we reserve the right to delete any message for any reason whatsoever. You remain solely responsible for the content of your messages, and you agree to indemnify and hold us harmless with respect to any claim based upon transmission of your message(s). Thank you for visiting clubcobra.com. For full policy documentation refer to the following link: CC Policy
Links monetized by VigLink