Club Cobra Keith Craft Motorsports  

Go Back   Club Cobra > Engine Building, Tuning, and Induction > Ignition

MMG Superformance
Nevada Classics
MMG Superformance
Main Menu
Module Jump:
Nevada Classics
Nevada Classics
MMG Superformance
Advertise at CC
Banner Ad Rates
Keith Craft Racing
MMG Superformance
MMG Superformance
Keith Craft Racing
March 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
31            

Kirkham Motorsports

Like Tree2Likes

Reply
 
LinkBack Thread Tools Rate Thread Display Modes
  #21 (permalink)  
Old 08-24-2017, 02:47 PM
cycleguy55's Avatar
CC Member
Visit my Photo Gallery

 
Join Date: Feb 2014
Location: White City, SK
Cobra Make, Engine: West Coast, 460 CID
Posts: 2,844
Not Ranked     
Default New Ignition Wires?

I tested the resistance of each of the ignition wires, partially to see how they compared to the 'High Performance' wires, and also how they compared to each other. I have Belden 'Performance Silicone' 8mm wires, and here's how they measured up:

Cyl - Ohms
1 - 10K
2 - 8K
3 - 10K
4 - 17K
5 - 6K
6 - 8K
7 - 7K
8 - 6K

Summary:
  1. Too much variance, wire to wire, even considering #4 is one of the longer wires - it's not that much longer.
  2. Many HP wires are much lower in resistance - often 50 - 150 ohms / foot - a fraction of what mine are. MSD’s 8.5mm Super Conductor Wire is about 50-ohms per foot while theire Street Fire wires are about 500 ohms per foot.
  3. Going to install a new set of wires.

One set of wires that seems to be well reviewed is these https://www.summitracing.com/int/par...r460/overview/

They're 9mm wires with the right ends and boots. It's not listed on Summit, but found elsewhere, is the indication these are 1,000 ohms/foot - much lower than what I currently have, but should I be looking for something lower? Taylor Spiro-Pro wires are 350 ohms/foot (https://www.summitracing.com/parts/tay-74299) and there appears to be no end of variety - from 40 ohms/foot up.

Thoughts?
__________________
Brian
Reply With Quote
  #22 (permalink)  
Old 08-24-2017, 04:54 PM
Texasdoc's Avatar
CC Member
Visit my Photo Gallery

 
Join Date: Feb 2012
Location: Keller, TX
Cobra Make, Engine: Lonestar Classics LS427. Self-built 408W, AFR 195 heads, Performer RPM Intake, Quick Fuel 750, 407rwhp, 479rwtq
Posts: 549
Not Ranked     
Default

Those numbers do seem high.

I've run both the street fire and the super conductor wires with my non-resistor plugs. I didn't see much difference.
Reply With Quote
  #23 (permalink)  
Old 08-24-2017, 09:17 PM
Gaz64's Avatar
CC Member
Visit my Photo Gallery

 
Join Date: May 2008
Location: Brisbane, QLD
Cobra Make, Engine:
Posts: 2,773
Not Ranked     
Default

About 3000 ohms per foot is a good silicon lead.

Any spiral wire lead is an improvement, but think about the airgap (rotor to cap terminal) resistance. Obviously there are two sparks occurring at the same time for each cylinder to fire. When you can run the gap down to near zero, there is less loss in the cap.

Gary

Last edited by Gaz64; 08-25-2017 at 06:34 PM..
Reply With Quote
  #24 (permalink)  
Old 08-25-2017, 05:55 PM
Dwight's Avatar
Senior Club Cobra Member
Visit my Photo Gallery

 
Join Date: May 2001
Location: Florence, AL
Cobra Make, Engine: RCR GT 40 & 1966 Fairlane 390 5 speed
Posts: 4,511
Not Ranked     
Smile

I buy and use the MSD kits that I have to make up one end. That way the wires are the correct length for what ever motor I installed them on. Much better looking that factory made wires.

The last set I measured was MSD 8mm and found two were twice the ohms reading of the others.

I removed the boots and check from conductor to conductor. On one the factory crimp was bad. The other wire I could not prove which end was bad, it might have been the end that I made up. So I replaced both ends and got a good reading.

I would suggest you measure the wire by putting the meter probe on the conductor not the steel terminals. If you get a different reading than terminal to termingal then check the crimp.

Dwight
__________________
''Life's tough.....it's even tougher if you're stupid.'' ~ John Wayne
"Happiness Is A Belt-Fed Weapon"
life's goal should be; "to be smarter than inanimate objects"
Reply With Quote
  #25 (permalink)  
Old 08-30-2017, 08:15 AM
cycleguy55's Avatar
CC Member
Visit my Photo Gallery

 
Join Date: Feb 2014
Location: White City, SK
Cobra Make, Engine: West Coast, 460 CID
Posts: 2,844
Not Ranked     
Default

Quote:
Originally Posted by cycleguy55 View Post
I've got the car running again, but get a surge / miss on light throttle cruise between 2,000 and 2,500 RPM. There's also more exhaust 'popping' or 'burble' on throttle-closed deceleration than before I replaced the ignition box and coil. There are no apparent issues at idle, when accelerating, or cruising < 2,000 RPM. I have not yet checked the timing but, other than replacing the magnetic pickup and distributor cap, the distributor was not touched.

Environment:
  1. MSD 8477 distributor (magnetic pickup swapped from old MSD 8577 distributor in process of getting car running)
  2. Summit Multi-Spark digital ignition control box p/n , mounted behind dash ( https://www.summitracing.com/parts/sum-850610 )
  3. Summit Epoxy coil ( https://www.summitracing.com/parts/sum-850500 )

Questions:
  1. Does this sound like an ignition or a fuel issue?
  2. Where do I start?
I've got it running well again. The fix was to disable the vacuum advance ("VA"). Right now it's running with only centrifugal advance ("CA"). Connecting the VA to either manifold or ported vacuum gives me the same result - popping and strong misfires - which I don't have when running only on CA.

Here's my thinking: There's enough timing (16° BTDC base, 21° CA in by 2,500 RPM) already, and any additional VA means it's too far advanced. So, why did I not have this problem with the old, analog, ignition box? My belief is the old box didn't react or respond as quickly to the signal from the magnetic pickup, whereas the new digital box does, making it more sensitive to the advance. If there's less inherent 'lag' in the new box, I suspect that will be more pronounced as the RPMs increase, though I haven't had the opportunity yet to give it a good road test.

FWIW, I've run across a few Internet threads to indicate I'm not the only one who has experienced this issue. Some suggested using an "inline smog vacuum reducer that only gives it 3 lb of vacuum", but that seems a waste of time, energy and money. I mean, what's the point of having VA at all if it's dialed back so far? Why not just go to a distributor w/o VA and keep things simpler?

Thoughts? Is there a fix for this, or should I just yank the MSD 8477 and put my old MSD 8577 non-VA distributor back in?
__________________
Brian
Reply With Quote
  #26 (permalink)  
Old 08-30-2017, 11:23 AM
Texasdoc's Avatar
CC Member
Visit my Photo Gallery

 
Join Date: Feb 2012
Location: Keller, TX
Cobra Make, Engine: Lonestar Classics LS427. Self-built 408W, AFR 195 heads, Performer RPM Intake, Quick Fuel 750, 407rwhp, 479rwtq
Posts: 549
Not Ranked     
Default

You have 16 base, 21 mechanical totaling 37. If you are using the stock MSD vacuum can, that will give you too much advance at light throttle - around 52°. You can either:

1. Run it without vacuum advance. Lots of people do. It is designed for fuel economy while cruising. Not a big need in a cobra. No need to switch out to your old distributor. You can leave the can disconnected and it won't have any effect. Just make sure to plug the carb side so you don't have a vacuum leak.

2. Change out the advance limiter in the distributor. If you use the black one, you will only get 18° of mechanical advance. Set your total to 34, still giving you a base of 16. Those few degrees *may* keep it from over advancing. (Doubt this will work with the stock MSD vacuum can. These number are for a SBF - YMMV)

3. Replace the vacuum can on the distributor with an aftermarket adjustable piece. I use the Accell 31034 unit (Ckicky - get the GM part, not the ford part) and can limit the vacuum advance to around 7° instead of the 15° the MSD one provides.

BTW, I recently switched to a CB Performance black box to control my ignition and can set any timing at any RPM/Vacuum.

Forget the inline smog vacuum reducer. Waste of time, money, and effort for the limited benefit it will provide.

Last edited by Texasdoc; 08-30-2017 at 11:59 AM..
Reply With Quote
  #27 (permalink)  
Old 08-30-2017, 12:10 PM
cycleguy55's Avatar
CC Member
Visit my Photo Gallery

 
Join Date: Feb 2014
Location: White City, SK
Cobra Make, Engine: West Coast, 460 CID
Posts: 2,844
Not Ranked     
Default

MSD says their VA is good for 10° of advance, but 47° is still too much. I could change springs to slow the centrifugal advance, but recommendations I've seen are pretty universal in calling for advance to be all in by 2500 RPM. I'll almost certainly be staying pure CA.

The curious part is why the VA and the same timing settings worked fine with the analog box, but not with the digital box.
__________________
Brian
Reply With Quote
  #28 (permalink)  
Old 08-30-2017, 01:09 PM
Texasdoc's Avatar
CC Member
Visit my Photo Gallery

 
Join Date: Feb 2012
Location: Keller, TX
Cobra Make, Engine: Lonestar Classics LS427. Self-built 408W, AFR 195 heads, Performer RPM Intake, Quick Fuel 750, 407rwhp, 479rwtq
Posts: 549
Not Ranked     
Default

Most MSD distributors vacuum cans add about 15°, regardless of what they tell you in the phone.

I expect you would be fine at light throttle with 47° advance. You are probably getting quite a bit more. However, when you start to accelerate and the throttles open, the manifold vacuum should drop, decreasing the advance added buy the VA system. The problem with the cobra is that with such a powerful engine in a light car you don't have to open the throttle much to get light acceleration so the VA system doesn't drop out and you start to detonate.

Make sure you disconnect (in your brain) the amount of vacuum provided from when it is applied. The springs control WHEN the mechanical advance occurs. The bushing controls (limits) how MUCH advance occurs. You can still have it all in at 2500, but only get 18 degrees by changing to the black bushing. Leave the springs alone to keep the curve (the when) the same.

The two light springs are ok if your idle is less than 800. If your idle is over 800 you can start to get some MA at idle. I ran one light silver and one blue spring. That way the advance didn't start until 1200 but was still all in by 2800 (numbers from memory and are close but maybe not exact). If your idle timing fluctuates, try switching one spring to the light blue one.

Quote:
Originally Posted by cycleguy55 View Post
The curious part is why the VA and the same timing settings worked fine with the analog box, but not with the digital box.
I agree. However, as Gaz64 mentioned, it has been noted there are significant differences between the analog and digital systems

Last edited by Texasdoc; 08-30-2017 at 03:02 PM..
Reply With Quote
  #29 (permalink)  
Old 08-30-2017, 03:31 PM
Gaz64's Avatar
CC Member
Visit my Photo Gallery

 
Join Date: May 2008
Location: Brisbane, QLD
Cobra Make, Engine:
Posts: 2,773
Not Ranked     
Default

Quote:
Originally Posted by Gaz64 View Post
You have changed from an analogue 6A to a digital summit.
I know changing from 6A to 6AL causes issues with rotor phasing.
Get a spare distributor cap, drill a large hole in the top, and observe phasing with a timing light.
Just another thought, the analogue and digital may trigger on different edges, one could be rising, the other could be falling edge.

So drilling a hole in the cap, checking with a timing light is on the agenda.
Reply With Quote
  #30 (permalink)  
Old 08-31-2017, 02:04 AM
CC Member
Visit my Photo Gallery

 
Join Date: Aug 2017
Location: Volo, Ill, il
Cobra Make, Engine: 2001 B&B cobra
Posts: 21
Not Ranked     
Default

Quote:
Originally Posted by cycleguy55 View Post
I've got the car running again, but get a surge / miss on light throttle cruise between 2,000 and 2,500 RPM. There's also more exhaust 'popping' or 'burble' on throttle-closed deceleration than before I replaced the ignition box and coil. There are no apparent issues at idle, when accelerating, or cruising < 2,000 RPM. I have not yet checked the timing but, other than replacing the magnetic pickup and distributor cap, the distributor was not touched.

Environment:
  1. MSD 8477 distributor (magnetic pickup swapped from old MSD 8577 distributor in process of getting car running)
  2. Summit Multi-Spark digital ignition control box p/n , mounted behind dash ( https://www.summitracing.com/parts/sum-850610 )
  3. Summit Epoxy coil ( https://www.summitracing.com/parts/sum-850500 )

Questions:
  1. Does this sound like an ignition or a fuel issue?
  2. Where do I start?
Had the same problem with a cobra I just purchased. The small red wire from the msd box has to see 12 volts all the time. Unplug the coil wire from the distributor. With the ignition on, check to see if there is 12v at the msd box small red wire. Now, have someone crank the engine over, with the coil wire disconnected, and check to see if there is 12v while the engine is cranking. If not, the small red wire is hooked up wrong. Install wire directly to ignition switch, ign. terminal. Someone hooked up mine wrong. Mike.
Reply With Quote
  #31 (permalink)  
Old 08-31-2017, 03:51 AM
Gaz64's Avatar
CC Member
Visit my Photo Gallery

 
Join Date: May 2008
Location: Brisbane, QLD
Cobra Make, Engine:
Posts: 2,773
Not Ranked     
Default

Quote:
Originally Posted by cycleguy55 View Post
I've got the car running again, but get a surge / miss on light throttle cruise between 2,000 and 2,500 RPM. There's also more exhaust 'popping' or 'burble' on throttle-closed deceleration than before I replaced the ignition box and coil. There are no apparent issues at idle, when accelerating, or cruising < 2,000 RPM. I have not yet checked the timing but, other than replacing the magnetic pickup and distributor cap, the distributor was not touched.

Environment:
  1. MSD 8477 distributor (magnetic pickup swapped from old MSD 8577 distributor in process of getting car running)
  2. Summit Multi-Spark digital ignition control box p/n , mounted behind dash ( https://www.summitracing.com/parts/sum-850610 )
  3. Summit Epoxy coil ( https://www.summitracing.com/parts/sum-850500 )

Questions:
  1. Does this sound like an ignition or a fuel issue?
  2. Where do I start?
The miss is happening at where you would have the maximum amount of vacuum advance, at light throttle, and also on deceleration if using manifold versus ported vacuum.

If the rotor phasing is now wrong because of the module change, you need an adjustable rotor, and a sacrificed cap for testing.

I experienced this phenomenon many years ago when I made my first electronic advance module in kit form, but rotor phasing wasn't taken into account at the time.

Gary

Last edited by Gaz64; 08-31-2017 at 03:54 AM..
Reply With Quote
Reply

Tags
coil, ignition, msd 6a, spark, switch

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

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 10:14 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