Club Cobra Keith Craft Motorsports  

Go Back   Club Cobra > Club Cobra Tech Areas > Tech Tips

MMG Superformance
Nevada Classics
Keith Craft Racing
Main Menu
Module Jump:
Nevada Classics
Nevada Classics
MMG Superformance
MMG Superformance
Advertise at CC
Banner Ad Rates
MMG Superformance
Keith Craft Racing
MMG Superformance
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            
  #1 (permalink)  
Old 10-12-2009, 08:18 AM
CC Member
Visit my Photo Gallery

 
Join Date: Jul 2009
Cobra Make, Engine:
Posts: 409
Not Ranked     
Default Mallory Distributor Tip

The problem with Mallory Distributors, at least the YL units, is that the drive gear 1/8" roll-pin can shear. I queried Mallory about it and was told the failure is normally associated with using a high volume oil pump.

What I did to resolve the problem was to re-drill the roll-pin hole through the drive gear and dist shaft with a #22 drill bit. I then pressed in a 5/32 roll-pin (the split kind, not the rolled up kind) with the split up (down also works) and then nested a 3/32" roll-pin inside the larger one, but with the split 180 Deg apart.

Despite the fact that a loose drive gear to shaft fit is also a problem with the Mallory (you get more bending of the pin), the mod has not failed me since, at least 4000 miles ago.
Reply With Quote
  #2 (permalink)  
Old 10-12-2009, 01:00 PM
bobcowan's Avatar
CC Member
Visit my Photo Gallery

 
Join Date: Feb 2007
Location: Colorado Springs, CO
Cobra Make, Engine: Backdraft, supercharged Coyote
Posts: 2,430
Not Ranked     
Default

That's a problem with all distributers. I've never had that problem with any Mallory Unilite I'v ever used. But it happend to a friend of mine at atrack day. He had a brand new MSD; he got 1 and 1/2 laps before it sheared.
Reply With Quote
  #3 (permalink)  
Old 10-13-2009, 07:33 AM
CC Member
Visit my Photo Gallery

 
Join Date: Nov 1999
Location: Rosemount, Mn
Cobra Make, Engine: SPF 1233-396C.I. Windsor
Posts: 121
Not Ranked     
Default

On my way to a local car show, blipped the throttle on a downshift off a freeway ramp and the engine died. Took of the distributor cap and found the rotor wasn't turning as I spun the engine. Flat towed the Cobra the last 6 blocks to the car show- I had the only Denali powered Cobra there! Pulled the distributor to find the dreaded roll pin failure. Trip to the local hardware store and 27 cents later it was running again. It still screwed up a perfectly good day, or at least a couple hours. Drained the oil when I got home into a very very clean drain pan and found part of the pin, stuck a magnet into the drain on my Aviad pan and pulled out another piece. Installed a magnetic drain plug and hope to catch the rest. Mike

Last edited by NRP/MN; 10-13-2009 at 07:57 AM..
Reply With Quote
  #4 (permalink)  
Old 10-13-2009, 07:44 AM
Jerry Clayton's Avatar
CC Member
Visit my Photo Gallery

 
Join Date: Jul 2005
Location: Bartlett, Ill
Cobra Make, Engine: Everett-Morrison LS1
Posts: 2,448
Not Ranked     
Default

If running a big pump---you can double/triple pin the gear by drilling more holes---of course then you run the risk of stripping the teeth off the cam gear
Reply With Quote
  #5 (permalink)  
Old 10-13-2009, 08:00 AM
Gunner's Avatar
CC Member
Visit my Photo Gallery

 
Join Date: Sep 2009
Location: Sacramento, CA
Cobra Make, Engine: ERA 707, 446ci FE
Posts: 1,115
Not Ranked     
Default

Aren't there roll pins (or rod material) with a higher shear strength?
__________________

= Si Opus Quadratum vis, angulos praecidere noli. =
Reply With Quote
  #6 (permalink)  
Old 10-13-2009, 10:09 AM
CC Member
Visit my Photo Gallery

 
Join Date: Jul 2009
Cobra Make, Engine:
Posts: 409
Not Ranked     
Default

Quote:
Originally Posted by Gunner View Post
Aren't there roll pins (or rod material) with a higher shear strength?
I looked into that, but there really wasn't anything I could find at the time. Seems to me, when I looked into it, those spiral roll-pins are even weaker. With solid pins, like tool steel or titanium, you may have a problem keeping them installed unless you have an expertly machined and "very tight" press-fit.

The big problem is the Mallory gear is a loose fit. The pin flexs every time it goes around and eventually fatigues and breaks. Ford distributors have an interference gear to shaft fit, and with the same size pin, there are a lot less failures as the pin is in direct shear with no bending moment.

It's also difficult to cross-pin the gear as the existing hole is in the middle of the available space, so another hole, even at 90 degrees is too close and weakens the dist shaft.
Reply With Quote
  #7 (permalink)  
Old 10-13-2009, 04:10 PM
PaulProe's Avatar
CC Member
Visit my Photo Gallery

 
Join Date: May 2006
Location: Manchester, MO
Cobra Make, Engine: Hurricane - FE
Posts: 617
Not Ranked     
Default Sympton of other error

When you change a distributor or its drive gear, it is essential you set the proper end-play. If you don't it and the drive pin is subject to higher than design forces.

Going to a larger drive pin is just a mask for an improperly located drive gear. That is the reason they come to you un-drilled, with a pilot hole. If installed properly, all the forces of the gear and camshaft are absorbed by the boss in the block, not by the drive pin.

Here is a link to the Ford bulletin: Distributor gear installation

Paul
__________________
www.65shlb.com
www.prdcrrct.com
Reply With Quote
  #8 (permalink)  
Old 10-13-2009, 04:50 PM
CC Member
Visit my Photo Gallery

 
Join Date: Jul 2009
Cobra Make, Engine:
Posts: 409
Not Ranked     
Default

Quote:
Originally Posted by PaulProe View Post
When you change a distributor or its drive gear, it is essential you set the proper end-play. If you don't it and the drive pin is subject to higher than design forces.

Going to a larger drive pin is just a mask for an improperly located drive gear. That is the reason they come to you un-drilled, with a pilot hole. If installed properly, all the forces of the gear and camshaft are absorbed by the boss in the block, not by the drive pin.

Here is a link to the Ford bulletin: Distributor gear installation

Paul
That's a different problem. Note that in the link you provided, it states "press the gear on the shaft". With a Mallory, it's loose. No pressing. That's a problem. I even thought of getting the shaft or gear knurled to help things, but just went with a pin upgrade. I am absolutely certain, in my case, there was plenty end-play clearance left after the dist was clamped down.
Reply With Quote
  #9 (permalink)  
Old 12-28-2009, 11:04 PM
CC Member
Visit my Photo Gallery

 
Join Date: Mar 1999
Location: TACOMA, WA
Cobra Make, Engine: Everett Morrision FE 427 so 2-4s
Posts: 2,008
Not Ranked     
Default

My Mallory distributer had a !/8" x 3/"4 spring pin. It failed in my alley once when I reved the engine leaving the yard with cold oil. I replaced it with a true roll pin I sourced from MSD.When you drill larger holes or multiple holes you have moved the weak link in the system to somewhere else. Just read the stories about the high volume pumps with really high releif preasures. Read the storiy about Brent and the Heli-coil piece that got left in the oil pan and stopped the pump. His distributer drive shaft looked like a peice of ornamental iron, and the bearings that got damaged. I can see the high volume pump with a realistic releife pressure a slight step up to the roll in. If something happens, everything just coasts to a stop no damage other than halving tp remove the distributer, replace the pin and then reset the ignition again retiming again
I'd think rather than going with an absured releif presure that assureing flow would be a better focus. Large hoses , large fittings , gentle bends ,in and out of block matching bearing and block oil holes and in particular, a large capacity oil filter or if you are going to run Ford style filter elements, Try a filter bracket that lets you use two elements in a parrallel arangement to increase flow and not restriction
__________________
Mike H

Last edited by Michael C Henry; 03-19-2010 at 03:58 PM..
Reply With Quote
  #10 (permalink)  
Old 12-29-2009, 10:00 AM
Senior Club Cobra Member
Visit my Photo Gallery

 
Join Date: Feb 2006
Location: Ft. Mitchell, KY
Cobra Make, Engine: B&B, 428 FE, toploader
Posts: 151
Not Ranked     
Default

My pin sheared after rebuilding my 428. Like Argess, I drilled it out and put in the larger pin. That was 5000 miles ago and it is still going fine. Chas
Reply With Quote
  #11 (permalink)  
Old 07-25-2017, 03:05 PM
CC Member
Visit my Photo Gallery

 
Join Date: Mar 1999
Location: TACOMA, WA
Cobra Make, Engine: Everett Morrision FE 427 so 2-4s
Posts: 2,008
Not Ranked     
Default

This time I suspected the pin because I knew that I had over revved the engine with cool oil. Once I removed the distributor I found that wasn't the case. But I messed it up from there. I should have left it alone and just reinstalled the distributor. The moving up to 5/32 in. pin sounds good if there is ever a next time. This time it was me, over my head. Turns out that I just ran out of gasoline , but it did run great for that short instance.
__________________
Mike H
Reply With Quote
  #12 (permalink)  
Old 07-25-2017, 03:37 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 Jerry Clayton View Post
If running a big pump---you can double/triple pin the gear by drilling more holes---of course then you run the risk of stripping the teeth off the cam gear
I'm glad of your response here Jerry.

Others seem to not realise that the roll pin only needs to be strong enough, but still the weakest link.
Reply With Quote
  #13 (permalink)  
Old 08-13-2018, 10:17 AM
CC Member
Visit my Photo Gallery

 
Join Date: Mar 1999
Location: TACOMA, WA
Cobra Make, Engine: Everett Morrision FE 427 so 2-4s
Posts: 2,008
Not Ranked     
Default

Mallory was taken over, CRAP. I found better true roll pins at ZORRO. They have different materials and strengths pins. I bought a bag of a hundred pins. The original roll pin was a great failsafe. If it sheared the engine stopped and no damage done and easy to fix. Bigger pin takes away from the shaft thickness and moves the weak link some where else. The distributer gear was drilled so it can and would only be reinstalled the one one way. The gear and shaft pin hole was slightly off center and angled downward slightly.
__________________
Mike H
Reply With Quote
Reply

Thread Tools
Display Modes

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 On
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -7. The time now is 04:59 AM.


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