classic car forum header
Classic cars forum & vehicle restoration.
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 
Register     Posting Photographs     Privacy     F/book OCC Facebook     OCC on Patreon

Has anyone had experience of Red Rotor Arms?
Goto page Previous  1, 2
Post new topic   Reply to topic    Classic cars forum & vehicle restoration. Forum Index -> Electrical Restoration
Author Message
jessejazza



Joined: 18 Mar 2009
Posts: 75

PostPosted: Thu Feb 24, 2011 10:46 pm    Post subject: Reply with quote

I have used the black from Halfords for many years. I regret to say that i haven't had a problem but quality of points, condensers, rotor arms and caps seems to be variable.

Of course electronic ignition is what folk are recommending... i have had problems with two units and returned to points. However, i do believe in using a TAC system (transistorised assisted circuit) which provides the benefits of electronic ignition (admittedly keeping the points for switching so there is a little heel wear but you can forget the condenser) - on each car i have and has transformed the running. Cost is negligable compared with electronic ignition.

Presumably you want to keep them original and such a system allows you to do that. I have had the red points and found them much better.
Back to top
View user's profile Send private message
michael1703



Joined: 22 Jul 2009
Posts: 349
Location: suffolk

PostPosted: Fri Feb 25, 2011 12:37 am    Post subject: Reply with quote

I got through 3 rotor arms in as many weeks one summer about 8 years ago and then never had a problem for 6 years, had a faulty one a year or two ago and been fine since
Back to top
View user's profile Send private message Visit poster's website
baconsdozen



Joined: 03 Dec 2007
Posts: 1119
Location: Under the car.

PostPosted: Fri Feb 25, 2011 12:14 pm    Post subject: Reply with quote

I think this is just one of the problems with cheap imported parts. A few years back the smaller parts that you bought for your car had a makers name and address on them and if they failed you could always give them an earfull if nothing else.
Now a lot of parts are made in the far east and made to a price,quuality being a secondary consideration.Leaving aside the fakes (I've seen brake lininings in boxes with "Girling" spelt wrongly) ,a lot of the stuff is sub standard and these rotor arms are just one example.They were probably made in huge quantities and sent to loads of distributors and wholesalers some packaged in fancy boxes and some sold lose. They are probably black because 1 its cheap to make and 2 it looks like the better older rotor arms we used to have.
The fact that it isn't the same spec or doesn't work as well matters little to the anonymous factory that made them.
_________________
Thirty years selling imperial hand tools for old machinery(Now happily retired).
Back to top
View user's profile Send private message Visit poster's website
john-saab



Joined: 06 Dec 2007
Posts: 341
Location: West Dorset

PostPosted: Fri Mar 11, 2011 10:08 am    Post subject: Reply with quote

Are those people who are having rotor arms fail using electronic ignition?...i'm wondering if the uprated coils used with these systems is causing premature failure?
_________________
Rust Junky & oil addict.
Back to top
View user's profile Send private message
therobbiesmith



Joined: 18 Oct 2009
Posts: 20

PostPosted: Fri Mar 11, 2011 11:07 am    Post subject: Reply with quote

No, my B had the original distributor/coil arrangement. It now has electronic ignition but the problem of the rotor arm had been solved before I upgraded the distributor and coil.

The fault is with the poor quality of modern black rotor arms. Smile
Back to top
View user's profile Send private message
Jim.Walker



Joined: 27 Dec 2008
Posts: 1229
Location: Chesterfield

PostPosted: Fri Mar 11, 2011 1:30 pm    Post subject: Reply with quote

john-saab wrote:
Are those people who are having rotor arms fail using electronic ignition?...i'm wondering if the uprated coils used with these systems is causing premature failure?


It doesn't matter what kind of ignition you have! The coil voltage and hence the voltage across the rotor arm will never get higher than that needed to fire the plugs, unless you have a high resistance somewhere between rotor arm and plugs, such as worn dist. cap poles with too big an air gap. Or of course if your plug caps are too wide or the plug electrodes rounded rather than square, which increases the required voltage at the plug.
Immediately a plug fires coil voltage ceases to rise and falls away rapidly.

I have never had particular trouble with rotor arms, but I did replace my last one with red because the black one had been in at least twenty years. However the red one was a tight fit and and the sleeve part split as I fitted it to the cam. Didn't seem to be loose though, so I left it in place and fitted my old one into the glove box just in case.
That was several thousand miles ago and no problems. Still carry the old black one though.

By the way. I have long suspected that rotor arms are often fitted by oily/sweaty hands. Does that have any repurcussions?
Jim.
_________________
Quote from my late Dad:- You only need a woman and a car and you have all the problems you
are ever likely to want". Computers had not been invented then!
Back to top
View user's profile Send private message
captain bobo



Joined: 02 Feb 2012
Posts: 43
Location: South West Cambs

PostPosted: Mon Mar 05, 2012 10:46 pm    Post subject: Reply with quote

A very late response to the topic (I've only been a forum member for a few weeks).

I run a 1969 Daimler V8 250 saloon: the work rate of the rotor arm is very high considering (a) the number of cylinders, and (b) the dwell angles used. It's the same engine as that used in the Daimler Dart.

In the Daimler owners club dozens of members with V8's have had problems using new rotor arms (myself included). Dozens of us have switched to the Distributor Doctor's red rotor arms and we all agree that we get more consistent sparking and fewer ignition issues.

Kind regards, Dave B
_________________
1937 Daimler 15 Mulliner Sports Saloon & 1969 Daimler V8 250 Saloon
Back to top
View user's profile Send private message
Jim.Walker



Joined: 27 Dec 2008
Posts: 1229
Location: Chesterfield

PostPosted: Tue Mar 06, 2012 12:11 pm    Post subject: Reply with quote

Before the days of red rotor arms we operated a fleet of about ten Daimler DR450 Majestic Major Limousines, with a bigger version of the 250 engine. I do not remember ever having rotor arm problems, but that was also in the days before pattern rotor arms were common. I suspect that the failure of black pattern type rotor arms are the reason that folk are changing to the red ones.
I wonder how long it will be before suspect red ones, copying the Distributor Doctor's become available?
I can see that the rotor arm on a V8 has to supply the plugs 8 times per revolution, but can you explain to me the significance of the dwell angle controlled jointly by the contact breaker and contact maker ( two sets of points) captain bobo?
Jim.
_________________
Quote from my late Dad:- You only need a woman and a car and you have all the problems you
are ever likely to want". Computers had not been invented then!


Last edited by Jim.Walker on Tue Mar 06, 2012 6:05 pm; edited 2 times in total
Back to top
View user's profile Send private message
Julian



Joined: 19 Apr 2010
Posts: 278
Location: Warrington

PostPosted: Tue Mar 06, 2012 12:54 pm    Post subject: Reply with quote

Just to throw another factor into the equation I wonder if the problems of failing rotor arms is due to poor rotor to cap phasing? Certainly this is a problem on Mopar dizzies and a factor addressed by many of the aftermarket tuning companies.

The ignition system on my 440 big block is an aftermarket FBO system and they talk of this issue on the website. If you have an old dizzy cap that you don't really need you can cut a 'kidney' shaped slot in the top, and via your strobe timing light actually watch the rotor arm as you play around with mechanical and vacuum advance.

From: http://www.4secondsflat.com/

Cap/Rotor Phasing:

This is another part of the ignition tune-up that is almost never addressed. So called Super Tune shops are aware of this inherent problem with Mopar distributors (and others) and it's one of the first things they check.

Simply this is getting the spark signal to the plug by aligning the rotor and cap contacts so the spark travels to the plug at the instant that the two components are aligned or phased.

The Mopar distributors almost never do this, the rotor is either not yet at the contact or it has long since past it's optimum point. What this does is cause the spark to have to jump or arch to the cap, this causes heat energy. If we go back to basic physics we know that "Energy cannot be created or destroyed it can only change form" so what we do here is convert electrical energy to heat energy and effectively reduce the power of the spark as RPM increases and pressure in the cylinder increases causing a higher resistance for the plugs the spark efficiency is drastically reduced...result....poor performance...lost HP and tork.

The cause of this phasing problem is multiple, the biggest thing we find is the vacuum advance plate on a Mopar distributor is really a poor design allowing it to tip and wobble in the distributor housing....when you get your distributor back from us you'll find that plate welded solid and the advance curve is controlled by the weights and springs. Bad bushings, worn gears, poor factory tolerance, cheap caps and rotors can all contribute to or multiply the phasing problems.

It's very common to find a Mopar distributor with the phasing so far off that at around 5000 RPM and up the rotor will get confused and start arching to either the contact ahead or behind it's position....ever heard this "I have a high speed miss I just can't find".....

Of course the investment in a high dollar MSD or similar type distributor is a solution and after we run them up on our machine, calibrate them to your specific engine they are excellent, but....most of us here are using our cars as daily drivers and go blast off a few 1/4 passes on the weekend. This is why we work over the stock distributors and or the Mopar Performance distributors (which are better for more performance orientated cars) and make them work to spec or "Blueprint" them for a fraction of the cost.



Julian.
Back to top
View user's profile Send private message
Kelsham



Joined: 18 Jan 2009
Posts: 349
Location: Llandrindod Wells Powys

PostPosted: Wed Mar 07, 2012 9:15 am    Post subject: Reply with quote

There used to be a transparent distributor cap available. I have seen them but, but never seen one on a car. Has anyone used one?

I am so paranoid that I currently carry two spare black rotor arms in the toolbox of my Morris 1800. I had one failure recently before I heard about the red caps.

Curiously I also had a rotor arm fail on my 1932 BSA three wheeler. It was about 70 odd years old. They are difficult to replace as they have a semi circular end contact.

Regards Kels.
Back to top
View user's profile Send private message
Julian



Joined: 19 Apr 2010
Posts: 278
Location: Warrington

PostPosted: Wed Mar 07, 2012 8:29 pm    Post subject: Reply with quote

I've heard of transparent dizzy caps, but always assumed they were made for the Kevins in their Corsas so they could lift the bonnet at night and look at the little light display!

This is what I made (not my idea, sadly) to check rotor to cap phasing. It works a treat. It may help shed some more light on the matter, ie bad phasing due to crap manufacture is the problem rather than failing plastic, per se....



Julian.
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    Classic cars forum & vehicle restoration. Forum Index -> Electrical Restoration All times are GMT + 1 Hour
Goto page Previous  1, 2
Page 2 of 2

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
OCC Merch link
Forum T&C


php BB powered © php BB Grp.