MGB: Smooth 450 RPM idle....cold or hot.

As I get older, I've noticed that I'm starting to find seemingly mundane accomplishments noteworthy. My latest non-event is the anticlimactic culmination of my Meticulously anal LBC fine tuning, which has born fruit in the shape of the smoothest, lowest idle I have ever had the pleasure to witness of any LBC, much less my MGB. It's internal combustion poetry , mechanical music....it's a rock steady, silky smooth idle at 450 RPM...hot or cold on a 1800 "B" series lump.

Wow - have you checked your tach? :)

David,

You list your car as using a MSD 6A Electronic Ignition, Pertronix LU143A ignitor, & MSD Blaster 2 Coil.

The LU143 Ignitor is used on the 45D which needs a 3 ohm coil. When I checked the specs of the MSD Blaster 2 coil it is rated at only 0.700 ohms primary with 4.70K ohms secondary, and 45,000 max volts.

How did you make this work? What exactly does the MSD 6A Electronic Ignition do.

Trying to understand your setup. 450 rpm idle, great. Is this carb or injection?

Ray

Ray The MSD 6A is a capacitor discharge ignition and the MSD unit triggers the coil and the points or in this case the Pertronix only time the unit and very little current flows through the distributor. Denis

Dennis,

With the Pertronix and using the MSD 6A shouldn't the coil still remain 3 ohms?
I thought I read in one post you have a MSD on your MGB?

Ray

As a teen, I used to have fun trying for the lowest idle possible in my B. I got it down to just above 200 RPM once. It would idle there all day. I don't think I'd attempt that now. There was little point other than the giggle factor of course.

Kudos for the idle David.

I play little mind games when no one is looking with every B that I try to tune.

450 is low and I can't say that I have ever gotten there. Usually I am satisfied for a few minutes of 650 or so, but then I decide that I don't trust the girl to stay steady and reliable, so I end up bumping things up to around 900. I just can't trust a girl, no matter how far she sticks her tongue in my ear. ;-)

Jack

You ARE still using the MSD ignition, right?

Just for the 'fun' of it I dropped my idle to around 4-500. I quickley raised it back up some after I saw the oil pressure dropped way low. Is the lower oil pressure at very low RPM's anything to be concerned about?

For anybody interested in MSD with Pertronix Ignitor & Ignitor II!

Last night I sent Pertronix Customer Support an e-mail:

Will the ignitor LU-143 for the 45D distributor, used with a 3ohm coil for an MGB work with the MSD-6A Ignition Controller and Blaster 2 coil at 0.7 ohms?

If not will the MSD-6A work with the Flamethrower 3 ohm coil?

If not will the Ignitor II work with the MSD-6A and Blaster 2 coil?

Any other suggestions? Thanks Ray



Recieved an e-mail from Pertronix Technical Support:

Ray,

The Ignitor and Ignitor 2 work fine with the MSD boxes. When using the
MSD 6A please use what ever coil MSD recommends for that box. We don't
recommend the 3.0 ohm coil be used with a CD box.

Marvin Grebow Jr.
PerTronix Inc.
Technical Department Ext. 1030

Pertronix's recommendation for the coil no longer applies when wired through the MSD control box. Its my understanding that the power pushed through the Ignitor module is minimized to the smallest acceptable amount to achieve a signal.

For those contemplating use of the MSD box, there can be issues with the tachometer function and plug wires which may be expensive to resolve, so go into the project with either a lot of luck or a lot of patience!

I wish I knew (more on) what you were talking about.

Why

Ray, the pertronix doesn't attach directly to the coil, it triggers the MSD 6a, which fires the coil. I don't really trust a Pertronix hooked directly to a coil because every burnt out Pertronix I've ever come across (and, as an automotive electrician, I've come across quite a few) was attached either to the wrong type of coil or one that was out of spec. Using the Pertronix to trigger the MSD 6a is a very safe reliable setup, unless the coil goes bad and fries the 6a, that is.

The MSD 6a is a multiple spark capacitor discharge unit that will basically just give you a fatter spark except when at idle. At Idle, instead of just one spark per trigger it puts out multiple sparks for each trigger which lengthens the duration of the spark, which, in theory and in application, smooths out the idle and gives you a more complete burn of combustion chamber gas's. MG's run better slightly rich, which can lead to slightly more un-burnt gas being sucked out the exhaust pipe and in extreme cases, can lead to piston wall scouring. The 6a eliminates that problem. At high rpm's , with spark testers on each plug cable, where you used to be able to see each separate spark firing, now it looks like one continuous spark, like a glow plug on a diesel.

The install did claim it's victim's. I had to change my OEM current sensing tachometer to a later model conventional tach because the current sensing tach would not function with the 6a installed.
You will also go through distributor caps and rotors faster with the 6a, as the higher voltage set up burns the contacts in the cap and on the rotor faster then an OEM type set up.

And Jack, I said it WILL run at 450 rpm smoothly, I didn't say that I drive around with it set there. I have it set at 700 rpm for my normal day to day.

David,

So how long will dsitributor cap and rotor last. 1 year - 10,000 miles?????

I have a VDO tachometer, what kind of tach did you actually change to.

Ray

Ray, I found a 77 MGB roadster at pull-a-part that I scavenged the tach from. The late model "B"s used conventional tach's OEM.
As far as the dizzy cap & rotor...The cap is what suffers the most. Especially caps with aluminum contacts ,such as is used on "Standard" and "Well's" caps, which are about all I can find locally. After about 3 months you will want to pop the cap and scrape the gray carbon tracking off the inner cap terminals and then every three months repeat until the terminals start to noticeably disintegrate which will be about 8 to 12 months depending on how much you drive. I had forgotten and not cleaned mine off for awhile and sure as sh_t while I was cruising through Hollywood on the 101 she started to miss a little. Had to pull over for a quick scrape of the cap terminals and I was on my way. If you live where theres inclement weather you'd probably want to not forget. Or, if you can find a cap with brass, copper or some other metal besides aluminum, you'd get much better wear from it.