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MG MGB Technical - Petronix for Mallory Dual Point

Sorry to being this up so soon again but I cannot find the topic in archives. Has any one used a petronix in a Mallory Dual Point dizzy. My old dizzy is shot, wobbles. But I can not get rid of a high spped skip with the 2 points and all combinations of springs in the Mallory.
Ken Knize

Ken,

I sent my distributor to Pertronics and they made a custom base plate. I was not too much more over a standard pertronics unit.

Shareef
Shareef Hassan

Ken-
Crane makes a pointless conversion kit for the Mallory distributor. It's part# 700-0309.
Steve S.

Ken,
I have one on my Mallary fit to my Spitfire. Includes the plate for the Mallary, as easy to fit as removing and reinstalling two screws. The Ignitor II is only 89.00 at http://www.carshopinc.com/index.php/cPath/21_24_25
Paul Slice

Ken-
A high speed miss is usually a carburetion problem. Have you rebuilt your SU carburetors? What year is your engine? Is it modified? If so, what modifications? If you don't know for sure which year your engine is, what are the engine numbers?
Steve S.

Yes I did rebuild my SU's in my 73 low compression. Don't have the numbers handy they are in the garage. When I put the K&N filters on I changed to the appropriate needle. The dizzy was the first and badly needed mod followed by K&N SU filters w/ appropriate needles. Peter Burgess exhaust custom built with Peco (I think, big red pipes) on the stock exhaust manifold. She did run rough prior to carb rebuild huge difference afterwords except for the skip. Good compression, good oil pressure.

Thanks for advice on electric ignition, I'll print out for future use.
Ken Knize

Ken-
You have the SU HIF4 carburetors with the spring-biased needles, I presume. These bear against the interior bore of the jet and cause it to wear. did you replace the jets at the same time as the needles?
Steve S.

A Mallory Unilte is Dual point body with an electronic module. A real fine piece of equipment. If your old Mallory has a wobble putting on a Petronix won't help. If I am not mistaken the bearings of a Mallory body can be replaced. Maybe that is where you should try starting. Good Luck. ED
E kulick

Ed's right. Don't waste your time trying to doctor a bad distributor with electronics. Fix the actual problem first, then try electronics if you're still not pleased. Do you use a dwell meter to adjust your points? Guessing at point settings with a feeler gauge is the number one ignition problem, and needs to be addressed frequently (more than once per year) for a very smooth idle and good performance. Getting both sets of points spot-on is as difficult as tuning a pair of SUs. Electronics eliminate that tuning, but generally give you a higher dwell, so your idle won't be as smooth.
Jeff Schlemmer

Using a feeler is gauge is fine for setting the basic gap but it should be fine-tuned with dwell for accuracy. The advantage of having a dwell meter is that it is a moments work to check the 'gap' without doing any dismantling, and putting a gauge between the points usually transfers a film of grease to them so they need cleaning. When I used to check by gap at service intervals it usually involved removing the points to reface them, by which time you might as well replace them. But since I started using dwell for the check I haven't had to touch the points between replacements. I was without a dwell meter for over a year after the old one packed up and only replaced it a couple of months ago. I checked both cars and found both were well in spec, and on both cars they have been on and not touched for well over 3 years and 10k miles each.
Paul Hunt

And if you don't have a dwell meter, they go pretty cheap ($20) on ebay, if you're into that sort of thing.

Jeff Schlemmer

The old dizzy I speak of was stock. The replacement is the Mallory, thought I would go for the best not knowing the technology was beond my knowledge. Any way I have been wondering about a dwell meter. I feel that I have a sound engine I just dont have the nack to tune it properly. I love a challenge and this seems like a challange I can accept.

Thanks, I'm going shopping for a dwell meter, I have a timing light but what should I look for in a meter? I like to go first class.
Ken Knize

There are several auto multi-meters around with dwell and tach for engines with different numbers of cylinders as well as amps, volts and ohms, continuity, diode, and more. Originally I had a gunsons but it packed up after a few years (I have analogue instruments that are still working after 40 years so I was a bit peeved) and didn't facny spending another eighty quid. I bought a Draper for less than half that which has everything the Gunsons has except 250v AC, but there isn't much of that on an MG.

Having a seperate tach is very useful for checking the one in the cabin as well as setting the engine revs to various values when checking the ignition advance curves.
Paul Hunt

Dwell meters aren't sold in most places because there are very few car on the road with points. If you have a flea market near you you can sometimes find a Sears Penske analyzer for reasonable prices. JC Whitney sells an Actron Dwell/Tach/Volt analyzer for $34.99.
Part #SD495938R. Autozone sells Actron instruments so they may carry them or may be able to order one. FWIW, Clifton
Clifton Gordon

Thanks everyone, I couldn't log on for a number of days and I departing on a trip this week (retirement is great) I'll get back to the Mallory when I return. When I get it sorted out I'll post my results.
Ken Knize

Mallory makes a conversion kit for the dual point distributors as well. They are about $90.

http://www.centuryperformance.com/detail.asp?product_id=MAL-563

I can't remember the series of the distributor, but I think this is the kit for ours.

Jayme
Schwartz

This thread was discussed between 01/05/2004 and 13/05/2004

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