MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Distributor advance springs.

G'day. I am looking to replace the centrifugal advance springs in my 25D4 distributor fitted to an 18GBH motor. Heritage spares in Sydney have a set but they say

"They are the dizzy springs but are heavier than standard, Performance spec. The standard springs are no longer available."

I'm sorry this is a bit vague but that is all I can get out of them, no other details are forthcoming. Does anyone know if a later heavier spring will be OK?

Cheers

Tony
Tony Oliver

Tony
It will all depend on what you are trying to achieve by replacing your current spring set The heavier springs will hold your advance back a bit right up till full advance is reached. If you are having pinging problems it could be a fix but if not you would just be wasting good power and economy. The only real way to check it all out is on a distributor machine and plot the curve to suit the state of tune of your engine. Cheers Willy.
William Revit

In order to attain maximum performance, the ignition curve should reach its maximum degree of ignition advance at an engine speed of 3000 RPM. The heavier springs may not do that, making for a loss of power due to a low amount of mechanical ignition advance when you really need it. Willy is correct when he advises you "The only real way to check it all out is on a distributor machine and plot the curve to suit the state of tune of your engine."
Steve S.

It depends on the engine. Some were designed to reach maximum advance at 2200rpm, some not until 6400rpm!

But before you put the distributor on a machine you need to put the *engine* on a rolling-road and plot just what curve it actually needs today. The original manufacturers specs for distributors aren't really relevant anymore with the change to unleaded and reduction in octane. Once you have done that you can recurve the distributor to suit. A very time-consuming, not to say expensive, process.
Paul Hunt

Tony,
As others have said, just buying springs is unlikely to help. You need to have the distributor curved to suit the engine.
I had two distributors recurved by Graeme Lord, who is a well-known B-series and Jaguar expert not far from where I live.
If you give him the details of the engine (cam, compression etc.) he will recurve to suit.
The 5-bearing engines in my MGB and Magnette are identical in terms of modifications, however Graeme used two different curves to take into account the different vehicle weights.
The difference in performance after recurving was amazing, particularly on the Magnette.

Because of his experience and knowledge, it is not expensive. He charged me $80 for two distributors, and that included finding a good body for the MGB distributor as the bushing was worn!

If you want to talk to him his details are:

Graeme Lord Automotive Services
37 Kingsford St
Fairy Meadow NSW 2519
ph: (02) 4283 6076


Regards,
David

David Overington

Tony,

I wish this was more convenient for you but we've got a guy over here in the northern hemisphere on the "other" side of the pond who really knows these things. His name is Jeff Schlemmer and his company is Advance Distributors. See: http://www.advanceddistributors.com/

Jeff rebuilds distributors completely. But much more important: he recurves them, and he knows how to do this to match today's fuels. At the least, I'd seek his advices before you do anything.

Cheers,
Allen
Allen Bachelder

Thanks gents. The reason I am after new springs is that one of them is kinked and I am also just re-furbishing the dist in general.

David, thanks for the tip. I am pulling the motor shortly to fit new bearings (damaged when the oil filter fell off) so I may as well send the unit to him and get it done right.

Tony
Tony Oliver

Tony Look up Performance Ignitions their in Nunawading Victoria. They are good to deal with and really know their stuff.
DENIS4

This thread was discussed between 01/09/2008 and 02/09/2008

MG MGB Technical index

This thread is from the archives. Join the live MG MGB Technical BBS now