Bud:
You are correct, you have the ported vacuum dist. hooked up
properly. I do not know a good source for good 25Ds'. Parts are a
problem, the points plate is not available new. Lucas discontinued
production of obsolete 25D components and has manufactured a new 45D
unit specifically for the early application. Lcs 41427, Moss 143-110
uses the later wiping points and has corrected a number of problems that
the 25D had.
Pertronix unit LU-143, 222-435 fits the distributer. To my mind
this is the most reliable set up that will give many years of trouble
free motoring. Pricey, but at what cost reliability.
One point that I might add. The Pertronix units seem to have
difficulty with worn dist. bodies. The optical electronic ignition
units such as Crane/Allison and Lumenition can handle very worn units
without a problem.
Also note, I am not a fan of the Mallory dual point. A lot of
thinking went into the design of the original specification vac/cent
advance curves for the car. For normal driving I do not believe that I
can improve on the original design without access to a rolling road.
Kelvin.
73 BGT with HS4 and 41427/Pertronix in boxes.
-----Original Message-----
From: Bud Krueger [mailto:bkrueger@ici.net]
Sent: Saturday, November 28, 1998 1:26 PM
To: Dodd, Kelvin
Cc: mgs@autox.team.net
Subject: Re: 25D4 vs 45D4
Hi Kelvin,
The distributor is a 25D4, Model 41220. Vacuum is being taken
off of the
rear HS4 at a small tube inseted into a hole in the carburetor just in
front of
the mounting flange, so I guess it's ported vacuum. A big problem is
that the
moveable plate in the 25D4 is badly worn at the the central hole where
it
rotates about the center shaft. The effect is to cause very erratic
ignition.
I suspect that it's causing an intermittent path to ground for the coil
primary. Do you know of a source of decent 25D4's ? Thanks.
Bud Krueger
Dodd, Kelvin wrote:
> Bud:
> It is important to make sure that all of the pieces work
> together. You will need to check the distributer number to make sure
> that it has the correct characteristics for the carbs. You can use
> either of the two distributers once you know what vac/cent.
> characteristics they have. With the HS4 carbs you can either plumb
the
> vac. adv. to the ported fitting on the rear carb. Or you can pick up
> vacuum at the manifold. Either system works with the correct dist.
The
> most documented layout would be the HS4 and an early (non-HIF) 25D.
> Once rebuilt with high comp. pistons and an early cam you would have
> specs similar to 62-67 cars. The factory designed this setup for the
> best balance of power for normal usage.
> Get me the dist. numbers and I will check to make sure they
are
> suitable. Also check the dist. shafts for wear and vac. units for
> operation. To my mind the best bet for you would be a new 45D dist.
> suitable for the HS4 carbs. Pricey, but set and forget. There is a
> Pertronix conversion for this dist.
>
> Kelvin.
>
> -----Original Message-----
> From: Bud Krueger [mailto:bkrueger@ici.net]
> Sent: Wednesday, November 25, 1998 9:32 PM
> To: MG List
> Subject: 25D4 vs 45D4
>
> A bit of advice, please. My '77MGB has HS4's and an early twin
downpipe
> exhaust
> system (once I get around to installing it). I will be using a
> Pertronix
> ignition system. My problem is this: I have a 25D4 and a 45D4
> available to
> me. Which one should I use? Why? TIA.
>
> Bud Krueger
> 52TD
> 77MGB
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