Subject: Re: [Mgs] MGA 180 out Distributor Mystery

From: "PaulHunt73" <[email-masked]>
Date: Sun, 21 Oct 2012 11:19:34 +0100

As the points weren't opening on the original distributor, that was the 
original problem.  You then fitted several distributors.  If you didn't 
remove the plug leads from either the plugs or the original cap (did you 
reuse that with each of the replacement distributors?) then the assembly of 
the rotor and the drive shaft of the original distributor was 180 degrees 
different to the others you tried.

Whether it is right now or not is another matter.  Static timing with the 
pulley mark by the appropriate pointer will show the points opening when 
No.1 *or* No.4 pistons are at TDC, but only one of those will be on its 
*compression* stroke.  You determine that by removing the plug from No.1 
cylinder, putting your thumb over the hole, and turning the engine until 
compression pushes your thumb off, then turn to TDC.  If the rotor is now 
pointing to about 2 o'clock, then either drive gear and distributor assembly 
are both correct, or both 180 degrees out.  If it's pointing to about 8 
o'clock then one or other is 180 degrees out.  Whether it is worth doing 
anything about it is another matter.

PaulH.

----- Original Message ----- 
> ... Two sets of newly installed points would not open when fully
> adjusted out.  A club member suggested that the distributor bearing was
> wearing out. I took the 1800's original 25D distributor and base clamp
> and installed it.  ... I got used another DM2 with the same result.  I 
> installed a new Lucas 25D, same
> result. Then I switched the wires replacing #1 with #4 and # 2 and # 3
> figuring it was 180 out.  Bingo, it purred like a kitten.  Mystery.  How
> could the distributor drive gear get 180 out when I never touched it? 
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From: "Clayton Kirkwood" <[email-masked]>
Date: Mon, 22 Oct 2012 16:40:37 -0700

Correct me if I am wrong please, but it seems the only reason to set the
distributor up "right" with the rotor pointing to the 1st cylinder (1
oclock) is so that everybody does it the same way and nobody gets confused
like this. If the distributor is 180 degrees out, one only need change the
wires around. In fact, you could technically put the distributor in in any
orientation and as long as you get cyl 1 tdc on the compression stroke and
turn the distributor body to line up the rotor with the cyl 1 ignition wire
you would be ok. Of course, you may have problems with the vacuum advance
alignment but that is a different story. I think it basically comes down to
everybody agreeing to one convention like driving on the left side of the
road is wrong:>)

Clayton

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On
Behalf Of PaulHunt73
Sent: Sunday, October 21, 2012 3:20 AM
To: Robert J. Guinness; MG List
Subject: Re: [Mgs] MGA 180 out Distributor Mystery

PaulH.

----- Original Message ----- 
> adjusted out.  A club member suggested that the distributor bearing 
> was wearing out. I took the 1800's original 25D distributor and base 
> clamp and installed it.  ... I got used another DM2 with the same 
> result.  I installed a new Lucas 25D, same result. Then I switched the 
> wires replacing #1 with #4 and # 2 and # 3 figuring it was 180 out.  
> Bingo, it purred like a kitten.  Mystery.  How could the distributor 
> drive gear get 180 out when I never touched it?

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From: "PaulHunt73" <[email-masked]>
Date: Tue, 23 Oct 2012 08:43:58 +0100

Quite.  It's a convention.  As the distributor will only fully engage with 
the drive gear in one position it is only of use when changing caps ... or 
removing plug leads from cap and/or plugs ... or installing a different 
distributor ... Come to think of it that's quite a few 'only's, and a bit 
like 'What did the Romans do for us?'.

However with the distributor inserted and the drive dog engaged with the 
gear you can turn the body all you like but the rotor won't move.  That's 
why you have to move the leads round the cap if the distributor assembly or 
drive gear orientation aren't as they were when the engine last ran.

PaulH.

----- Original Message ----- 
> like this.

> ... turn the distributor body to line up the rotor with the cyl 1 ignition 
> wire 

[email-masked]

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From: "Stephen West-Fisher" <[email-masked]>
Date: Tue, 23 Oct 2012 07:47:27 -0400

You are probably correct in this application, but...
I would not generalize this to all engines. I seem to recall something about
the lobe timing being different on some engines, but I do not recall the
application just now. It may have been high performance air cooled engines
trying to control the heat so different timing per cylinder.

--
Stephen West-Fisher
N4IK
-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On
Behalf Of Clayton Kirkwood
Sent: Monday, October 22, 2012 7:41 PM
To: 'MG List'
Subject: Re: [Mgs] MGA 180 out Distributor Mystery

Clayton

[email-masked]

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From: Richard Ewald <[email-masked]>
Date: Tue, 23 Oct 2012 05:41:03 -0700

Air cooled VWs had different timing on the #3 cylinder. The oil cooler sat on
top of #3 so it naturally ran hotter.
By playing with the cam and ignition timing they tried to get it to create
less heat in that cylinder.
This is why AC VWs have such an odd sounding idle.

Sent from my iPhone

On Oct 23, 2012, at 4:47, "Stephen West-Fisher" <[email-masked]>
wrote:

> application just now.

[email-masked]

---

From: "Stephen West-Fisher" <[email-masked]>
Date: Tue, 23 Oct 2012 08:52:50 -0400

I was thinking VW, but I haven't worked on aircooled VWs since the early
'70s.
One that would come in was a dragster, around 200 hp that didn't have
anything installed if it didn't provide power. Including the cooling system.
It only had to run for a minute or two at a time :-)

--
Stephen West-Fisher
N4IK

-----Original Message-----
From: Richard Ewald [mailto:[email-masked]] 
Sent: Tuesday, October 23, 2012 8:41 AM
To: Stephen West-Fisher
Cc: MG List
Subject: Re: [Mgs] MGA 180 out Distributor Mystery

Air cooled VWs had different timing on the #3 cylinder. The oil cooler sat
on top of #3 so it naturally ran hotter. 
By playing with the cam and ignition timing they tried to get it to create
less heat in that cylinder. 
This is why AC VWs have such an odd sounding idle. 

Sent from my iPhone

On Oct 23, 2012, at 4:47, "Stephen West-Fisher"
<[email-masked]> wrote:

> I would not generalize this to all engines. I seem to recall something 
> about the lobe timing being different on some engines, but I do not 
> recall the application just now.

[email-masked]