Something seems to be missing in this equation. I may be wrong, but it
seems very unlikely that the vacuum advance is designed to produce such a
linearly progressive advance, such that 1inch of mercury equals 1 degree of
advance.
I'm going to put a vacuum pump on my distributor so that I can plot the
advance. It's got me curious...
Lonn Howard
'70 TR6 -mine
'71 TR6 -in my garage, therefore it's mine (dad might disagree)
'70 MGB GT -mine, mine... all mine
"We are but temporary custodians with an obligation of preservation."
----- Original Message -----
From: Unger, Larry G <larry.g.unger@lmco.com>
To: 'Rene van Maanen' <renevm@support.neth.hp.com>; <mgs@autox.team.net>
Sent: Wednesday, December 09, 1998 6:45 AM
Subject: RE: 25d4 advancer distributer on a 68 B
>Rene van Maanen wrote:
>
>> Does someone know what the number of degrees is that the
>> vacuum advancer creates for the ignition?
>>
>> It's a 25d4 advancer distributer on a 68 B.
>
>Rene,
>
>Here is info that Kelvin posted awhile back ...
>
>
>> MGB Dist# Vac.# Vac.Adv. Type
>>
>> 18GF 40897 54411230 5.13.10 ported
>> 65-67 41288 54411985 5.13.10
>> 67 41290 54412170 5.11.7
>> 68 41288 54411985 5.13.10
>> 69 41264 54415625
>> 70 41288 54411985 5.13.10
>>
>> 71 18GK 41339 54414868 7.13.5 manifold
>> 72 18V 41370 54423989 7.13.3
>> 73-74 41491 54425359 10.15.5
>> 75 41599 54425516 10.15.5
>>
>> Note the change in advance characteristics in 1971.
>> The later units come in at a higher vacuum and gives
>> less advance.
>>
>> 10.15.5 = Movement starts at 10 ins of Mercury
>> Movement stops at 15 ins of Mercury
>> 5 distributor degrees advance at maximum movement
>>
>
>Hope this helps ...
>
>**********************************************************
>Safety Fast! ... larry.g.unger@lmco.com
>'61 MGA 1600 MkII
>
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