Well, just to further muddy the waters, most of the heads we have taken off
post 1975 MGB's in order to do valve jobs have not had hardened seats
fitted. The few that did appeared to have been off before and have had the
seats retro-fitted.
So, our belief is that no California MGBs came from the factory with heads
that had hard seats in them...............
Lawrie
British Sportscar Center
(Who has been working on MGBs since they were available new from the dealer)
-----Original Message-----
From: neil.cairns@virgin.net <neil.cairns@virgin.net>
To: RossOvercash <jroverca@tiac.net>
Cc: mgs@autox.team.net <mgs@autox.team.net>; carclub@mgcars.org.uk
<carclub@mgcars.org.uk>; mginfo@mgownersclub.co.uk
<mginfo@mgownersclub.co.uk>
Date: Thursday, August 06, 1998 11:42 PM
Subject: Re: Post '74 MGB heads, and MGB Register MGCC.
>RossOvercash wrote:
>>
>> I was under the impression there was no change in the head. The market
for
>> hardened valve seats and valves grew from that. Remember that leaded
>> regular gasoline was still avaialable in the US until the mid 80's at
least
>> I was still purchasing it in Texas!
>>
>> Safety Fast!!
>>
>> Ross Overcash,
>> >
>> >
>> > neil.cairns@virgin.net wrote:
>> > >
>> > > According to the August Issue of the MGCC magazine Saftey Fast, ALL
post
>> > > 1974, ( ie 1975 onwards,) MGB's have unleaded cylinderheads, both for
>> > > export and the UK markets. I was under the impression only USA
destined
>> > > cars were so fitted out.
>> > >
>> > > Anyone throw any further light on this, lots of us have spent money
on
>> > > having our heads fitted with hardend exhaust valve seats.
>> > >
>> > > Neil.
>> >
>> > See if you can get hold of the current and previous issues of the
>> > MGOC magazine,
>> > Emjoying MG. Roger Parker has written two lengthy articles on heads
and
>> > leaded/unleaded fuel for all MGs, not just MGB.
>
>> > PaulH.
>
>Like Ross I still believe that ONLY heads destined for the USA had
>'induction hardend' exhast valve seats. After Oct. 1975 the casting
>number 12H4735 was used on the 18V engine, ( offset oil feed to the
>rockers, as the water cavity was improved to cool the exhaust valve seat
>better.) This SAME HEAD was on over 1,000,000 1.8 Morris Marina's, and
>hundereds of thousands of Petrol versions of the Sherpa Van. Therefore I
>cannot see the idea of 'cheaper to produce if they are all the same'
>working when the MGB only use a tiny number. I know a 'Casting Number'
>only relates to the 'pattern' used in the actual casting of the item,
>and a PART NUMBER is the 'stores number' given to the item once machined
>and fitted out.
>
>I seriously doubt that BMC/BL/Austin Rover made ALL its 'B' series heads
>leadfree after 1975. I have a 12H4735 in the garage, and there are NO
>exhaust valve inserts in the head, nor do the seats appear very hard,
>no harder than the inlet seats. It is from a MGB not a Marina. Also, as
>a car nut I have had quite a few late heads modified to leadfree fuel by
>having seat inserts fitted, the engineers have never commented that the
>seats were ALREADY hard, they just machined out like any other
>grey-cast-iron.
>
>Roger Parkers article in Enjoying MG simply says cars destined for North
>America after 1976 were modified...and I quote " information on this
>area is a little patchy and fragmented". I totally agree with him here,
>it is 'fragmented' indeed.
>
>The MGCC 'MGB Register' say that North American Spec heads post 1975 are
>modified for leadfree, which is correct. They go on to say some of their
>cars have N. American Spec. heads fitted on their UK cars. How do you
>tell such a head from a European Spec Head, with the smaller inlet valve
>to comply with the post 1975 EEC Directive 15, Exhaust Emission???
>Regulations........after all both use the SAME casting 12H4735???
>
>And....18V engines use the engine prefix to denote the market the engine
>is for, ie for N.America it is 18V/Z, later 18V/AE for N.America using a
>catalytic converter, or 18V/Y for the European market, or 18V/F for the
>UK.
>
>Clear as mud, yes? Why give differing engine prefixes to engines that
>use the 'same' head. No, I think only the USA got the good heads, and
>California got the reaaly posh ones with hardend seats pressed in, as
>'induction hardend' seats were only 'unleaded tolerant'.
>
>Neil.
>
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