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From: Dave Baker
Subject: Re: Triumph 6 cyl head diff's
Date: 11 Jun 1998

>In article <>, Chris Morriss
><> writes
>>New point.  I was told that the valve sizes in the mark 2 head were too
>>big too have hardened exhaust seats fitted to allow unleaded running.
>>There's certainly only a tiny land area between the inlets and exhaust
>>valves.  Is this correct, or are hardened seats (stellite?) available
>>for the Mk2?

Almost any cylinder head can be converted to unleaded with straightforward
machining and readily available seat inserts. We do it all the time. Inserts
are not stellite. Stellite is a facing material used for the tips of 21/4n
stainless valves and for the seating area of the valve itself in some
applications. Seat inserts are high chrome steel normally with a rockwell C
hardness of around 45 which will stand any fuel or tubocharging. Only the
exhaust valve seat is critical in most applications, inlets don't usually run
hot enough to be affected by unleaded although replacing seat inserts on both
inlet and exhaust does lead to a bullet proof conversion.

Valves do not normally need to be changed despite what many people say,
provided that the exhaust valve head is 21/4n or similar rather than EN52b
non-stainless material. Most modern production unleaded engines still run
exactly the same valve material as older engines. One piece EN52b inlets and 2
piece exhausts with EN52b stems and friction welded 21/4n heads. For more info
or advice on converting any classic cylinder head to unleaded (and porting
improvements to increase power at the same time if required) please EM me.

Dave Baker at Puma Race Engines - specialist flow development and engine work.

From: Dave Baker
Subject: Re: unleaded conversion
Date: 10 Nov 1998

>Subject: unleaded conversion
>From: ".." <.@.>
>Date: 08/11/98  20:07  BST
>Message-id: <>
>is it possible to convert a C Reg Orion 1.6Ghia to unleaded petrol , will
>the MPG go down or stay the same.
>What sort of cost?

The valves and seat inserts are perfectly happy on unleaded just as Ford made
them. I build more of these than any other engine and drive one myself in my
XR2. Over the years I have cut seats on heads dating from 1980 right up to post
1989 XR2i derivatives. Some of the heads have bronze exhaust seat inserts and
others have steel. Inlets are always steel. There does not appear to be any
rationale (i.e. year or vehicle model) behind this and I suspect it is just
Ford sourcing from alternative suppliers. As a rule, any modern aluminium head
will have inserts of a high enough quality to run unleaded. Only cast iron
heads like minis, crossflows, MGBs, Pintos etc will suffer from seat recession
with unleaded and usually only on the exhaust side.

The only exception I ever came across was a Daimler Dart 2.5 V8 which had cast
iron inserts if I remember right.

Dave Baker at Puma Race Engines (London - England)  - specialist flow
development and engine work. Puma billet aluminium throttle bodies from £390
per 4 cylinder set. Grooved brake discs coming soon.

From: Dave Baker
Subject: Re: Unleaded in XR3i - conflicting advice
Date: 20 Nov 1998

>From: (John Armstrong)
>I have recently bought this car (1988 model) and am confused by
>conflicting information about the use of unleaded petrol.
>My previous car was an XR2, which as I understand it uses basically
>the same CVH engine without the fuel injection unit.
>The Haynes manual for the XR2 stated that engines from 1985 onwards
>(IIRC) could use unleaded and earlier ones could use unleaded with one
>in four tanks of 4*.
>The (Ford) owners manual for the XR3i says leaded only.
>The Haynes manual says consult your dealer.
>A mechanic friend of a friend who used to own one says it doesn't have
>hardened valve seats and is 4* only.
>Amongst the paperwork I got with the car is an invoice from a Ford
>dealer for adjusting the engine to run on unleaded - this was only £8,
>so I assume it was only an adjustment of the timing.
>I am currently using 4* just in case, but could do with being sure,
>especially when 4* is phased out next year.

We've just been through this at length for someone else but just to re-iterate.

The official advice is what ford offer. The practical advice is this: All CVH
engines have adequate seat inserts to run unleaded. There was never any change
to the valve or guide spec. I have seen no major change in seat inserts between
1980 and 1989. They all cut the same on the valve seat machine and they all
last perfectly well in road use. Some heads I see have bronze exhaust seat
inserts - they can be found in any year of head - no particular pattern to it
re make or year of vehicle.

Use unleaded and maybe knock the timing back a degree or two if it pinks.
Otherwise just don't worry.

Dave Baker at Puma Race Engines (London - England)  - specialist flow
development and engine work. Puma billet aluminium throttle bodies from £390
per 4 cylinder set. Grooved brake discs coming soon.

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