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<x-charset iso-8859-1>this is what I used to think too. Then I got an engineering degree, and started to think. if I recall from chemistry, reaction speed doubles for every 20C temp increase. The #3 cylinder ran slightly hotter (not for the reasons most think, I'll get to that in a minute), and so combustion speed is faster. The #3 retard just gave "equal timing" that the engine saw. Also, ALL 009s from the early 80s on do not have this retard, and if you add a compufire or pertronix, you are also removing the retarded timing on #3. # 3 &4 run hotter on upright engines on 70 and earlier models because the oil cooler preheated the cooling air to the 3/4 side. 1 & 3 run hotter than 2 & 4 because of the restriction of the heater boxes. 1 & 3 also get less oil than 2 & 4 (slight pressure drop, furthest away from the pump), and less oil means less heat removal. if you look at this, #3 has all the problems, so it's the worst cylinder regarding heat. John Aircooled.Net Inc. ----- Original Message ----- From: Per Lindgren <lindgre@online.no> To: <type3@vwtype3.org> Sent: Friday, December 28, 2001 12:09 PM Subject: Re: [T3] carbs v FI > > > Russ Wolfe wrote: > > > They did it to help with cooling on the emission control equiped > > cars. This didn't start until about 1968 MY. > > My understanding was that this was done to run #3 cooler on Bugs, as the #3 > exhaust valve was prone to breaking. Of course, it didnt help that the cooling > air for cyls #3 & 4 had to pass through the oil cooler first. This was solved > when they introduced the dog house fan casing. Of course, this isnt as much of a > problem for the type 3 as it was for the type 1 and 2, and AFAIK the problem > wasnt as big after the dog house and retarded #3 ignition was introduced. > > PerL > 73 Variant L > > ------------------------------------------------------------------- > Search old messages on the Web! Visit http://www.vwtype3.org/list/ > </x-charset>