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<x-charset windows-1252>All this talk of holes in the cooling housing got me thinking...... I had always assumed that we were concerned about cooling air leaking out of the holes for the air conditioner and such. But....I am pretty convinced that the sheetmetal housing that guards the belts is a negative pressure zone. Think about it...the main cooling fan is pulling air from this into the magnesium cast housing and then blowing it over the cylinders. I reached this conclusion based on my recent experience with my main bellows. If you saw my pictures from the Parma trip and were wondering about the duct tape repair to my bellows....wonder no more. I was running without the hose clamps on the bellows (not recommended, BTW). The bellows got soft enough in the heat of running all day that the bottom rear of the bellows got SUCKED into the sheetmetal housing and got eaten by the fan on the pulley. So the REAL concern is about letting in some hotter air from the engine compartment. Assume that the hole for the timing marks is 1" in diameter and the small end of the bellows is about a 6" by 12" ellipse. The relative areas of these two are 0.8 in2 and 56 in2. The timing mark hole adds about 1.5% to the total cooling opening area. Not much in my opening. If you compare this to the openings in the rear fenders (56 slots that are about 6 by 1/2" for a total of 168 in2) the percentage is even smaller. Closer to a 1/2%. Throw in a couple of more holes for the A/C belt and you have maybe got a few percent of your total cooling intake that is pulling in hotter air from the engine compartment. I don't think you are reducing your cooling air flow at all by adding the holes. Maybe changing the temperature of the cooling air by a few degrees but not significantly. Make sense or am I just blowing hot air ?(pun intended) Later, John Jaranson '71 FI Auto Fasty (Jane) '66 Square (Sophy) About Half a Late Square (Organ Donor) http://mywebpages.comcast.net/jaransonT3/jaransonT3/ (This is the new address for my website) ------------------------------------------------ To unsubscribe, E-mail to: <type3-off@vwtype3.org> For more help, see http://vwtype3.org/list/ </x-charset>