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Old 11-13-2018, 06:23 PM   #29 (permalink)
Isaac Zackary
Full sized hybrid.
 
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Join Date: Apr 2015
Location: Colorado
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Suzy - '13 Toyota Avalon Hybrid XLE
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Quote:
Originally Posted by redpoint5 View Post
My '69 Beetle had a valve burn up. Some say that was due to running lean. Either way, I treated the throttle as an on off switch. The car was gutless but fun, especially with the tiny aftermarket steering wheel which made it feel like a go cart.
Those Beetles where quite the cars!

Up through 1970 all Beetles had single port engines with the oil cooler in the cooling shroud. This made the #3 cylinder vulnerable for three reasons. 1. It and the #2 were offset farther from the center of the cooling shroud than the #1 and #4 cylinders which gave them less air to cool. 2. It and the #4 cylinder also were after the oil cooler, which gave them pre-heated air to cool them. And 3. the way the single port heads drew in air caused the #2 and #4 cylinders to get less air and fuel as they started the momentum of the air down the long skinny intake to the head, but the #1 and #3 cylinders got a whole lot more air and fuel as the intake charge was already moving in their direction making them do most of the work. The only cylinder to have all three disadvantages was the #3 cylinder. All the others only had one of these disadvantages. VW worked around this by making all their single port distributors run the timing retarded in the #3 cylinder compared to the others. But when the distributor was replaced most people dropped in the infamous 009 distributor which didn't have retarded timing on the #3 cylinder. At that point anything could make the #3 cylinder overheat, ping and burn up valves and such, including, but not limited to, running just a tad bit lean.

When VW went to the dual port engine they resolved all those problems. 1, they put air vanes on the cooling tin to direct the same amount of coolin air to all the cylinders. 2, the oil cooler was removed from the shroud that cooled the heads and cylinders so all received the same temperature of air. And 3, the new dual port design gave each port a longer individual runner to help make them all receive the same amount of fuel and air and do the same amount of work.
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