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Thread: 911 cylider leak down test

  1. 04-13-2025, 12:54 PM #1
    72t4tom
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    911 cylider leak down test

    Its easy to find TDC for #1, any tricks or short cuts for the other 5? Are there 2 cylinders having both valves closed at the same time?
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  2. 04-14-2025, 08:27 PM #2
    edmayo
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    The crank pulley is marked every 120* .Pulley TDC mark is for #1 and #4. When you're at TDC of compression for #1 both valves will be shut. And at the same time#4 will be at end of exhaust stroke. If you're at TDC compression for #1 then go in firing order and every 120* will be the next compression stroke for the next cylinder in firing order.
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  3. 04-18-2025, 08:22 AM #3
    NorthernThrux
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    If you want a sanity check while following Ed’s advice, also follow the distributor rotor. It will point at the right cylinder (look at where each lead goes). For example, the pulley TDC mark can be either #1 or #4. But the rotor will tell you whether you have TDC for #1 or #4. If you have #4, do a full rotation and you will be at #1. Then rotate 120 degrees at a time from there to get 6-2-4-3-5. Verify with the rotor if you really want, but if you got #1 right, you should be good.

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