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Join Date: Sep 2016
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912 engine

Hi. I received a 1969 Porsche 912 in my workshop. It was missing pretty bad. Initial observation showed 2 pistons on the left has a compression of only 60 psi, while the right side showed 180 psi. Opened the engine,didn't find much. Looks like The engine was worked on recently as the head and piston looks new. There are even traces of fresh silicon. However i noticed 2 things, 1. There was no had gasket and 2. The end ago on the oil ring was very big, almost 55 thow.
What should the end gap in the rings be?
What could be causing the missing?

Hope to get some help and advice. Its a big block, can i buy just rings for this?
Old 09-03-2016, 05:30 AM
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Are they stock pistons and cylinders? or they J&E's Any burnt valves? maybe had the rockers too tight? These pushrods will expand the valves need to be set correct cold unless you are using 4130 pushrods.
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Twinplug, head work, case savers, rockers arms, etc.
Old 09-03-2016, 08:10 AM
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The 912 engine does not have head gaskets
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Old 09-13-2016, 10:27 AM
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912

I believe there are two different piston crown configurations for 356/912 pistons. Visually inspect the top of the pistons and confirm that they are both the same from side to side. I would also measure the volume of the combustion chambers to see if there is any difference from side to side. Also take the oil screen cover off the bottom of the engine and visually check the camshaft for any lobes that might have excessive wear. The main issue here is the low compression. Even with low compression, an engine will still run without a miss, but will be way down on power. Find out why there is low compression, then deal with the miss.
The gap on the oil ring should have no impact on compression ratio.
As for the miss, if it is at idle, make sure the carbs are balanced side to side and cylinder to cylinder on each side. Then check the idle jets for clogging and needle valve settings. If the miss is under acceleration, check the ignition system and plug wires.
Please note that the copper gasket included in a head set is for cylinder to case sealing, and is NOT a head gasket.

Bob B

Last edited by NICE 69 S; 09-14-2016 at 11:41 AM..
Old 09-14-2016, 11:22 AM
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