Hi All,
I stripped my '78 911 SC engine down to the short block. At least 85K on the car.. could be a lot more as speedo was replaced by PO. Keep in mind this is the very first engine I have stripped down, so my experience is minimal. I am debating whether I should stop at a top end or do a complete rebuild. Here's why:
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Oil pressure: 4-5 bar when cold. Then, when warm, will match the revs up to 3 bar. It maxes out at 3 bar regardless of higher RPMs. I did not check the pressure sender nor do a mechanical pressure test before pulling the engine. I checked the connecting rods and all look good. Some side-to-side play (which I read is normal) but no back and forth play. Cylinder 5 rod has some pitting on the rod where the piston wrist pin goes through. See photo.
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Knocking Noise: Seemed to be coming from cylinder 4, 5, or 6 valve train but I don't want to assume. My cam rocker shafts were beginning to walk out on the exhaust side. If it is a rod knock, would it be obvious upon inspection of the rods in the short block?
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Compression/Leakdown: 110-120 PSI on all cylinders (consistent). 75% leak on cyl. 1 (intake) and 5 (exhaust). 20% on 6 and 2 (rings). 4 and 3 had good leakdown numbers. Guessing this will be solved by the top end valve job and new rings.
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Chain: Looks good but has obvious wear/darker spots.
What would you do? Top end or full rebuild? Note: this is going to be a street car and not a track car.
Supporting photos:
Pitting on cylinder 5 connecting rod (where wrist pin sits). This is the only rod that has pitting:
Rods on cylinder 4, 5 and 6 end: notice the gunk especially on #4 opening.
1, 2, 3 side of the case. Notice how the case openings on #1 and #2 are a lot darker than #3. Is this a problem? What is the cause?
Timing chain showing wear:
Pistons and cylinder heads. 1,2,3 on the left and 4,5,6 on the right.
Image showing carbon buildup on the piston. All pistons & rings seem to have a lot of carbon buildup.
