Thread: A new car!
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Unread 05-27-2018, 09:04 PM   #159
GlenL
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Default Crank in block

Moving right along...

The crank went in the block today. The Plasitgage numbers looked good but a little loose. They were close together with all between 0.07 and 0.09mm. The range is 0.02 to 0.098mm so in the upper range of acceptable. The crank turns very nicely with no hints of sticky spots.

The bearing set has all split bearings. These are NLA, last time I checked, and I spotted this on eBay a couple of years back. When cleaning the bearings, which were pretty tarnished, I found the marks "12 99" and presume these were made in December 1999. NOS trumps NLA every time!

It's not bolted in yet, though. I've gotta get the pistons in so I can fit the crank scraper kit. I got one from 928 Motorsports after giving up waiting for the one I ordered from Ishihara-Johnson.

I checked the ring gaps on the Goetz 97mm rings. One ring went into all holes to see if there are variations (not really) and then all the rings went into one hole. This way I can put longer rings into bigger holes.

As many people have found, the top rings are too short. The gaps are from 0.6mm to 0.83mm where the spec is 0.2 to 0.4mm. Rats. I'm going to look into getting some other top rings. The second rings are came in at 0.43 to 0.53 so not far from the 0.4mm max for those.

One confusing part was the the Goetz rings come in a three-part envelope that's numbered 1-2-3. I thought the rings were good until I realized that Porsche numbers from the top 1-2-3 and these were numbered backwards. (3-2-1) The #3 ring (oil ring) has a gap spec over 1mm so I thought the top rings were golden but the wide gaps I was finding bothered me into digging into it. The "tech spec" booklet has the gaps but doesn't say what 1-2-3 are. One of the exploded diagrams in the manual shows 1 is the top. Goetz thinks 3 is the top. Cripes. Other sources and the "rules of thumb" for gaps show that the top should be smaller and 0.4mm is appropriate.

Next up is figuring out what to do about the top rings and to get the scraper fitted. And check the rod bearings. I'll probably assemble and install the pistons using the rings I've got and hold off using the new rod nuts. Might need to take it all apart and I can move ahead while figuring out what to do with the rings, and while getting any new ones shipped in.
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