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Unread 08-03-2021, 06:28 PM   #241
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Default Fuel gravity valve

The best part were made in W. Germany unless they don't belong on the car!

I thought that the fuel gauge was wonky but realized it was the tank vent. The fuel pump would clunk off at about 3/4 tank. Then I thought to wait and see if it'd take more. Sure enough. Wait 15 seconds and it'd take 1 1/2 gallons more and do that 2-3 times.

So... I got to it and traced the fuel vent line. I started at the tank when I should have started at the end. 928s have a simple exit behind the bumper at the end of a solid line. Apparently, after the rear-end accident, someone improvised with a VW Fuel Gravity breather valve 161 201 753. From what I can find, it's supposed to cut off the vent if the car rolls over. It was mounted right-side up and just clogged.

No P-cars use this part!

That thing is almost completely blocked. I tried some brake cleaner but not much improvement. With it off, which is what the 928 basically has, the air flows through the vent line freely.
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Last edited by GlenL; 08-03-2021 at 09:00 PM..
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Unread 08-04-2021, 06:47 AM   #242
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Seems odd that someone would go out of their way to find a specific VW part for the tank vent. Could it have been a dealership service bulletin? Are you going to leave it open or replace with a new valve?
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Unread 08-04-2021, 12:31 PM   #243
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It's not for sale as a Porsche part and wasn't on any models. Now that I understand it, they had it hooked up backwards.

The 928 had a different approach to preventing gas from draining in a roll-over. This part is a valve that closes when it's turned over. The 928 has a fairly large expansion tank placed higher than the tank, some hose that loops down/up and then the vent again lower than the tank. Turning the car over wouldn't let gas stream through the vent.

My hunch is that a mechanic that knew VWs thought this was how it would be done on a Porsche.
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Unread 09-09-2021, 06:23 PM   #244
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Default Racing at Road America

I wish I was faster! With the weight mandate (3401#) and wheel width limited to 8", I do what I can.

The car had some issues. The oil ejection continued and I needed to short-shift at 5500 to control that. The clutch started to slip on hard shifts, too. Looks like I've got some car work coming up.

Still... I finished both races. The complete second race is in the following video.

https://youtu.be/s0m4sZv5mEw
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Unread 09-25-2021, 01:14 AM   #245
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Default Reringing the pistons!

Here's a pic that doesn't need much explanation. The engine is back out. The oil ejection problem just wasn't diminishing and I didn't want to short-shift the engine when racing. At BIR, the oil would stay in the engine with a 6000 RPM shift point. At Road America, it needed to be shifted at 5500 to prevent filling the catch can.

It could have been broken rings or that the top rings weren't breaking in. Maybe it's something else, but the rings weren't broken and new top rings are going in.

If ya go back a few dozen posts, you'll find where I substituted the top rings for a 930 from Mahle for the OEM rings from Goetze. The 930 is nikasil coated and the rings should have worked for Alusil...but apparently not.

I've sourced top rings from Total Seal. These are the same as I put in my other 928, and are working great. The engine is 98mm and this one is a a stock 97mm. When I was building this one, Total Seal said that they didn't have a viable ring for 97mm in stock. Now they do. The rings are for a 3.825" bore where 97mm is 3.818". Checking one ring, they'll fit great.

Total Seal P/N: 101896 AP 038250 0585 150 C-33 STEEL TOP#

That ring has pvd-applied chrome nitride [CrN] face coating.

The rod bearings all look good. Actually, #2 and #6 look less good but not worn or scored. The rest look new.

This will also be a good time to replace the clutch discs. Those started slipping in the 2nd race at RA. I had the discs re-lined locally as, at the time, only Porsche was supplying the replacements and they were super expensive. I'm getting some used discs that should have good life left. I'm not sure what the problem is. The dual-disc clutch should hold a lot of torque. Maybe the lining was not up to the job.

Quick and easy, so far. I want this done soon to get a track day in this fall. And to get the jobs done before winter.
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