Woodpile

I put the pump in - nothing special. 500 for the high pressure variant from spruce, and 100 refundable core. If memory serves I got a new set of very stubby wrenches, that and some wobble extension for your ratchet (a rubber arm would have been handy) plus the cost of a quick inspection

My fluctuating problem was cured with a new mech pump. My GI275 EIS seems to be related to a (likey false) low constant pressure - bottom of green.

Thanks, I am still not satisfied with my values and will have a look at this too...when I finally get a prop

I just replaced mine in in the 20F. I have the cooling shroud and needed to slightly raise the mag cover to get the shroud out. Surefly mag cover was quick to tilt up (just another set of safety wire). I removed the oil filter for better access from the top. - tape the gasket when re-installing - the hoses are a bear to align - never thought I could get my arm under the exhaust and come up the middle. Dropping lower cowl might be useful, but not worth the extra work - just the ram air duct would take me an hour. - less than 8 hours and I've never done one - no need to remove mag or tilt engine - exercise caution on Aircraft Spruce, as 3 different pressure versions of the same pump are on the same page. The compatibility sheet is spot on though.

I am still very happy with the cooler temps and the indications on my new GI275 engine monitor attest to the performance better than the old analog gauge

FWIW, I replaced the mech pump. Pressure is around 18 and no spikes noted on ground run. I guess I can say that the change to the Garmin Engine monitor made this issue apparent and was well worth it.

Thanks, I didn't see this on the analog, so I presumed it was similar to my manifold pressure drops. Looks more like a mech pump issue now.

So my fluctuation is on the low side, my cruise is around 15 psi (1 above red). I have a new fuel line, but maybe I just need more pressure. Can the mech pump be turned up, or time for a new one? Boost runs at 18

The description on their website was light oil or water, IIR. That would probably put 100LL right in the middle

I was very happy with the PS-8G to fix my wild MP swings

I'm hoping to contribute a bit to the topic. I just had a GI-275 EIS installed in my 1970 20F. Love the gauge; rebuilt fuel sensors and have much better info in cockpit. Two issues arose. The MP was bouncing all over the place. A different thread suggested a particular snubber; $14 later and nice stable MP. The second was with instantaneous fuel pressure dropping to 0 - continuous pressure was normal at 16-18 on the mech pump, and 18 with electric boost. Whenever the boost was off, the instant needle would periodically drop to 0 and trigger the alarm. This usually happens at max power and only with boost off. There are no abnormal indications in flow. I suspect this is only something that is visible due to the sensitivity of the transducer - never saw this on the analog. I just got off the phone with Garmin and they said the 275 display could not be adjusted (sensitivity reduced etc) - it only displays what the sending unit says. It is my thought that even a fraction of a second buffer would eliminate the indication. One mech suggested to replace fuel pump - other said don't waste time/$. After reading this thread, and the success with MP, I think a bit of extra fuel line or some sort of snubber is worth the effort.

Is there a particular type or thickness of aluminum required (or preferred) for this work?

That seems like a fascinating, and easy solution. Could probably be done without removing the rails, too. I'll look into that, thanks.

At my last annual, the mechanic pointed out that my rail holes were getting oval shaped and that I should consider new rails. There are no new rails, and the salvage ones I have found are not a significant improvement. Is there any general knowledge on what amount of oval is safe? Can they be sleeved? Or plugged and re-drilled?