Going to a 520 oil pump on the 470-50 and apparently the firewall needs to be dimpled? Who has done that and how much clearance is necessary?

Here is s picture of my 180K firewall. I am running the O470U integral filter oil pump on my 470-50 that was converted from a 470K. I ran this same pump on my K when it was on the "54" 180 with firewall I assume is just like yours. There wasn't much room but enough to clear that oil pressure adjustment shaft. When I first took the K to be converted the shop told me I would have to get a 520 pump even though I told them the U pump ran at top of the green. When i picked the engine up after conversion they said a Service Bulletin had made it okay to run the 470U pump. It runs in the middle of the green now which I like better than just getting into the green from being too much pressure. If you do change to 520 you will have to cut a hole and form a domed piece and rivet it in place. I doubt you can dimple it like the 185/180K firewall when they made it new.

Thanks Marty looks like the tack drive is going to be more of an obstacle than the regulatory adjustment screw.

Thread drift but I am hoping someone has an answer to the tach drive removal. I want to go electronic and remove the tach drive on my O-470R-50. It very very nearly touches the firewall on the 182P with a SPW mount.

Is there a reason you don't think this 470U pump will work for you. As you can see there are threads showing that can be screwed in for increased pressure but I'm happy with mine like it is. It fit my "54" 180 just fine.

Marty, I think you mentioned once that the 470U oil pump tach drive turns backward compared to the stock (K?) drive,
so you also had to replace the tach & cable?
BTW I love the looks of a brand spanking new engine!

Marty, I think you mentioned once that the 470U oil pump tach drive turns backward compared to the stock (K?) drive,
so you also had to replace the tach & cable?

It's been over 25 years since I first got this pump and used it on the K. This pump. modified crankcase, and modified crank are the same now that it is a 470-50. It might be a good Idea to make sure I am right about which way the tach drive turns on this pump vs an original K. When I changed engines back then, I went from an original "470A" to this. That might be where I got the wrong rotation idea. This pump has never turned a cable while I have owned it.

I did a search, here's your post from this thread

https://backcountrypilot.org/forum/cess ... ch#p316408

"I got lucky when I overhauled my "K" and a mechanic was doing a exchange on a 182 that had a "U" with the filter right on the oil pump. He let me put my old oil pump on the engine going back to the factory and I took the good one. All I had to do was swap out some studs since the pumps were different depths and the tach cable drive went the wrong way so that is when I put the Horizon P1000 in. Still plenty of room under the starter motor so I don't have to remove it when changing oil and I think it would still work with the Seaplanes West mount"

I've been wondering what Russ ended up doing with his project. I am putting a 520 pump on the Pponk that is getting built now and will have to deal with the flat firewall issue on my "54" 180----probably by swapping engines on the 180K that has the correct firewall for the 520 pump.I took an old O470A that I've had laying around for years apart since it is the same basic idea. It looks to me if one put a flat plate on for a rear cover and got rid of the original mechanical tack drive and went with a digital tach there would be lots of room on an early flat firewall 180. Here are some pic's of the tach cable drive train that some might find interesting.

Marty, We ended up using a sock full of lead shot and held it secure inside the plane on the firewall and the mechanic that did the engine reinstall used a ballpeen hammer and (beat) shaped the firewall until we had sufficient clearance for the tach drive. the pressure/bypass adjustment needle did not get the same treatment and as a result only has maybe 1/8" clearance.

All this was a result of a prop strike teardown inspection, the engine shop insisted that I have the larger 520 oil pump. I most likely will be pulling the engine at a later date and will have to correct an oil leak in the vicinity of the oil pump and going to a plan B resolve possibly like what you're suggesting in you previous post. Or go back to the standard O-470 oil pump. Or re modify the firewall to accommodate that whole cluster F.

It sounds like switching to a 520 oil pump is a big PITA--
I'm curious if it is required by the 470XP STC,
or whichever STC is being used to hotrod the engine?
Or is it just one of those "it'd be a good idea to do this" things?

I do like that 470U oil pump with the built-in spin-on filter fitting.
That will be on the short list of things to consider when I finally have to overhaul my 470K.

When I dropped the O470K off to get converted to 470XP I was told that I would have to change to the 520. When I picked it up it still had the 470 pump with integral spin on filter because they changed the "rules" and it was now okay. What is interesting is that I was told the 520 with spin on is actually cheaper than the 470 with spin on that I have used for years on the 470K.

I went to Omaha and picked up my second Pponk today. It was the 470U that came on the 180K. I had the 520 oil pump with integral spin on filter installed along with the alternator /engine mount leg that is one piece. Dan showed me that there is a factory oil pump back plate from another engine he is working on that doesn't use a mechanical tach cable but is electronic I think. It would provide clearance on a flat firewall early 180. Was such a nice day for December and thought this was a nice picture. Sometimes unused farm equipment comes in handy and I rigged up so stands to support the engine.

Marty, it looks like you've got the early crankcase legs on that engine.
Is that just for shipping, or is this going onto an early mount?

Eric, they are the new style legs. I used the same red tubes as with the old style legs and Lord rubber mounts and used some brackets from my corn planter for a better base. I used some plastic tubing surrounding the bolts and went through the holes where the factory barrel nuts should be. Was cheap and worked good enough for the 160 mile trip from Omaha. The electronic tach rear cover plate on the oil pump that he showed me probably goes back less than half of the mechanical cable drive version you see in my picture and if I had know would have had Dan order it with that. I might still change it since then no firewall modification is needed on early 180. Should have taken a picture but was in a hurry.

I finally found a picture on the internet of the rear 520./550 oil pump cover that will provide clearance on an early flat firewall 180.

Well, I'm pretty sure that the OP has already sorted this out, but in the interest of adding to the searchable knowledge database, here's how I did it. I wound up with a 520 oil pump, and have a mechanical tach. On teardown my oil pump was not reparable, a new 470 pump is pretty spendy, and my engine shop couldn't find an overhaulable used 470 pump, so on went a 520 pump. I dimpled my firewall by backing it up with a sandbag (A shot-bag probably would have been better, but you work with what you got) and working it inward with a rivet gun with a flush set. I used a set that had more of a curved face than most flush sets do. I made a fairly generous recess to provide better clearance for fastening the tach drive cable. You can, of course, deform it too much and get a split in your firewall. I don't recall exactly how deep the dimple is, but it's significant;y less than an inch. I got an old Cessna firewall from my local aircraft salvage yard and practiced my metal forming technique a bit before I went live on my firewall. The results don't look exactly stock, but they look better than some firewall modification's I've seen.

180Marty wrote: It runs in the middle of the green now which I like better than just getting into the green from being too much pressure.

Can you explain what you mean by that? Middle of what green? Oil Pressure? Oil Temperature?

Thanks.

Can you explain what you mean by that? Middle of what green?

I was talking about oil pressure.