So it is annual time. Our Pponked O-470R with just over 100 hours is leaking oil from the pushrod tubes, #2, 3, and 5. Not leaking a lot but on floats, any drip is environmentally unfriendly.
Mechanic says he has had better luck with SAP gaskets lately but O-470s are “notorious for leaking.” Overhaul shop confirms the pushrod tube gaskets are Continental. Internet says Real Gaskets gaskets are the best bet.

How common is this? Is it worth the AMU to try to stop the leaks? Any realistic data on which gaskets are better?

PNW,

The culprit is often two things and a third rarely is a miss formed out of the bag gasket.

The first I would see come out of the shop from time to time was a rocker shaft spacer in place of the proper push rod gasket retainer. The rocker shaft spacer is just a little smaller in the OD and doesn't seat the gasket. The OH shop should catch this but I had a few leakers back in the day with this issue.

The second is poor installation of the gasket. It takes a keen eye to see ether in situ but obvious once disassembled.

You didn't mention, engine end or head end.

The head end is often the problem with the gasket seated crooked and the retaining washers jammed at an angle and hard to tell because the back side of the casting is at an angle too, bit of a a mind F cause it's hard to see.

I check each gasket ring against another before installing cause I have found a couple over the years wrong. I found the best installation lubricant, albeit not in the overhaul manual, to be a vary liberal coating of saliva.

After installation I take carful note that the end of the pushrod tube does not move in the head end as if properly seated it is vary firm in place. It's obvious once you know what to look for.

Of course one needs to pull the lifters and bleed them down. I use a slick mag timing pin in a dixi cup of avgas, stroke a few times in the gas, then a few times out of the cup, keep it all spotlessly clean, wipe some lubraplate on the lifter sides and ends and reinstall.

Keep the pushrods indexed for position and end for end, each goes in the hole it came out of and each end accordingly.

Don't jack around with the pushrod in the lifter or you will pump it up inadvertently. I've snaked a piece of .040 safety wire through a pushrod to bleed down a 520 lifter in a bind out in the bush but not really the way to do it as a rule.

I made a handy removal/installation tool years ago out of a screwdriver and about 3 inches of conduit cut in half down the middle and screwed to a suitably bent end of the screwdriver heads countersunk for a smooth bore. Of course there are a couple tools made for this but I never had one...

Seems I never had luck just re-seating the used gaskets properly back in the day so just made a point of doing the whole operation at 100 hour, and ya mostly on the dock as float birds were my bread and butter.

Rocket

You should be able to get those pushrods sealed. Do as Rocket recommends, great info for sure. Since you'll have your rocker covers off anyway, make sure they are actually flat before you put them back on. I fought oil leaks on a customer's Pponked 470 for a while. One after the other. Most I could get sealed up but the rocker covers I could never get to stop leaking. Someone finally asked if I'd ever put them on a true flat surface and sanded them. Turns out they were WAY off. Took a good 6-7 hrs with fine grit sand paper to get them all true. No more leaking rocker covers. For the money spent on the rebuild I sure would've thought Steve's shop would've done this, but nope. This is by far the leakyest engine I work on.

Skinner,
Always kept a square of lexan in my field kit with 6" round sticky back 100 grit on one side and 220 grit on the other. Mostly for trueing up intake section faces that get distorted the same as the rocker covers but anything else that might need a touch of bush surface plate. Kept a 16" square of scrap countertop granit in the shop with the sanding discs covering it too.

About fifty other little details to do these pushrod seals, you'll need to move the prop so pull all the bottom plugs first, each cylinder at TDC compression stroke to unload the valve train, exhaust, intake... Fun times!

One rocker cover at a time or you'll pump oil all over the place each time you pull the prop...

What am I forgetting?


Rocket

At my last annual, I replaced all the pushrod gaskets on #6. I don't recall if there was a particular brand of gasket, sorry. It was very obviously leaking. The job was a little bit of a pain to accomplish, but worth it, as replacing those nearly 20 year old gaskets did indeed stop the leaking. My engine is an O470U which got the PPonk treatment. I am now oil leak free. (Well, the crank case does weep a little bit but not enough to create a drip.)

I need to do this on my motor too. nice to have some good info. Thanks

Final thing not mentioned here, check the engine breather. Twas the culprit no-one could find or my Continental once Made the pushrod tubes leak badly.

I just had all the lifters in my O470R replaced (found corrosion) which necessitated replacement of the PRT gaskets. My IA who has maintained a lot of these big bore continentals over the decades had me purchase the real gaskets. When installed properly, they should not be leaking - so my advice is find someone who knows what they are doing and replace them all.

This thread now has some good technical info so I will follow up with what was done.

“… Removed all rocker box covers and installed new RG-534857 silicone gaskets, torqued to 25 in/lbs. Dressed rough edged intake pipe flanges. Cleaned and/or painted over fuels stains on intake pipes. Reassembled all, using all new gaskets, packings, and hoses. Tightened oil fitting at crank case. …”

This feels like it should be warranty work on a 100 hour rebuild but I am not sure it would be worth pressing on either the rebuilder or the engine installer.

This thread now has some good technical info so I will follow up with what was done.

“… Removed all rocker box covers and installed new RG-534857 silicone gaskets, torqued to 25 in/lbs. Dressed rough edged intake pipe flanges. Cleaned and/or painted over fuels stains on intake pipes. Reassembled all, using all new gaskets, packings, and hoses. Tightened oil fitting at crank case. …”

This feels like it should be warranty work on a 100 hour rebuild but I am not sure it would be worth pressing on either the rebuilder or the engine installer.

This thread now has some good technical info so I will follow up with what was done.

“… Removed all rocker box covers and installed new RG-534857 silicone gaskets, torqued to 25 in/lbs. Dressed rough edged intake pipe flanges. Cleaned and/or painted over fuels stains on intake pipes. Reassembled all, using all new gaskets, packings, and hoses. Tightened oil fitting at crank case. …”

This feels like it should be warranty work on a 100 hour rebuild but I am not sure it would be worth pressing on either the rebuilder or the engine installer.

So it looks like they didn't do anything about the leaks on the pushrod tubes... or was it leaking from the valve covers and not the pushrod tubes? Keep in mind that the proper procedure for the torque on the valve covers is to torque them, then do a good run up or flight then retorque them.

The mechanic said he did a run up before putting on the cowling so I assume he retorqued per the procedure. And while the log entry doesn’t say it, he said he addressed the pushrod leaks.
If the weather improves, we will see if he succeeded.

The mechanic said he did a run up before putting on the cowling so I assume he retorqued per the procedure. And while the log entry doesn’t say it, he said he addressed the pushrod leaks.
If the weather improves, we will see if he succeeded.

I've fought leaking valve cover gaskets for ever. The overhaul shop said to use Loctite to keep the screws from loosening up.