Thoughts of the bearings issue

Johndavis · Johndavis's Garage

Guy just fresh build 3.0 hot rodded up ....the rocked arm bearing are pushing out as in the pictures .

Builder said they would last 100k ,,,,,,, what your thoughts ?

bpu699 · 08-04-2019, 05:53 PM

Push back in and torque to higher spec?

Nditiz1 · 08-04-2019, 05:56 PM

If he rebuilt it to specs from the factory then of course they are going to move.

Over time these have become worn. Torque to 21ft/lbs. While your in there you could put RSR seals on them to help prevent leaks.

timmy2 · timmy2's Garage

They will walk right out if you don’t address right away. Happened to me. You need to loosen the expansion bolts, re-insert and torque to the used specs as posted. The seals are a good idea as well.

Johndavis · Johndavis's Garage

Would this cause a bent valve ?

T77911S · 08-05-2019, 08:33 AM

i had one come all the way out.

this is just my theory
when putting back in if you have to hold the other end when torqueing it WILL come back out.
yes you will have to hold initially but once torqued it should not turn.

you also need to check how they are inserted.

that's not a good sign if multiples are coming out.

things look a little dirty for a fresh build, how many miles.

Nditiz1 · 08-05-2019, 11:43 AM

Check out the DIY RSR thread created by user DRACO A50G.

After an engine is rebuilt these need to be torqued more. He had one come all the way while the engine was running. Luckily caught it in time and no damage was done. After torquing to 21 ft/lbs he hasn't had a problem since.

Also be sure the 5mm head faces towards the inside as the factory did. Also, check the thread to ensure you are setting them in the hole correctly, otherwise it will leak.

LUFTKUL · 08-05-2019, 11:59 AM

TurboKraft has an expensive, but solid solution:
https://parts.turbokraft.com/collections/911/products/rocker-shaft-lock-set

proporsche · proporsche's Garage

after any rebuild on 911 the rocker arm shafts has to be rechecked in 1000 miles by the builder.
It is mandatory and basic procedure.Also re torque cyl. heads..
the rocker shaft should be in this position..as NDitiz1 mentioned

ivan

Johndavis · Johndavis's Garage

I am asking because i had a bent valve , after losing a cylinder and doing a leak down ..... found 1 cylinder gone you could hear the air leak out very well . Pulled the valve cover with a 40 year porsche mechanic when doing the leak down and the pictures show the bearing out so I called the builder in another state , that the reason i didnt get it to him to check after losing compression . Builder said it bent a valve due to a bad down shift ... haha 915 needs a build wish it would shift that well . He wants to charge me to repair a bad down shift that didnt happen ...again opinion are welcome . With 3 bearing out in the picture it had to bend the valve is my opinion.

Nditiz1 · 08-05-2019, 02:27 PM

I'm not sure the rocker shafts (bearing as you call them) being out that far would cause that. If anything it would sound like you had a problem if the rocker was allowed any additional play. The rocker appears to still have a decent amount within the rocker and the hole. You can almost slide them out halfway and the rocker will not budge.

Johndavis · Johndavis's Garage

Quote:

Originally Posted by Nditiz1

I'm not sure the rocker shafts (bearing as you call them) being out that far would cause that. If anything it would sound like you had a problem if the rocker was allowed any additional play. The rocker appears to still have a decent amount within the rocker and the hole. You can almost slide them out halfway and the rocker will not budge.

Thanks for everyones replies , but wouldnt the flex on the shaft allow for it to flex enough to cause the vave to be not correctly aligned...? Again total newbie on air cooled just didnt ever down shift as I was running it up to 5 k and letting it off per the builder to seat the rings

timmy2 · timmy2's Garage

Any evidence on the cam housing of the rocker arm being lodged in the compressed position on the bent valve position? Can usually only bend a valve stem if it doesn’t retract in time and gets hit by the piston.

Nditiz1 · 08-05-2019, 09:08 PM

Quote:

Originally Posted by timmy2

Any evidence on the cam housing of the rocker arm being lodged in the compressed position on the bent valve position? Can usually only bend a valve stem if it doesn’t retract in time and gets hit by the piston.

Good point Denis.

You should be able to turn the engine by hand to where it will free up the rocker. Loosen the rocker shaft by turning the 5mm side and holding the 8mm side firm so it doesn't move. Slide out the shaft and the rocker will fall out. Check for any kind of marring or damage. I have a feeling there won't be any. Do this for each one that is protruding too far out. Tighten back to 21 once it is in the correct place. Move on to the next.