Replacing Valve stem seals!

[AUSTmike]

Hi guys!...I'm just about to start replacing my valve seals on my 1977 Porsche 2.7 ltre !...and i just need to clarify some info before proceeding!

What would be the ideal PSI air pressure to hold the valves in the cylinders at TDC!

also after reading all the posts from others here at pelican forums on replacing valve seals, is it ok to release the air pressure in the cylinder once the valve spring has been removed to check for any play or movement in the guides!

Some say that they have done this because its a good idea while you have the valve spring off or removed to check your guide for wear!

one Porsche owner stated that when he checked his guides the valve with the piston on that particular cylinder would move down the guides about an inch or 2.5 cms

Is this correct!..in releasing the air out of the cylinder or is there another method!

any info from experienced Porsche 911 owners who have replaced their valve seals would be greatly appreciated!

[Walt Fricke]

I replaced an exhaust spring at the track once. With the piston down some I shoved a bunch of string into the chamber through the spark plug hole (of course keeping an end out), and then ran the piston back up until all was tight. No worries about air supply or pressure. You could back off a bit to check stem play, then move the valve back up.

[Walt Fricke]

Also, you might consider doing this only on the intakes. There really is no pressure differential around the exhausts to suck oil up hill. And what might get in there isn't going to get into the combustion chamber, is it?

[faapgar]

The exhaust seals are pretty easy in the car.60-100 psi will keep the valve in place.The older white nylon seals are the best replacement with the engine in.Why ? Because when you tap them on they bottom and the seal is square to the valve.The red Viton seals are way tougher to get square.To see if they are square you need to get the piston towards BDC bottom dead center then release the air and push the valve up until the 3 keeper grooves are at the top edge of the seal.Then look to see if the top edge of seal is level with the groove.Now you can wiggle the valve up & down to check for play.The Viton seals are tougher to remove as well.Then you have to scrape off what is stuck to the top of the guide.Other than that it is Easy Peasy.Ciao Fred

[AUSTmike]

Thanks guys for your quick reply's!...

Walt!..
Interesting with the rope method!..i did try this method to see if i could get rope down into a cylinder but i could only get a few inches of rope in there and no more as the cam towers where a pain in the ass to try and feed any rope down there!...i do like the rope method but trying to get the rope down there is a mission and a half!....how did you get your string or rope down there!..i even twisted the rope as i was feeding it down into the spark plug hole but the rope would only go so far and not much at all!...also with the air pressure method!..so it is OK to let some pressure off the cylinder to check for valve play and because the piston is at TDC you can move the valve back up to its closed position and then apply air pressure again to replace the stem seal!

faapgar!...interesting about what type of valve stem seals there are!..i have the black rubber victor reinz seals!...but if the white Teflon type seals are better i would rather the white ones if they last longer and are a more versatile seal!...i read somewhere also that the white Teflon type seal are so good in stopping oil from leaking past the valve that some make a little slit inside the seal itself for some oil to lub up the guide!... whats your thoughts on that and the seals and what would be the best named brand white seals to get!...cheers guys much appreciated

[faapgar]

Wrightwood Racing use to have them.Maybe check with Supertec.

[AUSTmike]

here at pelican they have the white Teflon seals!...When i search for stem seals on the internet the Teflon seems to be the same product!..just hope they are the same quality!

https://www.pelicanparts.com/catalog/SuperCat/911M/POR_911M_ENGCYL_pg4.htm

['78 SC]

Originally Posted by faapgar

...The older white nylon seals are the best replacement with the engine in...
Ciao Fred

Fred, what seal do you recommend if the engine is apart with full access to the heads?

[faapgar]

Those are the right white seals for in the car.For the engine stand I like the new ones,I use a piston pin for install because it has a beveled edge on the inside.Tap the seal down gently and check with the valve keeper groove to ensure it is square to the groove and not cocked.

[AUSTmike]

Good advice faapgar on how to install valve seals!...i also read somewhere that when installing the seals that you place some tape around the keeper grooves on the valve stem so that the valve seal lip doesn't get chaffed when pushing onto the valve stem!....

What would be the benefits of the white seals!..would they last longer than the rubber type?...some guys in the past have experienced their rubber type valve stem seals have cooked or hardened up because of heat very quickly of time!..hence the leaking of oil into the camber problems

[AUSTmike]

does anyone know how to correctly undo and slide out the rocker pin?...

[dannobee]

Originally Posted by AUSTmike

does anyone know how to correctly undo and slide out the rocker pin?...

HOLD the 8mm side, TURN the 5mm side. If you do it backward you could crack the rocker shaft. Push it out by hand (after backing off valve lash adjuster and verifying the cam lobe is down). If it's stuck, spray some carb spray or brake cleaner around the shaft then GENTLY tap out.

When reinstalling, keep the shaft flush with the skinny side boss on the cam housing and HOLD the 8mm side, TURN the 5mm side. Use the RSR seals to prevent leaks. Torque to 18 ft lbs if used shafts. The 5mm side should go toward the inside of the engine (doesn't matter on the middle shaft). If you reverse it, the next guy will have trouble removing the shaft if the engine is still assembled in the car. Don't be THAT guy.

[faapgar]

Main benefit of the white seal is the ease of installation with motor assembled in the car.You just tap down gently until it stops.Very little chance of the seal not being square to the valve.As far as not letting enough oil to the guide do not worry.Your guide will have play so the valve will be rocking the seal and opening it up and some oil will pass.O n race motors I would use a seal on the intake but none on the exhaust.In the 80,s in IMSA we would make a tower where the breather cap is and run a vacuum line to the collector point of the header.That would pull crankcase vacuum and help the motor rev.If you had worn guides it could smoke like crazy so we used an exhaust seal and drilled a 1mm hole from valve spring retainer to the center of the guide for lube.This was copied from a 935 engine.Those guys were smart.Ciao Fred

[AUSTmike]

Thanks Guys!...your info is so much appreciated!

dannobee!... i'm guessing when you say to turn or undo the 5mm side of the rocker pin!..is undoing it in anti-clock wise direction as in the normal way to undo a bolt and nut or is the rocker pin bolt and nut assembly left-hand thread!..I'm assuming the correct method of undoing or loosening the rocker pin is the normal way which is anti-clock direct!...

faapgar!....I know you mentioned earlier in post #9 that you use a piston pin to tap down the seals...some say they have used a 10mm long socket to tap the seals down without any issues!...what are your thoughts on this!...cheers

[faapgar]

10mm socket could work.Just set the seal up to it and see how it fits.If you use it make sure it is clean inside.Ciao

[AUSTmike]

OK!..thanks for that faapgar!..i have a brand new 10mm socket!..i have a few cars parts yards in my area and i will take a valve seal with me and see if they have an piston pin with a bevel edge that will fit to the seal...cheers and thanks for all your help!..you guys have given me a lot more confidence in doing the seals...cheers!

[AUSTmike]

just a quick question on the rope method!...once you get the rope or string down the cylinder, and compress the rope with the valves!...whats a safe way to get the rope out again once you finish holding the valve!...I heard that its not a good idea to turn the engine anti-clock wise as this can damage the tensioners in the timing chains!...or is it OK to turn the crank just a little or enough to pull rope out!...

[Walt Fricke]

To me, the business about never turning the engine counter clockwise is just an old wives tale. I've turned 911s backward many times, especially with the chain cover off. It certainly won't damage the tensioners - they are very stout. For sure, the pressure fed tensioners are unaffected by any of this.

For the older style, maybe this would force some of the oil in the tensioner out, though it should refill soon enough. But with the spark plugs removed there isn't all that much force on the tensioners while turning backward.

[AUSTmike]

Cheers!..Walt!..that is good news!...i guess if you are going to turn the engine anti-clock wise your'll do it to a minimum anyway!...

[AUSTmike]

Is it OK to tap the top of the valve spring retainers before decompressing the springs to loosen the keepers?...and is it OK to tap the retainers with a hammer after the spring has been depressed to make sure that the keepers have settled back in their proper place with the valve stem!