Second Round Valve Stem Seals...

[tortuga]

So in my seemingly never ending quest to reduce oil consumption, with the carb off i was endo scoping my intake and it sure looked like there was oil coming down the valves...I had done all the seals before using the compressed air in the cylinders method...

On reading some more about how to replace the seals i came across lots of chatter about using a drinking straw arrangement over the valve stem so that the seals don't get torn as they pass the sharp reliefs where the keepers plug in. I didn't do that.

So having another set of seals, ( i double ordered and just kept the batch).

I pulled them off and replaced them one by one, this time using a tricky straw arrangement to slip them on. ALL of the old seals were wallowed out. Is just jamming the seals down over the stems without a condom a mortal sin?

We'll see...

Im getting pretty good at it at this point.

Steve H
SPF 1764

[Jerry Clayton]

can you wiggle the valve stem in the guide?????????If the guides are history, no amount of changing seals will help

[Gaz64]

What guides are fitted?
What type valve stem seal are we using here?
Seals that have no flex (teflon), will not move with stems in "sloppy" guides.
And yes, any seal should be fitted using the thin plastic "condom" to stop the sharp edges of the keeper grooves damaging the seal lip.

[tortuga]

Originally Posted by Jerry Clayton

can you wiggle the valve stem in the guide?????????If the guides are history, no amount of changing seals will help

They do move in the guides, some more than others...Not crazy but you can definitely feel it by hand...Didn't want to get too crazy wobbling a valve being held up by air pressure...

Guess the heads are coming off at some point.

[tortuga]

Originally Posted by Gaz64

What guides are fitted?
What type valve stem seal are we using here?
Seals that have no flex (teflon), will not move with stems in "sloppy" guides.
And yes, any seal should be fitted using the thin plastic "condom" to stop the sharp edges of the keeper grooves damaging the seal lip.

Guides are what come with Ford z304da heads...

Seals:
https://www.cnc-motorsports.com/us-s...eals-2079.html

Steve H

[Gaz64]

Originally Posted by tortuga

They do move in the guides, some more than others...Not crazy but you can definitely feel it by hand...Didn't want to get too crazy wobbling a valve being held up by air pressure...

Guess the heads are coming off at some point.

Placing the piston at EXACTLY TDC allows you do open the valve off the seat to feel the guide.

I would have bronze guides fitted to tighten the clearance up.
The valves will seat more reliably, the engine make more consistent power, less likely to break a valve head off, and the valve seals should work better.

[tortuga]

Originally Posted by Gaz64

Placing the piston at EXACTLY TDC allows you do open the valve off the seat to feel the guide.

I would have bronze guides fitted to tighten the clearance up.
The valves will seat more reliably, the engine make more consistent power, less likely to break a valve head off, and the valve seals should work better.

They are bronze according to the literature, just a bit over honed i think...

[Gaz64]

Originally Posted by tortuga

They are bronze according to the literature, just a bit over honed i think...

A good guide should be a barely perceptable feeling of sideways movement with the valve head off the seat. Bronze guides can run tighter than cast iron.

[redmt]

If you can wiggle the valve with holding compression against it not only are the guides worn but the valve face isn't seating in the head.

[eschaider]

Steve, if you can wiggle the valve, the guide is history and needs to be replaced. Any time you replace guides you must do a fresh valve job.

Bronze guides are great for race engines not so much for street driven cars — their service life is too short. The OEM cast iron and powdered metal guides are often looked down upon because they seem to be lesser versions of the desirable bronze race style guides. They are not lesser versions. Those OEM material choices have a porosity that holds oil for lubrication which provides a longer service life for the guide.

Over the years there have been three different materials I am aware of that guides for street driven vehicles have been made from, cast iron, meehanite iron, powdered metal. I am sure there are probably others I am unaware of. All three of these materials are porous to oil (some more so than others) and will provide good service life for non race applications.

The first two are both cast iron although the meehanite iron is frequently used for high precision components. The powdered metal is the style used frequently today and is a very good daily driver sort of choice.


Ed

[cycleguy55]

Originally Posted by tortuga

So in my seemingly never ending quest to reduce oil consumption, with the carb off i was endo scoping my intake and it sure looked like there was oil coming down the valves...I had done all the seals before using the compressed air in the cylinders method...

On reading some more about how to replace the seals i came across lots of chatter about using a drinking straw arrangement over the valve stem so that the seals don't get torn as they pass the sharp reliefs where the keepers plug in. I didn't do that.

So having another set of seals, ( i double ordered and just kept the batch).

I pulled them off and replaced them one by one, this time using a tricky straw arrangement to slip them on. ALL of the old seals were wallowed out. Is just jamming the seals down over the stems without a condom a mortal sin?

We'll see...

Im getting pretty good at it at this point.

Steve H
SPF 1764

I believe the lips on valve stem seals are fairly easily damaged if installed over valve stems without some form of sleeve to protect them. It's those lips that actually seal against the valve stem to stop the flow of oil, so if they're damaged oil will get past.

[RallySnake]

Listen to Ed. I spent years chasing this problem on my Brodix heads only to learn that the bronze valve guides do not last very long. As an ultimate solution I bought AFR heads. Great heads, but had the same problem. A competent head builder took them apart and found that someone had installed the wrong size valve seals when they changed the springs and the valve guides were too tight. Once they were done correctly, oil consumption is normal.

RS