Stem Seals Coming Off the Guide

[JedIEG]

BACKGROUND: on my 318 I just swapped on a new carb trying to chase my rich running condition and decided to check the oil level. It was low by a quart which is odd since I have not run this engine long, just to try to get the carb tuned and up and down the street once. I pulled the left valve cover to check if a valve might be sticking and look at the oiling and found the stem seals had ridden up off of the guide on several valves.

HARDWARE: Stock '74 318 heads were cleaned, a few valves replaced due to surface rust and new seals installed my an engine shop with the existing hardware. Springs are OE 340 units with dampers. The seals appear to be riding up the damper.

QUESTION: Are there different seals between a stock 318 single spring setup and the 340 spring+damper setup? Or Did the seals just not get seated correctly?

 

[Bill76]

If they are umbrella seals they ride with the valve stem , the good seals are pushed on the valve guild and usually need machining on the valve guild for a tight fit mostly done when new valve guilds are installed.
Sounds like you got a low budget job done

 

[bm02tj]

Unless you paid extra for positive type seal you have the one that ride with the valve
Which is the most common type

 

[JedIEG]

I see now... not a fan. I'm not used to anything other than positive type seals that meter oil very strictly to the valves. Is there any control on the umbrella seal height on the valve? Some are at the top of the valve, some half way down.

Are there any positive type seals available without machining? It looks like magnums, G3 hemi and all other modern Chrysler engine use them but the valves are different diameter.

 

[miller]

Is there any control on the umbrella seal height on the valve? Some are at the top of the valve, some half way down.

No. Condition of the seals themselves, condition of the tops of the valve guides, condition of that section, the seals fit, on the valve stems, all say how those seals will act. Plain jane factory stuff.
Most better seals require machining at the tops of the valve guides.

If those umbrella seals are in one piece, not leaking oil...okay...for awhile. Over time, they get hard, brittle, break...

 

[PRHeads]

There are positive seals that can be used on stock SB heads, but they aren’t the style of seal that you’d find on newer vehicles.

The application should be something like mid-80’s 318/360’s, might be intake only.... but I’ve used them on both valves.
They’re only going to be a “positive” seal on unmodified/unaltered guide bosses.