Technical SBC valve seals

Admitting right up front I've never replaced valve seals before. With that out of the way, The seals I'm doing are off an '86 305 chev. The seals coming off are black and my replacements are white. There is a length difference. Is it important that the seal reaches deep enough to reach the "step" on the valve guide? Both seals in the pics are resting on top of the valve guide.
Thanks guys.

 

Being just an umbrella seal, that will work fine.

 

They need to be pretty tight on the guide boss. Some have "ridge" on the inside that makes them go on ez but hard to pull off. Over time the originals got crispy and cracked. Hope these are better.

 

Well then that sux. While the new white nylon seals are quite snug on the valve stem, they're absolutely sloppy on the boss. Maybe .025" wiggle. They will ride up and down with the valve. To me, these aren't any good...

 

While yours aren't " positive" seals , they'll shed excess oil away from the guide as designed... Are you guides tight ? , Don't expect seals to make up for sloppy guides ....

 

That is what a umbrella seal does.
Now a PC seal is a different story.

 

You were quicker to the draw.

 

I don't have a magnetic dial indicator to measure side play. The stem itself has a shiney section where it rides up and down in the guide, but theres no "notch" on the stem that you can feel with your finger nail. I'd say they are ok.

 

The majority of the wear with valve guides is the iron guide , not so much the valve stem ,( hardened )

 

Oh, ok. Well, like I said, I have no dial indicator. This is really just a "buy a used engine, clean it and re-gasket/seal it, replace the cam chain and gears, valve seals, rebuild the carb, new tune-up parts and throw it in my '54.
I bought and drove the truck home, so it was running ok at the time. It was just a leaking mess.

 

If you have the heads off , put the valve in about 3/8" from closed and single side to side , if they're slopping around you could get the guides knurled but then you'd have to grind them too. Dial indicator doesn't tell you much , not accurate enough to be worthwhile ....

 

I've never had much luck knurling guides and feel like it is a waste of time.
Maybe others have had better luck.
Pete

 

I've had them last 20k miles give or take , that's about it

 

Pull the valve out of the seat a little and give it a wiggle back and forth in all directions, if you think you can measure the movement with a tape measure then the guides will need help.

 

HAHAHA!!! Jesus...a tape measure? There isn't that much slop. I thought someone was gonna say so many thousandths of a inch. Hehehe,...that was a good one.

 

One done, re***embled with federal mogul pre-***embly lube. Went with the umbrella seals. Funny though, when I pulled the valves there was no evidence of the upper rubber o-rings anywhere.
Just a final cleaning of the intake ports surface for a good gasket seal.

 

I had valve guides knurled on a V 8 Pontiac. Worked for me .

 

There was an extra notch or ring cut in the valve stem under the keepers where the o-ring was placed along with the umbrellas over the tops of the springs was good enough for 100,000's of stock Chevrolets...

 

In the mid 60s I worked in a machine shop doing mostly head work. Oldsmobile v8 heads were knurled the big dealer in town would bring in several sets every week to get guides under warranty.

 

That's what you want. If the seal moves on the shaft, the hole eventually wears out. For the seal to work like an umbrella, it doesn't have to fit tight on the guide. All it needs to do is direct the oil around the guide.

 

Exactly Jimmy, I have those two notch valves. I made sure the seal kit I bought had those little o-rings for that extra notch. I installed them with a little oil on them so they slipped on without rolling over.