Quick valve seal question
Thread Starter
Melting Slicks
Joined: Dec 2000
Posts: 2,635
Likes: 0
From: Union Ontario
Quick valve seal question
When using a positive lock valve seal like a Crane 99819-16 do you also need to use the o-ring seal too... The parts store I went to says yes, I say no, you can but don't have to.
I got the wrong valve seals when I went to a speed shop so I am going to get the above seals tomorrow or thursday when I return the wrong ones(they required you to machine the guide down)
I got the wrong valve seals when I went to a speed shop so I am going to get the above seals tomorrow or thursday when I return the wrong ones(they required you to machine the guide down)
Drifting
Joined: Sep 1999
Posts: 1,908
Likes: 0
From: Manassas, VA, USA
Re: Quick valve seal question (MikeC)
No, you don't have to use the o-rings with posi-lock seals. In fact, you're better off not to - the valves need SOME lubrication, and posi-locks are engineered to allow it. If you use other valve seals in addition, you may "starve" your valves.
Also, I'm no machinist but all the posi-locks I've seen that replace o-rings on Chevy SB heads DO require machining the valve guides to fit the posi-lock properly. If you don't want to machine the guides, you need to use either o-ring or umbrella seals. I could be wrong here; like I say I'm not an expert. But I've never seen a posi that didn't require machining stock heads.
Also, I'm no machinist but all the posi-locks I've seen that replace o-rings on Chevy SB heads DO require machining the valve guides to fit the posi-lock properly. If you don't want to machine the guides, you need to use either o-ring or umbrella seals. I could be wrong here; like I say I'm not an expert. But I've never seen a posi that didn't require machining stock heads.
Team Owner
Joined: Aug 1999
Posts: 30,995
Likes: 99
From: Ontario
Re: Quick valve seal question (lyonsh)
You know that really begs the question of what are these Crane seals: umbrella or positive. I have never been ever to figure out from previous threads whether they ride on the stem (umbrella) or are hand-pressed onto the valve guide (positive). Or have to have the guides machined to fit. So they sit in the package. Surely someone must know what these units are designed to do. And how!
Thread Starter
Melting Slicks
Joined: Dec 2000
Posts: 2,635
Likes: 0
From: Union Ontario
Re: Quick valve seal question (paul79)
That's where I got the number from. You da man Paul!
They are called umbrella seals on the Summit racings website but I refer to them as posi locks?!?!
They are called umbrella seals on the Summit racings website but I refer to them as posi locks?!?!
Thread Starter
Melting Slicks
Joined: Dec 2000
Posts: 2,635
Likes: 0
From: Union Ontario
Re: Quick valve seal question (MikeC)
Oil control and durability
Chevrolet: 262-400, 11/32 in. diameter, umbrella style, valve stem seal set
Crane offers these valve spring seals for use with our stock diameter valve springs. These seals offer the correct oil control and durability and are installed with no machining to the head, saving you time and money.
Chevrolet: 262-400, 11/32 in. diameter, umbrella style, valve stem seal set
Crane offers these valve spring seals for use with our stock diameter valve springs. These seals offer the correct oil control and durability and are installed with no machining to the head, saving you time and money.
[Modified by MikeC, 8:21 PM 4/9/2002]
Le Mans Master
Joined: Apr 1999
Posts: 6,134
Likes: 46
From: Raleigh North Carolina
Re: Quick valve seal question (lyonsh)
O-Ring seals are the tiny "square cut" rings (not a typical o-ring per se) that slip onto the valve & into the groove cut in the valve stem.
Umbrella seals slip over the valve stem, but do not locate in the groove. They just hang out where they please on the valve stem.
They do not grasp the valve guide... they are tapered.
posi-type (or "Perfect Circle" type) seals will have a metal band (or two metal rings) around them to help clamp them onto the top of the valve guide. They are not tapered like umbrella seals. They require the top of the guide to be machined to a specific diameter in order to allow them to be pressed down over the guide. This causes them to stay put, unlike umbrella seals.
posi-type seals are OEM equipment on some engines... Ford 5.0 for example.
You have to make a determination to see if your heads are/are not already machined for posi-type seals before you purchase and try to install them.
The umbrella seals do not need any machine work, the o-ring type require the groove in the valve stem.
Umbrella seals slip over the valve stem, but do not locate in the groove. They just hang out where they please on the valve stem.
They do not grasp the valve guide... they are tapered.
posi-type (or "Perfect Circle" type) seals will have a metal band (or two metal rings) around them to help clamp them onto the top of the valve guide. They are not tapered like umbrella seals. They require the top of the guide to be machined to a specific diameter in order to allow them to be pressed down over the guide. This causes them to stay put, unlike umbrella seals.
posi-type seals are OEM equipment on some engines... Ford 5.0 for example.
You have to make a determination to see if your heads are/are not already machined for posi-type seals before you purchase and try to install them.
The umbrella seals do not need any machine work, the o-ring type require the groove in the valve stem.
