Tech / General EngineWhy is my car making that sound? My car won't start! Combination questions? Don't see a board for your problem or have other technical or engine specific questions? Post them here!
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I was wondering what all seals or parts would be needed when having heads rebuilt. I know that I need the valve seals and was told to get new umbrella seals. A friend mentioned something about posi loc seals. I called the machine shop and they said that they did not know what he meant by posi loc seals. I was wondering if anyone here knew what he was talking about or if they might be called anything else. My valves are good and I already know about the machine work parts, but I just wondered what he might of been talking about. I really need to know soon if posible. I would like to order them from the mashine shop tonight if possible, but at least tomorow. Unfortunately I think that the shop closes in about an hour.
Thanks
Ben
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the posi lock seals make more of a 90* angle when they change from the side to the flat top, they have several spiral springs around them. the last heads i rebuilt used them on the intakes and hard plastic umbrella seals on the exhaust and o ring seals on both.
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What would I tell the shop to get them to understand what i am talking about. Thanks for your help. Do I need these? I dont really understand. Can umbrella seals just be used on both or do I have to get these posi loc seals?
I just talked to another machine shop and they knew what they were but said that they would have to know the size of the valve guides. Does anyone know what size the valve guides would be on a 85 lg4. Thanks again
I haven't used them in awhile, but sounds like they're talking about Perfect Circle Teflon positive seals. They require machining of the top of the guide because they lock onto the top of the guide (using the spring described above). There is also a spring around the valve stem portion of the spring. The tool to machine the top of the guides runs about $40, and is specific to the application.
I think he said that they came on there, so would I need any special mashining or tools to replace them. Also, If I recall correctly he also said that they were only on one side of the valves also(probably intake like ede said). I am short on money right now and just trying to get this done. Does anyone know any more about these. I think that they should just install, without an extra tool right since they were on there to start with. Thanks for the help.
I am pretty sure its the same as the 85 LB9 heads and 86 LB9 and LG4 heads I have worked on, they have the positive seals on the intake side and hard plastic seals on the exhaust side from the factory. All you would need to do is get stock replacement seals. Fel-pro sells them as well as others.
Just order a Fel-Pro headset. Every thing you need to change the heads (including the seals) are in there. All the ones I did either had 16 of the Viton seals and 16 of the rubber o-rings for the top OR 8 Viton seals and 8 hard plastic umbrella seals and 16 o-rings.
The Viton seals are rubber with 2 metal bands on them. We always referred to them as positive locking seals. They work much better than regular umbrella seals. Don't use teflon seals on the street - at least not for a daily driver. I've seen too many burned guides from lack of lubrication because of those.
You're going to need to tell the machine shop cut the top of the guides for extra retainer to seal clearance to allow for more lift from a performance cam. If you've got more than .480-.490 lift, have them pin the studs at the very least. Screw in studs would be better, but will cost more.
The hard plastic seals I suppose you could call umbrella seals, but if thats what you ask for thats not what you will get. I'm pretty sure they are made of nylon, and as far as stock Chevy valve seals go, they seem to work fairly well. If you ask for an umbrella seal you are going to get something similar in shape but made of what at first is a soft rubber. After a few thousand miles, they turn to hard rubber, and after some more miles they start to leak. I dont really care for umbrella seals too much.
Just get the stock valve stem seals for the car. When you open it, you should see 2 packages, one will have 8 rubber things in it that have a metal spring or two around it, and the other will have 8 white/clear plastic things in it. There will probably also be a package of 16 o-rings.
Well, I got them. Thanks madmax, I wish I knew it were that easy. I thought that I needed something special other than what came with the normal seals. When I had asked for umbrella seals(which I guess was something totaly different), and posiloc seals(which I guess are also called postive seals) the parts store didnt know what I was talking about and the mashine shops would have given me the wrong thing. Its great being able to come here and ask you guys questions.
