So let me ask this, if the valve seals are starting to leak, does this mean that I will start losing a lil horsepower too? It won't have the correct compression with it not sealing right? Good compression=GO? I haven't been able to get over to my bud's house and do a leak down like he suggested, was wondering if the seals affecting overall running condition. Thanks for any replies, Blair

 

The valve seals will not affect your compression. They may let a little oil in which can foul a plug.

A leak down test will not determine if your valve seals are worn. The stock valve seals are little umbrella like rubber pieces that fit around the valve stem inside the valve spring. It keeps too much oil from being sucked past the valve stem to guide clearance. You need a little lube to keep the guides from wearing tho.

If your valves themselves are leaking that is aother story!

 

I'm probably all mixed up in proper terminalogy. (<==spelling) He said that the valves were probably leaking, and he mentioned something about seals later in our conversation. So if the valves are leaking themselves, what story is that telling? I'm guessing this is where the leak-down test comes in? If the valves are leaking, what if anything else should I be concerned with? Then if the valves are leaking themselves, then this is where I would lose compression right? Assuming no head gasket is blown or something to that effect. Trying to get a better understanding of what I may be in for. My helper is an experienced mechanic, but he doesn't answer questions to well. Hoping one of you gents could spell it out for me? Thanks for input and time, Blair

 

Blair, It sounds like you could have 2 possible problems that a mechanic might describe quite similarly.

1) Valves not sealing. This would be where the valve contacts the head and seals the combustion chamber. Result would be lowered compression, burnt valve(s), missing and generally poor running. Yes, a compression test or more specifically a leakdown test could verify this.

2) Valve seals leaking. This is when the "rubber" cups that ride on the valve under the spring deteriorate allowing oil to run down the valve stem causing excessive oil consumption, especially when first starting. Doesn't usually cause a performance problem unless the valve guides are excessively worn. A compression test won't verify this.

Note: Valve seals can be replaced without removing the heads if that is the only problem. Also the valve seals would be automatically replaced if a valve job was done (the heads come off and get reconditioned).

Hope this clarifies things.
Greg

 

Thanks Greg. That does make it much clearer. I believe my mechanic pal gets flustered with my many endless questions. She blows a lil' blue smoke on startup, but not during run on the roads. Runs a little rough, but not excessively so. She doesn't seem to have as much power as she used to, maybe he was leaning towards the valves not sealing. (1) I ran my first compression test ever on this motor, throttle plates closed, , high cylider was 125 psi, low cylider was 100 psi. Several were down around 100-105. He said a proper compression test with plates open, and then a leak down would confirm any suspicions he has. He helped me through timing chain replacement, intake reseal, and the carb work I have done, and also looked over my shoulder while we (I) tuned her up. Must be time to finally get the 12 pack, (pop for me) , and get this done. I feel that's the next logical step. I'm getting cross-eyed from my own questions. Thanks for your help, good explanations in layman's terms are hard to come by. Really, thank-you, Blair