What causes valves to stick?

[SavageC20]

Originally Posted by Wrenchbender Ret

If you are running gas with ethenal in it & it is old gas it can gum up the guides & stems & cause them to stick.

I did not realize that. When the event occurred the gas that was in the truck did contain ethanol. However, the gas in the truck was less than one week old.

[toolboxchev]

I am wondering about your machine shop buddies???

I can rebuild a top in my driveway and have less problems. If you have bronze valve guides the ethanol can be an issue, not to the point that you are describing. I have not seen that. Every car on the road would have problems.

You have other issues happening most likely a compound issue. How about some pics?

[SavageC20]

Originally Posted by toolboxchev

I am wondering about your machine shop buddies???

I can rebuild a top in my driveway and have less problems. If you have bronze valve guides the ethanol can be an issue, not to the point that you are describing. I have not seen that. Every car on the road would have problems.

You have other issues happening most likely a compound issue. How about some pics?

Yeah that's the thing, its not like this is a one off custom engine, its standard stuff that has been around for years.


Machine shop went with hardened one piece pushrods and roller rockers the second go around. They also thought there was an oiling issue because a couple of the rockers had oil burned/baked onto them, but were unable to determine a cause...

Here is a pic of the pitted cam and pushrods the first go around, keep in mind that the bottoms of the lifters were perfect. Also, I am not 100% sure if I have bronze valve guides , but I believe I do.

[toolboxchev]

Unfortunately that Cam does not look like it will make it. Comp Cams come nitride hardened now.

Second thing comes to mind is what did they use for oil. 99 percent of what is on the market will not do anything but destroy a new camshaft.

Vavloline VR1 is the only thing I use in my small block chevy with a hyd flat tappet cam.

Read up on motor oil below it is anything but the same. Even diesel oils have changed dramatically.

https://540ratblog.wordpress.com/

With the metal debris in it, I personally would do a complete tear down, disassembly and rebuild again.

[SavageC20]

Originally Posted by toolboxchev

Unfortunately that Cam does not look like it will make it. Comp Cams come nitride hardened now.

Second thing comes to mind is what did they use for oil. 99 percent of what is on the market will not do anything but destroy a new camshaft.

Vavloline VR1 is the only thing I use in my small block chevy with a hyd flat tappet cam.

Read up on motor oil below it is anything but the same. Even diesel oils have changed dramatically.

https://540ratblog.wordpress.com/

yeah I know the cam is toast, as I stated in the original post the engine has been completely gone through since this happened. I run high zinc oil exclusively in flat tappet engines (driven or torco).

[Mike C]

On a rebuild my guess would be the guide clearance was insufficient on the valves.

On an older engine, stuck valves happen usually because of excessive buildup on the valve stem of oil and then sitting for an extended period, or it can happen when running an engine on varnished gasoline and then shutting it down. The varnished gas may run, but it doesn’t all burn and then when it cools on valve stems it glues them open.

A bent valve can stick as well but that again is on the shop if that happened on a rebuild.

[SavageC20]

Originally Posted by Mike C

On a rebuild my guess would be the guide clearance was insufficient on the valves.

On an older engine, stuck valves happen usually because of excessive buildup on the valve stem of oil and then sitting for an extended period, or it can happen when running an engine on varnished gasoline and then shutting it down. The varnished gas may run, but it doesn’t all burn and then when it cools on valve stems it glues them open.

A bent valve can stick as well but that again is on the shop if that happened on a rebuild.

I was thinking the same thing, but I don't know why it keeps doing it if they went through the heads twice. Maybe their guy that does the heads needs to find another job lol?