Valve cover install

[JohnZ]

After building and working on small-block Chevys for over 40 years, I've found that 90% of the leaky valve covers that come to me leak between the gasket and the cover, not between the gasket and the head surface. The hot oil runs down the inner wall of the cover and "pools" in the crevice where the inboard edge of the gasket forms a "ledge", then it leaks out between the top of the gasket and the cover. I always clean the gasket mating surface on the valve cover thoroughly (and straighten/flatten it, as most are distorted from over-torquing the hold-down screws) and apply a thin bead of Permatex Ultra-Copper Hi-Temp RTV all the way around, with a little circle around each screw hole, and apply the (dry) gasket to the cover and let it set up before installing the cover. This holds the gasket in place during installation and seals the joint between the cover and the gasket, and doesn't damage the gasket later when you remove the cover again; I've NEVER had a leaker - can't STAND oil leaks.

Chevrolet knew this too, just took their time (30 years) fixing it in 1985 when they redesigned the valve covers for the center-bolt 350's as part of their "dry engine" initiative; the new covers were designed so the walls of the covers extend down below the head surface, then turn back up again, so the river of oil that runs down the inside of the cover dribbles off the bottom of the "U" section and can't run "up" the outside of that section to get to the gasket.

 

[tonyk72]

Well, the gasket is in (only did one side this weekend). The fit was very snug and once I fit it onto the valve cover, it stayed. Since it was that snug, I didn't moisten it...I just installed the cover onto the head and bolted it down...and used thread lock on the bolts. I let it run for 20 mins, didn't see any leaks...I'll check again over the week. Attached are some pics of the gasket...

 

[tonyk72]

one more...

 

[Tom Bryant]

I know I'm getting in on this a little late but I always use rubber gaskets on my solid lifter small blocks. Since periotic valve lash adjustment is necessary the rubber gaskets don't stick and can be used over many times. I also just give then a light coating of grease before installing.

On my wife's '81 when I got tired of the RTV sealer leaking I did the same as John suggested and used the Ultra Copper to adhere cork gaskets to the cover. Makes it a lot easier when you have to work them all around through that maze of hoses and stuff to get them back on the engine.

Tom

P.S. Tony.

Did you set the valve lash on that LT1 while you had the covers off?

 

[tonyk72]

Valve lash?
Does that answer your question...haha
I know solid lifter cars require periodic adjustment of some sort...is this what your taking about? I assume having the covers off is required to do this...

 

[Tom Bryant]

Yes. You are setting the clearance between the tip of the rocker arm and the valve stem. The ideal way to do it is with the lifter on the base circle of the cam lobe, valve fully closed. Loosen the rocker nut a little, half turn or so, if necessary and slip the proper thickness feeler guage between the rocker and the valve stem. Tighten the rocker nut down until you feel a slight drag on the guage but can still slide it out easily. Then turn the engine to do the next valve. There are also some shortcuts to this but having each lifter on the base circle will prevent any mistakes your first time.

The clearances listed for your settings are with the engine hot so you will want to warm it up to operating temps before you remove the valve covers to set the valves. I have a special set of feeler guages that are angled about 45 degrees on the end so they are easier to get under the rocker arm.

I'm not sure what the clearance is for the LT1 cam but if you have or get a GM service manual for your '72 Corvette it will list the clearance and take you through the entire valve adjustment proceedure.

Tom

 

[Alwyn678]

Moisten with what? water, oil? I just got them in today will be putting them on over the weekend...more pics to follow...

Sorry I am late getting back with you ...I use water when installing a Cork Gasket to moisten it

 

[tonyk72]

Thanks Tom, but other than going through that...how do I know if I need to have that done? How differently does the engine run if valve lash isn't properly adjusted? and how often should I adjust it?

 

[Tom Bryant]

Valve lash adjustment should be done as part of the tune up. Once you do it a couple times you will get an ear as to how loud the valves sound when adjusted vs. loose. If they haven't been adjusted in a while and are loose they will be noticably louder than when adjusted properly. If your adjusting nuts are weak the lash will require adjusting more often. A good idea is to install new locking nuts if it doesn't seem to hold the adjustment very long. Also if you compete in autocross or other events you will want to check the lash as part of your prep to make sure everything is maximized.

The aftermarket sells positive locking nuts that have a set screw to secure them. They usually don't require resetting once adjusted to specs but they won't fit under your LT1 valve covers with the drippers cast into them.

As for effect if your valves are loose your cam isn't operating to it's design specs. In other words too much clearance means the valves are not opening as far or as long as they are supposed to and performance suffers.

Hope this helps you understand valve lash.

Tom

 

[tonyk72]

Thanks, I'll read up some more this week...

 

[silver 80]

inch pound and foot pound.
these are two different torque wrenches. make sure you read what is on the wrench. you have.
tom