HiWind

bare ali and uncoated as supplied by Rennline - i always check mine on a thick piece of glass for any warp etc.. but obv the proper low torque values apply as stated above to prevent that.

dlpalumbo

I just noticed the thread below on powder coating best practices. They explicitly state that mating surfaces are NOT to be coated. ARE YOU LISTENING RENNLINE?

As no one has submitted an example of powder coated valve covers that don't leak, it looks like milling the coating off the mating surface will be my best approach.

What a CF.

Jacke2c

You are seeing something else leak and blaming it in the valve covers? I have a set of Rennline covers and they have both anodized and powder coated. The anodization is just the treatment of the metal on the surface unlike the buildup of the powder coat paint....

I used to have leaks and thought it was from the valve covers. What I did during my bi--annual valve setting is I noticed that on the side that leaked all the time, I had one rocker shaft that was not offset in the boreas it is supposed to be. If you set it in the center (as I once thought they should be) you will have the edge of the shaft too close to the edge of the casting and it will leak around the end of the shaft, drip down through the cooling fins, and then as you run the engine and drive around, the oil is splashed and whipped back onto the valve covers.

When I overhauled my first 911 engine, I discovered there is a lot of room laterally in the rocker shaft position. I found a few videos on-line that explains how they should be positioned. I know that others have had to install rubber rocker shaft washers in the grove to stop this kind of leak. I find it hard to believe that if you are using new o-ring type gaskets on your valve covers and are torquing them to the 84 inch pound spec, that you would have leaks. It was only recently that I discovered that I had been way over tightening my valve covers (and I was being cheep thinking i could re-use old gaskets)... I bought an inch-pound wrench and new gaskets, and reset my valves and set the shafts the way they are supposed to ride in their bores. I think I have one that still weeps, but I think it is getting past one of the rocker shafts and is leaking on the backside down onto the heat exchanger.

dlpalumbo

Good point turbo2. I phoned the tech and asked him to check the rocker arm positions while the covers where off. IIRC when I removed one of the covers, there was oil on the spark plug cable, which, I think, indicates the condition you describe.

Do you know if the rocker positioning is different for 964 than from earlier engines?

Rennline

All of our valve covers are initially anodized. The red covers then get meticulously masked off to ensure no powder touches any of the mating surfaces. From here they go out for powder coat, and come back, get inspected, and then ship out to our customers. We have not found a correlation between our properly powder coated valve covers vs. the anodized ones in regards to leakage.

@turbotwoshoes My thoughts exactly! We have seen the rocker shaft leak many times and it can often be mistaken for a valve cover leak sending the owner on a frustrating hunt to fix the properly sealed valve covers.

dlpalumbo

I have checked with shop. The rocker shafts were first thing they looked at. The builder races 911s and knows his way around air cooled engines. They are convinced its the covers. They go out to be milled tomorrow. This has been very frustrating for the builder as well as myself.

Derek911

I have the Rennline anodized covers, upper black and lower sliver, with gasket set from Pelican, and they have never leaked. My original covers were just roached and looked horrible.

Rennline

Would you mind sharing the shop name & contact info with us (feel free to PM us if preferred). We would like to discuss this with the shop, and if necessary, overnight a replacement set to them, so that we can get that set back for investigation with our CMM.

Jacke2c

I do business with Rennline! no affiliation other than a satisfied customer...

Jacke2c

txhokie4life

I've seen the rocker shafts have ovality issues causing leaks. Fortunately did not affect the cam tower.
Replaced the shafts and no more leaks.

M

dlpalumbo

I want to publicly acknowledge my gratitude towards Rennline for looking into this matter. PM has been sent with shop contact info. Thanks for all the help.

Dan

dlpalumbo

A lot has happened. First, I learned I can't tell powder coated from anodized finishes. I have been used to anodized finishes appearing as a thin, dull, film. My original covers (black) had a thicker glossy finish I assumed to be powder coated, especially since they apppeared similar to the red covers on the Rennline site that are said to be powder coated. Rennline reps have assured me that the original black covers were anodized. The new covers (supplied by Rennline) are also black and anodized and appeared (as far as I could tell) to be identical to originals. All underside surfaces of original covers were black. Don't know about new covers.

My tech said the rocker arms were not leaking. RS seals were not installed. New covers went on with supplied Victor Renz gaskets. These are what I used when I tried hylomar sealant. Several hose couplings were leaking. These were replaced.

Results: Car idled long time in shop on lift. One remaining leak thought to be a return tube. I drove home 45 mIles in 85 degree rush hour traffic and parked car over clean drip pan. Next morning a few dots of oil. One is known leak. Others are probably isulation bleeding out. I left that day for travel, so this is all I have to report, but wanted to post what I had to make you all know how Rennline supported me in this maddening cavalcade. I have no idea what caused original leak. Maybe Rennline will chime in with what they find during examination of original covers.
​​​​​​
Thanks again to Rennline not only for their support, but for their patience with my ignorance. I'm sorry to have misled the forum and hope this post sets things straight.

Dan

​​​​​​ps. Wish I had remembered to put car on charger before I left. There's always something.
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Rennline

Thanks a lot for the follow up Dan. We are happy to help!

We received the old valve covers back today and immediately cleaned them up and put them on the CMM. As far as flatness, both covers are flat within .0005" As far as groove depth, they are to spec within .003".




We did notice that there is a good amount of oil on the outside of the covers. This may be from oil blowing across the covers, but we thought it should be brought up. Additionally there were some very large globs of RTV on the inside of the covers. We do not recommend using RTV with Victor Reinz gaskets. When our valve covers are installed on flat cam towers, with dry Victor Reinz gaskets, and torqued correctly, they will not leak.

dlpalumbo

Here's a thought. I gave the shop the supplied VR gaskets with the covers for the rebuild. They returned the VR gaskets having used, I suppose, gaskets that came with gasket kit. That may have been original cause of leak. I then tried hylomar with VR gaskets. Twice. First a thin coat, then, in frustration, a thicker coat, thus the globs, for which I am not proud.

I will update once I put more miles on car.