Can someone with experience describe the milling tolerances needed to gain clearance on a 914-6 (3.0) with Turbo Valve covers. My jangled understanding is that in order to be able to do a valve tune, one must remove material from the raised fins on the Turbo covers / lower obviously?..

Also, can valve covers withstand the heat involved in powdercoating?

Yes, powdercoating is fine. I believe I had 5/8 milled off the fins

Did you see the recommendation earlier this week on another post regarding this topic that suggested replacing the offending locking nuts with cap head allen screws and spring & flat washer combinations since the torque values are so low?

I thought it was a really good suggestion to keep from having to mill the web on the covers and plan on ordering the needed hardware as soon as I pull a stud and get a measurement on the proper length.....unless someone reads this who already knows and is willing to enlighten us.

I like the new bolt verses nut-n-stud (cap screw) idea / if one doesn't need to mill. Ethan?

No, you don't use bolts for that application. Porsche used studs for a reason.

Agreed. Eventually you'll wallow out the hole in the mag or al by screwing the bolt in and out a number of times.

Also the correct milling procedure is to not install them until the motor is in the car
Then you mill them to install.

If you mill them enough to go on then you know they will come off

Every chassis is a little different tolerance. And motors can vary minutely also

I really like Brant's suggested method and the reasoning. Valve adjustments are done every 15000 miles on my 3.2 and I have not milled the turbo covers yet. Had the engine out several times to re-seal and transmission repair; gave it a general look see and adjusted valves then. What a pain just to adjust the valves.

Making my next project the valve cover milling.

The naro motorsports pivoting engine mount makes dropping the engine so much easier. It's more like opening a door vs taking it off its hinges.

I just milled all the fins off leaving about an 1/8".
Looks clean and doesn't hurt the strength of the turbo cover.

BTW if you already have SC covers the turbo covers are a waste of money, only the earlier mag covers were leakers.

I collected every discarded pair of SC lowers I could...
no turbo covers for me

I've taken 5/16" off the entire top of the ribs, and that's worked.

I will get the Turbo covers and use Brant's method. Thanks for the idea.

Damn you guys are good.

I will go the Perry Kiehl route once the engine is in and I can remill if needed.

Thanks guys.

In the 'for what it's worth' department, here are some shots of my covers and somewhat crude milling/filing I did 2 years ago . You have to look close on some of them; there wasn't all that much that needed to be removed. This a stock factory -6.

Click to view attachment Click to view attachmentClick to view attachmentClick to view attachment

Does the PMS mount qualify here, too?

don't go there,the threads on the cam box will eventually strip out ,personally I would stick with the stock covers and forget the milling job,as mentioned before the alloy covers don't stay flat ,mill off the ribs and that will happen faster (warpage) and that's according to the clever engine builders on Pelican who say they do warp in stock form.
Get your old ones and resurface them with a sheet of sandpaper glued to a piece of glass ,buy the correct exhaust cover lower gaskets and all will be golden,sell your turbo covers to a 911 guy.
Did my magnesium ones and bone dry now....they were really bent

That's a load of poop on the milling and about the mag covers.
The studs and squaring up info is good.

Turbo covers are over-kill it won't hurt them one bit by milling off the ribs.
SC don't have much in the way of ribs and they work fine.
It's the magnesium covers that have the issues, they can warp just bolting them up.

If you already have turbo covers keep them and mill or clearance them. If you have SC covers keep them. if you have mag covers, unless you have a concours car get the SC or turbo covers.


My covers, I looked and they're milled to just under 1/4". Same height as the stud/nut boss.