96 850 Use copper spray on head gasket, or not?

Post by **JimBee** » 10 Oct 2014, 07:37

Getting ready to replace the head and want to be careful to get it leak free. Will chase out bolt threads, some of which were a bit crusty. I'm using the Victor Reinz head gasket and kit. Tracy used copper spray on all gaskets, should I just follow that approach?

I had the head checked for straightness, it's about .004 off. The engine rebuilder said I wouldn't be the first person to put one back with only that much variation.

So to spray or not to spray?

Post by **tryingbe** » 10 Oct 2014, 07:52

I never spray copper spray on any new gasket.

Post by **erikv11** » 10 Oct 2014, 08:06

I have never used any spray on the head gasket. I've never used copper spray.

Clean those threads well, good call.

zandrew · Post by **zandrew** » 10 Oct 2014, 10:22

You really shoud have the head lapped. The big thing with any gasket is realizing what type of gasket it is and what type of surfacing is required for it to work. I have an Audi A4 that uses a MLS HG which is Victor Reinz as well. These gaskets have a viton rubber layer over the MLS part so the head must be surfaced to accomadate it for a proper seal. I personally hand lap all my parts by purchasing large sheats of sandpaper and gluing them a to a milling block. The block is ground granite and is accurate to within .00002" across its surface. I use 60 grit then 100 grit and it gives it a good surface. However for other gaskets this will not work.

Post by **precopster** » 10 Oct 2014, 13:37

My machinist recently charged me $60 cash to surface a head. It won"t hurt to ask a price. Just as important are you cleaning the valve seats and replacing stem seals or just bolting it back on?

As far as copper spray is concerned I recently spoke with an engineer about the copper spray and he indicated that it was better suited to old school iron lumps as copper may react with aluminium.

Post by **taxi** » 10 Oct 2014, 15:01

According to original specs, the head is allowed to be more "warped" than it can be machined. I'm unsure what you mean when you say "resurface": If you mean what I think, creating a better surface for the seal, then I guess it's a good idea. But it almost sounds like you mean "resurface to get it straight", which is probably unnecessary.

I recently did my first head gasket change, and the head was visibly warped before reassembly. But it worked fine (V40 -99, 2,0 t).

As I understand, if you want to resurface the head due to straightness (or lack thereof) first you have to tighten the head down to something straight (of course) and then see if it is still warped.

Please correct me if I got this wrong (and if you think the V40 will explode, someone deserves a warning in that case)

Thank you!

Post by **JimBee** » 10 Oct 2014, 21:39

Okay, no thumbs up on that one : )

Cleaning out the bolt threads seems really important to get a good tight seal that will stay at torque values. That's on the agenda for tomorrow.

Thanks to all for the feedback.

zandrew · Post by **zandrew** » 12 Oct 2014, 17:55

If it's a nitrile or rubber coated mls hg you should never use the copper spray. The rubber is designed to adhere to irregularities directly and is there for cold sealing properties. The big thing with hg is making sure to have the head surfaced appropriately for the style of hg. The mls hg needs a smoother surfaces to work properly.

http://www.rlengines.com/Web_Pages/Cyli ... gines.html

Scroll down to the part about mls gaskets. They need a significantly lower roughness average opposed to other gaskets.

Other points of significance is to chase the threads and blew any debris out. Also never reuse head bolts unless they are designed for it. Stock head bolts are not reusable as they are torque to yield.

Post by **rspi** » 12 Oct 2014, 18:44

I have never used the spray.

I always have the head made true (my guy charges me $45).

I usually replace the valve stem seals and hand lap the valves.