Hi Stefano, One of the things I REALLY wish I'd done when doing the Berlina engine rebuild, was to jet coat (or whatever) the exhaust manifold because it works. When my manifold later (recently) broke, I got the fiberglass looking insulation tape and had the new (NOS) manifold wrapped. This is allegedly better than jet coat, but if I could do anything I want, I'd do both. The difference in temperature and what that means to the hydraulics on the exhaust side are significant. As I now have a GTV6 that looks like a keeper, I really want to have a pair of Jet Coated manifolds "standing by" for when I need them.
If you tell them to sandblast the inside, they will likely do their best, but it's imperfect and not particulary relevant, once the engine is running between the heat and the carbon deposits, any residual rust won't matter. You will need to specifically instruct them about doing the inside. On mating surfaces: they're only truly flat if you make them flat, sand blasting shouldn't affect that, although I would instruct them to mask that surface unless it's severly compromised. On an exhaust manifold, it's difficult to imagine that it could be so far out as to affect seal, but while it's off, putting a straight edge on it will tell you if you need to do any surfacing. Another option is put ther piece on a flat surface and use a flash light (or rock it) to see what gaps may exist. It seems like a lot of effort for a part that should just bolt on, but if you don't check, you don't know. Stevan Thomas 73 Berlina 83 GTV6 being resurrected In a message dated 5/4/2011 11:32:33 PM Pacific Daylight Time, [email protected] writes: > -----Original Message----- > From: [email protected] [mailto:[email protected]] On Behalf Of > Stefano Iachella > Sent: Tuesday, May 03, 2011 10:30 AM > To: Alfa Digest > Subject: [alfa] Exhaust Manifold Prep > > Cats: > > The list has been pretty quiet, so I'll ask for some opinions. > > I have some spare manifolds to install and will be giving them a high temp > coating (POR15 Exhaust Gray). I need to prep them first. > > First question is about sand blasting. If I take them somewhere, will they > blast the inside as well, or do I have to specify that? > How about the mating surfaces? Do they loose there flatness and get > screwed > up? Do they need to be covered? > > I am also contemplating some sort of chemical soak. This should be able to > get inside and outside. The other advantage is I can be ready to put on > the > final product as soon as I get it out of the soak to minimize re-rusting. > If > I take it to a sand blaster, I should be getting the final product ready > to > apply as soon as I get the pieces home. I may not have the time to do it > right away. > > Any recommendations on chemicals and where to get them. It would be nice > to > get a product easily found at a hardware store or home box store. I'd > rather > not have to order some product and have to wait for shipping, and only > available in big industrial cans. > (unless someone has already bought a big industrial can and would sell me > a > smaller portion). > > Thanks, > Stefano > Concord, CA > > > - -- > to be removed from alfa, see http://www.digest.net/bin/digest-subs.cgi > or email "unsubscribe alfa" to [email protected] > > ------------------------------ > > Date: Tue, 3 May 2011 09:54:22 -0700 > From: Brian Shorey <[email protected]> > Subject: Re: [alfa] Exhaust Manifold Prep > > I would bite the bullet and send them out for ceramic coating (or whatever > hi > temp coating is the rage these days). I've done most of mine, the under > hood > temps are noticeably lower. > > bs -- to be removed from alfa, see http://www.digest.net/bin/digest-subs.cgi or email "unsubscribe alfa" to [email protected]
