Any prep needed before installing new manifolds/risers?

[mlange]

Need to do a new exhaust manifold and riser on a PCM 6L.  New stuff coming from Nautique Parts and from the pictures it looks like they are completely painted with no bare metal surfaces.

Should I be getting rid of the paint on the mated surface?  Or can I just slap the gasket in there, bolt it all together and go?

[Jody_Seal]

yes the mating surfaces need to be clean and paint free.

[mlange]

Thx!  Recommendation on best way to do that?

[BraceMaker]

That would suck if they're actually powdercoated I'd be bringing that to the machinist and having them cleaned up if that's the case. 

[dleenhouts]

Cut the heads off of two or three old bolts to use as a guide for the new manifolds - once you have the old manifold off and cleaned up the surface, loosely thread them into the block, hang the new gasket in place over them, put the new manifold in place, then after you've got 3 or 4 new bolts in remove the headless bolts and continue. 

Trying to have someone hold a 50 lb manifold in place while you're trying to line up the gasket and thread a new bolt in is really hard.

[jpwhit]

I use a combination of a razor blade window scraper and a putty knife to clean off the matting surfaces. 

[mlange]

@BraceMaker  I'm just going off the picture on the web site...

Thinking about using a palm sander with 80 grit and then switching to 200-ish.  Feels like it would be a lot easier than a razor blade @jpwhit

Edited August 7, 2023 by mlange

[buechsr]

Battery powered steel pad/wheel.  I think Milwaukee makes it.  Or dremel.

[BraceMaker]

@mlange I wouldn't do that.

Those surfaces need to be flat and a palm sander is going to round off the edges no matter how hard you try.

I don't even like the idea of the steel wool.  For small overspray I usually use a flat razor blade.  If there is rust or I need to check for high spots I use a sheet of plate glass with pressure sensitive abrasive film from 3M stuck to the sheet its essentially dead flat and then you try to work the whole area evenly while rotating the glass and sliding so that you can lap the surface dead nuts flat.  But then again the local NAPA by me has a machinist and small projects like that are affordable vs. the effort.  If you have a glass shop locally I was able to buy quite a few different sized bits of fairly thick glass and have it tempered.  When they make custom glass they cut sheets to size and then temper it.  So if you call them up and see if they have any drops that you can buy they're usually happy to sell it to you for not too much money.

[mlange]

Thanks for the recommendation NOT to use a palm sander.

[DW]

 

@mlange -  There are numerous exhaust manifold gasket options available, are they coming with your manifolds?  I have good luck with the Mr Gasket version.  Suggestion - check the gasket fit by lining them up on both the head and manifold to make sure they clear the ports and line up on the mating surfaces.  The bolts / studs will help with this.

[JackQ]

I always use a  large flat file ( 1-1.5 inches fine toothed), it takes off the rough edges, some of the matching marks and all the pain/powder coat.  You may be surprised at some to the imperfections that are on some of the surfaces.  I have done dozens this way without issues. 

[mlange]

@DWGot the gaskets that Nautique Parts listed.

[jpwhit]

Never use any kind of abrasive on a machined metal mating surface. Even with a razor blade or putty knife, you always want to keep a fairly shallow angle to the metal surface so you don't put any scratches in the surface. It's not typically difficult to clean off the surface with a razor blade based scraper. It's just easier with something sharp like a razor blade to get under any remaining gasket material. The only time it's difficult to clean a gasket surface is when the gasket was put on with some type of sealant. But that's typically never the case for exhaust system gaskets. 

[Mateo_Vargas]

The instructions with the manifold says to file the surface but I like the razor blade idea.

[HMan66]

I’d use an air die grinder with a red abrasive pad. Harbor Freight stuff. Worked like a charm when I did mine. 

[mlange]

Ok guys.  New stuff here tomorrow so I'll let you know how it goes.

ONE BIG QUESTION... I can't find anywhere the torque specs for the riser to exhaust manifold.  Looks like exhaust manifold to block is ~25 ft lbs.  Don't want to over tighten the riser and crush the gasket.  Anyone know what it should be?

[mlange]

Got this from PCM.  Hopefully it helps someone else in the future.  Only thing I'll need to do different is put the manifold/riser on at the same time as there's no easy way to get to one of the riser nuts otherwise.

Surprised as just how low the torque is on the riser.