Exhaust Manifold Question

[SPIKE]

Hi! It's been a long time BoaterED folks!

Replacing the exhaust manifolds on a Volvo 5.7 EFI. The new ones come painted with black paint, including the face where they are bolted to the head. Question - does the black paint need to be removed before install? If so, what is best method for removal? Thanks!

 

[Sandy]

I can only advise as to riser/elbow to manifold gasket mating surfaces which Crusader ( on a note in the box with the new exhaust parts) says must have the protective paint removed and surfaces decked flat before installing. I would expect the manifold to engine mating surfaces should be treated in the same manner though I'm sure that process is quite often ignored.

I always take a sharp flat mill bastard and deck the riser/elbows flat , filing only diagonally away from me to keep the file from dulling on a back stroke .

If they hadn't been painted at the factory I cover the surface with marker and when I start filing it becomes perfectly clear what previously looked very flat is far from that. When all paint or marker is completely removed , the surface is sufficiently flat and will then apply even pressure on the gasket.

I also retorque the fasteners to factory recommended spec. after a few heat/cool cycles on runs, then check again each year since gaskets get squeezed and fasteners stretch.

 

[SPIKE]

Thanks Sandy. It seems to make sense to remove the paint on that surface. Same with the riser and exhaust surfaces. Thought there might be a solvent to aide in removal. Good idea to re-torque after a few heat cycles as well.

 

[billm]

I always use chemical paint remover and plastic scraper to avoid making scratches on mating surfaces. Also do the surface that bolts to the engine block.

 

[cmariner32]

+1 on what Sandy does. A little extra attention to the mating surfaces prior to installing will pay big dividends on the life of the risers and slow up the appearance of rust at the joint.

 

[jtybt15]

Using a great big mill file can show high or low spots but there's no guarantee the block hasn't warped. A good gasket will make up for any low and high spots.

 

[billm]

I realize the importance of the manifold to riser joint, but I have always been afraid of hand filing them too much for fear of rounding off an edge. I like to use the metallic gasket with no gasket cement which seem to bond well to both surfaces. For the manifold to engine joint, I use the white cardboard gasket with a thin coating of ultra black on all surfaces. I do both manifolds and risers every 5 years as they are salt water cooled.