454/7.4L  502/8.2L Chevrolet/GM V8
Replaces 807078A6 807078T08 Manifolds,
807988A03 and 98504A3 Risers
454/7.4L  502/8.2L Big Block Chevy

Manifold Kit with 4" risers. #58242

Manifold kit with 3" riser.    #58241            
454 manifold to head gaskets
riser gaskets restricted
Comparison of 3-inch and 4-inch risers
Mercruiser Engines
may come with either
a 3" riser or a 4" riser.
The size of the riser is
determined by the
diameter of the hose
that connects the riser
to the exhaust pipe.  
A 3" hose or a 4" hose.
4-inch riser hose size
4-inch riser with bellows
Mercruiser 4" riser
(accepts a 4" exhaust
hose).  This riser is
used on 1987 - 2002
Mercruiser V6 and V8
engines with the center
riser manifolds.  
3-inch riser side view
Mercruiser 3" riser,
(accepts a 3" exhaust
hose).  This riser is
used on 1983 -1995
MerCruiser V6 and V8
engines with the
center riser manifolds.  
3-inch riser diagonal view
4-inch riser attaching bolts
The 3" riser is attached
with short studs
The 4" riser is attached
with 6" long bolts
3-inch riser studs for mounting
All manifold kits come with cylinder head to exhaust manifold gaskets, exhaust
manifold to riser gaskets, exhaust manifold to head studs or bolts, exhaust manifold
to riser attaching bolts and water inlet fittings with drain plugs.
Mercruiser Manifold kit with risers and gaskets
Mercruiser manifold showing quality
Riser gaskets open
Questions?  Call Dennis Moore @ 626-357-3573