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1996 7.4 Mercruiser 2 spark plug holes bridged over

4.3 manifold removal.JPG4.3 starboard cyl head removal.JPG4.3 #1a.jpg4.3 new cyl heads installed.jpg4.3 with new exhaust system.png

intake removal, cyl heads removal, cleaning up block deck surface, installed new cyl heads, all back together with new center riser style exhaust system
total parts cost including all new exhaust system is about $2000. Cyl heads, $550 (reman) gasket set and head bolts, $200, new center riser exhaust including V/P parts to replace old NLA OMC one piece manifolds, $1200. Rest was my labor. Impact tools are a must on raw water cooled engines, but be careful. Didn't break even one bolt!
 
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Agreed no point in doing all this if you have a cracked block. Then its new or reman engine time. On mine the block was good but the old cyl heads had small cracks in the center cyl exhaust seat area, from an overheat 3 seasons before. What caused the tear down was difficulty starting, rough running and a bit of water in 2 cyls but not enough to hydrolock. Found blown head gaskets (likely from the overheat) on both sides...
So went to my friendly local Hot Rod/Machine shop and bought a set of reman 4.3 cyl heads....

4.3 old cyl heads small.jpg
old cyl heads & blown head gaskets...
4.3 reman cyl head 2 small.jpg
reman 4.3 cyl head
 
Is it me or has that 454 had two cylinders lopped off? I know Ford cut a 460 in half lengthwise but I did not know GM made an V-8 block into a V-6 and to get it to 454 cu in, would they not have had to increase the bore and/or stroke?

Gene
 
The pics that Lou posted are of his 4.3l V-6...

the bolts are fairly tough unless they are severely corroded...you shouldn't have any problem with the head bolts (from the impact)...just use a good socket.

On the oil contamination, it would depend upon where the gasket failed or the block cracked.

Did you ever check the elbow gasket to see it it was leaking internally back into the manifold?
 
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