Slant Six Forum :: update on slant 6 jetboat engine

: Apparently the engine block, crankshaft and
: connecting rods are from a 1977 or later.
: The cylinder head is the early style with
: the aluminum tubes around the spark plugs.
: The rod and main journals are narrow and the
: crankshaft appears to be a cast piece, not
: forged.
: The valve seats are recessed a lot, probably
: due to using unleaded fuel.

: If you end up replacing the lower end, try for
: a pre-76 forged crank engine. If you want to
: replace the head and don't like drool tubes
: the post 1975 heads use the smaller plugs
: with no tubes. The most common castings end
: with the numbers "447" (with air
: pump hole in back for head) and
: "600"(without air pump hole...).
:
: Just FYI,
:
: -D.Idiot

: Good information. I am starting to believe that
: this engine should be sold off and an
: earlier block and a later cylinder head
: should be used instead. Everything I've read
: and everyone I have talked to about this
: project agrees that the forged crankshaft,
: block and rods is worth trying to find and
: that the later head is a much better design
: to start with for getting more power. I'd
: like to use an aluminum block for the weight
: savings but I assume that would be VERY
: difficult to find.
: I am getting somewhere finally in finding a
: place within a reasonable distance from me
: to have the crankshaft welded and reground
: to a 4.5" stroke.
: I'll keep posting my progress.
: Jeff Garber

Author:	Jeff Garber [ Fri Dec 14, 2001 1:39 am ]
Post subject:	update on slant 6 jetboat engine
The jetboat engine project is underway after much research and help from this group. My ignorance of this engine will become clear as anyone will see when they read this. Apparently the engine block, crankshaft and connecting rods are from a 1977 or later. The cylinder head is the early style with the aluminum tubes around the spark plugs. The rod and main journals are narrow and the crankshaft appears to be a cast piece, not forged. The valve seats are recessed a lot, probably due to using unleaded fuel. The valve guide holes are very worn out. The pistons and cylinders are .040" over. Crankshaft is undersized at .010" R and .020" M and is in very good condition. Camshaft appears to be stock with .267" lobe height. Now for my questions. Where can I get this crankshaft welded and reground to increase the stroke ? I have not found anyone in New England that has the equipment to weld the crankshaft and guarantee the end results so I assume the crank will need to be shipped somewhere to get this work done. Is it worth doing this work to this crankshaft or should I try to find a forged one (and block and rods) ? I have some pictures of the internal engine pieces. The most interesting thing I found is what appears to be a cam bearing that wasn't installed properly and does not line up with the oil feed hole completely. Is this a mistake on the previous assembler's part or some secret trick that I should duplicate. It's obvious that the cam bearing was installed fully lined up to the feed hole previously because there is still evidence (which can be seen in the picture) of where it was before the last rebuild. Thanks again for the help I've already received with this job. Jeff Garber tirebiter@compuserve.com

Author:	DusterIdiot [ Fri Dec 14, 2001 5:40 am ]
Post subject:	Re: update on slant 6 jetboat engine
Quote: : Apparently the engine block, crankshaft and : connecting rods are from a 1977 or later. : The cylinder head is the early style with : the aluminum tubes around the spark plugs. : The rod and main journals are narrow and the : crankshaft appears to be a cast piece, not : forged. : The valve seats are recessed a lot, probably : due to using unleaded fuel. If you end up replacing the lower end, try for a pre-76 forged crank engine. If you want to replace the head and don't like drool tubes the post 1975 heads use the smaller plugs with no tubes. The most common castings end with the numbers "447" (with air pump hole in back for head) and "600"(without air pump hole...). Just FYI, -D.Idiot

Author:	Jeff Garber [ Fri Dec 14, 2001 7:10 am ]
Post subject:	Re: update on slant 6 jetboat engine
Quote: : If you end up replacing the lower end, try for : a pre-76 forged crank engine. If you want to : replace the head and don't like drool tubes : the post 1975 heads use the smaller plugs : with no tubes. The most common castings end : with the numbers "447" (with air : pump hole in back for head) and : "600"(without air pump hole...). : : Just FYI, : : -D.Idiot Good information. I am starting to believe that this engine should be sold off and an earlier block and a later cylinder head should be used instead. Everything I've read and everyone I have talked to about this project agrees that the forged crankshaft, block and rods is worth trying to find and that the later head is a much better design to start with for getting more power. I'd like to use an aluminum block for the weight savings but I assume that would be VERY difficult to find. I am getting somewhere finally in finding a place within a reasonable distance from me to have the crankshaft welded and reground to a 4.5" stroke. I'll keep posting my progress. Jeff Garber tirebiter@compuserve.com

Author:	Dart270 [ Fri Dec 14, 2001 8:23 am ]
Post subject:	Re: update on slant 6 jetboat engine
Quote: : Good information. I am starting to believe that : this engine should be sold off and an : earlier block and a later cylinder head : should be used instead. Everything I've read : and everyone I have talked to about this : project agrees that the forged crankshaft, : block and rods is worth trying to find and : that the later head is a much better design : to start with for getting more power. I'd : like to use an aluminum block for the weight : savings but I assume that would be VERY : difficult to find. : I am getting somewhere finally in finding a : place within a reasonable distance from me : to have the crankshaft welded and reground : to a 4.5" stroke. : I'll keep posting my progress. : Jeff Garber If the head is '68 and up, it has the same combustion chamber as the '75-up heads. I prefer the older heads because you can pull the cam (lifters) without pulling the head, intake, etc... Also, it might be harder to weld and offset grind a cast crank, but some of the fastest slant six cars ever run 10's with cast crank engines. Lou

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