:
: Hi, this is a request for help with a 225
: slant 6 engine that happens to be in a 1965
: jetboat. That's right ... a 16'
: "Turbocraft, Contessa" jetboat
: with a Buehller jet drive. I've been asked
: to rebuild the engine and to make it more
: powerful. Any suggestions will be greatly
: appreciated. Most of my extensive mechanical
: experience is with British sportscars and I
: am very relieved to find a hotbed of slant 6
: enthusiasts. This engine will be built to
: operate at 5000 to 5500 RPMs maximum as the
: jetdrive unit doesn't work well over that
: RPM. The idle must be kept to 1000 RPM or
: lower because there is no clutch or
: transmission between the engine and the
: jetdrive unit. There is a sufficient budget
: to undertake this project and many of the
: "normal" modifications are
: planned. About the only other limiting
: factor is that the exhaust system must be
: retained since it is water jacketed. The
: plus side of the water jacketed exhaust is
: that the engine will never run hot with a
: constant supply of cooling water being
: pumped through, from the lake it runs in.
: Hard valve seats, guides, and valves will be
: used. The head will be ported with
: flow-bench testing and oversized valves
: used. I'm planning to use a high-lift, short
: duration camshaft to make as much power as
: possible in the low to mid RPM range.
: Compression will be in the 10:1 or 11:1
: range, perhaps lower since since pump gas
: and probably not very high octane is all
: that is available where the boat will be
: used.
: I understand that a .060" overbore is very
: possible and there is room for larger valves
: ... I've been researching this for a week
: now online. The engine arrived here
: Thursday, 11/1/01 and now it's time for me
: to finalize what work it will get and to
: start ordering parts. I believe the engine
: already has the forged crankshaft.
: This message is not a joke, I can supply JPG
: pictures of the engine and/or brass,
: "Chrysler Marine" name tag if
: anyone is interested.
: Again, any help or suggestions would be greatly
: appreciated. The goal of this rebuild and
: power increase is to make the boat so that
: it will "get up on plane" with 8
: adults on board, right now it can only do
: that with 6 adults on board.
: Jeff Garber

:
: Thanks for the post Jeff, this sounds like a
: fun project. Let's get some pictures posted
: if you have them available. (I will send you
: a seperate email)
: You are on the right track with your general
: build-up plans, the cam selection is going
: to be the trickest thing on this set-up. We
: need to ask the owner for more detail on the
: boat's jet drive set-up, at what RPM did the
: old engine "flash" to before
: working under full jet impeller load? (this
: works much like torque converter stall
: speed) The 5000 to 5500 redline target is
: good info. and easy to work with. What is
: the current induction (manifold / carb.) on
: this engine?
:
: Keep "feeding" us info, including any
: engine tear-down findings, questions or
: concerns. I will give you more info later
: after I "crunch some numbers".
: DD

:
: Jeff, first, Doug is going to want to know the
: specs of the cam you plan on using....ALL
: the specs.
:
: I'm a bit conservative, but I would suggest
: building it with a strong eye toward
: reliability, then add the perf goodies.
: First, hit the salvage yards and round up
: what you need to convert it to electronic
: ignition, and snag a later model head and a
: "super-six" setup while you're
: there. The later heads do away with the
: spark plug tubes, and consequently, the
: typical oil seepage from them. The super-six
: is a two-barrel intake and carb, and will
: help on the induction side.
: I'd suggest only boring it .030, but also
: decking the block .060, maybe .080, as well
: as taking off .060-.080 from the head, too.
: You can actually take more than that off,
: but the engine is going to need the
: reliability factor, so don't get too carried
: away. The block deck, combined with the head
: surfacing, will probably net you about
: 9.5-10 compression. (Just a guess, don't
: know the math right offhand.)
: I think it's small block Ford valves that fit
: into those heads rather well, and combined
: with a good valve job and port work, it'll
: really wake up the engine. Your biggest
: stumbling block will be that water-cooled
: exhaust. The slant responds really well by
: opening up the exhaust, and head work helps
: it that much more. If you could maybe size
: up any exhaust tubing coming off the
: manifold, that should help.
: Doug will probably respond with a more detailed
: set of suggestions, and all of us would like
: some feedback as to what you do, and how the
: engine, and boat responds, if you don't mind
: keeping in touch with the board.
:
: Roger

: Roger,
: The reliable reputation is why I took on this
: job. Any words of wisdom about what does
: break in these slant 6 engines ? All of the
: engine components will be fully blueprinted
: to far closer than factory specifications
: and the moving parts will be balanced.
: Electronic igniton has been added already by
: the owner. I have to make a sealed box to
: keep the added components waterproof unless
: I can find a marine equivalent.
: I will most likely use lighter pistons with a
: lower compression (pin) height and remove as
: much material from the head and block as I
: can, to cut weight. 20 or 30 pounds will
: make a difference in a boat this small.
: The later cylinder head is something I will
: look into. Does the later head have any
: performance improvements/drawbacks over the
: earlier head ? This engine does have the
: pocketed spark plugs.
: Why only to .030" overbore ? I would like
: to go as far as possible, is .060" all
: that can be done safely ?
: The biggest stumbling block is the exhaust in
: my opinion. Does the slant 6 engine in
: particular, loose out tremendously with poor
: scavenging ? More than other engine designs
: ?
: Thanks for your interest and suggestions,
: Jeff Garber

:
: Hi, this is a request for help with a 225
: slant 6 engine that happens to be in a 1965
: jetboat. That's right ... a 16'
: "Turbocraft, Contessa" jetboat
: with a Buehller jet drive. I've been asked
: to rebuild the engine and to make it more
: powerful. Any suggestions will be greatly
: appreciated. Most of my extensive mechanical
: experience is with British sportscars and I
: am very relieved to find a hotbed of slant 6
: enthusiasts. This engine will be built to
: operate at 5000 to 5500 RPMs maximum as the
: jetdrive unit doesn't work well over that
: RPM. The idle must be kept to 1000 RPM or
: lower because there is no clutch or
: transmission between the engine and the
: jetdrive unit. There is a sufficient budget
: to undertake this project and many of the
: "normal" modifications are
: planned. About the only other limiting
: factor is that the exhaust system must be
: retained since it is water jacketed. The
: plus side of the water jacketed exhaust is
: that the engine will never run hot with a
: constant supply of cooling water being
: pumped through, from the lake it runs in.
: Hard valve seats, guides, and valves will be
: used. The head will be ported with
: flow-bench testing and oversized valves
: used. I'm planning to use a high-lift, short
: duration camshaft to make as much power as
: possible in the low to mid RPM range.
: Compression will be in the 10:1 or 11:1
: range, perhaps lower since since pump gas
: and probably not very high octane is all
: that is available where the boat will be
: used.
: I understand that a .060" overbore is very
: possible and there is room for larger valves
: ... I've been researching this for a week
: now online. The engine arrived here
: Thursday, 11/1/01 and now it's time for me
: to finalize what work it will get and to
: start ordering parts. I believe the engine
: already has the forged crankshaft.
: This message is not a joke, I can supply JPG
: pictures of the engine and/or brass,
: "Chrysler Marine" name tag if
: anyone is interested.
: Again, any help or suggestions would be greatly
: appreciated. The goal of this rebuild and
: power increase is to make the boat so that
: it will "get up on plane" with 8
: adults on board, right now it can only do
: that with 6 adults on board.
: Jeff Garber

: Hi, this is a request for help with a 225
: slant 6 engine that happens to be in a 1965
: jetboat. That's right ... a 16'
: "Turbocraft, Contessa" jetboat with a SL6...

:Jeff, you can bore one .100" easy enough, and :it opens up a wider selection of pistons. I have :a Slant that is .060" over with 7" long 198ci :Slant rods and 2.2liter Turbo pistons in it. You :do end up with a higher pin height and a lighter :piston. The only drawback to the 2.2 piston is :that it has narrow rings, and that may lead to :accelerated wear in a high RPM use. Dennis

: Dennis,
: Thanks for the info. .100" will help a
: lot. I'll have to determine if the block has
: any core shift first as I understand it.
: I'll likely have pistons made especially for
: this engine but it's good to know that there
: are off-the-shelf ones available. The only
: high RPM use will be for a short time (
: hopefully ) until the boat gets up on plane
: and then throttled back.
: I've been talking to some other people who know
: about the jetdrive and it's a unanimous
: decision ... 8 people onbard a 16' boat is
: called "overloaded". I'll be
: having a very frank discussion with the
: owner of the boat and then determine if the
: project is doable. I have no doubt the Slant
: 6 can produce enough power but I'm pretty
: sure some "chassis" modifications
: will be in order, i.e. hydraulically
: controlled trim plates or a jet discharge
: nozle vane that can direct the water down
: until the boat gets up on plane.
: Thanks again Dennis, for your input,
: Jeff Garber

: Here are the PICs Jeff emailed and some info. I
: dug-out of my files. (see the link below the
: tag)
: DD Hey...Cool stuff..It reads in the info link that Chrysler engineered a water heated intake for the marine applications..??Anyone ever seen one of these???...