Re: 1974 340 Boat engine ?
[Re: MCTPhoenix]
#1899597
08/26/15 05:06 AM
08/26/15 05:06 AM
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Joined: Aug 2003
Posts: 43,292 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,292
Bend,OR USA
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In 1972 Mopar lowered the compression ratio on all car 340 motors to 8.5 to 1, that is in blueprint specification. Mopar never blueprinted any production motors so the average car motor had less than that spec. My message is to go ahead and buy good quality replacement piston for the 1972,73 car motors and check the deck hieghts, combustion chamber volumes and see what true compression ratio you get use the head gasket thickness to help achieve the compression ratio you want IHTHs
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: 1974 340 Boat engine ?
[Re: MCTPhoenix]
#1899608
08/26/15 06:48 AM
08/26/15 06:48 AM
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Joined: Jan 2003
Posts: 8,941 Holly/MI
Dean_Kuzluzski
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Holly/MI
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If the block doesn't check out to be good, do a stroker 318, not so common.
By late 72 340's had a very sturdy cast crank, forged went away. 340's, and 360's, have bigger port/valve heads than a 318.
But, since you said "restoration", do the 340.
R.I.P.- Gary "Coop" Davis 02/09/68-05/13/04
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Re: 1974 340 Boat engine ?
[Re: Dean_Kuzluzski]
#1899665
08/26/15 11:42 AM
08/26/15 11:42 AM
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Joined: Nov 2003
Posts: 36,041 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
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Lincoln Nebraska
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If you're wanting to be out on the water for what is left of the summer months what about dropping in the 318 to get you up & running then we can help you get the 340 rebuilt/setup for high rpm longevity. (simply) Sounds like the PO didn't use enough octane.
live every 24 hour block of time like it's your last day on earth
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Re: 1974 340 Boat engine ?
[Re: minivan]
#1899668
08/26/15 11:49 AM
08/26/15 11:49 AM
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Joined: Nov 2003
Posts: 36,041 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
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Lincoln Nebraska
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that jogged my memory & once I worked on an inboard 318 speedboat & it was reverse rotation! took awhile to figure that one out (firing order)
live every 24 hour block of time like it's your last day on earth
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Re: 1974 340 Boat engine ?
[Re: minivan]
#1900018
08/26/15 10:29 PM
08/26/15 10:29 PM
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Joined: Feb 2003
Posts: 8,020 Pangaea
B5 Bee
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I have always thought why didn't boat manufacturers reverse the rotation on the props made to accomodate standard rotation engines?? The prop on many single inboard engine boats turns clockwise(CW/reverse/right hand rotation) to help trim the boat. When a boat is operated by only one person sitting on the starboard (right) side, the operators weight creates a list to the right. If the prop turns CCW (std automotive rotation), the torque it produces will also create a list to the right. So by turning the prop CW, it's torque now creates a list to the left, which will help counter the list on the right caused by the drivers weight. Hopefully the two are near equal so the boat will trim up level. When more than one person is in the boat, they can shift their sitting positions to help with trim, one person doesn't have that possibility. A bit of trivia, Chrysler Marine V8s didn't use the AVS's, almost all used a AFB's modified for marine use.
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Re: 1974 340 Boat engine ?
[Re: ahy]
#1900050
08/26/15 11:07 PM
08/26/15 11:07 PM
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Joined: Feb 2003
Posts: 8,020 Pangaea
B5 Bee
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Most Chrysler Marine motors have special oil pans and timing cover, so if he went with a 360 he'd have to locate them.
If it were me and if I'm buying new pistons, might as well get new rods and a 4" crank to go with them and throw them in a 318 block. What's a plus .030 318 with a 4" arm? 390"? That should do it.
Yes, boat motors have a load on then all the time they are cruising. If it has the original dist, notice there is NO vac adv pod. It's easy for a prior owner to jack up the timing to auto specs and causing detonation. Check the owners or shop manual for total timing, it will far less than automotive, 10* less, maybe more.
First thing I'd do is verify that the 340 is a RH/CCW/standard rotation. Internal parts will be the same as automotive. If it's LH/CW/reverse rotation, careful with the cam and dist drive gear. There are new ones available for the SB and pricey but at least you can get them, only choices for the BB is used.
Last edited by B5 Bee; 08/26/15 11:09 PM.
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Re: 1974 340 Boat engine ?
[Re: B5 Bee]
#1901000
08/28/15 11:45 AM
08/28/15 11:45 AM
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Joined: Aug 2007
Posts: 294 Phoenix, AZ
MCTPhoenix
OP
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OP
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Posts: 294
Phoenix, AZ
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First thing I'd do is verify that the 340 is a RH/CCW/standard rotation. Internal parts will be the same as automotive.
Just to make sure... when checking for clockwise or ccw are we looking at the front of the engine or referenced from the rear? Thanks
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Re: 1974 340 Boat engine ?
[Re: minivan]
#1901147
08/28/15 02:54 PM
08/28/15 02:54 PM
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Joined: Jan 2010
Posts: 157 hawaii
pauly v.100
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hawaii
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I have always thought why didn't boat manufacturers reverse the rotation on the props made to accomodate standard rotation engines?? Can't do it, one engine would be pushing forward the other would be in reverse.
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Re: 1974 340 Boat engine ?
[Re: MCTPhoenix]
#1901184
08/28/15 04:28 PM
08/28/15 04:28 PM
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Joined: Jun 2010
Posts: 1,144 wellington ohio
68-scatpack-rt
In thin ice
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In thin ice
Joined: Jun 2010
Posts: 1,144
wellington ohio
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If the boat was raw water cooled, there's a good chance that the block is thin from years of rusting in the water jackets.
Find a good replacement block that had antifreeze in it.
Also, you really need to find a shop that builds marine stuff. There are LOTS of subtle differences that will bite you. (Carb setup, piston to wall clearance, valve guide clearance, oiling, cam selection etc........) don't think you can just drop in an automotive engine and be good to go.
unions....the folks who brought you the weekend!
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Re: 1974 340 Boat engine ?
[Re: MCTPhoenix]
#1901252
08/28/15 06:48 PM
08/28/15 06:48 PM
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Joined: Feb 2003
Posts: 8,020 Pangaea
B5 Bee
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Pangaea
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First thing I'd do is verify that the 340 is a RH/CCW/standard rotation. Internal parts will be the same as automotive.
Just to make sure... when checking for clockwise or ccw are we looking at the front of the engine or referenced from the rear? Thanks First, let me correct my post. "First thing I'd do is verify that the 340 is a LH/CCW/standard rotation."" From the rear or like you're in the drivers seat. Standard rotation is CCW or Left Hand. Reverse is CW or Right Hand.
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