1968 318 to 1973 340 water pump interchange

[Trogdoor]

I am swapping out the 1968 318 in my Dart convertable to a 1973 340 engine. My 1st problem is the brackets for the power steering do not work out for the water pump cover on the 73 340. The second thing is the water hose to the radiator is on the passenger side on the 73 340 and the drivers side on the 68
318. Can I just swap the almost new water pump from the 318 to the 340 or will I run into additional problems? Thanks

 

[67Dart273]

Only problem I know of is the timing marks. If you want to "build" a new mark on your 340 balancer to move it to the opposite side, you should be OK

 

[70aarcuda]

use the timing chain cover and water pump that fit the year of the car.....

318 and 340 timing chains will interchange....in 1970 mopar changed the water pump inlet...lower hose location on the pump....

 

[Trogdoor]

Thanks for the replies. My question would be- what is the sequence of events
to build a new timing mark on the 340 balancer? Would I have the 340 engine rotated to TDC on removal of cover and then make a mark after installation of
the 318 cover on the damper?

 

[swinger340]

did you use the torque converter/flywheel out of the 73 340 car, or an after market flex plate w counter weights? 68 318 is internally balanced and 73 340 is externally balanced. If not, you could run into vibration issues. Unless the engine has been altered and is now internally balanced and then you wont have any issues. I ran into this, and the vibration drove me crazy. Installed a TCI weighted flex plate and vibration went away. I ended up leaving the correct 73 water pump and timing cover and installed a 70 and later power steering pump. I just put a 70 or newer radiator in the car as well. I found that to be a lot less hassle (easier to come by the parts) and the 70 and newer radiators tend to flow and cool a little better because inlet and outlet are on opposite sides. The timing marks being off would bother me, although you could install a timing tape, but im anal like that. JMO

 

[Trogdoor]

I ended up swapping just the water pump and left the timing cover alone so that timing marks are still correct with the damper. This did require swapping the alternator brackets also, but then everything else is left alone. I will be putting a 998 style transmission with lockup and lower 1st gear ratio behind the 340. I have a B&M weighted flex plate to go with the externally balanced 340. When I called B&M they said it was discontinued, and no replacement. But thanks to ABodies only forum I found a thread that informed me that the 727 weighted flex plate has holes in it for a 904 also. I had called TCI and they said they did not have one either. Mabe theirs has two sets of holes like B&M's.

 

[swinger340]

I ended up swapping just the water pump and left the timing cover alone so that timing marks are still correct with the damper. This did require swapping the alternator brackets also, but then everything else is left alone. I will be putting a 998 style transmission with lockup and lower 1st gear ratio behind the 340. I have a B&M weighted flex plate to go with the externally balanced 340. When I called B&M they said it was discontinued, and no replacement. But thanks to ABodies only forum I found a thread that informed me that the 727 weighted flex plate has holes in it for a 904 also. I had called TCI and they said they did not have one either. Mabe theirs has two sets of holes like B&M's.

I just bought 1 off E Bay made by Hays for $54 including shipping. For external balanced 340 w/ both sets of holes for 727 or 904. Put it in this past weekend. No vibrations. It had a small vibration before because of neutral balanced convertor and stock flex plate.