What Problems converting from 273 to 340/360

[SB69GTS]

Hey all

Thinking about changing the 273 in my 69 Dart GT to a 340/360 ( still trying to hunt down a 340 ) and was wondering if anyone here has done this. I know I will have to change the motor mounts and possibly the sway bar but was wondering if the rest of the K-frame will be OK. It has a 904 tranny with the floor shifter and was thinking of going to the torqueflite ...727? Will I have to change the drive shaft ... I also am looking for a 8 3/4 rear with the sure grip. Any info would be great ....thanks and have a great night.

 

[70aarcuda]

904 to 727 will require the driveshaft to be shorten...

hunting down a 340....save your money and go with the 360...

only problem with 360 is that it is externally balanced....need 360 balancer and b&m flexplate for 360/727.

and then again...73 340 can be externally balanced also...

 

[J-MacsMopars]

I may be wrong, but I am pretty sure that a 273 uses the same mount locations as a 340/360. I don't see any need to change the sway bar. You can usually find a decent 360 with a 727 for around $500. Then you would have everything. The only thing is, is you would have to modify the actual motor mount from a 318/340 mouth to work on the 360 as the ears are closer together.

 

[70aarcuda]

340/360 share the same driver side mount...273/318 share the same driver side mount...

273 to 340/360 needs either new driver side mount or shimming the mount.

 

[chryslerfat]

Passenger mount engine side is different also. 340/360 has 2 ears at front 1 rear and the 273/318 has 1 ear front and 2 ears rear.

 

[cudavert]

I would say go for the 360, unless you wanna hold out finding a 340. And as was mentioned, 360's are externally balanced so you'll need an externally weighted flex plate or torque converter for your 904. I believe keeping the 904 would be the better idea, as they can be modified to handle the extra power, no problem.

I put a 340 in my convertible '67 where a 273 once lived. I used longer bolts with a small stack of flat washers to serve as spacers on the motor mounts. No problems. Or you can buy special mounts from Schumacher's I believe.

 

[djwhog]

Get a schumacher mount kit, much easier to resolve the block offset on the motor mounts.

Their mounts are stronger anywy and you most like need new ones right?

You can stay with a beefed up 904 or stuff a 727, water pump is another issue, timing cover etc.

Then when you go late model timing cover and water pump for a 340-360, you are also going to need a radiator to not only keep the larger engine cool, but the hose inlet will be on the pass side instead of drivers side, if you have an early 273 with an iron water pump.

Next all this may change your mounting for the alternator and PS pump too.

You need larger ex manifolds either iron factor or headers to fit your application.

360 is less $$ to find, and yes you can externally balance one, flex plate, balancer is diff than a 273-318 and a 340 , those are al linternal balance engines pre 72 and back.

Also if you have 5/16 fuel line and a 5/16 sending unit in tank, you may want to step up to a 3/8 line size front to back if you are going to drive her hard.

Well that is most of it.

good luck keep us posted on your progress buddy!

PS yes for sure get an 8 3/4 posi depends on your goal, cam etc, but a nice 3.55 gear would be a good all around setup, also you can get the larger companion flange for larger ujoints and have that added to a drive shaft for larger stronger front and rear u-joints too.

It all boils done to what you goals are..

 

[Vic Storm]

The same work as putting a BB in the car......hummm.....Food for thought.

 

[SB69GTS]

Get a schumacher mount kit, much easier to resolve the block offset on the motor mounts.

Their mounts are stronger anywy and you most like need new ones right?

You can stay with a beefed up 904 or stuff a 727, water pump is another issue, timing cover etc.

Then when you go late model timing cover and water pump for a 340-360, you are also going to need a radiator to not only keep the larger engine cool, but the hose inlet will be on the pass side instead of drivers side, if you have an early 273 with an iron water pump.

Next all this may change your mounting for the alternator and PS pump too.

You need larger ex manifolds either iron factor or headers to fit your application.

360 is less $$ to find, and yes you can externally balance one, flex plate, balancer is diff than a 273-318 and a 340 , those are al linternal balance engines pre 72 and back.

Also if you have 5/16 fuel line and a 5/16 sending unit in tank, you may want to step up to a 3/8 line size front to back if you are going to drive her hard.

Well that is most of it.

good luck keep us posted on your progress buddy!

PS yes for sure get an 8 3/4 posi depends on your goal, cam etc, but a nice 3.55 gear would be a good all around setup, also you can get the larger companion flange for larger ujoints and have that added to a drive shaft for larger stronger front and rear u-joints too.

It all boils done to what you goals are..

I found a 340 from a 71 Duster, so I should change the mount to a Schumacher 340 mounts, can I just drop the k-frame and rods/mount off the 71 duster and install the assemble right in to the 69 dart ...i would think this should all be the same a-body fit. Then engine is complete with the water pump, timing cover, alternator etc. Do you think the rad would be ok from the duster to dart mounting allignment. Not sure about the power steering pump and issues that I might have. If I repace the rear to a 8 3/4 posi and the 727 ....would the drive shaft have to be shorten, is there any advantage of the 904 ...have not heart of many people using them with a 340 set-up. What would u do to the 904 to get the shift and power improved and am I correct assuming the drive shaft lenght would be ok with the posi. I guess the unniversal would be weak. I was going to change the gas tank because it has be sitting for a while in california, good idea on the 3/8 line and sending unit ....will do that. thanks alot for the help so far, will post pics as i start this project soon.