Dodge 340 swap

[Tbob62]

Any pros/cons to a 340 v8 swap? I've found an 85 D250 4x4 beater parts truck (runs) with a swapped in 340 and 727 auto. Beginning to work on my 52 M37 and am new to the site as well. Any info is appreciated!

Mike

[W_A_Watson_II]

Ah, a 340, Nice. Should be no different than doing a 318 or 360 swap. Don't know why, I just like the 340's though. It's the same stroke as a 318, just bored larger.

[Tbob62]

Thanks, Will

I should get to hear it run tomorrow...the 727 is a reman so hopefully it's tight...Any chance the PS box is usable? Has to be reverse rotation, correct?

[MoparFreak69]

While a great motor, a 340 is really better suited for car duty. Because it retains the same short stroke as a 318, it is a motor that loves to wind real tight. For truck duty a 360 really is a better choice, IMO. Having said that, a 340 is the same basic block as a 360 with the exception of larger bores. You can fairly easily toss a 360 crank into it and build it to suit that stroke and have a nice motor. Only thing you have to pay special attention to if you do something like that is; 273's, 318's, and 340's are internally balanced. This means that all the counterweight necessary to balance the engine is already on the crankshaft. MOST (not all but the vast majority) of 360's are externally balanced. There just isnt enough physical room at the bottom of these suckers to swing that much weight around so engineers had to make due with what they had and use the flywheel/torque converter to finish the balance. You must keep a 273/318/340 flywheel/torque converter with a 273/318/340. You can mix and match between 273/318/360 all day long, just dont throw a flywheel or torque converter from a 360 on any of the other three, and dont throw a flywheel or torque converter from the other three onto a 360. Bad things happen.
You can however throw some magnum heads on that sucker and use newer magnum manifolds and such on it and make them perform a bit better. All it takes is factory parts except the special conversion push-rods, and a set of hydraulic lifters with an oil hole in the middle.
Just some ideas/info to chew on.

[W_A_Watson_II]

While more stroke makes more torque, and more cu in is always better. I've rarely wished for more low end power out of my 318 (OK 323 cu in) I put in my M37. I have needed more high end power from time to time to spin those huge wire/wheels I have though.

Use what you have or build what you want, it's your truck (but I pray no GovM please).

You are correct you will need a Reverse Saginaw Power Steering Box, and I believe the 85 was NOT one of those box's. Turn the steering wheel for a right turn, and if the pitman arm swings rearward, then it's a reverse box.

It will indeed be a tight build dropping in a torqueflite (auto) into the truck. Others have done it so it's doable though. I mounted my '68 V-8 about 3.5" further forward than than most as I was using a hydraulic clutch bell housing and needed more room with out relocating the transfercase. I did have to keep the '68 short snout water pump, and mount the radiator about 2" further forward.

Just take your time, do a lot of measuring and thinking ahead and it'll all fit nicely.

Merry Christmas,
Will

[Tbob62]

Local salvage yard contact called today with a 360 from a mid 70's truck. Depending on condition, might be worth talking trade, 340 for 360...decisions, decisions. He won't sell me the entire truck. I can only hand turn the 360 though for now..no starter. The 340 runs...both with automatics and neither steering box is usable.

[MoparFreak69]

If it were me and I had a 340 laying around (A real 340, not a bored and de-stroked 360) I would not trade it straight across for a 360, even in the same condition. 360's are a whole ton more common than the limited production 340's ever were, hence not nearly as valuable or sought after. 340's are a better overall block for someone looking to build a high performance road racing rig (what the motor was designed for in the first place) and are pretty sought after. If I had the choice between the 2 I would take the running 340 and put it in the truck. Drive it, but post it up for sale. Proof of running makes it worth more to the average buyer. When you get the right buyer to give you what its worth ($1500+/-), sell it to them, build a 360 and pocket the change. The 360 will fit exactly the same as the 340 so all you are talking about is a couple hours worth of work pulling one and putting the other in its place. You can even get stroker cranks for the 360 to push it up to 408 for all the cubes you could ever want and need. Google searching Dakota 408 will bring up quite a bit of forums discussing the topic, and how potent that combo can be in a truck.

Just a bit more information that I think would be valueable to you for your decision process. Use it however you like, I am not trying to force you one way or another. Just trying to educate you on what you have and what you are looking into.

[MoparFreak69]

Just a bit more reference info;
http://cgi.ebay.com/ebaymotors/RARE-...ssoriesQ5fGear

The only 340 on ebay right now.

[Tbob62]

Well, checked out the "340" today. Block stamp indicates it's a 318. The current owner says previous owner did some weekend racing and engine work maybe confused it with other engines, current owner never checked. Don't know if 318 to 340 is possible, so I guess I'm looking at a smooth running 318 and newly rebuilt 727(w/warranty). I'll part out the rest to recoup some costs.

[W_A_Watson_II]

From a bore/stroke the 340 is almost essentially a bored out 318.

318 & 340 both were a 3.31" stroke
318 was a 3.91 bore
340 was a 4.04 bore
360 was a 4.00 bore with a 3.58 stroke

http://www.allpar.com/mopar/318.html

[MoparFreak69]

W A, you are correct with your info, however a 318 block cannot be bored that large. That is almost .100 over which almost no engine is capable of handling and living through.
tbob62, a good running 318 with the right gearing will suit your rig fine, unless you are a speed demon and dont like revving the crap out of a motor. 318's LOVE revs, so gear a bit lower than you figure out and it will run just fine.

[Tbob62]

Brakes

Sorry for the long break...started tear down on the Dodge and am on brakes right now...Anyone know a civ equivalent for the wheel cylinders? I ran the NAPA number from Garbee's site and it came up master cylinder instead. I found NOS from online suppliers but trying to reduce shipping costs. Using the Chevy 1-ton master, so no problem there....Thanks!

Mike

[W_A_Watson_II]

The NAPA Part Number for the Brake Slave Cylinders are: UP9375 & UP 9376 and still show available at Napa Online.

[Tbob62]

Brakes

Thanks Will! I'll check it out...

[greg rider]

If it were me and I had a 340 laying around (A real 340, not a bored and de-stroked 360) I would not trade it straight across for a 360, even in the same condition. 360's are a whole ton more common than the limited production 340's ever were, hence not nearly as valuable or sought after. 340's are a better overall block for someone looking to build a high performance road racing rig (what the motor was designed for in the first place) and are pretty sought after. If I had the choice between the 2 I would take the running 340 and put it in the truck. Drive it, but post it up for sale. Proof of running makes it worth more to the average buyer. When you get the right buyer to give you what its worth ($1500+/-), sell it to them, build a 360 and pocket the change. The 360 will fit exactly the same as the 340 so all you are talking about is a couple hours worth of work pulling one and putting the other in its place. You can even get stroker cranks for the 360 to push it up to 408 for all the cubes you could ever want and need. Google searching Dakota 408 will bring up quite a bit of forums discussing the topic, and how potent that combo can be in a truck.

Just a bit more information that I think would be valueable to you for your decision process. Use it however you like, I am not trying to force you one way or another. Just trying to educate you on what you have and what you are looking into.

My thoughts to a tee. Buy the 340, prove it runs, and sell it to a motor head with an "A" body looking for one. A 318 is plenty with the proper gears--repeat--proper gears. If you already have the 318 then think about head and cam swaps. A 360 is a very good engine and the aftermarket has these in 408 cubes for a very reasonable price.