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340 vs 360?

J. Cower

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Okay so my 318 in my 71 SSP is worn out. I'd rather not throw money at it when I want a bigger motor anyway. So I have a 79 360 someone gave to me all apart and sitting in the barn or I can buy a 73 340 that says it was running when pulled but no carb or distributor. The 360 is also needs a carb and distributor and haven't gotten block checked yet even. So is it worth the $1200 for the 340 or just build the 360 I have and throw a Mancini weighted flywheel on to change from external balancing. I'm kinda of new to this and money is somewhat tight as I have small children.
 
I tore my 318 down to replace head gaskets as one was blown and it needs valve work, New umbrellas and a couple cylinders look like they're pretty worn. Rather not put the $600 or so into that...
 
The first thing that comes to my mind is why did someone pull the 340 then remove it's carburetor and distributor? Running when pulled, OK, but how well? Just something to ponder.

You already have the 360. If it's parts such as the block, crank and heads are good (as in salvageable) $1200 can go to towards rebuilding it.

If the 340 is nearby so you can check it out, sometimes you can tell a lot about an engine by looking it over. How has it been stored, can it be turned over with a flex handle and socket, etc.
 
I'd save the $1200 and rebuild the 360 instead of spending $1200 on the 340 and then rebuild the same 340.

The 360 makes a little more torque and very close to the same HP at a lower rpm because of the longer stroke. The 360 won't rev as high as the 340 or need to do so.

Cheaper, good power at a lower rpm with more torque. Except crank, oil pan, pistons & rings, it takes all the same parts as the 340.

Same power tricks apply.
 
Oh! Between stroking the two engines, stroke the 340. Bigger bore = more cubic inches. There is also more than just a 4.0 arm stroke crank. 4.15, 4.25 ...
 
You can make pretty good power with the 360, I'd guess nearly the same as a 340. On the 360 be sure to pocket port the heads. RPM potential should be close. Cast crank durability would likely be less than the 340 if you run the RPM up above 6000 often. I built a 360 for my van that made really good power, pulled my trailer/race car very well.
 
Why is it that so many folks are obsessed with making some high-power super engine for a car that's not destined for a life on the track? I would go with the 360 you have. If you have $1,200 to throw at a 340 you've got $1,200 to make that 360 into a much better engine than the 340. Rebuild it, shop around for a used Air Gap intake and a good carb for it, bolt on some headers, and you're ready for the streets.
 
The engines are very similar,even when stroked (408 vs 416) and if your not worried about being time period correct with your engine, I would personally recommend the 360(mainly because you already own it). Parts wise they are going to cost the same to rebuild and chances are, your are going to have to rebuild that 340. So why not spend the money on the 360 and be further ahead. Both will yield very similar results.
 
I tore my 318 down to replace head gaskets as one was blown and it needs valve work, New umbrellas and a couple cylinders look like they're pretty worn. Rather not put the $600 or so into that...

That is a lot of unknowns to make a decision on? The 340 sounds interesting but for $1200 it better be in really good condition, or you just paid alot for a builder.
You already have the 360, and it sounds like it is apart, so you should have a good idea of its condition.
You did not mention your plans for the engine, or budget.
I was thinking if the budget is really tight, you may want to use the 318 short block if it is in OK condition (good oil pressure, and cylinders not to badly worn) and then spend money on good heads, intake, carb, exhaust, ignition, and other parts that can later be used on the larger engine once the short block for it is built.
 
Thanks for all the input. Just worried about changing the external balance on the 360 as I've never tried that or had any dealings with it.
 
Not sure what your concern is with the balance. Keep it external, use the weighted flex plate. Wouldn't hurt to have the assembly spun once you get your parts combo together. Mopar balancing from the factory was less than precise. Whomever spins the crank would then do it with the balancer and flex plate bolted to the crank. Not a big deal at all.
 
Again, a 360 with pocket ported heads, moderate cam makes plenty of power for street use. You can't take 500" big block, but haven't spent the money.
 
340s are cool, but $1200 will go a long way in the world of mouse motors.

You could buy a set of aluminum heads and still have $$$ left
 
Similar to what others have said: If money is no object, the 340 is a better starting point. However, you said you have a budget, and the 360 will perform very close to the 340. Also, cast vs forged crank really won't matter if it is a street car - it's jut bragging rights on the street. So I'd suggest you build the 360.

Good luck whatever you decide.

Hawk
 
Again, a 360 with pocket ported heads, moderate cam makes plenty of power for street use. You can't take 500" big block, but haven't spent the money.
Having built a bunch of 360's, even without pocket ported heads, it can be a good performer. While I don't know what kind of time slip your looking for, an everyday driver w/ street performance type engine can do very well even with a stock intake and carb.

Thanks for all the input. Just worried about changing the external balance on the 360 as I've never tried that or had any dealings with it.
As mentioned, use a B&M flexplate designed to be used with a neutral balanced converter. The 360 stays externally balanced and will bolt to a neutral balance converter without issue. No vibrations.
Build the 360, you already own it and you're on a tight budget.
Best most sensible advice.
 
If you decide to do the 360, you can leave it external balanced and use the B&M flexplate. This allows using the normal balance torque converters.
When I did my 360 the machine shop balanced the engine with all the parts including the flexplate and damper.
The 360 oil pans don't exchange with the 318/340, so that may be an issue if starting with a 360 that was not from a passenger car?
I think the drivers side motor mount ears are also about spaced about 1/2" different? I could be wrong, been a long time since I swapped a 318 to 360.
I also thought the boss for the engine to transmission support brace was about 1/2" forward as I had a spacer between the brace and transmission?
I'm sure someone will post the specifics of doing the swap?
Depending on your performance goals, I'm not sure I would invest time and money in the stock heads. To me that is money that could be going towards new and better flowing heads, and that is really where to spend money to make power.
 
Don't worry about cast crank durability of a 360 if you keep the RPM's down to about 6000. Do make sure the converter you choose has the correct balance weight. BTW a good torque converter makes all the difference, both street performance and at the track. All Mopar heads need a bit of pocket porting.
 
I need spacers and the motor mounts are different? I thought I just needed the B and M weighted flex plate and everything else would match up?
 
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