Building a 318 vs 340

[Matt13]

My Barracuda has a 1971 318 in it now; headers and swirl port heads. My question is, should I put money into this motor or get a 340 and build that. The 340 I can get is a 1973 long block. In the end, I'd like a nice cruiser with around 300+ hp

[7212Mopar]

I vote for 340. Is that the original bore 340 block from your other post?  They are hard to find now.

[Scooter]

If the 340 is cost effective (or otherwise in your budget) go for it.

If not a 360 is a pretty available option as well and the extra cubes never hurt. 

[EB3-GranCoupe]

With the right pistons (KB167), cam, head porting & valve springs, you can achieve 300hp.  You might just want to consider the fun factor of claiming its "just a 318" & then surprise them with its performance.  of course, 20 more cubes never hurts!!

[YellowThumper]

X2 for the plentiful supply of 360s gets my nod as well.
360 standard bore is 4.00 vs 4.040 for the 340.
360s long stroke provides better low end grunt.
340s are for revving.
Large valve 340s can provide more at top end. At some expense of low end as well.
As previously commented, if 340 is reasonable in cost. Go with it. They however tend to be pricey. 360s not an issue due to their abundance.
Conversely the 318s can be made to perform quite well with a decent set of heads. There was a recent budget build I read that I believe they were in the 400hp range and still had good street manners.
Single point I will make against the 340 is most have been abused hard for a long time now. As their std bore is already 4.04. There have been many issues with thin walls in their castings when bored even further. If available motor is already 030-040 over and bore is not clean. I say to walk away.
360 will require a different pan due to journals (not sure of 340).
Harmonic balancers are different as are the flexplate or flywheels. Externally balance vs 318 internally balanced.
Drivers side motor ears for the motor mounts are different on 340s and 360s compared to the 318s. Your 318 mount (drivers side) will work but will need to have spacer on 1 (only) of the legs. Initially did mine 30 years ago and used a stack up of washers.
Passenger side mounts are all the same regardless of motor.
318 exhaust manifolds bolt on but will be worthless due to port sizes.
340 and 360 all bolt on and their ports are both about the same.
Hope this helps...

[YellowThumper]

Found the link to the 318 build I saw.
Even though we Mopar people think of the 318 as the lowly bastard stepchild. They are still 16ci over the touted 302 Fords.


https://www.hotrod.com/articles/mopp-0409-318-engine-build/

[Chryco Psycho]

I thought we went over this in another thread
Bang for the $$ build a 360 , best would be 87-92 , stroke it to 408
Best value & result for the $$ spent & 360s are almost free !!

[nsmall]

Do the math and which ever one gets you there I vote go for that path.  I wish you were closer to LA as a guy has had a rebuilt 340 and 727 for a decent deal for over a month now and would probably let it go for cheap.  The 360 makes the most sense mathematically. 

[Matt13]

Do the math and which ever one gets you there I vote go for that path.  I wish you were closer to LA as a guy has had a rebuilt 340 and 727 for a decent deal for over a month now and would probably let it go for cheap.  The 360 makes the most sense mathematically.

I think I saw his CL ad. $3,500, right? I just found a complete 340 in a 1969 Dart. Guy wants $1,500 for it and will pull it out. It's been sitting 15+ years, but I would rebuild it anyway.

[Matt13]

I thought we went over this in another thread
Bang for the $$ build a 360 , best would be 87-92 , stroke it to 408
Best value & result for the $$ spent & 360s are almost free !!

We did. I'm a slow learner though.  I now have 2 - 340's available to me; either one $1,500. Might be some wiggle room though on either of them.

[Shane Kelley]

I thought we went over this in another thread
Bang for the $$ build a 360 , best would be 87-92 , stroke it to 408
Best value & result for the $$ spent & 360s are almost free !!

We did. I'm a slow learner though.  I now have 2 - 340's available to me; either one $1,500. Might be some wiggle room though on either of them.

If that 340 in the 69 Dart is a 69 340 I would go that one. It will have big valves, good compression and all the goodies.

Somebody mentioned that 340's have thin cylinder walls and could have issues being bored. While I don't want to get into any debates I can say from personal experiences that I have had several 340's bored .060 over with zero issues. I actually have a fresh machined that I will be doing a stroker build. 

Another point no one has made is stand point of having a 340 in your car. Some say that doesn't matter but for me it does. What's under hood? 318? 360? or 340! That's just my personal opinion. There would be some value added as well. IMO

[Katfish]

I agree with above, the 340 is the way to go

[HP2]

318 with high swirl heads....I'd put a turbo on it with a blow through 4bbl carb. 

[RUNCHARGER]

Instead of $1500 for an old 340 I would buy a roller 360 core for $200-$300, bolt some trick flow heads on it and call it good. that's probably more performance than you're looking for though. You could substitute the iron Magnum head copies for less cash and still get around 350HP easily.

[drew43a]

The only thing my 340 wont pass is a gas station.