Need advice: 318 or 340 for a 68 Dart?

[RustyRatRod]

I might be mistaken, but I thought the 360 shares the same bore size as the 340 (?) if that is the case, a 360 could be somewhat considered a stroked 340! Whatever the case, a 360 is not one of his options. We don't know a lot about his options, limitations, and variables, but my recommendation would be athe 318 with a 340 cam. My last engin had that combo, and it went pretty good.

The 340 is a 4.040 bore and the 360 a 4". .040" will never be seen in power output though because they essentially are the same bore.

 

[skrews]

The 340 is a 4.040 bore and the 360 a 4". .040" will never be seen in power output though because they essentially are the same bore.

This ^^^

 

[JBurch]

I will never understand why you would pick the 318 over a 340. Or a 360 over 340.

When will the Chrysler people learn bore size is where it's at. That's why a Predator on a BBM won't run like Big Chief's on BBC. You can't expect a 4.5 bore to run with a 4.65 bore?

Go with the biggest bore you can get.

Always.

I will never understand why people don't realize that 20 more cubic inches will make 20 more horsepower all other aspects being equal.

 

[barbee6043]

to me one big obstacle is finding a 340 that hasn't been overbored and woreout.

 

[BlueDream]

If it were me I'd go with a 318 for this build. Save the 340 for another build that's more performance oriented. For a daily driver a 318 would be a lot of fun and if you ever blew it up you could find a replacement for dirt cheap. Add in a 340 spec cam and good dual exhaust and I think it would suit your needs just fine.

 

[rumblefish360]

Nothing compares to smoking a 350 with a lowly 318

LMAO! You got that right!

I will never understand why you would pick the 318 over a 340. Or a 360 over 340.

When will the Chrysler people learn bore size is where it's at. That's why a Predator on a BBM won't run like Big Chief's on BBC. You can't expect a 4.5 bore to run with a 4.65 bore?

Go with the biggest bore you can get.

Always.

Well, considering his post and how I read it, understand it, the bigger bore really doesn't come into play here.
While you do have a good point in a race application it also doesn't allway pan out that way. Reason I use is often the cars owned is t interested in flat out speed. A long stroke introduces more torque which is very good for general driving, mileage concerns and if it is in a race setting, off the line launch or coming out of the corners on a circle track and/or spirted street driving around the streets which are not allways straight.

I myself like a longer stroke engine for general driving, general performance and even some racing. The engine often makes neat identical HP but at a earlier RPM. Spinning an engine less is easier on the engine and helps longer life.

Hence why I recommended a 360. But! To each there own and there own strong points will be used.

I will never understand why people don't realize that 20 more cubic inches will make 20 more horsepower all other aspects being equal.

Almost exactly true but it is more in how the engine is. Big bore short stroke OR big stroke small bore.
If you have a desk top dyno, create an engine combo nation and then rearrange the bore and stroke combo but keep the displacement as close to exact the same for each engine.
Now the DDD program is a fairly simple one and maynot be the most up to date dead on accurate, but it is certainly good enough for this.

I think BlueDream's answer is a good one and probably the route the OP should take and eventually will.

As a side note, I NEVER build a car with an engine for its possible resale value. That's just plain stupid IMO. Now purchasing a car to resell...... That's different all togther. But rarely profitable.

 

[Josecuda]

This will be my daily driver. -Considering gas mileage as well,

For daily driving and best gas mileage i'd go the 318 way. Both engines share the same stroke but the 3.91 vs. 4.04 in bore and valves / cam setup really marks a difference in MPG and Performance.

Have you considered an EFI setup for your build?:glasses7:

 

[ir3333]

i think you should use the 318...I'll take that worthless 340 off your hands for you.

 

[duster360]

Yes I have a choice of 318 or 340 at my disposal right now. No 360 in this group. I'm leaning towards the 318 in case I'm in a generous mood and eventually give the car to my daughter who has a leadfoot. Maybe less damage potential with less power. But I see the arguments for the 340 as well so I'm stuck. I'm not going to be doing anything more serious than freeway driving. Yes I want a nice throaty muffler. I don't intend to "beef up" the motor in any way it's going to be left stock whichever option I go with... Thanks for your opinions it's good to have other POV's!

This comment says it all. Do the 318.

 

[DartVadar]

Find a roller cam 318 and be done with it (Ive got a good roller block/crank/rods/heads etc just sitting in my garage lol, want to get rid of it, too bad you arent closer to me) I will probably never go back to a flat tappet cam again after my last one was starting to go flat after 3000 miles, rollers are just better.

I opted to go with a 360 with my build though. But like everything it snowballed...lol but my car isnt a daily driver either.

 

[madscientist]

I will never understand why people don't realize that 20 more cubic inches will make 20 more horsepower all other aspects being equal.

You would be the ONLY engine builder/tuner/dyno guy that thinks this. It is FACTUALLY wrong.

20 inches won't guarntee you squat. A 340 engine will always make more power than the 20 CID bigger chevy copy. If it doesn't get a new builder.


To the OP...build the 340. Just don't weld it into the car. You can always take it out.

 

[Deleted member 39531]

I'd stick with the slant if this were ever the case.

Old cars, hot motors, and people who don't understand them is a recipe for trouble.

The Dart's 6 cyl was removed by someone, it has no motor currently. And yes if this car was going straight to my daughter I would put a /6 back in. But I plan on enjoying it for a while first. And if you're wondering why I would ask a seemingly obvious question it's because I'm a girl so I have limited experience in that department. I can change the oil and do my own brakes but I'll leave everything else to the guys. So thanks for the help, my husband's not a car nut so he can't help.

 

[madscientist]

LMAO! You got that right!


Well, considering his post and how I read it, understand it, the bigger bore really doesn't come into play here.
While you do have a good point in a race application it also doesn't allway pan out that way. Reason I use is often the cars owned is t interested in flat out speed. A long stroke introduces more torque which is very good for general driving, mileage concerns and if it is in a race setting, off the line launch or coming out of the corners on a circle track and/or spirted street driving around the streets which are not allways straight.

I myself like a longer stroke engine for general driving, general performance and even some racing. The engine often makes neat identical HP but at a earlier RPM. Spinning an engine less is easier on the engine and helps longer life.

Hence why I recommended a 360. But! To each there own and there own strong points will be used.



Almost exactly true but it is more in how the engine is. Big bore short stroke OR big stroke small bore.
If you have a desk top dyno, create an engine combo nation and then rearrange the bore and stroke combo but keep the displacement as close to exact the same for each engine.
Now the DDD program is a fairly simple one and maynot be the most up to date dead on accurate, but it is certainly good enough for this.

I think BlueDream's answer is a good one and probably the route the OP should take and eventually will.

As a side note, I NEVER build a car with an engine for its possible resale value. That's just plain stupid IMO. Now purchasing a car to resell...... That's different all togther. But rarely profitable.

I could quote a half dozen well know people who would disagree with most of this post.


Go look up the RPM range for a 1971 340 and the RPM range for a 1971 360 and get back to us.















HINT: they are the same so you don't need to "twist" the short stroke big bore engine tighter.

 

[BlueDream]

if this car was going straight to my daughter I would put a /6 back in.

hmm..

lead foot + 340 = speeding tickets

lead foot + 318 = less speeding tickets

lead foot + 225 = no speeding tickets


My vote is still for 318 though. They're fun engines. I've got a couple of questions about the car though. What parts does it have? Rear end, brakes, etc. And what parts do you have for the 318? Complete running engine or is it just a buildable core?

 

[Deleted member 39531]

We haven't pulled it apart yet to see what's going on with the brakes it was stock drums all the way around when I had it. Still sporting my rally wheels from my 16th birthday so the stock wheel size hasn't changed. I'm assuming it still has the original rear end and all 6 cyl standard components but I can't be sure because someone put a floor shift in it even though it still has the original steering column shifter on it. Based on seeing that, everything could have changed. Maybe they blew whatever bigger motor they put in it and that's why the motor's missing. A lot of unanswered questions yet.

 

[rumblefish360]

Madsci, there is something wrong with you on the fundamental level.

You would be the ONLY engine builder/tuner/dyno guy that thinks this. It is FACTUALLY wrong.

20 inches won't guarntee you squat. A 340 engine will always make more power than the 20 CID bigger chevy copy. If it doesn't get a new builder.


To the OP...build the 340. Just don't weld it into the car. You can always take it out.

His post is actually more correct than not though in a general manor rather than exacting. The two pronged problem here is the different size engines are the just different in there configurations.
The second one is you personally. You keep making a reference to the 340 vs. some Cheny engine half the time.

If a bigger bore that equals 20 cubes doesn't get you more HP, then why recomend a 330 over a 318?

I could quote a half dozen well know people who would disagree with most of this post.

Go look up the RPM range for a 1971 340 and the RPM range for a 1971 360 and get back to us.

HINT: they are the same so you don't need to "twist" the short stroke big bore engine tighter.

Then there is something wrong with the people you know since dyno graph's are readily available to prove otherwise.
Trying to prove your right with engine power curves from stock engines? Seriously?

You have this habit of talking smack and spreading B.S. While turning threads into shyst shows. Your arguments turn into bashing anyone how disagree's with you with child-ish remarks.
It's no wonder your making peoples ignore lists.

Argue your point like an adult and move on.