340 or 383 for 1968 Dart

[440 Mike]

And there's the rub- having to modify one to achieve the same weight as the other in stock form. Not a fair comparison.
Throw the same parts and money at both, and you will still be back to the original weight difference (or very close to it).
An aluminum-headed small block will still weigh less than a similarly equipped big block, providing even better weight distribution and inherently better handling.
BTW, I'm not dissing big blocks, I've had many. Just saying that if you use the same type parts on both engines, the SB will always be lighter.

There is no rub, a big block with aluminum parts will handle the same as a a factory small block car. It will also share the same weight transfer characteristics on the drag strip.

I can't comment on how a small block A-body car that is lighter than stock would handle (torsion bar change required?), but that wasn't the original point.

 

[abdywgn]

340. nose is lighter and easier to change plugs when engine has been running.

 

[71GSSDemon]

340. nose is lighter and easier to change plugs when engine has been running.

Big block with front engine plate and fenderwell headers makes plugs and all life super easy too

 

[rmchrgr]

Th OP did not specify much in his question beyond the basic 340 vs. 383 idea. If I had to guess, it seems like he was most likely asking about stock-configuration engines - no aluminum heads or what have you. He hasn't replied yet but maybe he has a '68 Dart that he is thinking about making into a GTS or some such thing. Or maybe he just wanted to start a debate, IDK.

Beyond the engine itself there's a few other things to consider;

• In regards to exhaust manifolds, either engine would require specific and relatively expensive parts.
• The 383 equipped car would have come with larger torsion bars to support the weight of the BB and maybe larger brakes as well but don't quote me on that.
• The cooling system would have been configured to accommodate the big block
• I'm not sure on this either but could buyers even get power steering and/or A/C in a '68 383 Dart? I'm sure it can be done but it may not be an easy thing to accomplish.

I'm sure there's way more differences to consider.

It's a little comical to think that the factory engineers thought they needed to step up some of the running gear in the BB cars to "heavy duty" status to accommodate a few more advertised horsepower so that was really more about the extra weight than anything. Besides, most everyone knows the 275hp rating of the 340 was laughably underrated so in reality the two engines were probably closer in output than claimed. The 383 was marketed as a premium engine in an A body so in fact Chrysler couldn't say the 340 made as much power as the big block or no one would have bought them.

The top performing 383 "Roadrunner" cam (335hp) was similar to the 340 cam - .450"/.458" 268º/284º vs. .430"/.444" lift 268º/276º. Both were hydraulic. Solid cams would have woke both engines up.

I had that 335hp Roadrunner cam in my 383 and again, it wasn't anything to write home about as it struggled to get past 4,500rpm.

 

[matthon]

Deja vu thread, starts a hurricane of replies, sometimes the op is never heard from again.

Ya get what ya get in these parts.

Blown apart 340s are $1k plus to start, 440s in the same condition are more, running or built big $.
A running 383 in a drivable car is the same $ with all the pulleys pumps and parts to boot.

The only correct answer:
Whatcha need - whatcha got in the garage <= your bank account

If whatcha want <= your bank account move along

 

[rmchrgr]

Yep. Still debating this stuff in 2025 even though both engines have been obsolete for almost 55 years. Mopar or No Car.

Even in stock form the Gen III Hemi is better than all of them anyway!

 

[junkyardhero]

Deja vu thread, starts a hurricane of replies, sometimes the op is never heard from again.

Ya get what ya get in these parts.

Blown apart 340s are $1k plus to start, 440s in the same condition are more, running or built big $.
A running 383 in a drivable car is the same $ with all the pulleys pumps and parts to boot.

The only correct answer:
Whatcha need - whatcha got in the garage <= your bank account

If whatcha want <= your bank account move along

this is the correct answer.

short of "the heart wants what the heart wants" or "lizard brain sez: vroom vroom big block" the answer is what is your budget and what do you have holding down the shop floor or could conceivably get at a reasonable price.

 

[273]

What would be your preference and why?

You're usually all about low end torque, more displacement = more torque especially low end, bigger bore more potential hp, a rebuilt 383 is only about 20 cid smaller than a 408 find a 400 and be about the same size. B engines are basically same stroke as 340 just a lot more bore even the 361 has a decent bore size.

 

[A56]

​

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1969 440 'cuda ~ Original Road Test​

• Thread starter69 Cuda 440
• Start dateDec 31, 2014

This 'nose-heavy' Barracuda weighs in at a comfortable #3279 lbs. {Shipping Weight, but is has a horrible 61/39 Front-to-Rear weight distribution.

 

[ir3333]

Just got home guys...lots of super responses! I screwed up and should have mentioned the gentleman actually has a 68 340 GTS, but the original 340 is gone. He has a 383 with the correct 383 K frame, motor mounts, exhaust manifolds and rebuilt big block rad! Also has a '70 340 with hi flow manifolds and correct rebuilt 340 rad.
A tough decision for sure. I think the 383 with the correct pieces may edge out the 340?

 

[matthon]

Either way, upgrade the suspension, shocks, torsion bars, sway bars, and that will make all the difference.

Throw on some aluminum parts, heads, intake, water pump housing, radiator, even better.

Selling the bb radiator and manifolds would help pay for hot rod goodies.

 

[33IMP]

Just got home guys...lots of super responses! I screwed up and should have mentioned the gentleman actually has a 68 340 GTS, but the original 340 is gone. He has a 383 with the correct 383 K frame, motor mounts, exhaust manifolds and rebuilt big block rad! Also has a '70 340 with hi flow manifolds and correct rebuilt 340 rad.
A tough decision for sure. I think the 383 with the correct pieces may edge out the 340?

Real 340 GTS? IMO, a no-brainer, the 340. He has one, it's a 340 car, it needs a 340. Once the numbers matching engine is gone, date codes don't mean much to me, whether it's a 68, or 70.
Ordinary Dart? Sure, throw whatever you want in it.
If it were a 383 car, again a no-brainer. Put a 383 back in it.
Again, MY opinion only. I know what I would do.

 

[fishmens67]

431 or 451 stroker, I wouldn't put a 340 in anything if I had the choice of a 383, then again, a 360 would be far superior to a 340 too.

 

[skep419]

Exhaust manifolds with a dominator

 

[Ottmundr]

 

[Professor Fate]

Just got home guys...lots of super responses! I screwed up and should have mentioned the gentleman actually has a 68 340 GTS, but the original 340 is gone. He has a 383 with the correct 383 K frame, motor mounts, exhaust manifolds and rebuilt big block rad! Also has a '70 340 with hi flow manifolds and correct rebuilt 340 rad.
A tough decision for sure. I think the 383 with the correct pieces may edge out the 340?

You really can't go wrong either way.
I know what I'd do, but this gentleman needs to do some soul-searching and go with his heart. It is his car...
Try this on for size:
If it's a four speed, go with the 340. Nothin' like buzzin' a healthy 340 up through the gears.
If it's an automatic, go 383.
JMO, of course.

 

[ir3333]

It's a 4 speed.

 

[rumblefish360]

If it’s a dead stock engine with no future upgrades, small block.

If the future has upgrades, the big block. Pound for pound in swapping iron for aluminum, the big block weighs in less after everything is changed to aluminum save the block and what’s inside of it.

383’s and 400’s are dirt cheap over a 340. If I didn’t have a 340, a 360 would be used as quick as snapping your fingers.
The drawback of the 383/400 is limited piston selection and custom piston costs. Both are pricey.

What I like about the big block once it’s lightened for weight competitiveness is simple more cubes and better cylinder heads. Standard headers start @ 1-3/4. MoPars single plane M1 requires no mods with the use of a Holley. RPM for the street until l”mid to low 11’s.

 

[BSB67]

I'm biased having owned a 68 383 4 spd GTS for over 40 years. The 383 will rpm with the 340 if that is what you like, so that is a non-issue.

The biggest drawback to the 383 A-Body is the driver side exhaust manifold. If you are looking for performance with original exhaust manifolds, I would probably lean toward the small block. Folks have used the 68-70 hp big block manifolds on an A body with a little massaging, as well as modified C body hp manifolds. And then there are headers, of course

 

[BSB67]

The drawback of the 383/400 is limited piston selection and custom piston costs. Both are pricey.

Icon 687. But you are stuck with the 1.094" wrist pin.

 

[rmchrgr]

A tough decision for sure. I think the 383 with the correct pieces may edge out the 340?

If we're talking stock engines, the 383 that was in a '68 GTS was rated at 300hp = 1.2hp/c.i. That low rating was due to the restrictive driver's side exhaust manifold. The 275hp rating for the 340 is also 1.2hp/c.i. Since it's generally accepted that the 340 was underrated that number is going to be a little better.

As one would expect, road tests from back in the day of both engines in a GTS produced nearly identical 1/4 mile ETs - 14.3 for the 383 and 14.4 for the 340. If the 340 had steeper rear gears it would have been at least 1/10th or 2 quicker. They all said the 340 equipped model was a better handling car.

From a logical standpoint, 340 all the way. If you gotta have a big block well, that really has nothing to do with which engine is actually better for the application.

 

[mopowers]

Is this a trick question? 383>340

Dare to be different.

 

[Professor Fate]

A 300hp 383 would be a little over 0.78hp/c.i.
A 275hp 340 would be almost 0.81hp/c.i. and was admittedly underrated, like you said.

 

[dart4forte]

Unless it’s an original H or P car, I’d stick a 360 in, drive it and have fun

 

[dart4forte]

If we're talking stock engines, the 383 that was in a '68 GTS was rated at 300hp = 1.2hp/c.i. That low rating was due to the restrictive driver's side exhaust manifold. The 275hp rating for the 340 is also 1.2hp/c.i. Since it's generally accepted that the 340 was underrated that number is going to be a little better.

As one would expect, road tests from back in the day of both engines in a GTS produced nearly identical 1/4 mile ETs - 14.3 for the 383 and 14.4 for the 340. If the 340 had steeper rear gears it would have been at least 1/10th or 2 quicker. They all said the 340 equipped model was a better handling car.

From a logical standpoint, 340 all the way. If you gotta have a big block well, that really has nothing to do with which engine is actually better for the application.

The 300 rating was not due to the exhaust manifolds, it was due to the camshaft profile. Camshaft in the 383 GTS was not the same as the 383 in the Roadrunner