Should I Stroke my 340?

[autoxcuda]

No replacement for displacement. 416 vs 408. Ha Ha.

Also the larger bore unshrouds the valves some for better flow.

[kawahonda]

I've ended up that stroking a 340 is a waste.

The 340 is awesome the way it is. Bag and tag it and find a roller 360.

Wow. Big block torque in a small block package is certainly not a waste. Anyone that's driven or built a stroked 340 can attest to the big time performance these things generate. In fact, I stroked my numbers matching 340 and would do it again...

I could be more specific. Stroking a 68-70 340 is a waste, especially if your build requires replacement of the heads! They are HiPO from the factory and should be left alone the way they are. JMO. They are not "plentiful" like the 360s are.

I'm looking forward to having a beautiful cleaned up and repainted 70 340 on the stand for porn while a 408 Roller 360 (that will look identical to a 340) is in the car!

If I had a low compression 340 like your 73, I guess it might make things different. But a 68-70 340 is a very well oiled machine and is far more powerful than a 73 340. Smaller valves, log manifolds, and low compression left it around 50 HP less....those 340s alone at stock displacement will be a big difference, especially with the heavier weight of the 72-74 challengers.

[7212Mopar]

Stock 340 heads are open chamber. Better to get aftermarket heads if stroking a small block to make power with zero deck piston. Lots of choices from cast irons to aluminum. Some body needs to build one with the Trick flow heads.

[bennydodge]

I've ended up that stroking a 340 is a waste.

The 340 is awesome the way it is. Bag and tag it and find a roller 360.

Wow. Big block torque in a small block package is certainly not a waste. Anyone that's driven or built a stroked 340 can attest to the big time performance these things generate. In fact, I stroked my numbers matching 340 and would do it again...

I could be more specific. Stroking a 68-70 340 is a waste, especially if your build requires replacement of the heads! They are HiPO from the factory and should be left alone the way they are. JMO. They are not "plentiful" like the 360s are.

I'm looking forward to having a beautiful cleaned up and repainted 70 340 on the stand for porn while a 408 Roller 360 (that will look identical to a 340) is in the car!

If I had a low compression 340 like your 73, I guess it might make things different. But a 68-70 340 is a very well oiled machine and is far more powerful than a 73 340. Smaller valves, log manifolds, and low compression left it around 50 HP less....those 340s alone at stock displacement will be a big difference, especially with the heavier weight of the 72-74 challengers.

Stroking ANY engine, no matter if it's the vaunted early 340 or a lowly 273, will create more torque and performance. This is simply not debatable. Remember, you're increasing the crank stroke from 3.31" to 4.0". In fact you could argue that 68-70 340's would pick up even more because of the larger intake valves and better flowing exhaust manifolds.

Who told you that 72-74 Challengers were heavier than 70-71's? I wouldn't be surprised if a 1970 Challenger A66 weighs the same or more than a similarly equipped 1973 Challenger 340. Chrysler severely de-contented the 72-74 E-Bodies, meaning less options and cheaper materials-a lot less "bling" to be sure.

Me personally, I'm using a known good engine, you can have your engine "porn" lol, engines don't belong on engine stands they belong in engine bays....

[Chryco Psycho]

I weighed my 70 R/T 440 4 spd & it was just under 3600lbs
I also weighed my 74 After removing the front & rear bumper supper beams & other excess weight & it still weighed in over 3800lbs with the 340 in it

[bennydodge]

To the OP's original question, I think one downside to stroking would be diminished long term durability-piston ring side loading on the cylinder walls, higher stress on the main bearings and poorer rod ratio. I don't know if anybody has actually tested this, maybe someone can chime in. Another option would be modern light weight connecting rods and pistons, lighter rotating weight means a revvier, snappier engine, plus you maintain the superlative and proven factory-engineered design.. 

[bennydodge]

I weighed my 70 R/T 440 4 spd & it was just under 3600lbs
I also weighed my 74 After removing the front & rear bumper supper beams & other excess weight & it still weighed in over 3800lbs with the 340 in it

According to Bandimere's scale mine is 3668 with me in it and a 1/2 tank of fuel. Granted I have aluminum heads and intake, but I also added 15" rallye wheels and have retained the ugly 1973 bumper setup.

[autoxcuda]

To the OP's original question, I think one downside to stroking would be diminished long term durability-piston ring side loading on the cylinder walls, higher stress on the main bearings and poorer rod ratio. I don't know if anybody has actually tested this, maybe someone can chime in. Another option would be modern light weight connecting rods and pistons, lighter rotating weight means a revvier, snappier engine, plus you maintain the superlative and proven factory-engineered design..

The stroker rod ratios are the same or better than many long used stock production engines. SB Mopars have bigger bearings than Chevy and Ford counterparts. Plus with modern: oils, bearings, tolerances don't need all that.

All scat stroker kits have much lighter pistons and rods than stock. They rev up quite well.

Also with a 6000 redline vs 7500 redline...much less abuse and wear at 6000 rpm.

[bennydodge]

To the OP's original question, I think one downside to stroking would be diminished long term durability-piston ring side loading on the cylinder walls, higher stress on the main bearings and poorer rod ratio. I don't know if anybody has actually tested this, maybe someone can chime in. Another option would be modern light weight connecting rods and pistons, lighter rotating weight means a revvier, snappier engine, plus you maintain the superlative and proven factory-engineered design..

The stroker rod ratios are the same or better than many long used stock production engines. SB Mopars have bigger bearings than Chevy and Ford counterparts. Plus with modern: oils, bearings, tolerances don't need all that.


All scat stroker kits have much lighter pistons and rods than stock. They rev up quite well.

Also with a 6000 redline vs 7500 redline...much less abuse and wear at 6000 rpm.

Doesn't a lower rod ratio create more side loading of the piston into the cylinder wall?
stock 340 rod ratio-1.85
stroker 416 rod ratio-1.53

This gets my attention but then again I may just be sweating the small stuff..

[gzig5]

Regarding the rod ratio, if these were daily drivers seeing  10-15k miles a year I might be a little concerned about wear.  But the reality is that most of these cars see far less miles.  One option would to to grind the mains on a 3.58" stroke 360 crank to fit the 340 and you'll have 372ci.  Not a bad compromise.  I know I'm more likely to hurt the motor missing a shift or something like that than I will be wearing the bores out. 

[7212Mopar]

My 416 HP peaks at 5500 based on the Dyno test so I set the rev limiter around 5800. I have yet go pass 4500. Acceleration at freeway speed is instantneous and a lot of fun. You hit 90+ before you know it. I have no regrets from my decision to stroke my 71 340 block. The block is the only original factory equipment reused. I imagine the aluminum heads and air gap intake saved close to 80 lbs from the front end but I did not weight the before and after.

So if HP and torque is what you are after, stroke a 340 or 360 and have fun.

[cudaragtop]

Stroked is nice but I'd rather be blown! 
Seriously though, I've had 340 cars since 1980 and stroked my non-numbers matching 340 5 years ago and love it.
10.5:1
Edlebrock Performer Heads
Full roller cam
LD340 intake
Stock 340 HiPo Exhaust Manifolds
Full TTi Stainless 2.5" including Tips with H Pipe
Dynomax Ultra Flow Mufflers
QF 650 DP
3.55:1 Sure Grip
A833 4speed
480 HP @5700, 511 Torque @ 4300
Not a track car just fun too drive. I don't live around 6000 RPM, Don't need too.
.040 overbore, 4" stroke = 418 C.I. Small Block
Never a single ping running 91-92 octane.
Runs cool as a cucumber in all driving conditions.
26" stock style rad and 7 blade clutch fan with shroud.

All that said it cost me more to stroke the 340 I had than a fully rebuilt 6.1 Hemi cost me for our A-Body Barracuda but apples and oranges...
Stroked can always be un-stroked... can't imagine why but it's just a rotating assembly.
Nothing wrong with a quick rapping, high revving 340. I've driven both. Enjoy the stroker more for the seat of the pants feel of the bottom and mid range pull. I could get more HP with Headers, a Single Plane Intake and bigger carb but why? It would all be at the top of the RPM range and I don't drive around at 6500 RPM...

What do you want it to do? How much do you want to spend?

Have Fun! 

[autoxcuda]

To the OP's original question, I think one downside to stroking would be diminished long term durability-piston ring side loading on the cylinder walls, higher stress on the main bearings and poorer rod ratio. I don't know if anybody has actually tested this, maybe someone can chime in. Another option would be modern light weight connecting rods and pistons, lighter rotating weight means a revvier, snappier engine, plus you maintain the superlative and proven factory-engineered design..

The stroker rod ratios are the same or better than many long used stock production engines. SB Mopars have bigger bearings than Chevy and Ford counterparts. Plus with modern: oils, bearings, tolerances don't need all that.


All scat stroker kits have much lighter pistons and rods than stock. They rev up quite well.

Also with a 6000 redline vs 7500 redline...much less abuse and wear at 6000 rpm.

Doesn't a lower rod ratio create more side loading of the piston into the cylinder wall?
stock 340 rod ratio-1.85
stroker 416 rod ratio-1.53

This gets my attention but then again I may just be sweating the small stuff..

1.53 is same as a 454 chevy

Old 455 = 1.58
Pontiac 455 = 1.57
Chevy 350 = 1.64
Lots of common motors 1.66 to 1.63

340 just has a high number. That alone does not make it walk on water. And the high numbers need longer heavier rods and taller deck height with heavier blocks.

[autoxcuda]

Stroked is nice but I'd rather be blown! 
Seriously though, I've had 340 cars since 1980 and stroked my non-numbers matching 340 5 years ago and love it.
10.5:1
Edlebrock Performer Heads
Full roller cam
LD340 intake
Stock 340 HiPo Exhaust Manifolds
Full TTi Stainless 2.5" including Tips with H Pipe
Dynomax Ultra Flow Mufflers
QF 650 DP
3.55:1 Sure Grip
A833 4speed
480 HP @5700, 511 Torque @ 4300
Not a track car just fun too drive. I don't live around 6000 RPM, Don't need too.
.040 overbore, 4" stroke = 418 C.I. Small Block
Never a single ping running 91-92 octane.
Runs cool as a cucumber in all driving conditions.
26" stock style rad and 7 blade clutch fan with shroud.

All that said it cost me more to stroke the 340 I had than a fully rebuilt 6.1 Hemi cost me for our A-Body Barracuda but apples and oranges...
Stroked can always be un-stroked... can't imagine why but it's just a rotating assembly.
Nothing wrong with a quick rapping, high revving 340. I've driven both. Enjoy the stroker more for the seat of the pants feel of the bottom and mid range pull. I could get more HP with Headers, a Single Plane Intake and bigger carb but why? It would all be at the top of the RPM range and I don't drive around at 6500 RPM...

What do you want it to do? How much do you want to spend?

Have Fun! 

What are the cam specs?

I'm at 9.7:1 measured compression same heads.

On California 91 octane 9.7:1 is max with my setup. At 800 ft altitude, 90+ degree weather. With quench, sharp edges smoothed in chamber, chamber bore matched to block bore.

I'm pretty sure my cam is smaller; XE274 solid Comp.

[bennydodge]

To the OP's original question, I think one downside to stroking would be diminished long term durability-piston ring side loading on the cylinder walls, higher stress on the main bearings and poorer rod ratio. I don't know if anybody has actually tested this, maybe someone can chime in. Another option would be modern light weight connecting rods and pistons, lighter rotating weight means a revvier, snappier engine, plus you maintain the superlative and proven factory-engineered design..

The stroker rod ratios are the same or better than many long used stock production engines. SB Mopars have bigger bearings than Chevy and Ford counterparts. Plus with modern: oils, bearings, tolerances don't need all that.


All scat stroker kits have much lighter pistons and rods than stock. They rev up quite well.

Also with a 6000 redline vs 7500 redline...much less abuse and wear at 6000 rpm.

Doesn't a lower rod ratio create more side loading of the piston into the cylinder wall?
stock 340 rod ratio-1.85
stroker 416 rod ratio-1.53

This gets my attention but then again I may just be sweating the small stuff..

1.53 is same as a 454 chevy

Old 455 = 1.58
Pontiac 455 = 1.57
Chevy 350 = 1.64
Lots of common motors 1.66 to 1.63

340 just has a high number. That alone does not make it walk on water. And the high numbers need longer heavier rods and taller deck height with heavier blocks.

Yes the long rods are heavier but this is offset by running a shorter and lighter piston and those tall decks are 1 reason(high camshaft tunnel as well) you can stuff a 4" crank in a small block Mopar. IIRC all of the old Mopar engines ran long rods.