Choosing the right stroke for a 340

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@340inabbody you mentioned nothing else about the rest of the build besides stroke so let’s start there.

My ‘68 340 GTS sports stock manifolds and exhaust, a 284/484 cam, edelbrock replacement 625 carb. It needed to be rebuilt. I went the 3.58” stroke route given the limitations of the intake and exhaust systems.

My oldest son built a 4” stroke motor, ported aluminum heads, single plane port EFI system, race headers and 3”
Exhaust.

Both work great for their intended application, what’s your application?

Cliff Ramsdell
 
:popcorn: Following
Good photos soon enjoying
Holidays in NC !!

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There are many ways to skin a cat. A over square motor or overboard motor almost always will be a more efficient per cubic inch/more horsepower for the cubic inch the reason one reason being angles of rod and crankshaft begin to sideload cylinders as the stroke goes up if the rod length remains the same. Also piston speeds increase dramatically as stroke increases requiring premium parts to achieve the same RPM. Stroked motors develop more torque which is desirable and relatively easy to achieve. Horsepower is more a product of the head and induction system for the most part. Going to a 4 inch crank is the easiest way to make more overall power from a 340 but definitely not the only way.
 
RPM potential has more to do with airflow capabilities of the combination and less to do with the stroke.

Head flow/intake style/cam specs will dictate rpm range of a combination, more so than stroke.

The longer arm will wear things out at high rpm faster, but that's a different topic.
 
Stock stroke 340’s and 360’s are just as fast as 4” strokers…….. just saying

And high rpm is not needed either with 3.31/3.58 stroke engines. 6200-6500 is more then enough
 
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People are hilarious in what they take away from a particular post or question.

Not one person has directly said a stroker wont rev like a stock stroke will. Not one.
Only thing said..was a member liked the 340 because as he said its "born to rev". That's not saying a stroker won't.... imo even entertaining the idea takes away from the question of the op.

Like I pointed to in post #3..
If you have good cylinder heads...either works good...and the trans/gear will decide...as in do you want to cruise at high rpms..say 4000 rpm down the freeway? Or do you wanna cruise at 2800-3200 rpm on the freeway. They both can. Thing is the stroker will build all that torque you want that the 340 will take many rpms to make and still fall short without a very stout combo.
Stroker is like adding 4.56 to a 340 car..minus the astronomical cruise rpms

Nutshell -stroke it if you run an auto and 3.23/3.55 gears, you'll be happier driving around town and stop lights...stay 340 if you have a stick car and 3.91+ gears.
If ultimate power is the goal-stroke it regardless of drivetrain and cater to the motor.
Like said...many ways to skin it.
 
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People are hilarious in what they take away from a particular post or question.

Not one person has directly said a stroker wont rev like a stock stroke will. Not one.
Only thing said..was a member liked the 340 because as he said its "born to rev". That's not saying a stroker won't.... imo even entertaining the idea takes away from the question of the op.

Like I pointed to in post #3..
If you have good cylinder heads...either works good...and the trans/gear will decide...as in do you want to cruise at high rpms..say 4000 rpm down the freeway? Or do you wanna cruise at 2800-3200 rpm on the freeway. They both can. Thing is the stroker will build all that torque you want that the 340 will take many rpms to make and still fall short without a very stout combo.
Stroker is like adding 4.56 to a 340 car..minus the astronomical cruise rpms

Nutshell -stroke it if you run an auto and 3.23/3.55 gears, you'll be happier driving around town and stop lights...stay 340 if you have a stick car and 3.91+ gears.
If ultimate power is the goal-stroke it regardless of drivetrain and cater to the motor.
Like said...many ways to skin it.
Thanks so my set up is a 1970 Sport Satellite 904 auto with 3:55 rear end. Heads tbd but want to go with aluminum like eddy or trickf. Mostly local driving no strip racing. Want it reliable but would like that flat torque curve a stroked engine provides. Have a high rise square mopar intake with a 4150 650 Holley. Would like to do a roller hydraulic cam.
 
Scat 4 inch stroke with Scat I beam rods....
bob weight 1746........I think it is going to Rev...
Actually in 71 Duster

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4 inch stroke, hands down. A B body with a stroker small block makes a very happy cruiser. As far as a four inch stroke and revving, the ones I’ve seen with good heads and large cams were still pulling hard at 6500 rpm and beyond.
 
Thanks so my set up is a 1970 Sport Satellite 904 auto with 3:55 rear end. Heads tbd but want to go with aluminum like eddy or trickf. Mostly local driving no strip racing. Want it reliable but would like that flat torque curve a stroked engine provides. Have a high rise square mopar intake with a 4150 650 Holley. Would like to do a roller hydraulic cam.


Thanks for finally posting this up as you saved me time recommending something. My suggestion would have been more strip, strip street. Good luck with your build and have FUN.
 
I run a 340 with a 4 inch stroke and .04 over (418) no clearencing needed.
Ported indy 360-1 heads
Passon hemi OD
4.30 gears.
325/50/15 tires

I have only street driven it.
It takes off like a bat out of hell. When it was just a 340 it took off fast but the torque of the stroker is alot more fun and makes alot of chevies hide.

Now i see the 4.180 stroker kits popping up in places and scratch my head. (435 cu) apparently no clearancing needed
So i decided big block instead ;-)
 
Thanks so my set up is a 1970 Sport Satellite 904 auto with 3:55 rear end. Heads tbd but want to go with aluminum like eddy or trickf. Mostly local driving no strip racing. Want it reliable but would like that flat torque curve a stroked engine provides. Have a high rise square mopar intake with a 4150 650 Holley. Would like to do a roller hydraulic cam.
Stroke it, small street solid roller cam, trickflow heads/intake, tti step headers.

Itll be all you want and then some without being radical sounding...maybe a little..
 
I know most love their stroker small blocks, but there is something to be said for a nice stock stroke small block build, especially when combined with an overdrive trans so you can have your gear but still cruise as well.
 
Mostly local driving no strip racing. Want it reliable but would like that flat torque curve a stroked engine provides.
My alloy headed 11/1 367 has more torque than 325/50-15s can handle on the street. I have run it with a 292/292/108, a 270/276/110, and she currently has a 276/286/110; the 270 was my favorite. She went 93 in the Eighth with the 276 cam@ 3457 pounds. Her normal weight is 3650 me in it.
Forget a long flat torque curve; one of two things will happen; 1) if a stroker, it will have freight-train torque impossible to harness.
2) if a 360 it will still have a preponderance of low-rpm power meaning lots of tire spin, but the top end is no weak.
We are not in the 80s anymore, there is no good reason to compromise your combo with low-compression. Alloy heads will support cranking pressures up to 200psi still on pump gas. I have run 185/190 on 87E10

Lemmee show you something;
Say your engine has a dead flat torque curve of 400ftlbs from 2000 to 6000. the formula to convert torque to horsepower is
torque times rpm, divided by 5250
watch this;
400 x 2000/5250= 152hp
400 x 2800/5250 = 213hp
400 x 3600/5250 = 274hp
400 x 4400/5250 = 335hp
400 x 5200/5250 = 396hp
400 x 6000/5250 = 457hp
Is that what you want?
I don't think so.......
Because ;
1) yur not gonna run a 2000 stall, so kiss 152hp goodby
2) yur not gonna run a cam on the street, that would get you 457hp at 6000, so kiss that goodby.
3) the 396hp at 5200 is already pushing the power peak pretty high for a streeter.
4) the faster you drive, the more power you need.
5) the slower you drive, the less power you need
6) if your combo can smoke the tires with 3.55s all thru first gear, then you obviously have more power at slow speed than you need.
Therefore do I say, for your combo, forget a long flat power curve.
Instead, tailor the power to what the chassis can handle, and still provide the kick you want, and let the torque be what it will be.
Here is what you might like; simple easy cheap and effective. the dip at 3200 is obviously an anomaly, probably a fueling issue, Ignore it and extrapolate from say 3800 to 3000 in a straightline.
Look at the powerpeak up near 5700. This is more peak than you need. 5700rpm with 3.55s and 27s is 46mph in first/77 in second .............. so not the best fit. It really wants more gear or less cam for your combo.
More gear will destroy your cruise-rpm.
Less cam will increase your cylinder pressure and increase your low-rpm power, at the expense of high-rpm power. But honestly, 437hp at 46mph is still spinning the tires, and as a streeter, ask yourself how often will you be at WOT at 77 mph. So, IMO, you can easily ditch that 5700rpm cam.
> now, draw a line, right across the graph at 400ftlbs. With a 360engine it will not be possible to pull the torque up to your 400ftlb line, in the rpm range that you will normally be driving, unless maybe you stroke it; even then 400@3000 is a heck of a thing for the chassis to try and deal with, and there is NO good reason to go there, as you can make the numbers down there, with gearing. That's why you have a transmission, and a Convertor..
So again; forget a long flat torque curve.
> now go back to the power peak at 5700. Do you see how slowly the power is dropping off? there is at least 300 maybe 400 more rpm left in her. Lets say a first gear outshift at 6200. With 3.55s and 27s, that is now 50 mph. In the zero to 60 contest, that only leaves you 10mph to pull in second, beginning at 3660 rpm, down around 250/260 hp, on this graph.
This is messed up.
For a streeter; You have waaaaay to much power in First gear, and are seriously choked in Second gear.
IMO, again, you would be better off with a much smaller cam, and hit Second gear much sooner.
Now I know you said "no strip racing" but
who builds a 437 hp engine and never stretches it out. What would be the point of that?

What you really need/want is another lower gear in the trans, or an overdrive, and any old SBM, at that point; Ask me how I know.



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AJ buddy our posts kinda get to the same point, but one of us takes the scenic route to get there. :)
 
My alloy headed 11/1 367 has more torque than 325/50-15s can handle on the street. I have run it with a 292/292/108, a 270/276/110, and she currently has a 276/286/110; the 270 was my favorite. She went 93 in the Eighth with the 276 cam@ 3457 pounds. Her normal weight is 3650 me in it.
Forget a long flat torque curve; one of two things will happen; 1) if a stroker, it will have freight-train torque impossible to harness.
2) if a 360 it will still have a preponderance of low-rpm power meaning lots of tire spin, but the top end is no weak.
We are not in the 80s anymore, there is no good reason to compromise your combo with low-compression. Alloy heads will support cranking pressures up to 200psi still on pump gas. I have run 185/190 on 87E10

Lemmee show you something;
Say your engine has a dead flat torque curve of 400ftlbs from 2000 to 6000. the formula to convert torque to horsepower is
torque times rpm, divided by 5250
watch this;
400 x 2000/5250= 152hp
400 x 2800/5250 = 213hp
400 x 3600/5250 = 274hp
400 x 4400/5250 = 335hp
400 x 5200/5250 = 396hp
400 x 6000/5250 = 457hp
Is that what you want?
I don't think so.......
Because ;
1) yur not gonna run a 2000 stall, so kiss 152hp goodby
2) yur not gonna run a cam on the street, that would get you 457hp at 6000, so kiss that goodby.
3) the 396hp at 5200 is already pushing the power peak pretty high for a streeter.
4) the faster you drive, the more power you need.
5) the slower you drive, the less power you need
6) if your combo can smoke the tires with 3.55s all thru first gear, then you obviously have more power at slow speed than you need.
Therefore do I say, for your combo, forget a long flat power curve.
Instead, tailor the power to what the chassis can handle, and still provide the kick you want, and let the torque be what it will be.
Here is what you might like; simple easy cheap and effective. the dip at 3200 is obviously an anomaly, probably a fueling issue, Ignore it and extrapolate from say 3800 to 3000 in a straightline.
Look at the powerpeak up near 5700. This is more peak than you need. 5700rpm with 3.55s and 27s is 46mph in first/77 in second .............. so not the best fit. It really wants more gear or less cam for your combo.
More gear will destroy your cruise-rpm.
Less cam will increase your cylinder pressure and increase your low-rpm power, at the expense of high-rpm power. But honestly, 437hp at 46mph is still spinning the tires, and as a streeter, ask yourself how often will you be at WOT at 77 mph. So, IMO, you can easily ditch that 5700rpm cam.
> now, draw a line, right across the graph at 400ftlbs. With a 360engine it will not be possible to pull the torque up to your 400ftlb line, in the rpm range that you will normally be driving, unless maybe you stroke it; even then 400@3000 is a heck of a thing for the chassis to try and deal with, and there is NO good reason to go there, as you can make the numbers down there, with gearing. That's why you have a transmission, and a Convertor..
So again; forget a long flat torque curve.
> now go back to the power peak at 5700. Do you see how slowly the power is dropping off? there is at least 300 maybe 400 more rpm left in her. Lets say a first gear outshift at 6200. With 3.55s and 27s, that is now 50 mph. In the zero to 60 contest, that only leaves you 10mph to pull in second, beginning at 3660 rpm, down around 250/260 hp, on this graph.
This is messed up.
For a streeter; You have waaaaay to much power in First gear, and are seriously choked in Second gear.
IMO, again, you would be better off with a much smaller cam, and hit Second gear much sooner.
Now I know you said "no strip racing" but
who builds a 437 hp engine and never stretches it out. What would be the point of that?

What you really need/want is another lower gear in the trans, or an overdrive, and any old SBM, at that point; Ask me how I know.



View attachment 1715845108
My alloy headed 11/1 367 has more torque than 325/50-15s can handle on the street. I have run it with a 292/292/108, a 270/276/110, and she currently has a 276/286/110; the 270 was my favorite. She went 93 in the Eighth with the 276 cam@ 3457 pounds. Her normal weight is 3650 me in it.
Forget a long flat torque curve; one of two things will happen; 1) if a stroker, it will have freight-train torque impossible to harness.
2) if a 360 it will still have a preponderance of low-rpm power meaning lots of tire spin, but the top end is no weak.
We are not in the 80s anymore, there is no good reason to compromise your combo with low-compression. Alloy heads will support cranking pressures up to 200psi still on pump gas. I have run 185/190 on 87E10

Lemmee show you something;
Say your engine has a dead flat torque curve of 400ftlbs from 2000 to 6000. the formula to convert torque to horsepower is
torque times rpm, divided by 5250
watch this;
400 x 2000/5250= 152hp
400 x 2800/5250 = 213hp
400 x 3600/5250 = 274hp
400 x 4400/5250 = 335hp
400 x 5200/5250 = 396hp
400 x 6000/5250 = 457hp
Is that what you want?
I don't think so.......
Because ;
1) yur not gonna run a 2000 stall, so kiss 152hp goodby
2) yur not gonna run a cam on the street, that would get you 457hp at 6000, so kiss that goodby.
3) the 396hp at 5200 is already pushing the power peak pretty high for a streeter.
4) the faster you drive, the more power you need.
5) the slower you drive, the less power you need
6) if your combo can smoke the tires with 3.55s all thru first gear, then you obviously have more power at slow speed than you need.
Therefore do I say, for your combo, forget a long flat power curve.
Instead, tailor the power to what the chassis can handle, and still provide the kick you want, and let the torque be what it will be.
Here is what you might like; simple easy cheap and effective. the dip at 3200 is obviously an anomaly, probably a fueling issue, Ignore it and extrapolate from say 3800 to 3000 in a straightline.
Look at the powerpeak up near 5700. This is more peak than you need. 5700rpm with 3.55s and 27s is 46mph in first/77 in second .............. so not the best fit. It really wants more gear or less cam for your combo.
More gear will destroy your cruise-rpm.
Less cam will increase your cylinder pressure and increase your low-rpm power, at the expense of high-rpm power. But honestly, 437hp at 46mph is still spinning the tires, and as a streeter, ask yourself how often will you be at WOT at 77 mph. So, IMO, you can easily ditch that 5700rpm cam.
> now, draw a line, right across the graph at 400ftlbs. With a 360engine it will not be possible to pull the torque up to your 400ftlb line, in the rpm range that you will normally be driving, unless maybe you stroke it; even then 400@3000 is a heck of a thing for the chassis to try and deal with, and there is NO good reason to go there, as you can make the numbers down there, with gearing. That's why you have a transmission, and a Convertor..
So again; forget a long flat torque curve.
> now go back to the power peak at 5700. Do you see how slowly the power is dropping off? there is at least 300 maybe 400 more rpm left in her. Lets say a first gear outshift at 6200. With 3.55s and 27s, that is now 50 mph. In the zero to 60 contest, that only leaves you 10mph to pull in second, beginning at 3660 rpm, down around 250/260 hp, on this graph.
This is messed up.
For a streeter; You have waaaaay to much power in First gear, and are seriously choked in Second gear.
IMO, again, you would be better off with a much smaller cam, and hit Second gear much sooner.
Now I know you said "no strip racing" but
who builds a 437 hp engine and never stretches it out. What would be the point of that?

What you really need/want is another lower gear in the trans, or an overdrive, and any old SBM, at that point; Ask me how I know.



View attachment 1715845108
Re-reading to try and fully comprehend what you are saying and recommending.
 
My alloy headed 11/1 367 has more torque than 325/50-15s can handle on the street. I have run it with a 292/292/108, a 270/276/110, and she currently has a 276/286/110; the 270 was my favorite. She went 93 in the Eighth with the 276 cam@ 3457 pounds. Her normal weight is 3650 me in it.
Forget a long flat torque curve; one of two things will happen; 1) if a stroker, it will have freight-train torque impossible to harness.
2) if a 360 it will still have a preponderance of low-rpm power meaning lots of tire spin, but the top end is no weak.
We are not in the 80s anymore, there is no good reason to compromise your combo with low-compression. Alloy heads will support cranking pressures up to 200psi still on pump gas. I have run 185/190 on 87E10

Lemmee show you something;
Say your engine has a dead flat torque curve of 400ftlbs from 2000 to 6000. the formula to convert torque to horsepower is
torque times rpm, divided by 5250
watch this;
400 x 2000/5250= 152hp
400 x 2800/5250 = 213hp
400 x 3600/5250 = 274hp
400 x 4400/5250 = 335hp
400 x 5200/5250 = 396hp
400 x 6000/5250 = 457hp
Is that what you want?
I don't think so.......
Because ;
1) yur not gonna run a 2000 stall, so kiss 152hp goodby
2) yur not gonna run a cam on the street, that would get you 457hp at 6000, so kiss that goodby.
3) the 396hp at 5200 is already pushing the power peak pretty high for a streeter.
4) the faster you drive, the more power you need.
5) the slower you drive, the less power you need
6) if your combo can smoke the tires with 3.55s all thru first gear, then you obviously have more power at slow speed than you need.
Therefore do I say, for your combo, forget a long flat power curve.
Instead, tailor the power to what the chassis can handle, and still provide the kick you want, and let the torque be what it will be.
Here is what you might like; simple easy cheap and effective. the dip at 3200 is obviously an anomaly, probably a fueling issue, Ignore it and extrapolate from say 3800 to 3000 in a straightline.
Look at the powerpeak up near 5700. This is more peak than you need. 5700rpm with 3.55s and 27s is 46mph in first/77 in second .............. so not the best fit. It really wants more gear or less cam for your combo.
More gear will destroy your cruise-rpm.
Less cam will increase your cylinder pressure and increase your low-rpm power, at the expense of high-rpm power. But honestly, 437hp at 46mph is still spinning the tires, and as a streeter, ask yourself how often will you be at WOT at 77 mph. So, IMO, you can easily ditch that 5700rpm cam.
> now, draw a line, right across the graph at 400ftlbs. With a 360engine it will not be possible to pull the torque up to your 400ftlb line, in the rpm range that you will normally be driving, unless maybe you stroke it; even then 400@3000 is a heck of a thing for the chassis to try and deal with, and there is NO good reason to go there, as you can make the numbers down there, with gearing. That's why you have a transmission, and a Convertor..
So again; forget a long flat torque curve.
> now go back to the power peak at 5700. Do you see how slowly the power is dropping off? there is at least 300 maybe 400 more rpm left in her. Lets say a first gear outshift at 6200. With 3.55s and 27s, that is now 50 mph. In the zero to 60 contest, that only leaves you 10mph to pull in second, beginning at 3660 rpm, down around 250/260 hp, on this graph.
This is messed up.
For a streeter; You have waaaaay to much power in First gear, and are seriously choked in Second gear.
IMO, again, you would be better off with a much smaller cam, and hit Second gear much sooner.
Now I know you said "no strip racing" but
who builds a 437 hp engine and never stretches it out. What would be the point of that?

What you really need/want is another lower gear in the trans, or an overdrive, and any old SBM, at that point; Ask me how I know.



View attachment 1715845108
Ok so I agree that curve is not what I want. I’ll be driving a lot around town at 2500rpm so I would like the torque at the lower rpm range. What are my options to go with? I also have my original 1970 318 that I suppose I could build but my original concept was this…….
“What if Mopar built the 1970 Sport Satellite with a real performance oriented small block ie the 340 instead of the 318”.
I mean they called it a Sport Satellite but there was nothing nothing “Sport” about it ie two barrel carb single exhaust lol. But what if they did? What would it look like?
Though I said to drag strip I still would drive it like I was 16 again because WTF at 60 I need some of that in my life still lol
 
@340inabbody you mentioned nothing else about the rest of the build besides stroke so let’s start there.

My ‘68 340 GTS sports stock manifolds and exhaust, a 284/484 cam, edelbrock replacement 625 carb. It needed to be rebuilt. I went the 3.58” stroke route given the limitations of the intake and exhaust systems.

My oldest son built a 4” stroke motor, ported aluminum heads, single plane port EFI system, race headers and 3”
Exhaust.

Both work great for their intended application, what’s your application?

Cliff Ramsdell

even with stock intake and exhaust, and all else the same… the 4” stroke would up the HP and Torque.
 
have you got a 340 yet? if not the same 4'' stroke will get you 390-396 from your original 318. with no very expensive 340 core to buy as well you'll have more left for better heads etc. just a thought?
neil.
 
Absolutely! But my thoughts are if you're going with a 3.58 stroke, then just start with a 360 and save yourself the cost of a stroker crank for the 340. In that case, a set of pistons and you're there. Even if you want a bigger bore than you feel comfortable with in the 360, sleeve it and go big (under $80 a hole locally).
Hmm... now I'm thinking of a 273 block sleeved to a 340 bore with a 360 crank with the mains turned down... and being able to just keep pointing out the "273" cast into the side of the block to all the 5.0 blue oval boys...
i've known of 'class' circuit race guys that cheat by cutting the 273 casting numbers out of the side of the block and welding them into the side of 340 or 360 blocks.
 
Yeah, the 318 stroker would be my go to, especially if I didn't have a 340 block. It will do everything you want and then some. I would talk to Ken at Oregon about the hydraulic roller cam.
 
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