340 or 408?

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I have raced and street driven 350 chevy, and 406. I reved the pee out of the 350, It probably would have been faster, shifting it sooner
The 406 would rev just as fast as the 350, but it was completely unnecessary.
The 406 ran nines/low tens n/a, shifting at 6200. It would go to 7500, just like the 350, but there was NO REASON to.
 
33IMP said:
500 hp out of a 414/416/408 is a lot easier, and probably a lot easier to live with, than a 500 hp 340.
The extra stroke doesn't mean it can't rev as high as a 340 stroke, it just means the power might drop off a little sooner, and you won't NEED to rev it as high.
Imo, revability is determined by head flow, and valvetrain, not stroke length.
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Stroke length certainly affects rpm, the ability to rpm and what it takes to make rpm.
 
67_Slimer said:
OK I know this is done to death and I apologize in advance. I'm a huge 340 fan and currently have a mildly build one in my 67 Dart now. 10.5/1 , Eddy heads solid flat 525 lift cam , 1.6 RR , Hooker headers , Eddy Victor intake , Quickfuel 750 race carb , 4 speed with 4.56's. Fun car. Motor is super strong but wanted to start slowly building a small block for down the road. I currently have a 360 block (1976) .030 over that I planned on building a 408 with but then I have a chance to buy a 340 (1970) block but has a sleeve for a decent price. I am looking for minimum 500 HP at the flywheel. I'm a huge 340 fan and leaning towards the 340 but My concerns are the following. Is 500 HP too much to ask from a standard stroke 340? I'd look at 11/1 compression , I'd port my current eddy heads and Victor intake and obviously go Roller cam with more lift and duration. Another concern I would have is if I go with the 408 , Would the 4.56 gears I have be too steep for that? I really don't feel like changing out my rear gear. It's a Dana. The car is driven locally , cruise nights , shows and to work etc. Looking to rip some gears and have fun , maybe take it to nostalgia day at the track. Never was or will be a daily. Just looking for realistic answers. Thank you in advance.
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What do you want the stroker to do that the current 340 doesn't do for you already?
 
67_Slimer said:
I probably wont run anymore but if I do it will be 1/4 mile. I'm just looking to street drive it and have fun like my current set up but faster. I'm just asking if 500 hp out of a 340 is fairly realistic. I don't care about cam size because its a 4 speed or if I go with the 408 will it be straining with my 4.56s beacause I'm told 408 are more of a lower revving motor.
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It’s realistic if that’s what you are asking.

The fact you keep asking tells me you need to build a stroker.
 
67_Slimer said:
I probably wont run anymore but if I do it will be 1/4 mile. I'm just looking to street drive it and have fun like my current set up but faster. I'm just asking if 500 hp out of a 340 is fairly realistic. I don't care about cam size because its a 4 speed or if I go with the 408 will it be straining with my 4.56s beacause I'm told 408 are more of a lower revving motor.
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Rpm is mainly depends on head flow for any given cid, if you threw on your 340 top end as is probably lose 500-800 rpms off the top. Porting the heads and maybe intake and larger cam will give back most/all of that lost rpm. A 408 can rev just needs the parts to support it.

If building a 408 forget about hp, where do you want it to make peak power 5500 ? 6000 ? 6500 ? Rpms
Then build to make her breath to that rpm (500 hp is around 6000 rpms depending on efficiency) you probably want enough port size to carry on 500 rpms or so past peak for shift points.
 
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33IMP said:
500 hp out of a 414/416/408 is a lot easier,
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I don't get this easier idea, it's gonna take a certain carb, intake, heads, cr, headers, cam etc.. For each to make 500 hp. What's so hard about getting the right parts for a 340 vs a 408 ? Doesn't take a Nascar level build to get 500 hp out of a 340 bet the parts are very similar.
 
67_Slimer said:
So if I go 408 from a 360 , would my top end work if the right cam was selected? (edelbrock heads and Victor intake) I would port them as well.
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If you are building a stroker a lot of folks (including me) used a roller cam. Which in today’s world opens up a lot more options. And roller cams will make more power with more drivability. The bonus of using an early magnum block is it will accept the LA style edelbrocks or other similar heads and it is already setup for a roller cam. There are a LOT of people on her with more knowledge than me..
Make a plan explore all of your options. And select a pathway that suits your needs.. Either way a mild stroker will easily make 500+HP and a similar torque value as well. The torque will be coming on hard in the lower RPMs so no need to run such deep gears like 4:56 on the street..

Best of luck
 
We pretty much just had this discussion except it was for a 450 horsepower build. It’s a sliding scale of work involved, planning, and money. As the horsepower goes up the money graph follows right along. Now if you really want to spend a lot of money build a low cubic inch Competition eliminator type of build. Wind that sucker to the moon and skip right over those 9 and 10 second 1/4 mile times. But you might have to put in some overtime hours
 
Heywodja said:
If you are building a stroker a lot of folks (including me) used a roller cam. Which in today’s world opens up a lot more options. And roller cams will make more power with more drivability. The bonus of using an early magnum block is it will accept the LA style edelbrocks or other similar heads and it is already setup for a roller cam. There are a LOT of people on her with more knowledge than me..
Make a plan explore all of your options. And select a pathway that suits your needs.. Either way a mild stroker will easily make 500+HP and a similar torque value as well. The torque will be coming on hard in the lower RPMs so no need to run such deep gears like 4:56 on the street..

Best of luck
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Good point 408 and 4.56 is gonna be a hard one to hook up in the street :)
 
273 said:
I don't get this easier idea, it's gonna take a certain carb, intake, heads, cr, headers, cam etc.. For each to make 500 hp. What's so hard about getting the right parts for a 340 vs a 408 ? Doesn't take a Nascar level build to get 500 hp out of a 340 bet the parts are very similar.
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I believe the 408 can make the same power as the 340 (at 500 level) with less cam and less compression. I consider that easier.
Even easier, with less of everything..... with a 512.
 
Could always go with a 3.79" crank if looking for some compromise between the two.
 
pittsburghracer said:
I baby my 408 and 422 shifting them at 6800 but they would handle more.
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PBR's version of babying the engine and launch may be different than yours! lol "You're results may vary" as not too many on here leave with the front end 2 feet in the air!! (Some probably wish they had that option!!)

I've shifted my 408 at 6700+ and it runs the same number as shifting it at 6200. So of course I shift it at 6200. My engine is cyl head limited with a cam to match.
 
67_Slimer said:
So if I go 408 from a 360 , would my top end work if the right cam was selected? (edelbrock heads and Victor intake) I would port them as well.
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Your Edelbrock heads and Victor340 intake will work fine getting you to 500-600 plus horsepower. Both of course will need ported and I recommend a 2.055 valve and a 5 angle valve job. Then I recommend a .625-.650 lift cam to take advantage of your porting gains. I’ve proven both a solid lift or roller cam will get the job done. I still have 93 octane pump gas available 3 miles from my house so I would plan my compression around that. I suggest at least an 850 Holley carb. If you go with a solid lifter cam research lifters and try to find EDM ones. Good luck.
 
Demonx2 said:
PBR's version of babying the engine and launch may be different than yours! lol "You're results may vary" as not too many on here leave with the front end 2 feet in the air!! (Some probably wish they had that option!!)

I've shifted my 408 at 6700+ and it runs the same number as shifting it at 6200. So of course I shift it at 6200. My engine is cyl head limited with a cam to match.
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SAME experience with my cylinder head limited 406 (twenty year old track 1's, out of the box virgins).
 
33IMP said:
I will agree, with the stipulation that we are talking LOTS of rpm, 9,10, 11,000.
With the right pieces, I believe a street 408 can rev, just like a 340.
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Until you run out of cylinder head. You ain’t making power out of cylinder head.

A W2 struggles to feed 340 inches at 8500. And that’s fully ported. That’s a W2.

A W5, like the Indy 360 makes 8500 on 340 inches a bit easier.

I’m taking about making power up there.

I’m saying on the dyno and at the track, if you are running 400 inches and your rockers are in line you don’t have enough cylinder head/induction to make any power above 6500.

Period.

You can can the **** out of it, but you’ll kill power coming off brake or clutch. It will be horrible in the gear changes and the more gears you have the more it hurts.

To argue that these engines aren’t under headed is absolutely refusing to look at and understand what it takes to make power at higher rpm.

If the OP wants to help himself, he can find a 3.79 stroke.

He can add 500 rpm up top with the same cam timing and it will beat the brakes off a 4 inch engine.
 
273 said:
Rpm is mainly depends on head flow for any given cid, if you threw on your 340 top end as is probably lose 500-800 rpms off the top. Porting the heads and maybe intake and larger cam will give back most/all of that lost rpm. A 408 can rev just needs the parts to support it.

If building a 408 forget about hp, where do you want it to make peak power 5500 ? 6000 ? 6500 ? Rpms
Then build to make her breath to that rpm (500 hp is around 6000 rpms depending on efficiency) you probably want enough port size to carry on 500 rpms or so past peak for shift points.
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It has very little to do with flow. It’s a cross section issue.
 
33IMP said:
I believe the 408 can make the same power as the 340 (at 500 level) with less cam and less compression. I consider that easier.
Even easier, with less of everything..... with a 512.
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No it won’t. To get the bigger engine to rev the same rpm it will take more cam.
 
Newbomb Turk said:
Until you run out of cylinder head. You ain’t making power out of cylinder head.

A W2 struggles to feed 340 inches at 8500. And that’s fully ported. That’s a W2.

A W5, like the Indy 360 makes 8500 on 340 inches a bit easier.

I’m taking about making power up there.

I’m saying on the dyno and at the track, if you are running 400 inches and your rockers are in line you don’t have enough cylinder head/induction to make any power above 6500.

Period.

You can can the **** out of it, but you’ll kill power coming off brake or clutch. It will be horrible in the gear changes and the more gears you have the more it hurts.

To argue that these engines aren’t under headed is absolutely refusing to look at and understand what it takes to make power at higher rpm.

If the OP wants to help himself, he can find a 3.79 stroke.

He can add 500 rpm up top with the same cam timing and it will beat the brakes off a 4 inch engine.
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Agree. The great majority of big and small block mopar heads are under-headed compared to what is available for a big or small block chevy.
 
33IMP said:
Agree. The great majority of big and small block mopar heads are under-headed compared to what is available for a big or small block chevy.
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I can run the math to show the different cam timing requirements for two different displacements at the same rpm with the same compression.

Just tell me how much compression and at what rpm you want peak torque and peak power and I’ll post up the cam timing numbers.
 
33IMP said:
I believe the 408 can make the same power as the 340 (at 500 level) with less cam and less compression. I consider that easier.
Even easier, with less of everything..... with a 512.
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I see your point but your definition of harder differs from mine ordering different pistons and cam to me ain't harder.

And a 512 still needs heads cam carb etc.. That supports 500 hp, it ain't gonna pull 500 hp from stock 440 RV parts.

To me harder is going above and beyond with parts, machining, assembly and spending ridiculously more $$$.

Like if you needed a tunnel ram W# engine that needed months of research and development to make 500 hp would be harder, ordering different off the shelf parts that are probably relatively close since were talking a relatively narrow amount of air flow needed to make 500 hp be it a 2l or a 10l engine.
 
273 said:
I see your point but your definition of harder differs from mine ordering different pistons and cam to me ain't harder.

And a 512 still needs heads cam carb etc.. That supports 500 hp, it ain't gonna pull 500 hp from stock 440 RV parts.

To me harder is going above and beyond with parts, machining, assembly and spending ridiculously more $$$.

Like if you needed a tunnel ram W# engine that needed months of research and development to make 500 hp would be harder, ordering different off the shelf parts that are probably relatively close since were talking a relatively narrow amount of air flow needed to make 500 hp be it a 2l or a 10l engine.
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Right.

I can make 500 hp on 340 at 6500 rpm.

It will still need a 4.10 screw. But it will make 500 hp.

And my wife could drive it. And she’s far from manly.
 
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