340 or 408?

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To me if your ok with running more rpm build the 340 if not build a larger engine there's a few strokes to choose from you can tailor the powerband to your liking and gear ratios.
 
If you want to guesstimate peak power rpm for a given cid at around a decent 1.25 lbs-ft per cid.
Obviously if less efficient more rpm, higher efficiency lower rpms to make 500 hp.

500 hp
2,626,000 / (cid x 1.13 ) = peak hp rpm

(Hp x 5252) / (cid x 1.13) = peak hp rpm
 
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Turk, I think you and I are on opposite sides of the coin.
Engine masters did a comparison test of a 500hp sbc, and a 500hp bbc.
The 363" chevy rpm-ed like mad, cost about half again as much as the 454, needed better gas and much more gear.
The 454 made the same power, WAY more torque at street car levels, and would have been much more livable on the street, cheaper gas, better mileage, less freeway rpm. (and I believe if optimized, faster at the track)
I suspect you would take the 363, with 4.56. I'd take the 454, with 3.55.
 
Here are cam timing numbers for three different engines. Same bore, different stroke.

4.04 bore
10.5:1 compression
3.313, 3.79, 4.0 stroke
6.123 rods

The only change is stroke length. The effective compression ratio is the same for all three at 8.75:1.

I'll post the 3.313 stuff first. Then 3.79 and 4 inch. Cam timing numbers will be @ .006 lift, .020 lift and .050 lift with lobe lift and valve lift with a 1.5 rocker in that order.

3.313 stroke:
296/287/255/.430/.645 intake
306/297/265/.430.645 exhaust
The open/closing events are as follows:
IVO:46
IVC:70
EVO:81
EVC:45
OL:91

3.79 stroke:
302/293/261/.433/.650 intake
316/307/275/.430/.645 exhaust
The opening/closing events are as follows:
IVO:48
IVC:74
EVO:89
EVC:47
OL:95

4.00 stroke:
304/295/263/.450/.675 intake
320/311/279/.453/.680 exhaust
The opening and closing events are as follows:
IVO:48
IVC:76
EVO:90
EVC:50
OL:98

The same everything except stroke length. This is for peak torque at 5000 and peak power at 6500. If we moved the RPM up to say 7200 the numbers would diverge even more.
 
33IMP said:
Turk, I think you and I are on opposite sides of the coin.
Engine masters did a comparison test of a 500hp sbc, and a 500hp bbc.
The 363" chevy rpm-ed like mad, cost about half again as much as the 454, needed better gas and much more gear.
The 454 made the same power, WAY more torque at street car levels, and would have been much more livable on the street, cheaper gas, better mileage, less freeway rpm. (and I believe if optimized, faster at the track)
I suspect you would take the 363, with 4.56. I'd take the 454, with 3.55.
Click to expand...


You make the assumption I would build something the way Freiberger would. Not likely.

Second, yours (and theirs) is a piss poor example and it's a shame people do **** like this. They ought to be ashamed for pulling the wool over people's eye like that.

I watched that episode and lost a ton of respect for ALL of them. They are shoveling horseshit and they have to know it.

In my above example, I left everything the same except stroke. That's THE issue is it not? You think everyone wants to drive a tractor engine. I know I detest **** that drives like that. Always have. And its usually slower too.

In your example, they changed everything to make the test fit their narrative. And that I more than hate.

So lets see, how did they willingly and knowingly manipulate the results? They tried to compare a small block to a big block.

Only a sniveling moron would do that. Or, someone with an agenda does nasty **** like that. Again, they should be ashamed for producing garbage like that.

Why do I say that? Because the increase in bore size is HUGE. I know there is a whole contingent out there who think bore size is useless (or close to it) and stroke is everything. That's wrong.

What else? How about bore spacing? That's just as critical as bore size and they go together. Bigger bore spacing, bigger bores. Bigger bores, bigger valves. Of course, with wider bore spacing and room for bigger valves means you'll have more room for bigger ports.

I could go on showing other examples of what a flimflam test that was.

In your case, I would build the longest stroke I could for you because that's what YOU love.

We have the OP, who says he LOVES his 4.56's and we have a bunch of guys posting **** about ****.

He doesn't have an issue with the gears, but most guys do. So instead of helping the guy, we talk him into something he doesn't want.

Typical.
 
33IMP said:
Turk, I think you and I are on opposite sides of the coin.
Engine masters did a comparison test of a 500hp sbc, and a 500hp bbc.
The 363" chevy rpm-ed like mad, cost about half again as much as the 454, needed better gas and much more gear.
The 454 made the same power, WAY more torque at street car levels, and would have been much more livable on the street, cheaper gas, better mileage, less freeway rpm. (and I believe if optimized, faster at the track)
Click to expand...
True if those things matter to the OP or not, if streetability and rpm ain't a huge deal to you then the advantages of cid might not be a huge selling point, depends what the OP wants. But yes seem most generally would prefer the advantages of cid.
33IMP said:
I suspect you would take the 363, with 4.56. I'd take the 454, with 3.55.
Click to expand...
They should/could be putting similar torque to the ground.

The OP should have no shortage with torque even with 340 and 4.56.

say at 1.25 lbs-ft per cid

363 x 1.25 x 4.56 = 2069 lbs-ft
454 x 1.25 x 3.55 = 2015 lbs-ft
 
Keep the 4.57's and build a decent 340 and go beat up on under headed and under cammed 408's. lol
 
273 said:
True if those things matter to the OP or not, if streetability and rpm ain't a huge deal to you then the advantages of cid might not be a huge selling point, depends what the OP wants. But yes seem most generally would prefer the advantages of cid.

They should/could be putting similar torque to the ground.

The OP should have no shortage with torque even with 340 and 4.56.

say at 1.25 lbs-ft per cid

363 x 1.25 x 4.56 = 2069 lbs-ft
454 x 1.25 x 3.55 = 2015 lbs-ft
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Okay. Now do the 454 with 3.91s. (I'm putting 4.10s and a spool behind my 540)
 
This poor guys head will be spinning after we are done with him. Tomorrow I’m guessing will be all racing formula day so I’ll stay away as it will be way over my head. Lol.
 
We know the power wanted (500 hp) and the gear ratio to be used (4.56).
To me the question is at what peak rpm X would work best for this combo in the street and run the crank that's gonna make 500 hp @ X rpm.
 
pittsburghracer said:
Bull crap. Common sense and testing trumps a pen and paper. You guys make this game way to complicated. You should have every horsepower menu etched in your brain from 200-600 plus.
Click to expand...


I’ll make sure all the engine builders I know who put pen to paper before they build something and use computers to help cut down on testing time how stupid you think we are.

The math for all 3 cams took half an hour.

Post up your compression ratio, stroke, bore size, rod length and where you want peak torque and peak power and I’ll run the math for your engine.

I’m betting it won’t be a match to what you have.
 
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.
Click to expand...
''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''

This.....on the 340.
Nuff said. :thumbsup:
 
Newbomb Turk said:
I’ll make sure all the engine builders I know who put pen to paper before they build something and use computers to help cut down on testing time how stupid you think we are.

The math for all 3 cams took half an hour.

Post up your compression ratio, stroke, bore size, rod length and where you want peak torque and peak power and I’ll run the math for your engine.

I’m betting it won’t be a match to what you have.
Click to expand...


No I’m good. 5200.00 engine (plus carb) and it will run 9.30’s. No number 2 pencils were harmed during this build.
 
PRH said:
I look at it this way……..

It’s unlikely 4.56’s would be the “right gear” for a 500hp combo that’s running a 4” stroke in a Dart.

*Unless it was primarily a race car and had suitably sized rear tires to make the overall gearing work out.
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I have to ask why it would be unlikely?
 
furrystump said:
So, I think you are asking it the 4:56 would hurt the longevity of the 408 more than the 340 you have been running. I have 60,000+ miles and 1000’s of passes on my 4” stroked 360. Went through it in 2016, bearings, rings, pistons(compression bump). Only needed a dingle ball hone. I spin mine to 6300-6400 to shift and 6800 at the stripe. 4:10 gear. In my opinion, there is ZERO difference in longevity between a 340 and a 4” stroked LA. I would go 408.
Click to expand...
THIS is what I wanted to hear. Thank you , Having the 360 block ready to go , I don't have to get taken on a 340 block. Thank you. Would like to get 500-550 hp out of it with my current top end and 11/1 compression. Looking into solid roller as well. Ant info or recommendations are appreciated! Thank You.
 
Just for the heck of it I ran my sons horsepower numbers from his stock crank 360. Budget build that ran 6.54 four or five different times. .030 over 360, Molnar rods, stock crank, set of my Edelbrock heads I ported, Victor340 I quickly ported, 750 alcohol carb, 4:10 gears, 727 transmission with 5600 stall shifted at 6600 rpm and weights 3200 pounds at the line, caltracks with 20 inch radial. Ohhhh a used 100.00 Reed roller cam I bought used. (.625 lift)

IMG_4612.jpeg
 
pittsburghracer said:
Just for the heck of it I ran my sons horsepower numbers from his stock crank 360. Budget build that ran 6.54 four or five different times. .030 over 360, Molnar rods, stock crank, set of my Edelbrock heads I ported, Victor340 I quickly ported, 750 alcohol carb, 4:10 gears, 727 transmission with 5600 stall shifted at 6600 rpm and weights 3200 pounds at the line, caltracks with 20 inch radial. Ohhhh a used 100.00 Reed roller cam I bought used. (.625 lift)

View attachment 1716307304
Click to expand...

What does it say if you use MPH?
 
pittsburghracer said:
Just for the heck of it I ran my sons horsepower numbers from his stock crank 360. Budget build that ran 6.54 four or five different times. .030 over 360, Molnar rods, stock crank, set of my Edelbrock heads I ported, Victor340 I quickly ported, 750 alcohol carb, 4:10 gears, 727 transmission with 5600 stall shifted at 6600 rpm and weights 3200 pounds at the line, caltracks with 20 inch radial. Ohhhh a used 100.00 Reed roller cam I bought used. (.625 lift)

View attachment 1716307304
Click to expand...
Woah!! Impressive numbers.
 
roccodart440 said:
I have to ask why it would be unlikely?
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Well, let’s put it this way……….
I felt 4.56’s were the right gear for my stock headed 383 in a 3670lb B body running low 11’s with 30” tires.
I feel like a 408 with better heads, a roller cam, lighter car, and likely smaller diameter tires(28”?)……..wouldn’t need to run as much gear.
 
this is my 340 build. this engine is ''happy''. the parts are working together. you don't need a roller cam, 4'' stroke, big compression........sometimes less is good. shift at 6800.

340 block
3.46 stroke
11.4 comp
Hughes SFT cam, 264/268 @ .050
W2 heads, 2.05/1.60 valves
ductile iron rockers
Indy intake

904
5600 stall
4.86 gear
 
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