Ironracer
Gearhead
A Chrysler 383 Mag, will Kill a 454.... No Doubt in My mind. .BUT, I'm thinking you're talking bout a 400 bowtie crank in a 350.block?
How does cid make power?
- Thread starter 273
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A Chev 454 is not going to beat a Chry 383 with similar parts used. The factory heads available for a 454 have a distinct HP advantage over the 383. The 454 intake ports flow more because [a] they are bigger & the staggered valve angle reduces shrouding.
Ironracer
Gearhead
Ironracer
Gearhead
Might be a bit of a mental masterbation thread but it does have merit.
Were all at different levels of understanding hence the purpose of this site plus People are making expensive decisions on info this site gives.
Lot of the question on here are about displacement type things, 273/318 being very popular, strokers etc...
Lot's on here don't seem to fully understand the relationship between tq and hp but endlessly go on about half truths like torque is king, no replacement for displacement etc... Which can occasionally lead to bad choices $$$$$
Ironracer
Gearhead
Ehhh, IF you Follow a Combination, OF A WORKING DEAL, You Can HAVE A killer mill that'll stand up to the tests of Abuse, and Time! Me? I Follow decades old MP builds.... they work for me, always have, always will! Do I want a 500+ aluminum head HEMI? Heck Yeah! Is it realistic, not for me.... I've had a 318 SNATCH a 74 D200 4 Dr allover the place too... with factory manifolds..
If you got a system that works for you no point trying to reinvent the wheel, think why so much squabbling on this site everyone fighting for their build philosophy and can't accept others.
What worked out even?
One would build a stroker for that increased rod and that torque shows up pretty good at the track. On the around town drive, that extra 133 lbs of Tq is an awesome feeling and very noticeable at the track.
In a “Speed Contest”, (Pertaining to cars like we have and reasonably similar engine builds) the basic rule is, first one to 100 mph will very well most likely win.
Thats a 3% different by equal or even I mean practically, there a less than 2% peak hp difference in the curve it's a wash and with gearing torque is basically wash too, for a 50 cid $3000-4000 I wouldn't call these wins and be upset if I was convinced this was the way to go. 2% got to be in the margin of error between to identical engines. I picked those gears with 26" tires in mind that difference is equalled if the 410 had a 27" instead of a 26" 410=3904 vs 360=3912, If you want to see these as wins that's up to you.
A side note yes more torque is a gain but less powerband rpm is a negative when it comes to power not always cancelling each other out but when I laid the two power curves over one another it practically did. Losing rpm in the powerband might be a bonus in driveablity but negative in power production.
33IMP
Well-Known Member
So, If you don't adjust the combo for the increased stroke/displacement, you get "disappointing" results. What if you do? What if you improve the cam and heads and exhaust?
Take your 273, exchange it for a 408 shortblock with the same compression, and use your 273 heads, a two barrel intake, .398 lift cam, tiny exhaust manifolds, and sure, you'll be disappointed.
Match the combo to the displacement, and a 408 WILL be better than a 340/360 for STREET use. (Disregarding race use of a 340 with rpm to the moon, and 5.something gear)
When I build a 400 into a 512, I'm not gonna keep the 7 1/2 to one, .420 lift cam, 906 heads, and log exhaust. I'm gonna use parts to match the 512 displacement, and expect a LOT more than 2%. I would expect more than a horse per inch of increase.
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67autocross
A new iron curtain drawn across the 49th parallel
I’m lost over the $3000 to $4000… why would it cost that much more to build a stroker?
Rat Bastid
Dunamis Metron
Once again, you need to make a different comparison. Why a 273 and a 408? Why not look at a 360 verses a 408? Or a 340 verses a 408? Then you are looking at engines with similar bore sizing.
I could do the same as you and compare your 408 to a say, 520 inch engine. The 408 has a .400 larger bore than the 273 and that 520 has a .400 bigger bore than the 408.
That 408 would get shredded simply because the 520 has a bigger bore and wider bore centers. That means you can use bigger valves, which means you can use bigger ports. And THAT makes more horsepower.
That’s why all the paper tiger arguments set up like you did skew the results to the favor of everyone who thinks displacement rules. It does IF the rules are set up in its favor.
If you are talking which platform has a higher horsepower density (I don’t like that phrase but it’s what everyone uses so I’ll stay with common vernacular here) the smaller engine would win. In other words, if the 408 made 550 hp, and the 520 made 718 hp, they would have the same horsepower density. I say it horsepower per cubic inch. In the above case, both engines made 1.38 hp/cid. It would be unlikely that the 520 would make that hp/cid if both engines were built for the same purpose.
I won’t even get into BMEP but it’s an important number that should be carefully considered.
Phreakish
Well-Known Member
I spent $2600 on an assembled 408 shortblock. Where you get $3-4k is a mystery.
Stroker kits for a 360 block are $1300, in-stock today from SCAT with forged pistons. Last I checked, forged pistons are around $4-500 a set - so if you build a comparable 360 with new piston (since any build will require a re-bore) the cost difference is about $900.
That's a misleading snapshot only at peak. Area under the curve is what the experience will be dictated by. Not to mention the torque gets packed in under the original peak HP, which means more useable power for a street machine - no need to run 4.10's on the street and give up highway cruising.
$3-4k is laughable. A SCAT stroker kit is $1300 with forged pistons. Since any build will require pistons, the actual build difference is going to be about $900. The work needed to install a stroker kit in a block is quite minimal in a mopar, no way it adds more than $200 at the machine shop - or $0 at home with a die grinder.
The low cost of the stroker proposition is what got me to make the jump, and I'm glad I did. The way the engine runs even with a 'big' (by chevy standards) cam is amazing. I'd have been even happier stroking a 400 - but the cost delta is greater when factoring in all new exhaust, bellhousing, etc.
33IMP
Well-Known Member
I DID compare the 408 to the 340/360 for the street.
The comparison of the 273/408 was intended to exaggerate the comparison of a 360 versus a 408, without optimizing the 408 combo for the larger stroke.
It's been asked, what do I gain with the stroker "if everything else remains the same". The answer to me is "not as much as you might think" if you don't match the rest of the combo. Nobody builds a 632 Chevy short, to go under a peanut port. (Which, by the way flows better than a 906).
And as for horsepower density/hp per cu in, the ricers like to brag on their 200hp two liters, "way more power per cube than your v8!" Okay ricer, you take you hopped up 300hp Honda with 1.6 density or whatever, I'll take my weakass old 800hp 632. Wanna race?
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I'm Canadian everything cost more up here.
Here the under the curve if you lined up the peaks like you would if gearing properly.
410 3000=250 3500=310 4000=365 4500=399 5000=420 5500=431hp
360 3300=252 3800=315 4300=360 4800=399 5300=418 5800=423hp
Cid, lbs-ft, 1st rear , torque to tires
410 480 2.45 x 3.73 = 4386 lbs-ft
360 444 2.44 x 3.91 = 4253 lbs-ft
This thread not about which ways better to build power cid vs rpm or that you shouldn't build strokers or whats more streetable but does cid make hp?
Which to me it doesn't.
Wouldn't you figure if you built the 400 like your gonna with the 512 you'd get similar hp?
33IMP
Well-Known Member
33IMP
Well-Known Member
What would be stopping the 400 from turning enough rpm to displace the same amount of air/fuel/hp as the 512 ?
This thread not about which ways better to build power cid vs rpm or that you shouldn't build strokers or whats more streetable but does cid make hp?
Which to me it doesn't.
Phreakish
Well-Known Member
$900 going to $4k doesn't sound reasonable just for being Canadian.
Your previous post is the one which turned it into "does it make sense to build a stroker" when you brought cost into it.
CID by definition makes power. The volume of air expanded is exactly what creates HP. If you start with less air, you have less expansion. Look at it this way: expanding air is work. Work is HP. More air requires more work in order to expand it - which equates to more HP. HP is work, work is HP. It's physics 101.
33IMP
Well-Known Member
Phreakish
Well-Known Member
If you remove all practical limits, then displacement doesn't matter if all you want is to hit a pre-determined HP number. But if 'max' HP is the goal, then max size is an absolute condition.
HP is work. A 512 is 22% larger than a 400. So the 400 needs to turn 22% more revs to match the HP potential. But like @33IMP says: why not turn the 512 22% faster again? This gets completely circular in a hurry. The 512 will do more at a lower rpm - which is a good thing because reality sucks compared to thought experiments.
So what it comes down to is that since we're all crippled by an RPM limit which is the result of spring and valve technology. As a result, in order to obtain more power in an acceptable RPM range, we increase size. No matter HOW you increase size, it will increase HP output because the torque potential at most operating points goes up. If you increase size without increasing flow potential, the HP increase is crippled, but torque will move up in all places where flow can keep up.
You paid $2600 is hard to believe it would a lot more here.
my OP
"But let me clarify what I mean, I understand if you raise torque at any
Rpm at that rpm hp will also raise. Torque is obviously heavily related to displacement
If I was to say I'm gonna build a 440 without any other info you could ballpark guess how much Torque will be made. Because torque happens in a narrow range for an naturally aspirated engine 1-1.5:1 lbs-ft per cid and for most engines we deal with would be narrower, your not gonna get 550 lbs-ft NA out of a 100 cid engine but could get 550hp since there about 0.5-5.5:1 hp per cid range.
Torque is basically one powerstroke and hp is the sum of all the powerstrokes added up over time.
So obviously displacement has a huge impact on one powerstroke and only has one powerstroke to do it.
The limit on hp is mechanical limitations and ve% limits of rpm so as long you can keep spinning it higher while filling the cylinders you'll make more hp."
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