cubic inches vs power

[Quik]

lets talk about cubic inches and the amount of gains you see in power

 

lets put two motors together one a 364 and a 408 both have same setups but difference is 44 cubic inches now i know roughly thats a gain of 40 hp if i relate to the mustang sene. now what do you think honestly an dhow much more torque

 

i know thta one combo would be effiecent well other would be tamed but just wanting and idea on what to figure in on things

[misterp]

Well in that question you are dealing with apples and oranges; the stroke of the two engines is different by a LOT, they will breathe differently. The motor with increased stroke (408) will have far higher average piston speeds, meaning higher vacuum and more torque below 5000-rpm, meaning you can use much more aggressive heads than an "all-bore 408" (if we could even make such a thing). What this means is that the stroker motors run best up to about 6500-rpm, but they are making a lot of power at that point (think Big Block Chevy). Shorter stroke motors can wind-up to 7500 or even 8000-RPM and that's a whole hell of a lot of RPM hence a whole hell of a lot of power, but you've got to keep the engine really up in the Rs the entire pass and not only is that hard on engine/valvetrain parts but death on automatic trannies. After following your project the last few months I would say that you will be far happier with a stroker, because 1) all things being equal you will get 44 more cubes, 2) all things *won't* be equal and you can get more agressive heads/cam than normal, 3) it should do wonders for your 60-ft times, 4) it will be racing at an RPM that will live well on the street.

 

Mr. P.

[BenKey]

Just put it this way - an all out 408 in your truck can do sub-12sec passes.

 

All out = stgIII heads, big cam, L/Ts, big exhaust, a tune for 100+octane, at least 3000 stall, etc.. - nothing left untouched.

[Quik]

Just put it this way - an all out 408 in your truck can do sub-12sec passes.

 

All out = stgIII heads, big cam, L/Ts, big exhaust, a tune for 100+octane, at least 3000 stall, etc.. - nothing left untouched.

<{POST_SNAPBACK}>

thats dissapointing if it only gets a 12 NA. theres 5.3s cammed going 12s

 

408 better hit 11s NA

[BenKey]

Sub - meaning below. 11s.

 

In your truck should be doable - ours - a different story. Again, an all out setup, nothing less.

[Quik]

Sub - meaning below.  11s.

 

In your truck should be doable - ours - a different story.  Again, an all out setup, nothing less.

<{POST_SNAPBACK}>

yeppers

[zippy]

What you're going to find is that naturally asperated the 6.0L will make close to the same HP numbers as the 6.7L using the same heads and same cam. The main difference is that the 6.7L will do it at a much lower rpm and be much more driveable. The key to making the big HP numbers is in the bore size. The bigger the bore, the bigger the valves can be. This is why the 7.0L puts out so much more power than the 6.7L in a naturally asperated setup. The old idea that the short stroke allows you to spin it higher really doesn't come into play in small block's. The limiting factor in how high you can spin the Gen III is in the valve train and cylinder head flow. (This applies to the Gen I and Gen II also). As you can see, the LS7 in the current Z06 has a 7,000 redline with a rev limiter if I recall at 7200. All that rpm with only Hypereutectic pistons even. With some more work done to it such as lighter forged pistons you could turn it 7500rpm as long as you had enough head flow and big enough camshaft. With the 4.8L having such a small bore you could never really spin it that high efficiently even though it has the shortest stroke of the Gen III group. My point to all of this is when you pick a specific quarter mile time you want to run you decide on how much power it's going to take to get there. Next you pick the camshaft and cylinder heads that is going to allow enough air to get in and out to make the desired power level. From here you decide the cubic inches that it's going to take. This is where the tricky part comes in. The reason to go with the 400+cube engines is that they will produce enough velocity at a much lower rpm to run the cam and head combo needed to make the chosen power level. This allows for a lower stall speed converter making the vehicle much more driveable as well as a much lower idle since it will require much more air at the lower engine speeds than say a 364 creating a higher velocity/vacuum. Basicly if you took a 6.0L and built it with lightweight forged pistons, good rod bolts, AFR 225's, 90mm Fast intake with 90mm Fast throttle body and cam of 24xº of duration and 6xx" lift it would run within a few tenths of a 6.7L using the exact same parts. Weight is a big factor in that though as a much heavier vehicle is going to react better to the bigger initial torque. Either way, the difference in the two is simply going to be shift points and converter stall speed. With your current configuration, if you replaced only the short block with a 6.7L using everything else that you currently have in the 6.0L including the cam and keeping the compression the same, you'd only see a few tenths gain in quarter mile time. You would however have a truck that drives much nicer and doesn't require as much stall speed and shift points in the low 6k range instead of high 6k.