33IMP
Well-Known Member
Who says so? Not the thread title.
What would it take to make 1.44 lbs-ft per cid ?
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It was the point, basically what would it take to make a 365 (NA) have similar power and torque at similar rpms as the 408 in the dyno graph in post 1#. Was trying to figure out some of the design criteria when trying to build high torque per cid over the more normal 1.15-1.29 lbs-ft per cid the average guy gets.
I'm not playing follow your bread crumb trail game, if you got a point make a statement.
junkyardhero
Well-Known Member
the two of you sound like two batty old ladies arguing about who made out with Tad Ansen under the Wildwood boardwalk back in dickety-three when peach schnapps was a nickle and worsted wool undergarments were all the rage.
finish off your cape codders and get a room already, sheesh.
finish off your cape codders and get a room already, sheesh.
You always read into what people say, as a confirmation of your obsession to prove your strawman argument.
RAMM
Well-Known Member
In this case It Is What It Is. J.Rob
Newbomb Turk
Well-Known Member
None of this stuff is hard to do…until you have to do it.
You aren’t going to do normal tuning and find 91 pounds of torque unless you are starting out so bad you shouldn’t be building engines anyway.
Dale Davies
Well-Known Member
Watch David Vizard Powertec 10 videos. High compression (10.5+), good heads with high velocity ports, quench, and careful combustion chamber porting and contouring. Port the piston valve reliefs as DV describes in his BBC book, and also in How to Build Power.
That torque per cube is getting into pro builders territory.
Dale Davies
Well-Known Member
As per Darin Morgan; velocity, velocity, velocity.
In addition, any porting should also involve increasing swirl. This is mixture motion. A tight quench like 0.025" is another aid. Combine that with Somender Singh grooves to direct compression air/fuel coming out of the quench to aid swirl and toward the spark plug. Brian Salter described this in a Live with David Vizard and Andy Woods. Building as high compression in as possible and use water injection to control detonation. Distilled water with 2% water soluble oil. Methanol is to prevent freezing.
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Yes this is true but right port velocity, and that is the question what is the right velocity ? and most seem to worry about it being too low but as I look at the velocity of available heads it seem to be too high, from what I understand average velocity of 250-310 fps being acceptable range and 260 fps being the ideal and up to 285 fps still being somewhat ideal.
So based of the 260 fps as ideal and the calculations to get there, (I'm not saying this is proven right).
So a 365 with peak hp @ 5500 rpm.
Minimum csa (push rod pinch) 1.825"
Average csa 2.263"
Port cc 184 cc
Port cfm 246 cfm
A 184 cc port seems fairly big for 246 cfm we would expect at least 270-280+ cfm for that size which would bring the velocity up to 290-297 fps which is still acceptable but outside the supposedly ideal.
Yes but meaningless without more context.
Dale Davies
Well-Known Member
I have that book.
fat-360
Member
G’day. I’m building a 273 over here with this sort of thing in mind. 360 crank, 253 Holden pistons, 300ci. 400ft/lbs-430 should be doable. Airspeed/compression/V/E and a small cam is how we’re going to do it.Getting the engine stroke/bore “square” is another thing. Very confident in getting 350hp/420ftlbs atm. 273’s are a “torque” engine ( ask Richard Ehrenberg), valves are too shrouded by the bore, gotta make the little thing efficient.
Dale Davies
Well-Known Member
The highest you can get. Now you do not want to choke flow volume to get velocity.
In his second BBC book, DV has a chart with flow velocities for different heads, like stock factory, ported factory, aftermarket as cast, aftermarket ported. F1 heads are pretty straight down and flow in the 380 - 400 feet per second range.
A bunch of the torque you want to find will be found by attempting to get the port flow rate up to 350ft/sec. That high velocity comes at reduced pressure (Bernoulli), is converted to high pressure lower velocity in the bowl. This higher pressure aids the intake air/fuel to squirter through the valve curtain area.
Something to consider is 40° exhaust seats. This aids blowdown and allows tightening up split pattern cams for more low RPM torque. To get the result you are looking for, you need to have a loaded tricks bag, and use most of it.
As I stated, look into David Vizard's books; How to Port and Flow Test Heads, How to Build Power, BBC Power on a Budget.
Yes, you are looking at a Mopar engine and there are differences, but essentially the principles are the same. SBC head design is more like SBM in having the intake valves next to eachother, and sort of similar combustion chambers.
You definately want quench chambers and an exhaust scavenge plateau. You may want pistons with scavenge director to aid aiming the exhaust out the exhaust port at TDC. DV BBC book.
400-430 lbs-ft is 1.33-1.43 lbs-ft per cid is it possible yes, likely probably not. Is it needed for 350 hp 300 ci engine probably not.
1.25 lbs-ft per cid x 300 ci x 90% (tq @ peak hp) = 338 lbs-ft @ peak hp.
350 hp x 5252 / 338 lbs-ft = 5438 rpms
350 hp @ 5438 rpms and 375 lbs-ft @ 3900-4400 rpms.
A 300 ci engine making 420 lbs-ft would make 350 hp around 4850 rpms.
Dale Davies
Well-Known Member
An American V8 is not going to be close to 450 fps. Pretty darn good as in Top dollar can be 350 fps. 'Em are going to cost.
If you look at what port size cc is needed for a given cfm to make a velocity of 260 fps are roughly.
225 cfms = 170 cc, 250 cfms = 190 cc, 275 cfms = 205 cc, 300 cfms = 225 cc, 325 cfms = 245 cc.
If 260 fps is the ideal for best balance of torque and hp. Supposedly above 320 fps hurts hp below 240 fps hurts torque. If correct it seems like we generally don't have enough port for a given amount of cfm.
225 cfms = 170 cc, 250 cfms = 190 cc, 275 cfms = 205 cc, 300 cfms = 225 cc, 325 cfms = 245 cc.
If 260 fps is the ideal for best balance of torque and hp. Supposedly above 320 fps hurts hp below 240 fps hurts torque. If correct it seems like we generally don't have enough port for a given amount of cfm.
fat-360
Member
If your buddy regularly pumps out engines that make that much lbs-ft per cid then everything should be fine, not saying he can't. I was just pointing out for the average guy it's a little up there basically that's a decent 340 torque number. And even if you don't still should make 350 hp at a reasonable rpm.
Be nice to see how it turns out, I like kick *** little engines.
If you look at the calculated fps of stock 273/318/340/360 heads they seem to fall in the 260-280 fps range. And as we modify them for higher cfm velocity goes up not down cause the ease of cfm gain is easier and obviously not linear to volume gain, it lags behind creating higher velocities.
Dale Davies
Well-Known Member
When you get the port too big, lower RPM torque suffers. Look at the Ford Boss 302 and Clevelland 4V heads. Huge ports and low RPMtorque suffered. They came alive at 4000RPM. CHI developed Clevelland/Boss heads they call 3V that are 4 barrel quench combustion chambers and 2 barrel ports. Realise Ford Australia used the Clevelland engine for a while after Ford North America dropped it. They also built piles of 302 Cleveland engines.
Airflow in a port stalls at some point, limiting velocity and flow. Working to get high flow velocity builds pressure in the bowl and aids cylinder filling as the piston rises before the intake closes on the "compression" stroke. This greatly aids cylinder filling and density.
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