How far to rev this 273 commando build

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prorac1 said:
What are the full specs on this cam? Duration @ .050, lift, etc.

Sounds very similar to the cam we installed in Jason’s 318
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I thought so too. I think the @.050 specs are on the ISKY spec sheet he posted.
 
toolmanmike said:
I thought so too. I think the @.050 specs are on the ISKY spec sheet he posted.
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2B983DF7-3F9E-4427-8B6E-E42FD07699E8.jpeg


This one?
 
stroker402 said:
Go to #1 post ............all specs are there.
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Ok. That second picture just showed up as a blank for me.

This cam is similar to ours.

Elgin cams. “Pro stock “

214/224, .444/.466, 110 lobe separation, installed on a 105 ICL if I’m remembering.

So far we’re very happy with it and it has lots of bottom end.
 
www.youtube.com/watch?v=S5fTqKlqDTs&feature=youtu.be...................I posted the video of my old dartcharger with the commando to youtube . check it out ...... this engine was a Freak / monster. this is the engine I told you guys about that revs to the moon. all oem internals . I shifted this car at 7000 all day long. engine was tire and smoked some . but when I got on this thing................. all hell broke loose !

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IMG_1998.JPG
 
stroker402 said:
AJ ..............Ron at Isky made the cam with 2* advance , giving the 273 more grunt on the bottom end . which it sure does . That is what I specifically asked for . I don't think this cam has that radical of a sound when idling . imo. sooooooooooooso if the cam is advanced 2* then lsa is at 106 is that correct ?
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I didn't hunt the cam up.
Try not to confuse LSA (Lobe Separation Angle), with ICA ( IntakeCenterAngle, or sometimes called Intake CenterLine; or InstalledCenterAngle; all same thing)..
LSA numbers usually fall between 106 and 114. ICA numbers usually fall between 100 and 110. So it's easy to imagine confusion. LSA is ground into the cam and cannot be changed in your driveway. ICA can be put anywhere you want,and some have, with catastrophic results. But if you stay within 6 to 8* of straight up, most street combos with flat-top pistons will be safe; domed pistons not included.
SO
If the cam was ground on a 108 LSA and you installed it 2* advanced, then it is in at 106* . This is a different way of saying you installed your 108cam at 106* for a 2* advancement; different lingo, same end result.Usually it is written something like; 268/276/110+4. The first two series (268/276) tell the intake and exhaust duration, and the 110 tells the LSA, and the +4 tells the ICA to be 4* advanced. From that simple series of numbers, every design cam-timing event can be figured out just with a bit of math.
But
if your grinder took the patterns that he normally grinds on a 108 LSA and tightened it up to 106*; this is a whole different animal, and it will run a lil different. And if you install this 106LSA cam 2* advanced, it will be in at 104*, fully 4* advanced from the original "straight-up".
Try not to confuse LSA with ICA.
Tightening up the LSA, closes the intake valve earlier, builds more low-rpm cylinder pressure, and so that builds low-rpm torque, and usually brings a few more ponies at high rpm.The idle vacuum usually increases and you might have a slightly smoother idling engine, but not always.
Increasing the LSA closes the intake later,reduces low-rpm cylinder pressure, and so softens the low speed torque. It usually also sacrifices a bit of absolute power, to gain some powerband.
And so
a manual-trans car, with tighter ratios, running a deep low, can use a tight LSA(like 108*) cam and wham thru the gears closer to peak power, and ET lower, than if it had the opposite.
But an automatic-car with street gears, and a street-stall, needs powerband to not die on the 1-2 shift. So he might chose a wide LSA cam, like 112 or 114*. This is particularly important with smaller engines that don't have a lotta torque to start with.
When choosing a cam then,
you select the .050 duration to put the power where you need it to be. Then select the LSA to adjust the powerband to suit your transmission. Then let the cam-grinder select the lift according to how often you are willing to replace valvetrain components, or how much money you sunk into your valvegear in the first place, or whatever he is willing or able to give you. And finally you fine-tune the ICA, in the field for best results, or just install it where the cam-card says to.Moving the ICA on a typical streeter, away from the recommended install, rarely results in anything of substance......... unless you got the wrong cam for your combo in the first place. Yes;it happened to me.
If you are happy with your combo, then Congratulations, the cam is doing exactly what you want it to, and don't mess with it.
_____________________________
Here's another trainwreck tip;
the more gears you have, usually the tighter the splits will be; and so the tighter the LSA can be, sacrificing powerband for absolute power. This is how small engines can compete with bigger, on the street.
Small engines, to be fun on the street like lightweight, or; lotsa gears, and modest cams, tuned to the trans. There is no way I could or would, run a 273 in my fat 3650# street-Barracuda (me in it) with a 3-speed TF and 3.23s....... But stick it in a 3000# early-A (driver included) with a tight LSA cam,a 5-speed, and 4.30s and watch her fly! The deep low rear gear lets the engine get up on the cam right away, and the tight-split manual trans keeps her on it. Whereas
3.23s would take forever for the cam to wake up, and the wide gearsplits will keep the engine off the cam for a lot of the time.
You see;
performance cams have a very a limited effective operating range, where the engine is said to be "on the cam" of perhaps 1000rpm. You can increase/decrease the operating range with engine displacement and by manipulating the LSA. But after that power is dropping off, and faster on the top than on the bottom.
But the transmissions Mopar gave us have much much wider powerband requirements, so we have had to invent ways to adapt. The hi-stall TC is one of them. And stealing off-brand 5-speeds is another. And 4-series street gears is a third. All of these help get the engine up on the cam where the power is. But only multi-gears can keep it on the cam, cuz they reduce the powerband requirement to better fit the cam's operating range. For example
The standard TF 3-speed has ratios of 2.45-1.45-1.00, and the splits are 59% and 69%. This means that at whatever rpm you shift at, the Rs will fall to those percents. Lets say you have a cam that wants to be shifted at no more than 6000. Well, going into second, the Rs will drop to .59x6000=3540 .. which being a powerband requirement of 2450 rpm. What do you do with that? You sit back and wait for the engine to get back up on the cam. And the smaller the engine is, the longer you gotta wait. This isn't fun anymore. So what do you do?.... Well next step up is a 4-gear with ratios of 2.66-1.92-1.40-1.00. And with splits averaging 73%.. So now when you shift at 6000, the Rs drop to .73x6000=4380 for a pb requirement of 1620; halleluja to the 4-speed for getting you closer to the cams pb. At 4380 your little engine will be making a good bit more power than at 3540. ...... So what's the next step?
Well you got two choices; more rear gear making it a city car. Or a 5-speed, to keep hiway travel on the table.
So suppose you found a way to bolt this one onto your 273;
3.83-2.33-1.44-1.00-.79od with splits of .61-.62-.69-.79 This ain't looking all that good cuz .61x6000 is 3660 and you are back in the basement. But are you really? Say the earlier combos ran 3.55s about the highest most streeters are willing to run. Now you have .79overdrive, so now you can run 3.55/.79=4.49s for the same hiway rpm. Lets round down to 4.30s, use 27" tall tires, and lets keep the 6000rpm shift speed for now. And lets compare to the standard TF with its 3.55s.
First the TF; You will be shifting at
53,89,130 revved out. When you shift, the Rs will fall to 3540 and 4140. On the way to 65mph, you will pass thru the powerpeak just one time and finish at 4360, seriously choked for low-ET.
Next the AX-15 with 4.30s;You will be shifting at
29,48,78,112 into overdrive. When you shift, the Rs will fall to 3660,3720,4140 and 4740 into od.On the way to 65mph, you will pass thru the powerpeak twice and ending at 5000rpm in third gear; bang on the money!..... three trips thru the powerpeak trumps powerband plus one-trip and choked, any day. This is the magic of TM; Torque Multiplication.
But lets back up a bit. Lets switch to
the Commando A833(3.09low) and regear the back to match the AX-15 and compare those two.This will take 4.42s, lets use 4.56s. Here goes; your shiftspeeds will be;
34,55,76,106 revved right out. On the way to 65mph you will pass thru the power peak twice and finish at 5150 in third gear; hey that looks pretty good! But here's what you don't see; With the Commando box,on the run to 65mph, shifting at 6000, the Rs drop to 3730&4380 versus 3660&3720 with the AX-15. I know which box I want for a 273.

Ohcrap Ididit again, wrong forum, sorry.
 
Ron at isky told me he built the cam with 2* built in, on a 108 lsa. I installed the cam with dots together facing each other on the sprockets. . Seems to working great !
I have a low first gear 833 trans with 355 gears in my barracuda . I tried a 3.91 gear last summer and did not see any improvements just had to shift sooner and more frequent . put the 3.55 back in .
 
67Dart273 said:
It's simple Rob. A dyno DOES NOT measure HP. It measures torque. HP is a mathematical calculation from torque, look at the formula. "There is no such thing" as HP in effect. It is in fact a product of mathematics

Horsepower = torque X rpm / 5252

EDIT read your link LOL, explains it better.............

Torque Vs. Horsepower



Have you ever wondered why “torque vs. horsepower” has always drawn so much debate?

I think it’s because since the definitions involve trigonometry and physics most people don’t want to go through the hassle of deciphering it all.

Let me try to simplify it a bit.



Here’s the short of it: Horsepower (HP) doesn’t really exist, just torque!

You don’t believe me?

Here’s definition: Horsepower = (Torque x Engine Speed)/5252.

So, HP is just a function of Torque.



But first we need to understand a few concepts:



Force is the pressure of one mass against another. In the metric system force is calculated in “Newtons”. Gravity is an easy example of a natural force and in the English system its unit is pounds. So we also use pounds as a basic unit of force.



Work is defined as force over distance and is calculated as Work = Force x Distance.

Work is achieved when a force causes an object to move. The force placed on the object and the distance it moves is the work done.



Power is the amount of work that can be done in a certain amount of time and is calculated as Power = Work / Time. Power was originally defined by James Watt (inventor of the steam engine) who noted that a horse could lift at a rate of about 550 lb-ft per second in an 8 hour shift.

View attachment 1715286170


Torque is the tendency of a force to rotate an object about an axis and is defined as the force at any one point on the edge of a circle in the exact direction of rotation, multiplied by the radius (distance from the center).

As we explained above, in the metric system, force is calculated in Newtons, and distance is in meters, so the standard torque unit is Newton-Meter (N-M). In the Standard/English system, force is calculated in pounds and distance in feet. So the torque unit is lb-ft, usually called “foot-pounds” and sometimes also written as “ft/lb”.



Torque is the measure of the turning force of an object, such as a flywheel or a bolt. For example, pushing or pulling the handle of a wrench connected to a nut or bolt produces a torque (turning force) that loosens or tightens the nut or bolt.



Horsepower is a unit of power. It can be defined in multiple ways, but in its basic sense , it is defined as work done in a straight line as described above under “Power”. When the work is not done in a straight line (as in an automobile engine), it must be defined in a different way: Torque.

Horsepower = (Torque x RPM) / 5252.

It’s worthwhile noting that horsepower is not recognized in the International System of Units.



The reason Horsepower started being used was to compare the output of horses (which everyone understood) with that of the (then new - 1702) steam engines that could replace them. In a study done in 1993 to try to prove (or disprove) the theory it was found that one horse could produce a peak power over a few seconds as high as 15 hp. However it was observed that for sustained activity a work rate of about 1 hp per horse is consistent with what was determined in 1702.

Going back to the formula: HP = (Torque x RPM) / 5252 we can see that at an engine speed of 5,252 RPM Torque and HP are equal. That’s why when we see a graph of Torque / HP we see the lines always cross exactly at 5252 RPM.

View attachment 1715286171
But where does the 5252 come from?



Watt’s definition for HP says: 1 HP = 550 lb-ft / sec, or 1 HP = 550 lb x 1 ft / 1 sec



If we convert straight-line work to its rotational equivalent the formula becomes:



1 HP = 550 lb-ft x 1 rad / 1 sec (a rad is a unit-less measure of a circular distance)



When we convert radians (rad) to revolutions and seconds to minutes the formula again evolves. Note: 6.28 rad per revolution (2 π) and 60 seconds in 1 minute



1 HP = (550 lb-ft x 1 rad / 1 sec) x (1 rev / 2 π rad) x 60 sec / 1 min)



Multiplying and canceling, the formula simplifies to:



1 HP = 5252 lb-ft x 1 rev / 1 min which is the same as: 1 HP = 5252 lb-ft x 1 RPM



So, Horsepower = Torque x RPM / 5252.



If you’ve rear this far I applaud you, since you now know where 5252 comes from and why the HP and Torque curves cross each other.
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HP is not just a function of torque . It a a function of torque and speed (rpm).
A steam engine can produce full torque immediately (0 rpm). 0 hp.
There is nothing magical about 5252, its just a number that results because of the units of measurement that are used. There is no way to calculate hp directly from torque.
Of course a dyno measures horsepower. It measures torque and rpm at every point in time and reads out horsepower and torque.
Doesn't an ammeter measure amps? It actually measures a voltage drop across a resistance.
 
RichB said:
HP is not just a function of torque . It a a function of torque and speed (rpm).
A steam engine can produce full torque immediately (0 rpm). 0 hp.
There is nothing magical about 5252, its just a number that results because of the units of measurement that are used. There is no way to calculate hp directly from torque.
Of course a dyno measures horsepower. It measures torque and rpm at every point in time and reads out horsepower and torque.
Doesn't an ammeter measure amps? It actually measures a voltage drop across a resistance.
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You are playing with words. If you are going to say that a dyno measures torque and rpm, the answer is THE DYNO CALCULATES HP from those two measurements. Torque can be measured DIRECTLY. It's called foot and pounds, IE length of the arm or linear measurement of a weight over distance

The point is that there is no basic singular device which can measure HP as such.

and yeh. Some ammeters measure amperage directly. Not all ammeters have a shunt and a meter. A moving vane meter pretty much measures the strength of a magnetic field through the conductor in the meter. A hot wire meter is another The wire changes with heat cause by current. A basic d'Arsonval meter........the basic meter, not with added external multipliers or shunts........also measures current due directly to magnetic action. It could be argued that a gigantic d'Arsonval movement could be constructed that would measure substantial current directly with no shunt.
 
The point I was attempting to make, earlier, is that in order to find max performance shift points, you need a HP, or a torque, or an acelleration curve for at least one gear throughout the extended RPM range of the engine. With that done, you can plug the addtional transmission ratios in and find where the progressive gears cross in the curve.

There's no reason you could not fabricate a load cell into your motor mounts and use that
 
All I know is that my 318 with RHS heads done by IMM, Edelbrock RPM cam and manifold ran very good with my 3.09 first gear 4 speed, 3.55 gears, rear tire was 24.5" diameter (245/45/17)

Ran so damn good and revved very easy, and quick. I blew it up at 7200 rpm, I wasn't watching what I was doing. ...Cracked a wrist pin. But it sure sounded good.

I want another high winding 318 built with forged internals and solid roller. Too much fun.
 
toolmanmike said:
This thread is a loaded question. We can't tell the op how high rpm he can take his 273. Each engine is different. I hope 7000 rpm doesn't come up and the op scatters it all over the neighborhood.
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I agree each engine is different, i run my 273 with a stock lift cam to 7300, but your valve springs must good.
 
stroker402 said:
Ron at isky told me he built the cam with 2* built in, on a 108 lsa. I installed the cam with dots together facing each other on the sprockets. . Seems to working great !
I have a low first gear 833 trans with 355 gears in my barracuda . I tried a 3.91 gear last summer and did not see any improvements just had to shift sooner and more frequent . put the 3.55 back in .
Click to expand...
With the 3.09 low, and on the street,I found the same thing 3.09x3.55=10.97 and 2.66x4.11=10.93; making them take off equally in first gear.
Where things change is on and after the 1-2 shift. On the street with a torquey engine, I found 4 gears didn't really benefit from deep rear gears, and I tried a lot of them, from 5.38s on down to 3.91s. Also tried less than 3.55s which turned out to be the best all-round with my GVOD, so they are stayin.
But I totally agree with; "I tried a 3.91 gear last summer and did not see any improvements just had to shift sooner and more frequent . put the 3.55 back in"
 
AJ/FormS said:
With the 3.09 low, and on the street,I found the same thing 3.09x3.55=10.97 and 2.66x4.11=10.93; making them take off equally in first gear.
Where things change is on and after the 1-2 shift. On the street with a torquey engine, I found 4 gears didn't really benefit from deep rear gears, and I tried a lot of them, from 5.38s on down to 3.91s. Also tried less than 3.55s which turned out to be the best all-round with my GVOD, so they are stayin.
But I totally agree with; "I tried a 3.91 gear last summer and did not see any improvements just had to shift sooner and more frequent . put the 3.55 back in"
Click to expand...
Thanks AJ !
I fired up the commando after 4 months of hibernation . Couple new changes coming. My flowmaster 40's are coming off and new dynomax ultra flows are going on this week. Also a new change to carburation.... off with the stock 500 cfm afb and on with a 600-625 avs stock to 340 dart/cuda and 383 RR. and see how that performs at a later date .

my cuda at point burger NICE.jpg
 
Well , I got around to installing my new dynomax ultra flo mufflers on the fish today . off with the flowmaster 40's.
ultraflos are are quieter at idle...........
The drone is gone at 35 - 50 speeds. but ...... when you run thru the gears with rpms shifting at 4000..... there are all kinds of different sounds coming from these mufflers. It's weird. and when you get on it real hard, it rattles your ear drums . The flow masters were quieter when you got on it hard .
I have to drive it a little while longer to get the feel of them. They do have unique sounds for sure . I might have to ad the h or x pipe.
mufflers are dumped in front of axle .
 
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