Cams How do you choose one?

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I am curious as to where that graph came from, and what engine it might apply to....?? The reason I ask is that it does not strike me as correct in general, but might be so for a specific engine and setup. So, forgive me, but I just can't subscribe to the above graph as generally accurate.

Example: My 351C was solidly in the torque band from 2000 to almost 6000 RPM and had a best shift point of around 6500 RPM. That was with a cam with .050" lift duration of 192 on the intake LOL. So its actual performance did not match up at all with the above graph. The modifiers that come to mind that may have moved that engine waaay off the above graph were:
  • The very good 351C intake ports
  • 1-7/8" headers with 18" collectors
  • A gen 1 Torker single plane manifold
  • Long cam ramps from .050" to .006" lift at the lifter
  • The 351's 1.73 stock rocker ratio (a lot more lift versus duration compared to a 1.5 rocker ratio)
  • 10.3 SCR and 8.3 DCR
  • All on a 600 cfm carb
Edit to add: BTW, I generally think a couple of the trends on that graph are right: the rising RPM of the torque band with cam duration increases, and the narrowing of the torque band (ratio of the high to low RPM's) with cam duration increases. It is just in the absolute RPM numbers presented, particularly at the low RPM end of the graph. Again, I suspect this may more closely apply for one specific engine setup.
 
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Great chart in general
note the wider power band with shorter cam and if not big heads the longer cams have an even smaller power band
calculate rpm drop at shift and cam no bigger
also small heads limit upper durations or give a narrow power band think stock heads and a big cam for certain class racers very unstreetable
and too big heads limit lower durations think Boss Ford
and 340 heads of this build- to big a cam for the heads and compression
 
Thanks Nm. And Wy. I took the heads in to get freshened they said their going to put on new seals and springs and check the valve job they had a port job from where he bought them good thing is nobody wants these heads as they want alum so the deal was for me. For this engine you are correct that’s the most I can get without changing pistons but that works for me since I still going to use the 69 exhaust manifolds which have been polished inside and exit is 2 1/2”. The one measurement I do have is the pistons are down .090 took it when I put the motor together to make sure it was square and the dish is 8cc found the paper work lol. Sorry for not passing numbers on still think I got wrong answer lol.But still interested in my cam options- voodoo 700 , Jones 256 have to call them , will look at Howard’s and mopar any one else ? And any personal ones I’m open.yes stock 340 cast intake with carter 625
 
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OK, tnx for the deck height number and dish volume. I sued .100" down and 8-9 cc's..... so my SCR/DCR numbers push up 0.1 with that info.... not enough to change any conclusions.
 
get the spring specs required from the cam vendor before doing springs
I know Jones grind does not take too big a spring and he has some hyd profiles that only take 105 on the seat (IDK if MOPAR- been awhile)
your stock type small block heads and manifolds is about the only place left where much additional exhaust duration is warranted (sbf is another)
Mike can figure it out with is computer program
others like Racer Brown and Porter use their long time experience
Comp tech will not have a clue
most catalog grinds assume headers which can use less exhaust but have long exhaust anyway- go figure
 
From you mag article
Cam and Lifters, Hydraulic Flat Tappet, Advertised Duration 276/288, Lift .441/.441, Chrysler, Small Block same as
441 276/288 (54) 218/228 0 38 53 -5 109 LCA 109 ICL 119 excl Elgin 1223P (that's a long exhaust compared to intake and a narrow 109 LCA
but for example
480 276 220 136 (@200) 61 Crane .903 H3 H-220/320 here the 276 duration is at .004 just like Summit and Elgin a lot more area under the curve
IMHO you are better off with one of the three smallest Voodoos - Catalog p 20 a 276 voodoo or Howard (or comp) is BIGGER than a 276 Summit/ Crane/ Elgin so go 10 degrees shorter

Camshaft, Hydraulic Flat Tappet, Advertised Duration 255/261, Lift .479/.494, Howard HRS-711381-10 (110LCA)
Camshaft, Hydraulic Flat Tappet, Advertised Duration 256/262, Lift .454/.475, Lunati 701 Lunati all 112LCA

Camshaft, Hydraulic Flat Tappet, Advertised Duration 262/268, Lift .475/.494, Lunati 702
Camshaft, Hydraulic Flat Tappet, Advertised Duration 265/273, Lift .502/.525, Howard HRS-711651-10

Camshaft, Hydraulic Flat Tappet, Advertised Duration 268/276, Lift .494/.513, Lunati 703
couple of bucks more but shop around- well worth it
 
did you just compare a .441 lift with a .525 lift?

I'd like to know in terms somewhere in between just posting numbers and assuming we all know the scientific terminology, what the comparisons mean.
 
Mopar Budget Build

Just came across this looking for 360 build ,still waiting for cam builders to get back.Intertesting cam choice.
Cheap cam choice..... and realize a lot of these build articles use free parts, are for promoting the magazine and advertisers, and the suppliers provide what the suppliers want..... hence the Summit cam.

That cam is not what I would use for a low compression engine at all for street driving and wanting it to 'scoot' when starting off. It is just not made for that use.

BTW, with the heads and putting on new springs..... can you ask the shop to wait on the springs until you choose the cam? I assume they would put on stock springs. Since you are doing it, it would not be any big thing to put on some 340 springs, which will be of benefit if you ever rev this thing up past maybe 4.5-5k RPM.
 
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Yes they are waiting for a cam specs to put springs on ,the heads are real good shape not much $ into them yet. Traded welding for heads. Heard back from 2 cam company. Just waiting to hear from jones
 
Interesting how Crower describes the same cam in different engines. Goes to show you that a fairly mild cam in a 340-360 is more radical in a 273-318.

The reason is because in the simplest form to describe an engine is "Airpump". How much air they pump "Via cubic inches" and any given cam will work at different RPM ranges for different cubic inches. Breaking it down to this form of 2 strokes make them and air pump "Intake, exhaust" and the 2 extra strokes that make them an engine "Compression, ignition" this is as simple as it gets.

Also every cam we sell that has a part number has been tested many times so we know how it runs.
 
The reason is because in the simplest form to describe an engine is "Airpump". How much air they pump "Via cubic inches" and any given cam will work at different RPM ranges for different cubic inches. Breaking it down to this form of 2 strokes make them and air pump "Intake, exhaust" and the 2 extra strokes that make them an engine "Compression, ignition" this is as simple as it gets.

Also every cam we sell that has a part number has been tested many times so we know how it runs.
Are those ground for Mopar lifters?
 
Yes they are waiting for a cam specs to put springs on ,the heads are real good shape not much $ into them yet. Traded welding for heads. Heard back from 2 cam company. Just waiting to hear from jones
OK, good on that. One other thing... .the Bullet and Lunati cam's look to be trading off lift and adding duration to make up for it. Tends to lessen the low RPM torque...

The Crower cam has more lift and less duration. Have you told Bullet and Lunati that the heads are stock? If so, then they may be limiting lift to around .450-.460" based on that assumption. Know that the heads in stock from limit the lift to around these numbers before the retainers tart to get too near to the seals/guides. But for a more lift/less duration cam (since you say you want to to take off on the low end), your heads are in the shop and they can easily take a bit off of the guides' heights top accommodate a higher cam lift. That might change minds a bit.
 
Hi I gave the specs you have but change the heads to the Indy Lax heads which have a max lift of .525 since I going to use them ,and thanks dart 19666 for the crower cam , been running the numbers on calculators and using AJ icl cal and the cams are in the 67- 60 area isn’t that to high for me? Back to opening words confused lol, back to toolmanmike words sit back and learn. And thanks to anyone else for ideas and comments I’m listening.
 
Choosing a cam can be done like drinking a beer.... be it through the tab...or poking a hole in the bottom and cracking tab.

It all comes into play of you wanna pick "once".
 
Lumpy, Lumpier and Lumpiest ! I've been known to always build up. Pick one for your driving style, probably best with shorter duration and as much lift you can use.
 
I think the best answer is, it depends on what you're doing. My last build, this 396 Chevy I've been working on, for example, I wanted to sound way nastier than it is. I chose the largest of the Comp Thumpr flat tappet hydraulic cams. It's a big block Chevy. They have a reputation of big power production anyway, so it's GONNA run good. I'm not interested in getting every ounce of power out of it. Honestly, that's the way most people building street cars should look at it. If you try to pick a camshaft based on getting the last little bit of power per a given combo, you'll be forever chasing your tail.
 
bullet 272 cam with only 454 lift?
here's what's on their .904 master list Bullet Cams Master List

HC273/330 273 220 137 .3300 .000 CTA
HC272/336 272 224 140 .3360 .000 CTA
.330 x 1.5 ==.495

$220 is a lot of money for a chevy cam
back to the drawing board Bullet
HC267/320 267 214 131 .3200 .000 CTA .480 lift 5 degrees less duration but fatter
HC260/296 260 212 126 .2960 .000 CTA .444 lift 12 degrees less seat duration than the quoted 272 cam and about the same lift
would work without guide work and have a much better DCR- what say you DC guys?
Without going back over the thread
what did the mechanical compression come out to be
and this is stock ports and 340 HP exhaust manifolds- or am I confusing my builds?
 
Just when I thought I was getting a handle on cams the cam guys came back with big cams with 60s Icl. And I thought I needed in the low 50s with the low comp. But anyway comp I came up with for the new heads and thin gasket was 8.58 -1.yes hp cast exhaust pics of the heads I got .one more thing on Howard’s site they don’t give the one set of numbers like 255/261 how does one figure those out? The flow would be a little less I have 1.92 int. Valves.will try and figure out vp and that tomorrow

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Hi , just a little confused which one to choose. I’ve asked the cam company’s got no answer to wild cams. So here goes this is what I have 65 Barracuda #3200 car, A 833 2:66 first gear, 3:55 sure rear 215-60-15 tires, 79 360 stock yes 8:1 with hippo manifolds 2 1/4” exhaust dynomax mufflers, stock 4 bbl intake with carter afb Just a cruiser but fun one. Motor has been rebuilt and heads, since winter is here thinking maybe a cam to have a little more fun.any help on this subject would be appreciated. Can list some cams might be good but don’t know?

The problem with cams is everydoby has there own idea on what would be good. And as you have seen, so do the cam companies. Call them all back and re ask your question just so you’ll see that you’ll more than likely get different answers again even from the same companies.

This is not a scientific way of picking a cam but it will get you really close to what you want without racking your brain out.

Be honest in what you want from your car.

How do you want it to sound rhythm wise?
The lobe separation angle can largely be viewed like this.
116, smooth like melted butter
114 smooth
112 mild idle chop
110 typical muscle car
108 radical muscle car
106 racer
Anything lower, way radical

Pick the rpm you travel in. This is the duration of the cam. As a general guide, the cam companies have listed there basic rpm range. Though this Varys with many other factors that come into play, it is still generally an OK guide line. The cam companies generally list the ranges with the popular engine of what ever make they are. In our case, the 340 is the popular engine. You can raise the rpm band a few hundred RPMs because the engine is smaller. If it were a stroker, you can lower the rpm band down a few hundred because it is a bigger engine. For a driver, error on the smaller one, usually the next one down.

Lift. It helps to know how much the head flows at given lifts. For a street car, yield before max flow and lift.

Rate of lift of the cam lobe. Faster is better but also harder on valve springs. With that said, there is no crime in choosing a cam that doesn’t have the fast ramp rate. You’ll never feel the difference. Long life street cars have slow ramp rates.
Don’t fall for the old cliché bullshit of “That cam has Chevy lobes.”
The engine doesn’t know, you’ll never know, they’ll never know.
The car is a cruiser with fun every once in a while. Worry not!

Many people here will roast you for not following there thoughts and choosing a fast ramp, high lift, low centerline cam because your going to loose power. While they are correct, just what is it your building for YOURSELF!

To this end, if you asked me what you would like after reading your guide that you posted.....

A Hyd. cam from Crane;
1:
Crane Hydraulic Flat Tappet Camshafts 693511
2: (IIRC, I’ll check my cam card, the rpm band doesn’t start where Summit listed it at 2K but at 1500.)
Crane Hydraulic Flat Tappet Camshafts 693941
 
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Seems like the recommended Bullet cam specs are very similar to the Summit 1789 , but with a hair more exhaust duration. Summit Racing® Camshafts SUM-1789

That’s because these professionals know how to grind/spec a mild cam that will see a lot of time in the street!
That kind of cam will live half way to forever and get decent mileage while providing a reasonable increase in power. Summit cams are (or were) ground by Crane. Another ICON in cams.
 
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