272 cam specs

[923.4v6]

does anyone have the Intake Closing Point (degrees)
ABDC @ 0.050 lift for the crane 272 cam? Should be on the cam spec card.

[torq455]

I don't have the spec card. I did print all the specs out way back in 2005. Intake closing point is 35 degrees ABDC.

[923.4v6]

Thanks, Thats what I found while searching, But it doesn't sound right. That would give me a dymanic compression ratio of 10.14, while the 260 would have a 8.7. The bigger the cam the less compression your sopposed to have. Does anyone know the abdc of a stock cam?

[kitabel]

The DCR requires the nominal IVC point, not the .050" point, that's why the numbers don't match.

[923.4v6]

The DCR requires the nominal IVC point, not the .050" point, that's why the numbers don't match.

The calculator actually calls for it at .050 and add 15 to it.

[kitabel]

Just a guess, but Vizard suggests that a good indicator of functional cam duration for resonance tuning is nominal - 30°, which mean -15° for any single point such as IVC.
This has been mis-applied all over the place.
The difference between nominal (typically .006" for a mechanical cam), nominal - 30° (and -15° for the closing point), and .050" can't be done except by actually plotting the cam motion, since the ramp factor, accel rate, etc. vary all over the place.
Chances are that there's a big difference between the factory cam and any aftermarket cam: shorter degrees between .006" and .050".
More information? Read my article: http://victorylibrary.com/mopar/cam-tech.htm

[ForcedFirebird]

Shane,

Don't buy into the DCR calculators, it's garbage. I just ran the Crane 272-2 and Comp 260h on Dynomation and the trapped mass is not that far off from one another. You have to realize that dynamic compression is just that, dynamic - ie forever changing. Those calculators give you a static number.

kitabel

Nice article sir!

After seeing some of the cams and compression numbers that have been run with the 60 degree engine, I have thrown my DCR calculator in the recycle bin.


I plugged the Crane specs (both .050" and .006" numbers) and here's what I came up with via Dynomation...

Seat to seat:

IVO 24
IVC 68
EVO 74
EVC 30

.050" :

IVO -4
IVC 40
EVO 44
EVC 0

overlap at seat to seat is 54, overlap at .050" is -4


EDIT:


For giggles Comp 260h...

seat to seat:

IVO 8
IVC 49.1
EVO 48
EVC 9.1

.050" :

IVO -4
IVC 36.4
EVO 36
EVC 3.6

After running numbers in the sims, I checked back at cam cards I have and they are almost spot on (+/- .2)

[923.4v6]

FF what I have in mind is I think that my cam maybe worn. Due to that at idle it used to have a lope and would crank 6000 easy. Now it idles like a stock car and won't crank over 5500. I even went back to a base bin from a while back that I know had the lope. I'm thinking of buying a comp 260 so it will have a little more low end and more cyclinder pressure. I'm showing around 210 and was wanting about 230-240. What do you think.

When you said that you ran the Crane 272-2 and Comp 260h on Dynomation and the trapped mass is not that far off from one another, what does that mean?

[ForcedFirebird]

Man, that was fast. Are you sure you broke the cam in properly? Are you using oil with zinc in it?


You will definitely have more cranking pressure. Chris' car was around 265psi IIRC cranking with the 260h.

EDIT: Dynomation5 is software that I was using today to run cam simulations. Trapped mass is how much fuel is trapped in the combustion chamber during an engine cycle.

[923.4v6]

The cam was given to me and had been ran in 3 other engines with the lifters mixed up, and when I first got my car running it was getting water in the oil due to gasket leak. Not sure its worn but things just doesn't add up.

[ForcedFirebird]

You could have used new lifters. Would have been a wiser choice than using them all mixed up. I would put a dollar to a penny the lobes are wiped.

I am running these cam simulations so that we can offer a nice cam for the hybrid guys that will meet/exceed performance of the Crane. How soon are you looking to purchase?

[923.4v6]

You could have used new lifters. Would have been a wiser choice than using them all mixed up. I would put a dollar to a penny the lobes are wiped.

I am running these cam simulations so that we can offer a nice cam for the hybrid guys that will meet/exceed performance of the Crane. How soon are you looking to purchase?

The cam was from a friend that used it in 3 other engines he blew up and didn't keep the lifters in order. When he gave it to me he said don't worry about it and just stick the lifters in. It was no money out of my pocket though so I did. Lobes probly are about gone.
I would like to get one within a month, so I can get it somewhat tuned in before the meet if I get to attend.

[z284pwr]

Lobe gone without the lifters being messed up? Usually when they start going flat they turn into grinders and take the lifter with them.

Just pull the front valve cover off and rotate the engine and see how much the rocker arms are moving. Hell if the pushrods have been used for awhile you can generally see how much they are suppose to move, base if off that.

Here is what our poor lifters looked like, front 3 are normal....

http://www.edwardsracing.net/off_topic/cam/Lifters5small.jpg

[923.4v6]

I haven't tore into it yet but I'd say that there gone to.

[Lilchief]

ForcedFirebird: P.M. sent