To compare cams, you also have to look at the advertised (total) duration (0.005" or so lift), and the valve overlap.

Edelbrock 2172
282/292, 63 degrees overlap

Comp 255DEH
255/263, 39 degrees overlap

Going by the 0.050" duration, the Edelbrock cam looks fairly mild, but when you look at total duration and valve overlap, the Edelbrock is very long.

For comparison, the only OEM cams with similar total duration are the highest performance 351C 4V cams (CobraJet, Boss, and HO). And the only OEM cam that's even close on valve overlap is the 351C Boss, with only 58 degrees.

Long valve overlap will push the power range up to higher rpm (more hp) at the expense of low rpm torque and fuel economy.

That said, I still like something more aggressive than the 255DEH, but one of my favorites, the Comp 265DEH, still has less total duration than the Edelbrock 2172 and less valve overlap.

Comp 265DEH
265/275, 50 degrees overlap

And I've seen the 265DEH blow away the Edelbrock cam on both torque and horsepower in the Ford 400.

 

Does that explain it dogdays?

The 255DEH or the 265DEH are both good cams. My perfect choice is the custom 260/268HR cam I am using. It is a little bigger than the 255 and smaller than the 265 but it is a HR cam which ups performance. Last time I checked a custom cam did not cost any more than a std cam but it takes longer to get and is not returnable.

 

Bubba, where'd you find the overlap specs? I looked for them for my cam, but I didn't see it on Crane's website. The cam card that came with it has a few numbers such as:

cam timing @ .004:
intake opens: 19.0° BTDC closes: 61.0° ABDC
exhaust opens: 69.0° BBDC closes: 27.0° ATDC

By the look of all of the high 60s, it looks like I might fall into the "high overlap" catagory? Comparing it to the stock performance units, it looks like it would make a fairly good lower end cam.

 

Overlap is the time (crankshaft rotation) between when the intake valve opens and the exhaust valve closes. It's easy to figure out if you have the valve event timing specs.

In your specs, intake opens at 19 BTC and exhaust closes at 27 ATC, so the valve overlap is 46 degrees.

Although the duration at 0.050" lift and the gross lift is very similar to the Edelbrock 2172, I would expect the Crane H-260-2 to give better low-rpm torque and better fuel economy than the Edelbrock unit because of the shorter overlap and shorter total duration.

 

what real world difference would one notice between the 255DEH and 265DEH?

 

Well there are 9 different 255DEH's

Camshaft, 255DEH, Comp Controlled/Dual Energy, 255/261-203/212-.460/.485-110 Tomorrow $99.88

Camshaft, 255DEH, Dual Energy, Hyd Flat Tappet, 255/261-203/212-.421/.451-110 Tomorrow $93.95

Camshaft, 255DEH, Dual Energy, Hyd Flat Tappet, 255/275-203/219-.422/.462-110 2-17 $99.95

Camshaft, 255DEH, Dual Energy, Hyd Flat Tappet, 255/275-205/219-.422/.462-110 2-17 $116.69

Camshaft, 255DEH, Dual Energy, Hyd Flat Tappet, 255/263-203/216-.434/.467-110 2-17 $99.95

Camshaft, 255DEH, Dual Energy, Hyd Flat Tappet, 255/265-203/216-.465/.495-110 Tomorrow $99.88

Camshaft, 255DEH, Dual Energy, Hyd Flat Tappet, 255/265-203/216-.469/.495-110 Tomorrow $99.95

Camshaft, 255DEH, Dual Energy, Hyd Flat Tappet, 255/265-203/216-.469/.495-110 2-17 $119.95

Camshaft, 255DEH, Dual Energy, Hyd Flat Tappet, 255/263-203/216-.434/.467-110 2-17 $99.95

the 2-17 is a ship by date.

 

how about this one:
Camshaft, 255DEH, Dual Energy, Hyd Flat Tappet, 255/265-203/216-.465/.495-110

for the 351M/400

Somedays I feel like banging my head against the desk...

 

The "255DEH" is just a model name. Comp makes only one 255DEH cam for a particular engine type.

You need to go by the specific part number (or grind number) for the engine you're interested in.

For the 351C/351M/400, the 255DEH part number is 32-206-3. The grind number is FC 255DEH-10.

As for the "real world" difference between the 255DEH and 265DEH cams, the 255 gets on the torque curve a bit quicker under 2K rpm, but by 2.5K rpm I couldn't tell the difference.

The torque above 3K rpm is night-and-day different. The 255 is well over the hill by 4K rpm, and the 265 is just hitting its stride (peak torque at about 4.2K rpm).

The 255 slacks off by 4.5K rpm, and it runs out of breath by 5K rpm. The 265 keeps pulling strong up to 5K rpm, starts to slack off at about 5.5K rpm, and probably runs out of breath around 6K rpm.

These are my personal seat-of-the-pants impressions, based on driving several trucks with these cams in the 400. I wouldn't call this an all-apples comparison, though, because there were significant differences in the engine specs other than the cams, and those differences tend to favor the 265's mid-to-high-rpm performance advantage.

 

The 255DEH might give you an additional 1 or 2 mpg (depending on your vehicle setup) over the 265DEH if you call that a real world difference.

 

I didn't buy this truck to save gas,

I probably do more highway driving, but I do a lot of running around town too. I have a problem with my carb right now that i need to get resolved before I consider what my mileage is going to be. I knew 16-18 MPG was too good to be true.

 

I am building mine for mileage as well as power

Lunati also has a #06114 cam to look at

 

usually power doesn't come with mileage.

Maybe I can tinker with it when I am at Wyotech. I'm really surprised that I am getting 16MPG, but I think its about to end, I noticed that my carb is sticking and making some odd noises. It whistles on idle, loudly, and even with an 8' box, it can't carry a tune.

I'm not much for following the crowd, I'm gonna look into the Lunati cam.

 

Compromise sir, compromise, -the "art" of Engineering.

 

My original build was a stock 400 bottom end with a performer intake and ported heads running a 750 edelbrock and 1 3/4 headers with dual 2 1/4 exhaust with turbo mufflers.

I picked a pretty big cam and advanced it 4 degrees. 218 at .050 intake/exh duration .536 lift 105 degree int centline.

It lopes hard at idle, sounds really mean with open headers. It pulls like a banshee from 500 rpm to 4500. Everybody at Comp and Crane told me that it would be a dog from idle to 3K rpm with that big a cam. I disagree. Other than not being able to smog it due to the rough idle and too high HC. I love this engine. It has returned 13-14 mpg if I keep it to 55 mph or less. Running hard it will go down to 5 or so. But it accelerated a 4500lb truck with A/T radials and a truck 4 spd to mid 15's in the quarter on a really slick track. On a good track I managed a few mid 14's spinning for the first 15 feet off the line. In it's youth it would catch scratch going into 3rd gear at 30 mph. Not bad for a smog motor that everybody told me to dump in the trash.

Compromise is a hard art. Back then I was just guessing at everything and asking lots of questions of everybody else that was building motors. Now I have desktop dyno and this site to find ideas on. I've built a few of these engines for other people and they are really impressed by the torque and top end that I can wring out of them. All of this with mostly stock parts and not a whole lot of money.

The things I learned about compromise is this. It is easy to under cam an engine that is 400 or more cu-in. It is easy to over-cam 302's and 351's. Stock valves suck, they lose their heads when you run them too hard. ( over 5000rpm ) Stock timing chains stretch out within 5K miles. Stock valve springs break as soon as you put in a biggger cam. A 350 cu in engine will turn 7K rpm at the drop of a hat with a Comp Cams 268H and a 4bbl carb. ( Can you say Boom!!! if you don't have good rods and bolts...) Low compression doesn't mean low power, it might not be as efficient or powerful as an engine that can have quench and high compression. But then again, I run 85-87 octane fuel all the time and never have any problems. And last but not least, I've learned that as good as I get, I can always be bested or better myself by research and actual hands on trial and error.

Good luck and don't ever give up learning and progressing.

 

DD is a fun program if you use it properly. It is real easy to get strange and usually high numbers tho.

The high HC numbers are probably due to overlap and represent wasted fuel.

The cam is the heart of the engine and must be picked very carefully keeping in mind what your goals are.