More cam questions

[Orionsax7]

I have been planning this build for a street 1971 Demon with a few passes down the 1/4 about once a month for fun.

360 + .030
stock crank and rods
KB 107 pistons, zero deck
71 360 j heads 2.02 in 1.6 ex, gasket matched
eddy air gap intake
750 DP
3.91 rear end

question is this:

I've input many many different cams into desktop dyno with some surprising results. Originally, I was planning on using Comp Cams XE274H but desktop dyno seems to say that a milder cam would work better such as their Magnum Muscle 268AH-10 cam. DD gives this cam more than 410 torque from 2500 to 5500 and tops it out at 451hp at 6500. it only give the xe274 433toque at 4500 and 440 hp at 6500.

I'd like this to be a 12.5 second range car.

At what duration does idle lope come in? I really don't care, just curious.

Anyway, I know Desktop Dyno doesn't translate to real world results so what have you guys seen in the real world? If you could help me limit the cam selection I would greatly appreciate it.

Mostly street driven with 1/4 mile passes once in a while for fun. I'd like the lopey sound too and I'd like to idle around 750-850.

Thanks all.

-Alex

 

[moper]

The only thing DD is good for is noting trends. I don't think a set of stock J heads will make 450hp with either cam. Better heads, possibly. But not factory stock ones. If you want high 12s, you need to make around 400 hp at the crank. The XE268 should be close, but IMO may come out a hair shy. And, the idle will be fairly smooth. I would probably go with the XE274H, or perhaps the Magnum line's 280H for an old school sound with really good power. I've made over 400hp with the Magnum 270H with decent heads before. As far as the lope, the whole package makes the sound. A large cam, with matched parts, will lope. A small cam, with the wrong intake or installed on the wrong centerline will lope. For me, idle sound means nothing when I'm choosing a cam. Power band, vaccum, and idle quality are big. Making the idle worse for sound is equal to running drag slicks in the rain. Sure you can do it...but why would you want to...lol

 

[Sanguine]

Id be more interested in torque and not HP if you are going to drive it mostly on the street
You wont have any fun on the street with an engine that thats powerband doesnt start until 3000rpm

The XE cams are designed to work well with stock heads, allowing the exhaust to breathe a bit better
I have a XE268 in my 340 with stock /j heads and highly recommend for the street

 

[rumblefish360]

The XE cam is larger so it moves the power band around (UP) and the heads are lacking for the cam.
Did you use actuall head air flow specs and cam specs in the program.
Moper is right about the program. It's a good learning tool. It can fairly do a good job. Remember, it's a $40 program. It can help in things like choosing a cam, but do not take a ton of stock in it.The more acurate the info, the better the result.

 

[Orionsax7]

Yeah. I used the flow numbers from the Shady Dell Speed Shop. Looks like it'll either be the XE274 or the 280H. I'll research a little more too.

Moper, you brought something else up I had been debating myself...head selection. Would it be better to sell the 915 J heads and maybe get some Magnum style heads? If so I would go the the Eddy Air Gap intake for magnum and get the mopar conversion kit and measure the pushrods, but I'd do it if it's worth it. Are there other reasonably priced heads available that would also suit my needs?

I've been looking through the Hughes website as well and their prices seem pretty good for their head selections. How do their cams compare? I read their whole FAQ section and understand the design aspect of their cam to take advantage of the mopar lifters...anyone have real world experience with their cams, good or bad? Would they have one available for my application? The only problem I could think of off the bat is that if I choose to go with Magnum style heads, i think I read somewhere that there is a lift limit of about .512 or so. Would the Hughes cams be too big? I have no problem sending my stock heads to be rebuilt but I'd rather not have to do any machining to a brand new set of magnum style heads.

Thanks for all the info. I feel like the more I learn about cams, the more confused I am. ha ha.. I'm getting there.

-Alex

 

[moper]

Well, Hughes has made a great business of that Mopar lifter bit. They are of course right, but if you even read the MP catalog, you'll see the idea was around a long time ago..The mushroom lifter cams. A few others, like Ultradyne, and Isky, used faster ramp speeds as long as 30 years ago too. Hughes just marketed it. You should note among engine builders, cam design is a hush hush deal. So unless you profile a cam, you really don't know much about two sitting side by side. Your eye can't pick up much that way. Hughes has had great results, and has decent product. I personaly don't want to have to deal with the people for a variety of reasons. But facts are facts. They have stuff that performs. It certainly is not the be all end all that they will try to convince you of, but they do some decent work for Mopars there. As far as changing heads...You didnt bring it up. So really, I would think it's not a realistic option. You can spend years thinking "I'll get 'X' if I just run that instead..." There are better ways to accomplish your goals. But, what you must start with after the results you want, is how much can you afford to spend? And keep in mind the whole package. Fuel systems, cooling systems, exhaust, braking, tires, suspension, transmission, rear axle, alll need beefing when you start going mad on power. Only you can answer the $$ question. And only you should. I think at this point, perhaps a new thread on "I want 110s and have this for a car now, and this much money..How do I do it?" might be warranted. And be prepared for as many opinions as there are users logged on....lol.