360 cam recommendation

Greyhounds_AMX wrote: Since your compression ratio is a little low (9:1), you'll find improvements in performance by advancing the cam 2-4 degrees. That advances the intake closing point, increasing the dynamic compression ratio. This is a common methodology used by engine builders on Speedtalk to compensate for lower compression. Using stock rockers prevents you from using the Lunati Voodoo 702 and 703 cams if we honor a 0.500" lift limit, and I think most of us agree that the Comp Xtreme Energy cams are too likely to round off lobes and have too much valvetrain noise. If we rule out other cams with similar aggressive lobe issues, we're left with a pretty tight list: Typically "lope" starts at about 1.5 Overlap Factor, so anything below that can be dropped from the list. The Air Gap's fully divided plenum results in a much smoother idle than a single plane or even a stock intake with has a notched divider, so I'd tend to drop anything that's really close to the 1.5 mark as well. That leaves even fewer cams: The last fellow on the AMC Forum that ordered the Comp 280H was really upset with the quality as it was unusable and he had to return it. It's also about as big a cam as you can run with power brakes, and might even be troublesome if you have vacuum leaks or some other issue. In my book that trims it down to the Erson Street Fighter and the Isky 270-HL. The Isky will have the more aggressive idle of the two. So I'm thinking an Isky 270-HL installed at 4 degrees advanced should meet your needs, which of course unclejohn has been telling us all along. In this case for every 1/4 point of compression ratio above 9:1 you can eliminate 2 degrees of advance, so if your final CR ends up at 9.5:1 instead of the 9:1 you are assuming then you could run the Isky straight up per the cam card.

Excellent writeup Greyhound!

What do you think about the Lunati Street Strip 275?

http://www.lunatipower.com/Product.aspx?id=2902

It breaks the .500" rule by .008",
 but I'm guessing it's close enough for the stock drivetrain with a spring and seal change.

It looks great spec wise for something off the shelf that's faster acting, and hotter, while keeping the 108* lobe center's (which I like for this build) and not going crazy:

• Advertised Duration (Int/Exh): 275/275
• Duration @ .050 (Int/Exh): 225/225
• Gross Valve Lift (Int/Exh): .508/.508
• LSA/ICL: 108/104
• RPM Range: 2500-5500

I like the Isky 270/280's as well,

 this cam would be closer to a 280, with a bump in lift & lobe intensity,

 though not in the same intensity level as a Voodoo or an Xtreme cam.

I've never run one,

and I didn't run the dynamic compression ratio,

but in my humble opinion,

I really like the specs for a low compression, manual trans street 360.

From reading the specs,

 I'd say it may be a little hotter in a 360 than the description implies:

"Hydraulic Flat Tappet. Mild performance use with increased carburetion and headers. Works well with small converter. Noticeable idle."

Thoughts?

Edited by jpnjim - Sep/07/2016 at 11:23am

That Lunati S/S 10100505 is a nice filler between the Isky 270-HL and the Comp 280 in this case, and gives a little higher DCR then either of them at 7.47. Definately a possibility if you'd want a rougher idle than the Isky 270-HL, but it should still run power brakes OK on the 360.

I don't see anything absolutely magical about the 0.500" lift limit for stock rockers, as it's just a rule of thumb like anything else. That extra 0.008" of lift wouldn't be a problem at all.

The Howards cams are really nice looking and are .904 lifter specific, but they just run too much lift for most hydraulic flat tappet folks. And if you plot out the flow capacity it's apparent that our heads don't really gain anything from wicked high lift unless you move to bigger valves with 45 degree seats. If the heads have stock valves and 30 degree seats on the intake there's really no need for lifts over 0.500". I'd really like to see a dwell nose lobe made in a .904 profile for our stock head street engines.

There are limits to how fast you can move the lifter before you incur noise and wear - flat tappet cam design hit those limits decades ago. Comp Cams realized that most of the vehicles using their cams wouldn't be used regularly like a daily driver, so increased noise and wear weren't as critical. With that in mind they designed the XE lobes that exceed those known limits, as it's the only way to get any additional performance from flat tappet cams at this point. These quick opening profiles also happen to work well with computer controlled vehicles, where previous slow opening ramps wouldn't.

As we aren't privy to the actual details of the ramps used by Comp, but they do publish the durations that allow us to calculate the Hydraulic Intensity. The Hydraulic Intensity as defined by Harvey Crane is the difference between the duration at 0.004" and 0.050", and it gives us a method to compare the ramp aggressiveness of different cams. Here's a look at a bunch of the cams that fall into range of duration at 0.050" that we might want to use for this 360. Note that the most aggressive Hydraulic Intensity (the lowest number) is that of the two Comp XE cams (HI=46), next is the Comp 270H (HI=48), next is the VooDoo 703 (HI=50), and then the Comp 280H (HI=52).



For comparison:
   Crane cams are using HI = 56 to 62
   Isky cams are using HI = 64 to 69
   Summit cams are using HI = 75 - 76

Comp is simply ramping these cams steeper than anyone else, and that's why they make more noise and will wear faster or possibly fail outright. Most folks won't have any problems with a Comp XE cam if:
1) The lifter bores in the block are not worn
2) The lifter bores are machined truly perpendicular to the camshaft centerline
3) The lifters used are exactly the correct diameter
4) The lifter face is a proper hardness
5) The cam doesn't walk
6) The oil used has correct amounts of zinc, etc.
7) The correct break in additive is used
8) Dual springs are separated down to a single spring for break-in
9) The correct break-in procedure is followed (rpm, etc.)
10) And also if your cam is not the 1 out of every 100 cams that fails based on Comp's expected failure rate

Comp does a lot of things really well. On the XE series though I think they really need to advise folks to expect increased noise and wear beyond that of a standard aftermarket camshaft. I think that's what's surprising people the most.

http://www.nastyz28.com/forum/showthread.php?t=221553

http://www.corvetteforum.com/forums/c3-tech-performance/1011290-wiped-out-xe-268-h-cam-during-break-in.html

http://www.hotrodders.com/forum/xe268-wiped-lobes-214952.html#/topics/214952?page=2&_k=hlrcrd

http://www.corvetteforum.com/forums/engine-mods/1011993-cam-ratio-v-failure-rate.html

http://forums.vintage-mustang.com/vintage-mustang-forum/644974-comp-cams-using-imported-chinese-cam-blanks.html#/topics/644974?_k=qjgisg

Edited by Greyhounds_AMX - Sep/08/2016 at 12:48pm

Flat tappet cam lobe contact starts near the edge of the lifter and moves across the face to the opposite side. That's why the lobe is pointy. A larger diameter lifter allows lift to start sooner and end later, so more net lift and duration throughout the curve is possible for same seat duration without being too aggressive.

Roller lifters have a narrow contact width, so lobes are more square, e.g. mild AMC roller vs. stock flat tappet:



Comp has XE lobes for 0.904" lifters, but IIRC, the AMC catalogue XE grinds use Chevy 0.842" lobes, so if you want a 0.904", need to custom order.
Comp lobe catalogue:http://www.compcams.com/Technical/Catalogs/CamLobeMasterCatalog.pdf

Crane has 0.904" lobes available from mild to more aggressive ... but also need to custom order (see pg.9 of lobe catalogue http://www.cranecams.com/uploads/lobe/masterlisting.pdf)

If it's running fine with the XE cam you've got, I'd say just run it.

For the OP, any hydraulic cam in the 215-224 @0.050" range will likely be fine. Stay smaller to be conservative, bigger for something more lumpy.

Hope this helps,RD.

WOW! There's some pretty cool information here that I didn't know. Thanks Grey for educating us!