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Best Cam Upgrade for stock 360???

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WesternRed View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Posted: Jun/20/2018 at 7:30pm
Just for reference I think from memory the factory cam has 266 degrees advertised duration and 0.424" lift. Most aftermarket cams around the 260-270 degree mark are mostly just adding more lift.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Sonic Silver Quote  Post ReplyReply Direct Link To This Post Posted: Jun/20/2018 at 7:36pm
Originally posted by Dave Z Dave Z wrote:

I'm sure any of the cams recommended here will work fine. But just because everyone has an opinion, here's mine. Call Bullet Racing Cams at (662)893-5670. Tell them what you have and what you want it to do and they will custom grind a camshaft for your specific application. It doesn't get better than that.

Dave Z
That's what I did a couple of years ago, and that is why I recommended (in the 3rd post) what they sold me for a stock 360. It does exactly what I want it to do . Are there cams that make more horsepower? Sure, but I just wanted an improvement over stock with great throttle response, and smooth drivability. I have had a Comp 268.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Sonic Silver Quote  Post ReplyReply Direct Link To This Post Posted: Jun/20/2018 at 7:40pm
Originally posted by WesternRed WesternRed wrote:

Just for reference I think from memory the factory cam has 266 degrees advertised duration and 0.424" lift. Most aftermarket cams around the 260-270 degree mark are mostly just adding more lift.
And the factory cam has only 196 degrees duration at .050 valve lift. Most aftermarket 260-270 advertised duration cams have 10-20 degrees more duration at that lift.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote amxdreamer Quote  Post ReplyReply Direct Link To This Post Posted: Jun/20/2018 at 11:49pm
I have the comp 268 in my 360. Decent all around cam for a driver that sees occasional track time.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Steve_P Quote  Post ReplyReply Direct Link To This Post Posted: Jun/21/2018 at 7:59am
The factory cams are very tame; these were station wagon and sedan cams. Even a 260 Comp Cam is a huge difference and will lose ~2" idle vacuum vs factory. I would use something small like a Comp 260 and nothing bigger than the 268
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ralph G. Quote  Post ReplyReply Direct Link To This Post Posted: Jun/21/2018 at 8:56am
This is very close to the Isky 262 Supercam in my 390. Very smooth, lots of torque, good low and mid-range, but as my dyno guy said, "anything over 5000 r.p.m. you're just making noise."
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ralph G. Quote  Post ReplyReply Direct Link To This Post Posted: Jun/21/2018 at 8:58am
I was comparing my cam to the Lunati. Sorry for any confusion.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Greyhounds_AMX Quote  Post ReplyReply Direct Link To This Post Posted: Jun/21/2018 at 12:27pm
I'd take a few things into account on this engine:

1) DCR - With the stock low CR of 8.25:1 you need to maximize the DCR in order to get the best power. This is mostly influenced by the IVC event - the lower the better, all other things being equal. So here's a short list of some of the recommended cams so far plus a few other common ones tossed in:

   Summit K8600 = 6.49

   Isky 270HL = 6.58

   Lunati 10100276 = 6.74

   Comp 270H = 6.75

   Isky 262 Supercam = 6.77

   Comp 268H = 6.79

   Edelbock 2132 = 6.85

   Lunati 10100700 = 6.92

   Comp XE262H = 6.95

That's about as high as you'll be able to get though due to the static CR being so low. You should be able to run 87 octane up to a DCR of about 7.00 though. Anything below 6.5 really isn't optimized for even 87 octane fuel, so we can drop the K8600 and probably even the 270HL as there are plenty of better choices.

 

2) OVERLAP - With a hydraulic flat-tappet cam you need to meet a basic threshold of overlap in order to get the performance level you want. The simple difference between the IVO and EVC event doesn't tell the story very well, and the "overlap triangle" does a better job, but doesn't take into account the flow capacity of the heads involved. That's where "overlap factor" values come into play, as it takes all of that good stuff into account. Anyway, for "Street Performance" we want an overlap triangle of 0.70 to 1.65 or so (per David Vizard). Here's the Overlap Triangle for each of the cams left in our pile:

   Lunati 10100700 = 0.39

   Isky 262 Supercam = 0.76

   Edelbock 2132 = 0.80

   Lunati 10100276 = 0.81

   Comp 268H = 0.81

   Comp XE262H = 0.83

   Comp 270H = 0.96

Based on these numbers I wouldn't want the Lunati 10100700 at all, it's just too wimpy for street performance use in this engine. The overlap will dictate the idle quality as well as the powerband, and I think most of us have heard the Edelbrock cam in a few engines, as well as the Comp 270H, so it should be pretty easy to get an idea of the idle you'd get from these.

 

3) INTAKE FLOW CAPACITY  - The relative amount of intake flow capacity of the cam/head combo will indicate the relative amount of power each can make. The best way to compare this is to calculate the flow related to each lift point for each cam and integrate to get the area under the capacity curve. Here's how the remaining cams stack up in that regard:

   Edelbock 2132 = 520

   Isky 262 Supercam = 525

   Comp 268H = 563

   Lunati 10100276 = 575

   Comp XE262H = 577

   Comp 270H = 594

The Edelbrock and Isky 262 are well below the other cams in the group, so I think it's safe to drop them from further consideration. Even the Comp 268H might be worth dropping, as it's over 5% lower than the 270H.

 

4) EXHAUST VALVE OPENING - The EVO point will influence efficiency and the overall exhaust loudness. If the exhaust valve is opened too early it lets out cylinder pressure that could have been used to push down on the piston, and the higher the cylinder pressure is when the exhaust valve is opened the louder the exhaust "pop" will be. Open it too late though and exhaust can't escape, resulting in pumping losses and intake charge dilution, both bad.

But our AMC heads have extremely good exhaust ports, and in this application the engine has headers as well, so there's no need to make additional efforts at the cam to extend the exhaust flow capacity.

   Comp XE262H = 46

   Comp 270H = 46

   Comp 268H = 43

   Lunati 10100276 = 43

All of these are pretty close together (within 3 degrees), and I think are reasonable. In my experience the poster child for too early EVO is the Crane H-272, a cam very similar to those listed above, but it uses an EVO of 51. That's 5 degrees off from any of these others and I'd have tossed it out of the list.

Also interesting is that the Isky 270HL is a proven performer in many AMC applications, and it runs an EVO of 38!

Here I'd lean toward the 268H and the Lunati as they have the lower EVO of the group, but all would work I'm sure.

 

5) LOBE INTENSITY - The aggressiveness of the shape of the lobe is often characterized by a number called the Hydraulic Intensity. It's the amount of degrees from 0.004" lift to 0.050" lift, so the larger the number the gentler the ramp. Cams with lower HI numbers are going to be more aggressive, and will have higher noise levels, have higher risk of failure, and will need more spring to keep them in control. Here's how our group compares in the intake lobe HI numbers:

   Comp XE262H = 46

   Comp 270H = 48

   Comp 268H = 51

   Lunati 10100276 = 56

These come out just as expected, with the Comp XE being the most aggressive, followed by the Comp High Energy, then followed by the Comp Magnum, and lastly the Lunati. Just for a comparison point, the Crane HMV lobe uses a HI of 56. 

So for this engine my vote would be for the Comp 268H or the Lunati 10100276, whichever brand you like better. If you are super paranoid about cam lobe failure possibilities then chose the Lunati as it's a little less aggressive. 

Comp 268H: 110/106, 0.456/0.456, 268/268, 218/218

Lunati 10100276:  110/106, 0.488/0.488, 268/268, 218/218


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Post Options Post Options   Thanks (0) Thanks(0)   Quote xspiriment Quote  Post ReplyReply Direct Link To This Post Posted: Jun/21/2018 at 5:40pm
There is a cam grinder under the name DEMOS CAMS, may have done work with reed cams. If he has reed grind masters those were some of the best AMC cams. 

Demos Cams
Steve Demos
279 Meadow Lane
Jefferson, GA 30549
Office: 706.367.2417

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Post Options Post Options   Thanks (0) Thanks(0)   Quote jpnjim Quote  Post ReplyReply Direct Link To This Post Posted: Jun/21/2018 at 7:28pm
Nice analysis Grey!
Thanks for taking the time to post it!

I have a couple questions if you don't mind:

"3) INTAKE FLOW CAPACITY"


^
Is there a formula, or computer program you use to get this number?
I've never seen it put like that.




EVO:
"Open it too late though and exhaust can't escape, resulting in pumping losses and intake charge dilution, both bad."

^do you think there's a real risk of opening the exhaust too late in an off the shelf cam?
or was that part mostly just to simplify the explanation?

I understand the risk of too much overlap from a late exhaust event, and the reversion you could get,
 but I hadn't considered there's a point where the exhaust would be too "lazy" (not enough 'pop') from opening too late.

I guess a wider exhaust lobe would help here,
 it would open soon enough to benefit from the higher cylinder pressure earlier in the cycle,
 while still be being wide enough to have decent overlap as it as closing.

My belief has been that using a wider exhaust than intake always comes at the expense of bottom end torque.

Thanks again,
 I enjoy reading your cam explanations. Smile


Originally posted by Greyhounds_AMX Greyhounds_AMX wrote:

I'd take a few things into account on this engine:

1) DCR - With the stock low CR of 8.25:1 you need to maximize the DCR in order to get the best power. This is mostly influenced by the IVC event - the lower the better, all other things being equal. So here's a short list of some of the recommended cams so far plus a few other common ones tossed in:

   Summit K8600 = 6.49

   Isky 270HL = 6.58

   Lunati 10100276 = 6.74

   Comp 270H = 6.75

   Isky 262 Supercam = 6.77

   Comp 268H = 6.79

   Edelbock 2132 = 6.85

   Lunati 10100700 = 6.92

   Comp XE262H = 6.95

That's about as high as you'll be able to get though due to the static CR being so low. You should be able to run 87 octane up to a DCR of about 7.00 though. Anything below 6.5 really isn't optimized for even 87 octane fuel, so we can drop the K8600 and probably even the 270HL as there are plenty of better choices.

 

2) OVERLAP - With a hydraulic flat-tappet cam you need to meet a basic threshold of overlap in order to get the performance level you want. The simple difference between the IVO and EVC event doesn't tell the story very well, and the "overlap triangle" does a better job, but doesn't take into account the flow capacity of the heads involved. That's where "overlap factor" values come into play, as it takes all of that good stuff into account. Anyway, for "Street Performance" we want an overlap triangle of 0.70 to 1.65 or so (per David Vizard). Here's the Overlap Triangle for each of the cams left in our pile:

   Lunati 10100700 = 0.39

   Isky 262 Supercam = 0.76

   Edelbock 2132 = 0.80

   Lunati 10100276 = 0.81

   Comp 268H = 0.81

   Comp XE262H = 0.83

   Comp 270H = 0.96

Based on these numbers I wouldn't want the Lunati 10100700 at all, it's just too wimpy for street performance use in this engine. The overlap will dictate the idle quality as well as the powerband, and I think most of us have heard the Edelbrock cam in a few engines, as well as the Comp 270H, so it should be pretty easy to get an idea of the idle you'd get from these.

 

3) INTAKE FLOW CAPACITY  - The relative amount of intake flow capacity of the cam/head combo will indicate the relative amount of power each can make. The best way to compare this is to calculate the flow related to each lift point for each cam and integrate to get the area under the capacity curve. Here's how the remaining cams stack up in that regard:

   Edelbock 2132 = 520

   Isky 262 Supercam = 525

   Comp 268H = 563

   Lunati 10100276 = 575

   Comp XE262H = 577

   Comp 270H = 594

The Edelbrock and Isky 262 are well below the other cams in the group, so I think it's safe to drop them from further consideration. Even the Comp 268H might be worth dropping, as it's over 5% lower than the 270H.

 

4) EXHAUST VALVE OPENING - The EVO point will influence efficiency and the overall exhaust loudness. If the exhaust valve is opened too early it lets out cylinder pressure that could have been used to push down on the piston, and the higher the cylinder pressure is when the exhaust valve is opened the louder the exhaust "pop" will be. Open it too late though and exhaust can't escape, resulting in pumping losses and intake charge dilution, both bad.

But our AMC heads have extremely good exhaust ports, and in this application the engine has headers as well, so there's no need to make additional efforts at the cam to extend the exhaust flow capacity.

   Comp XE262H = 46

   Comp 270H = 46

   Comp 268H = 43

   Lunati 10100276 = 43

All of these are pretty close together (within 3 degrees), and I think are reasonable. In my experience the poster child for too early EVO is the Crane H-272, a cam very similar to those listed above, but it uses an EVO of 51. That's 5 degrees off from any of these others and I'd have tossed it out of the list.

Also interesting is that the Isky 270HL is a proven performer in many AMC applications, and it runs an EVO of 38!

Here I'd lean toward the 268H and the Lunati as they have the lower EVO of the group, but all would work I'm sure.

 

5) LOBE INTENSITY - The aggressiveness of the shape of the lobe is often characterized by a number called the Hydraulic Intensity. It's the amount of degrees from 0.004" lift to 0.050" lift, so the larger the number the gentler the ramp. Cams with lower HI numbers are going to be more aggressive, and will have higher noise levels, have higher risk of failure, and will need more spring to keep them in control. Here's how our group compares in the intake lobe HI numbers:

   Comp XE262H = 46

   Comp 270H = 48

   Comp 268H = 51

   Lunati 10100276 = 56

These come out just as expected, with the Comp XE being the most aggressive, followed by the Comp High Energy, then followed by the Comp Magnum, and lastly the Lunati. Just for a comparison point, the Crane HMV lobe uses a HI of 56. 

So for this engine my vote would be for the Comp 268H or the Lunati 10100276, whichever brand you like better. If you are super paranoid about cam lobe failure possibilities then chose the Lunati as it's a little less aggressive. 

Comp 268H: 110/106, 0.456/0.456, 268/268, 218/218

Lunati 10100276:  110/106, 0.488/0.488, 268/268, 218/218


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