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Best Cam Upgrade for stock 360??? |
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WesternRed
AMC Addicted Joined: Aug/03/2010 Location: Australia Status: Offline Points: 5787 |
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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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Sonic Silver
Supporter of TheAMCForum Joined: Nov/23/2011 Location: East Tennessee Status: Offline Points: 7903 |
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Sonic Silver
Supporter of TheAMCForum Joined: Nov/23/2011 Location: East Tennessee Status: Offline Points: 7903 |
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amxdreamer
AMC Addicted Joined: Jul/30/2008 Location: Vancouver, BC Status: Offline Points: 8494 |
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I have the comp 268 in my 360. Decent all around cam for a driver that sees occasional track time.
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Tony
Vancouver, BC 1970 AMX 1972 Badassador AMO#10333 |
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Steve_P
AMC Addicted Charter Member Joined: Jun/28/2007 Status: Offline Points: 3760 |
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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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Ralph G.
AMC Apprentice Joined: Apr/06/2016 Location: Cincinnati Status: Offline Points: 185 |
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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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Ralph G.
AMC Apprentice Joined: Apr/06/2016 Location: Cincinnati Status: Offline Points: 185 |
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I was comparing my cam to the Lunati. Sorry for any confusion.
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Greyhounds_AMX
AMC Addicted Joined: Nov/14/2009 Location: Kansas City Status: Offline Points: 1268 |
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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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1968 AMX 390 w/T5
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xspiriment
AMC Nut Joined: Apr/27/2009 Location: New Mexico Status: Offline Points: 376 |
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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
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jpnjim
AMC Addicted Joined: Nov/25/2007 Location: New England Status: Offline Points: 2752 |
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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.
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71 P-code 4spd Javelin/AMX
some Jeeps and some Fords |
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