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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: 5798 |
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It's really good to see a more scientific explanation behind why you would choose a particular cam
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Greyhounds_AMX
AMC Addicted Joined: Nov/14/2009 Location: Kansas City Status: Offline Points: 1268 |
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I worked up a spreadsheet with all of the common aftermarket off-the-shelf AMC V8 cams a while back that does all the calculations. It started out as a super detailed DCR calculator, but then I took it a bit deeper and added a ton of crazy features. I'll hunt down that thread and post the latest version of the spreadsheet on it. For the intake capacity I'm taking the cylinder head flow test data for a typical head, and using that with the camshaft lobe profile to plot the cylinder head flow curve corresponding to the cam lobe lift curve. The area under the lift curve of the cam doesn't dictate the capability of the cam if the head runs out of capacity before the cam reaches full lift. Plotting the flow capacity curve gives a real representation of how they work together, and will show you how a better head will get more out of the same cam than a stock head would. Calculating the area under the capacity curve gives us a nice single number we can use for comparison. The spreadsheet lets you pick between generic head types, but it's good enough for cam comparison purposes. The exhaust opening event location is something I don't know enough about in order to say exactly where it should be for a given application. But based on experience and common sense you can see how opening it really early will give you a louder exhaust because there will be higher pressure in the cylinder when you open it. Also, since that pressure is released so it can't get converted to work. The overlap period is coming from the exhaust closing event, and how it overlaps the intake opening. |
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1968 AMX 390 w/T5
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dbomb
AMC Addicted Joined: Jul/22/2012 Location: new jersey Status: Offline Points: 705 |
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Great info greyhound just curious if you tested the summit 8601
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rebuiling 73 amx need parts
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Greyhounds_AMX
AMC Addicted Joined: Nov/14/2009 Location: Kansas City Status: Offline Points: 1268 |
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Yes indeed - the spreadsheet compares the attributes of 103 different off the shelf cams (well, sometimes they are the same cam just with a different name). Both of the Summit cams are in there.
On this engine combination the Summit K8601 cam would give a DCR of 6.09, which is pretty low, when you consider that most engines will run 87 octane with a DCR up to 7.00. And if I was building the engine and wanting the best power from pump gas I'd aim for something closer to 7.75 and run it on 93 octane. So you can see that 6.09 is really not optimal. That being said though it's hard to get and 8.3:1 engine up to a DCR of mid to high 7's with the off the shelf cam offerings that are out there. The best are coming in just shy of 7.0. One thing you can do to increase the DCR is to advance the cam a few degrees, and on these lower compression builds that might be a good solution. When doing that though keep in mind that the EVO point moves as well, so for example the nasty Crane H-272 EVO of 51 degrees gets even worse at 53 degrees. But cams with a earlier EVO like the Isky or Lunati would actually end up with a pretty traditional EVO point after you advance them 2 degrees.
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1968 AMX 390 w/T5
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WesternRed
AMC Addicted Joined: Aug/03/2010 Location: Australia Status: Offline Points: 5798 |
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How did you go with finding that old thread and updating the spreadsheet?
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Greyhounds_AMX
AMC Addicted Joined: Nov/14/2009 Location: Kansas City Status: Offline Points: 1268 |
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Ok, I just loaded the latest version so the thread should be toward the top of the list now and easy to find. It seemed to be working ok, but when I add new stuff there's always a chance it causes some sort of problem and may need a little tweak. Let me know if you have any questions.
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1968 AMX 390 w/T5
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amx73
AMC Nut Joined: Aug/28/2009 Location: NJ Status: Offline Points: 294 |
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I called Howard's cam about another project I've got going and asked them to spec out a cam for a stock 360. This is what they came up with:
.475/.475 lift, 215@.050, 111LSA What do you think? |
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Red means run son, numbers add up to nothin'!
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SC397
AMC Addicted Joined: Apr/30/2009 Location: Michigan Status: Offline Points: 5476 |
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Sounds to me like it is close to the Comp268H and Isky 270HL
ISKY - CAM ONLY Good All-Around performance. Fair idle. stock Converter. 370-411 Axle Ratio. Up to 650 CFM Carb. 9.51 Compr. RPM-Range (2000-6000) Valve Lift (.475 .475) Valve Lash hot (.000 .000) ADV. Duration (270 270) .050 Duration (216 216) LC 109 |
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Greyhounds_AMX
AMC Addicted Joined: Nov/14/2009 Location: Kansas City Status: Offline Points: 1268 |
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I suppose it depends on what you want the engine to do. If you're looking for a muscle car sound and lumpier idle with the best power for street performance I think a tighter LCA would be better - 111 is pretty wide.
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1968 AMX 390 w/T5
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Sonic Silver
Supporter of TheAMCForum Joined: Nov/23/2011 Location: East Tennessee Status: Offline Points: 7949 |
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I have a Sig Erson cam in my 70 AMX 360 (9.2 comp, 4 speed, 3.54 gear) that has the same specs at .050 as that Howard cam. I am sure that it may not be the latest and greatest, but it is easy on the valvetrain, idles well, and pulls strong to 5,500 rpm.
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