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Help on cam selection

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Sonic Silver View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Sonic Silver Quote  Post ReplyReply Direct Link To This Post Posted: Feb/25/2018 at 11:11am
Originally posted by Greyhounds_AMX Greyhounds_AMX wrote:

I should have given more of the details of those three cams - here they are:

  1) Lunati 10100276: 268/268, 218/218, 0.488/0.488, 110 LCA, 106 ICL
  2) Elgin E1041-P:     284/284, 218/218, 0.488/0.488, 110 LCA, 105 ICL
  3) Isky 270-HL:       270/270, 216/216, 0.470/0.470, 108 LCA, 106 ICL

These three are also fun to look at because they all use a different lift as the basis for their "advertised" duration (the first numbers I listed above). Comparing them all at 0.006" though shows quite a difference:

1) Lunati: 268/268 @ 0.006"
2) Elgin:  276/276 @ 0.006"
3) Isky:   274/274 @ 0.006"

The Elgin cam used an advertised duration at 0.004" in order to make it look larger, while the Isky cam is advertised at 0.007" so it ends up looking a little smaller.
 

The way I figure it, the opening /closing figures at .050 are :

Lunati: 3 35  43 -(5) overlap -(2)
Elgin:   4 34  44 -(6) overlap -(2)  
Isky:    2 34  38 -(2) overlap  0


Edited by Sonic Silver - Feb/25/2018 at 11:21am
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pjsst View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote pjsst Quote  Post ReplyReply Direct Link To This Post Posted: Feb/25/2018 at 11:18pm
Man all this info kinda hard to take in LMAO
Kinda leaning towards the comp 268 but the big question is could i run this with out any machine work done to the heads ..or what set up could i run with out taking the heads off for machining

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Post Options Post Options   Thanks (0) Thanks(0)   Quote HughesEngines Quote  Post ReplyReply Direct Link To This Post Posted: Feb/26/2018 at 5:49pm
We are Hughes Engines, a Mopar exclusive machine shop. We just joined this AMC forum this morning (2/26/18). We are looking to provide more AMC services, and in this case, I think we can help. We have some exclusive "real" Mopar cam lobes that are designed to take advantage of the large 0.903" lifter diameter shared with both AMC and Mopar. All of our competitors use common GM 0.846" lifter cam lobes. Grinding lobes for the larger .903" lifters gives you faster rates of lift, more lift, and more area under the curve - giving you more power than the .846" lobe with the same sized (duration @ .050") cam. If you look at our website, http://www.hughesengines.com - www.hughesengines.com under " http://www.hughesengines.com/TechArticles/2choosingacam.php - Choosing a cam", we ask you 22 questions to make sure you get the best cam for your combination. 

We also guarantee our cams will outperform our competitors (of the same size) or we'll buy ours back. 

Pick a cam or lobe and we'll get you a "real" AMC cam. You will need new springs and lifters. We can supply them too.
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Greyhounds_AMX View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Greyhounds_AMX Quote  Post ReplyReply Direct Link To This Post Posted: Feb/27/2018 at 1:31pm
Originally posted by HughesEngines HughesEngines wrote:

All of our competitors use common GM 0.846" lifter cam lobes.

Perhaps you meant to say all EXCEPT for Crane, Engle, Lunati, and Howards. These four manufacturer's offer off-the-shelf AMC cams with 0.904 specific lobe profiles.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Babycakes Quote  Post ReplyReply Direct Link To This Post Posted: Apr/12/2018 at 11:07pm
I was considering The Isky 270-HL.  The catalog lists 9.5:1 CR.  Is this minimum recommended?  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Greyhounds_AMX Quote  Post ReplyReply Direct Link To This Post Posted: Apr/13/2018 at 11:37pm

The Isky 270-HL would give a DCR of about 6.6 with the stock 360 compression ratio, which is pretty typical for engines targeting 87 octane fuel. More compression would be better of course, and the Isky would be happy at 9.5:1 static CR as well, but with 93 octane of course.
1968 AMX 390 / T5
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