Re: Hemi cam lobes
[Re: mopar dave]
#2911893
04/19/21 11:09 AM
04/19/21 11:09 AM
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Joined: Sep 2005
Posts: 625 Deep DEEP SOUTH
LAD 524
mopar
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mopar
Joined: Sep 2005
Posts: 625
Deep DEEP SOUTH
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Hey Dave from what I've seen the bigger inch, street /strip Hemis all seem to be cammed around 112, mine included.
Typically intake lift is more than exh lift as the exh is so efficient, and usually see with intake durations in the 270s and exh in the lo/mid 280s.
The Bullet roller I'm running is on a 112 LSA, due to this the idle great and relatively "mild" given the size of the cam. Most race Hemis seem to run 108 LSAs or tighter ie 106...providing a narrower power band.
What car is it going in and what's it weigh ?
Last edited by LAD 524; 04/19/21 11:10 AM.
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Re: Hemi cam lobes
[Re: LAD 524]
#2911924
04/19/21 12:58 PM
04/19/21 12:58 PM
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Joined: Jul 2004
Posts: 1,145 Arizona, USA
gsmopar
super stock
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super stock
Joined: Jul 2004
Posts: 1,145
Arizona, USA
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Hey Dave from what I've seen the bigger inch, street /strip Hemis all seem to be cammed around 112, mine included.
Typically intake lift is more than exh lift as the exh is so efficient, and usually see with intake durations in the 270s and exh in the lo/mid 280s.
The Bullet roller I'm running is on a 112 LSA, due to this the idle great and relatively "mild" given the size of the cam. Most race Hemis seem to run 108 LSAs or tighter ie 106...providing a narrower power band.
What car is it going in and what's it weigh ? Same here! IMG_8495 by Greg Ault, on Flickr and the idle: https://rumble.com/vfcpz1-cars-and-coffee-march-2021.html
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Re: Hemi cam lobes
[Re: mopar dave]
#2912315
04/20/21 01:51 PM
04/20/21 01:51 PM
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Joined: Aug 2003
Posts: 43,307 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,307
Bend,OR USA
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I was taught that the lobe separation angles affect the power band, close LSA make more power below 6000 to 7000 RPM and wider affects it above 5000 RPM on N/A motors. Also 4 speed cars wider and automatic cars closer works well for me, Pro Stock are suppose to be using 118 to 120 LSA, maybe not
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Hemi cam lobes
[Re: mopar dave]
#2912805
04/21/21 10:35 AM
04/21/21 10:35 AM
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Joined: May 2019
Posts: 714 Lake Villa Il
INTMD8
super stock
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super stock
Joined: May 2019
Posts: 714
Lake Villa Il
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Well you would start with picking the valve events.
Large displacement generally results in more duration so as duration increases, lobe separation usually does as well to keep overlap in check.
If you just keep increasing duration without ever widening lsa you end up with a ton of overlap.
69 Charger. 438ci Gen2 hemi. Flex fuel. Holley HP efi. 650rwhp @7250 510rwtq @5700
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Re: Hemi cam lobes
[Re: mopar dave]
#2913490
04/22/21 04:20 PM
04/22/21 04:20 PM
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Joined: Jan 2003
Posts: 3,505 DFW
mr_340
master
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master
Joined: Jan 2003
Posts: 3,505
DFW
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I've heard from a few guys that the Hemi chamber design allows the fuel/air flow to go straight out the exhaust on overlap. If you look through the intake port of a Hemi head without valves you can see a little daylight on the exhaust side of the head. I would think a wider LSA would help kill some of the overlap and keep the fuel in the chamber. Also the a/f mixture just tumbles out the intake valve and doesn't seem to spread to the sides of the pistons. The pistons get a carbon track between the valves and the quench areas are fairly free of carbon.
Floyd Lippencott IV
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