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02-05-2006, 04:18 PM
#21
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No confusion: The 'Duntov' reference was to the '67 -'69 302 engine; the '..milder cam... from '70 on' reference was to the cam used from '70 on in the 350 c.i. LT1 engine for the Z-28, which was available with an auto.
Note that between the wider LCA and the shorter intake duration, the LT1 cam has 18 degrees overlap vs. 26 for the Duntov.
Note that between the wider LCA and the shorter intake duration, the LT1 cam has 18 degrees overlap vs. 26 for the Duntov.
02-05-2006, 05:06 PM
#22
Originally Posted by Beast96Z
OK, so even a car like mine, that will have virtually minimal exaust, will still benifit from the long duration split? My exaust will consist of 1 7/8 to 2" headers, 3 1/2" collectors into 3 1/2" pipe w/X, into 4" Borla or Magnaflow mufflers, then dumped at the axle. It should scavenge quite well with the stepped headers and the X. I just want to make sure I don't hang the exaust out there to bad. I would look into the diffrent ratio rockers, but the Jesels for these heads don't come in any other sizes. BTW, I just noticed in another thread that one of the cam grinders spec's a 256* hydraulic intake lobe for a 408. He had the high intake lift, low exaust lift thing going, but are cams like this really making the most power? Seems like he would get into the problems that I was looking at with my initial cam choice at the begining of this thread???
02-05-2006, 06:19 PM
#23
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Everything I've seen can benefit from longer exhaust duration ('reverse split' philosophy notwithstanding) as long as the LCA isn't too narrow (i.e., open it sooner, don't close it later). As far as rocker ratio, on the Jesel site here: http://www.jeselonline.com/index.php...ryid=59#J2K_GM
they seem to be saying ratios of over 2 are available. Crane and/or Comp Cams have 1.8:1 shaft rockers.
OK, Beast, I need to move on now
; maybe some others will have further thoughts re your cam selection if necessary..
they seem to be saying ratios of over 2 are available. Crane and/or Comp Cams have 1.8:1 shaft rockers.
OK, Beast, I need to move on now
; maybe some others will have further thoughts re your cam selection if necessary.. 
02-08-2006, 08:16 AM
#25
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Just to make a few generalizations as we are doing something that is some what similar. When you reference these 408s Beast make sure you realize that they use heads typically which do not even come close to the ET Heads you'll be running and are even that much farther behind when you take into acount the intake manifold you will be running in comparison to the lsx stuff. It seems as if you just don't need that much cam for a motor with a effecient as your setup is type situation.
http://www.compcams.com/community/pr...69camaro-1997/
This is one of my most favorite examples of this taking effect. Notice how much power this car made with what most would consider to be a baby cam even in a 346. This motor is a bit smaller then yours but those sb2 heads, depending on what's been done to them, can flow a good bit more air then even your ET Heads. Although if I had to guess these can't be some of the bigger 400+ cfm offerings based on the size and power range of this motor but who knows.
http://www.compcams.com/community/pr...69camaro-1997/
This is one of my most favorite examples of this taking effect. Notice how much power this car made with what most would consider to be a baby cam even in a 346. This motor is a bit smaller then yours but those sb2 heads, depending on what's been done to them, can flow a good bit more air then even your ET Heads. Although if I had to guess these can't be some of the bigger 400+ cfm offerings based on the size and power range of this motor but who knows.
02-08-2006, 12:22 PM
#26
That's exactlly the thought path I've been taking. More efficency= less camshaft needed to make power. Now it's more or less finding a exaust lobe that meets some of the criteria we've talked about above. I may stick with the 243/254 I mentioned earlier. I think it fit's nicely with what we've talked about.
