z-ya Posted May 1, 2006 Share Posted May 1, 2006 Anyone use this cam? Hear are the specs: MFG: Comp Cams Model: 280S Duration: INT 280 EXH 280 Lift: INT .460 EXH .460 Lobe Angle: 110° My question is how much vacuum should I have at idle? Mine is running around 10 inHg. Stock is around 20 inHg. Is this right? I've checked everywhere for vacuum leaks, and haven't found any. I also had the head and intake checked for leaks before assembly. Also, the idle below 1200RPM is pretty rough. Over 1200 it smooths out. I've checked the valve lash, and they are all within spec. Help Appreciated. Quote Link to comment Share on other sites More sharing options...
naviathan Posted May 1, 2006 Share Posted May 1, 2006 Very similar to the MSA stage III grind. It will have a rough idle, but should have a nice pull from 3k-6500. Your vacuum at idle will be less because of valve overlap. Quote Link to comment Share on other sites More sharing options...
Cruez Posted May 2, 2006 Share Posted May 2, 2006 I think I have that grind in mine.. its a Comp Cam also.. I don't have much vacuum in mine either.... and it sounds like this.. http://www.cruez.com/cars/z.wmv Except your exhaust probably doesn't whistle (burned out resonator) Quote Link to comment Share on other sites More sharing options...
z-ya Posted May 2, 2006 Author Share Posted May 2, 2006 That's the sound! What is the idle RPM? Thanks Quote Link to comment Share on other sites More sharing options...
JMortensen Posted May 2, 2006 Share Posted May 2, 2006 Can someone explain to me the importance of measuring vacuum at idle? I've seen posts on the subject and the idea of why you'd do it for any reason other than to make sure the vacuum booster would work eludes me. BTW Cruez, sounds good to me! Quote Link to comment Share on other sites More sharing options...
z-ya Posted May 2, 2006 Author Share Posted May 2, 2006 In a speed density based EFI setup, because it measures engine load by manifold pressure, it is important. With a stock cam, max vacuum is at idle. With a more aggressive cam, the idle vacuum can actually be lower than under load. This has a big effect on the fuel map (pressure vs. RPM) For carbs, it doesn't matter except for brake booster vacuum as you said (oh, that matters for EFI too). Quote Link to comment Share on other sites More sharing options...
JMortensen Posted May 2, 2006 Share Posted May 2, 2006 Thanks Pete, that makes sense. Shows how little I know about EFI... Quote Link to comment Share on other sites More sharing options...
Cruez Posted May 3, 2006 Share Posted May 3, 2006 From what I remember.. it idled around 8-900 .. Quote Link to comment Share on other sites More sharing options...
2126 Posted May 4, 2006 Share Posted May 4, 2006 Can someone explain to me the importance of measuring vacuum at idle? I've seen posts on the subject and the idea of why you'd do it for any reason other than to make sure the vacuum booster would work eludes me. BTW Cruez' date=' sounds good to me![/quote'] Additionally, and this doesn't apply to you Jon, lower than stock vaccum will effect the folks that still have a vaccum advance distributor. I thought you might get a good laugh out of this one Jon! Quote Link to comment Share on other sites More sharing options...
JMortensen Posted May 4, 2006 Share Posted May 4, 2006 Additionally, and this doesn't apply to you Jon, lower than stock vaccum will effect the folks that still have a vaccum advance distributor. I thought you might get a good laugh out of this one Jon! Vacuum wha...??? Quote Link to comment Share on other sites More sharing options...
v8260 Posted May 4, 2006 Share Posted May 4, 2006 would this be a good cam for a turbo motor? Quote Link to comment Share on other sites More sharing options...
Pyro Posted May 4, 2006 Share Posted May 4, 2006 With a cam that big, you should run your efi in the "idle mode" at low rpms so it doesn't try to use manifold pressure as an efi parameter until the rpms come up a bit. However, not all efi systems have that capability. But, 10 inhg seems just a little low for a 280 duration cam. Try using 1000 rpms, 20 degrees of initial timing, and riching up the idle mixture. I think 11 or 12 should be obtainable. Quote Link to comment Share on other sites More sharing options...
Silent Posted May 5, 2006 Share Posted May 5, 2006 comp doesn't grind cams for the L series anymore. hate to burst your bubble. Quote Link to comment Share on other sites More sharing options...
z-ya Posted May 5, 2006 Author Share Posted May 5, 2006 I hate to burst yours, but the one that I'm using I ordered from Summit Racing, and they ground it to order. It was ground by Comp cams in February 2006. Quote Link to comment Share on other sites More sharing options...
Silent Posted May 5, 2006 Share Posted May 5, 2006 i'll be damned, i called comp back in feb and they told me "we don't do any grinds for the L series anymore" even had grind numbers and part numbers hmmmmm i hate being lied too. Quote Link to comment Share on other sites More sharing options...
z-ya Posted May 7, 2006 Author Share Posted May 7, 2006 Maybe when Summit Racing asks Comp Cams for one, they deliver.... Price was great through Summit also. Quote Link to comment Share on other sites More sharing options...
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