JohnnyRed Posted February 14, 2007 Share Posted February 14, 2007 I've having a bit of a problem figuring out what to do about cam choices. I'm looking for a bit more power, but not increase where the power lies. I would like to keep my rev's to ~6500. I would also like a somewhat lopier idle. Ok my current setup includes Chevy 350 bored to 355 Holly systemax II package Holly 750 carb ~10:1 compression I forget what type of headers etc... With the systemax II came this cam: http://store.summitracing.com/partdetail.asp?part=LUN%2D07104LUN&autoview=sku 07104LUN Duration 235/240 @ .05" Lift .49/.49 I'm assuming from the spec sheet that center line of lobe is the LSA which is 108* however the website says it should be 112* Assuming I'm correct I should have 21.5* of overlap. Now, I've found some cams below with more lift, and more overlap, but will I see that much of a power increase from ~.01"to .03" more lift? Cam 1 http://store.summitracing.com/partdetail.asp?part=CCA%2D12%2D224%2D4&autoview=sku 248/248 @ .05" Lift .504/.525 LSA 110 Overlap 28* Cam 2 http://store.summitracing.com/partdetail.asp?part=LUN%2D00012&autoview=sku 246/246 @ .05" Lift .515/.515 LSA 108 Overlap 30* Cam 3 http://store.summitracing.com/partdetail.asp?part=CCA%2D12%2D250%2D3&autoview=sku 240/246 @ .05" Lift .507/.510 LSA 110 Overlap 23* Cam 4 http://store.summitracing.com/partdetail.asp?part=LUN%2D07102&autoview=sku 235/235 @ .05" Lift .507/.507 LSA 108 Overlap 19* Or should I just stick with what I have? Thanks for the help. Quote Link to comment Share on other sites More sharing options...
A. G. Olphart Posted February 14, 2007 Share Posted February 14, 2007 You haven't mentioned what your heads are; they are the key to power. These are nice, but you'll need to compute your CR: http://store.summitracing.com/egnsearch.asp?Ntt=BRO-1021001&searchinresults=true&N=700+400033+316186+115 You are running a pretty healthy cam already: http://www.holley.com/data/Catalogs/SysteMAX%20Engine%20Kits.pdf It does have 112 degree lobe center separation, so you could get more lope (and maybe less gas mileage due to increased overlap) by closing that a bit. I've not looked closely at the overlap figures you provided, but they seem way low... the need to be figured from advertised durations, not .050. This is a Harold Brookshire (was Ultradyne) design with similar .050 and tighter centers: http://holley.com/60104.asp I think they are the newest designs that Lunati/Holley has. If you are all about sound, Check out the "Thumper" cams. Not for me. I'll back off and let the experts give you a hand. <> Quote Link to comment Share on other sites More sharing options...
grumpyvette Posted February 14, 2007 Share Posted February 14, 2007 take your time and read thru these http://www.newcovenant.com/speedcrafter/tech/camshaft/1.htm http://www.chevyhiperformance.com/techarticles/95298_camshaft_lobe_phasing/ http://www.symuli.com/vw/camp1.html http://www.symuli.com/vw/camp2.html http://www.popularhotrodding.com/tech/0607phr_camshaft_basics/ digest that and you won,t get confused look a cam does nothing more than control the valve timing, for a given rpm, displacement ,compression, port size,scavaging length on the headers,ETC. theres a narrow range that will maximize the cylinder fill efficiency, in most cases thats a lower total durration and tighter LCA than most guys sellect, because the wider LCA runs smoother at low rpms and they want more durration to compensate to get the overlap into the effective range, this tends to cause some problems, like reversion, yes youll still have reversion with a tight LCA but the power comes on faster and the low rpm torque tends to be better look heres two nearly identical cams http://www.cranecams.com/?show=browseParts&action=partSpec&partNumber=114681&lvl=2&prt=5 http://www.cranecams.com/?show=browseParts&action=partSpec&partNumber=110921&lvl=2&prt=5 top makes a better street combo, the bottom makes a better race engine, look at the timing and figgure out WHY and youll be well on your way......BTW HINT cylinder pressure/piston location/scavaging Quote Link to comment Share on other sites More sharing options...
grumpyvette Posted February 14, 2007 Share Posted February 14, 2007 take your time and read thru these http://www.newcovenant.com/speedcrafter/tech/camshaft/1.htm http://www.chevyhiperformance.com/techarticles/95298_camshaft_lobe_phasing/ http://www.symuli.com/vw/camp1.html http://www.symuli.com/vw/camp2.html http://www.popularhotrodding.com/tech/0607phr_camshaft_basics/ digest that and you won,t get confused look a cam does nothing more than control the valve timing, for a given rpm, displacement ,compression, port size,scavaging length on the headers,ETC. theres a narrow range that will maximize the cylinder fill efficiency, in most cases that a lower total durration and tighter LCA than most guys sellect, because the wider LCA runs smoother at low rpms and they want more durration to compensate to get the overlap into the effective range BTW that lopey idle indacate the engine in reversion, NOT A GOOD THING Quote Link to comment Share on other sites More sharing options...
JohnnyRed Posted February 14, 2007 Author Share Posted February 14, 2007 Yea, I calculated those overlaps at .05, I'll edit the orig. post here in a min. A link to the systemax II package, with some details http://store.summitracing.com/partdetail.asp?part=HLY%2D300%2D503%2D1&autoview=sku Valve Angle: 20º Intake Runner Volume: 184cc Exhaust Runner Volume: 68cc Combustion Chamber Volume: 68cc Intake Valve Diameter: 2.02" Exhaust Valve Diameter: 1.60" CFM flow @.5" lift 223/173 Deck thickness: .5" It looks like my Compression is 9.55:1 4.03" Bore, 3.38" Stroke, .039" compressed head gasket, and 68cc cylinder head vol. Stock pistons Quote Link to comment Share on other sites More sharing options...
lbhsbZ Posted February 14, 2007 Share Posted February 14, 2007 I ran that same package on a 350 with flat top pistons in a 3600lb chevelle with a stock converter. The cam didn't come on until about 4000rpms. I was really unhappy with it. In a lighter car with a stick shift, it would probably be a lot more fun though. The holley heads are supposedly the same as the brodix track1 heads....an entry level aluminum head, along the lines of the edelbrock performer. The heads are good for about 450hp in stock trim. If you are running it with an automatic, run a higher stall converter and you'll probably be fine with the cam that came with the package. Quote Link to comment Share on other sites More sharing options...
dustin280zx Posted February 14, 2007 Share Posted February 14, 2007 just call comp cams. they're very helpful but you have to know weight,heads,carb,type of cam,intake,c/r,rear gear, stahl, and power adders, bore and stroke, what will be used for, and your max rpm and headers, i think thats it. Quote Link to comment Share on other sites More sharing options...
JohnnyRed Posted February 14, 2007 Author Share Posted February 14, 2007 Is there any downside to just increasing my rocker arm ratio from 1.5 to 1.6 other than possible valve spring bind? I suppose that's another option. Anyone recomend a good 1.6 ratio rocker arm? Quote Link to comment Share on other sites More sharing options...
grumpyvette Posted February 15, 2007 Share Posted February 15, 2007 good http://store.summitracing.com/partdetail.asp?part=CCA%2D1302%2D16&autoview=sku better http://store.summitracing.com/partdetail.asp?part=CRO%2D73640%2D16&autoview=sku Quote Link to comment Share on other sites More sharing options...
jnjdragracing Posted February 15, 2007 Share Posted February 15, 2007 I run the COMP Cams Pro Magnum roller rocker 1.6 rocker but use the 7/16 stud along with a double bar stud girdle, have not had any issues with them. It has been about 5 years now. John Quote Link to comment Share on other sites More sharing options...
lesd Posted February 15, 2007 Share Posted February 15, 2007 You guys really know your cams ! Can someone help me out and make a couple of cam suggestions for a LT1 with stock Aluminum heads and 8.5 CR ( turbo motor build ) ? Revs will be limited to under 6000. Boost target is 12 - 15 PSI. 42lb injectors, after market computer. Low stall speed , street car. Thanks a bunch! -Les Quote Link to comment Share on other sites More sharing options...
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