dr_hunt Posted September 29, 2009 Share Posted September 29, 2009 (edited) Actually they kind of lack at low lift. 28" of h2o which is the standard. Kind of weird, but if you think about it you have no vacuum at WOT. Not sure how that standard came about. A larger motor is going to draw more air than a smaller engine, but manifold pressure will still be zero guage no matter what, which is 14.7 psia at sea level and less than that at altitude of any kind. I thought I'd try them just for kicks and grins, they certainly flow better than most heads and they are aluminum so get the weight savings, repairable and of course the WOW factor when you pop open the hood. I think to take advantage of those flow numbers your going to have to run a cam with at least .500 lift. I'm planning on running a lunati voodoo with .507 lift, 238 or so at .050 and then I've got some 1.6 roller rockers so that should bump it up to about .530 or so give or take. Just thought for the price he might want to check them out since they are about the same price. Edited September 29, 2009 by dr_hunt Quote Link to comment Share on other sites More sharing options...
Pyro Posted September 29, 2009 Share Posted September 29, 2009 I didn't see the flow pressure listed in the flow results.??? make sure to use an oil additive if you use regular engine oil. A Voodoo cam with heavy springs will eat lobes in no time using regular low emissions engine oil (low zinc). check out http://www.zdpplus.com. use a can at each oil change. racing oil still has the correct amount of anti wear stuff in the oil. Quote Link to comment Share on other sites More sharing options...
bschiltz Posted September 29, 2009 Author Share Posted September 29, 2009 Hey, those heads look pretty nice thanks Doc. How would this cam match up with those heads? http://www.summitracing.com/parts/CCA-08-422-8/ 218/224 @ .050 .495/.502 110 lsa I would likely 1.6:1 rockers as well Quote Link to comment Share on other sites More sharing options...
dr_hunt Posted September 29, 2009 Share Posted September 29, 2009 I think it would work fine IMO. I'd run some 1.6 rockers on that for a test. My Crane gold race rockers are adjustable, 1.5, 1.55 or 1.6. I think these alum heads are probably every bit as good as the ones you were looking at but have the advantage of less weight, probably better flow, smaller ports = better response, and of course the "BLING" factor of aluminum. As for voodoo cams, not sure what your thinking about there pyro. Cam calls for 100lb on the seat at 1.750, so hardly alot of seat pressure. IIRC the open pressure is something like 250 or 275, so no it's not alot of spring rate. I was trying to get the isky circle track grind 201284/6 which has almost identical lobes but couldn't find it, so I went with the lunati, besides I think the lunati was cheaper anyway although the lobe center is 108 instead of 106. But what is 2 degrees amongst friends. And yes I prefer tight lobe centers on street engines for better mid range TQ over say 112 or even 110LSA's. IMO it's better to have TQ hit early and hard IMO, it wins races. Quote Link to comment Share on other sites More sharing options...
bschiltz Posted September 30, 2009 Author Share Posted September 30, 2009 Cool, well I bought a pair of those heads tonight. Thanks again for the tip Doc Quote Link to comment Share on other sites More sharing options...
Pyro Posted September 30, 2009 Share Posted September 30, 2009 voodoo cams and compcam xtreme cams have very quick rates (advertised-at 0.050" duration). Therefore are much harder on the lobes. That combined with any spring stronger than stock will eat lobes quickly with todays crappy oil. But it's a free country (for now), use any oil you want. Just giving you a heads up so your engine doesn't eat itself up. At least you will know why when a lobe goes flat and chews up the bearings. There are lot of theories with lobe centers. One popular theory is, if the head flows well then you don't need as tight of a lobe center to help fill the cylinder. See, a poor flowing intake ports gets a boost filling the cylinder from exhaust scavaging so more over lap helps that. old design (poor flowing) cylinder heads do well will tighter lsa and new heads with wider. Quote Link to comment Share on other sites More sharing options...
dr_hunt Posted September 30, 2009 Share Posted September 30, 2009 We will try them and see how they work. Here is the cam card for the cam I have http://www.lunatipower.com/Product.aspx?id=1950&gid=277 Quote Link to comment Share on other sites More sharing options...
Pyro Posted September 30, 2009 Share Posted September 30, 2009 that is not a voodoo cam. the ramps aren't as aggressive. 285 - 235 = 50. However, still much more aggressive than stock and still would be good to use oil additive. I have chewed up 6 or 7 cams of this size and ramp rate over the years before learning oil was changed (very disheartening and expensive). I like the fact the cam has equal intake and exhaust durations. The heads flow well enough on the exhaust to not require more exhaust duration. Quote Link to comment Share on other sites More sharing options...
bschiltz Posted October 1, 2009 Author Share Posted October 1, 2009 How do you figure spring rates for a cam? http://www.compcams.com/Cam_Specs/CamDetails.aspx?csid=187&sb=2 That's the cam I linked to above. It lists part numbers for two sets of springs, one 322 in/lb and one 344 in/lb, I'm sure both work but I'm curios how you go about finding what is needed. In Vizard's "Small blocks on a Budget" book he says 220-240 lbs is adequate for a street motor and 350 lbs is the maximum. Am I confusing measurements? Quote Link to comment Share on other sites More sharing options...
Pyro Posted October 1, 2009 Share Posted October 1, 2009 How do you figure spring rates for a cam?http://www.compcams.com/Cam_Specs/CamDetails.aspx?csid=187&sb=2 That's the cam I linked to above. It lists part numbers for two sets of springs, one 322 in/lb and one 344 in/lb, I'm sure both work but I'm curios how you go about finding what is needed. In Vizard's "Small blocks on a Budget" book he says 220-240 lbs is adequate for a street motor and 350 lbs is the maximum. Am I confusing measurements? spring rate and spring force is two different things. spring rate is how much force increase per inch and not how much is on the seat or at max lift. so for a 0.500" lift cam the pressure force will change by 161 pounds or 172 pounds more (depending on which spring you use). furthermore, the cam you have is a roller cam, so it will require much more spring force than a flat tappet cam. 130 lb on the seat and 300 at max lift should do it. The spring installed height controls the pounds on the seat. Quote Link to comment Share on other sites More sharing options...
bschiltz Posted October 1, 2009 Author Share Posted October 1, 2009 spring rate and spring force is two different things. spring rate is how much force increase per inch and not how much is on the seat or at max lift. so for a 0.500" lift cam the pressure force will change by 161 pounds or 172 pounds more (depending on which spring you use). furthermore, the cam you have is a roller cam, so it will require much more spring force than a flat tappet cam. 130 lb on the seat and 300 at max lift should do it. The spring installed height controls the pounds on the seat. Ok, that's kinda what I was thinking. So "over the nose" pressure is full lift, correct? So to figure change you just take the rate by the lift, 322 lbs./in*.500in= 161lbs. I see how installed height effects seat pressure, but is there a way to get a ballpark or a common pressure required? Quote Link to comment Share on other sites More sharing options...
Pyro Posted October 1, 2009 Share Posted October 1, 2009 comp gives a free length and you should know the installed height. so find the difference and use the rate to find the seat pressure. Then add in the pounds at max lift. yes, over the nose is at max lift of the cam. performance flat tappets need 90 to 110 pounds on the seat and around 230 to 260 on the nose mild/moderate performance rollers need 120 to 140 on the seat and 275 to 325 on the nose. Quote Link to comment Share on other sites More sharing options...
dr_hunt Posted October 2, 2009 Share Posted October 2, 2009 (edited) How do you figure spring rates for a cam?http://www.compcams.com/Cam_Specs/CamDetails.aspx?csid=187&sb=2 That's the cam I linked to above. It lists part numbers for two sets of springs, one 322 in/lb and one 344 in/lb, I'm sure both work but I'm curios how you go about finding what is needed. In Vizard's "Small blocks on a Budget" book he says 220-240 lbs is adequate for a street motor and 350 lbs is the maximum. Am I confusing measurements? Cam manufacturers have the spintron and have spent thousands of hours determining the correct spring and installed spring height and what works and doesn't work with their grind of cam. It is really kind of pointless to try to out engineer, out guess, and out theorize the cam manufacturer as to what spring rate, seat pressure and open pressure you should be using. There are guides, which is what Vizards book is about, a general guide. IMO I would use the cam kit as provided by the manufacturer and leave guesswork and theories where they belong and use tried and true solid engineering from the manufacturer. lbs is a measure of force, lb-in is a measure of rate. I think you have it right in what your reading. Stick to the manufacturers cam card and go from there. Interestingly enough if you look at the cam card for the cam I have versus the voodoo grind pn 60104, they use the exact same spring, same installed height and same seat pressure. The GM z/28 spring was 110lb seat pressure and about 325lb open pressure at max lift of .550, works very well with a variety of hyd and solid flat tappet cams, has for years. In actuality you just want enough spring to control the valves during operation, anything in excess of that just is wasted energy and causes heat build up in the oil. Edited October 2, 2009 by dr_hunt Quote Link to comment Share on other sites More sharing options...
bschiltz Posted October 2, 2009 Author Share Posted October 2, 2009 Yeah, I understand what you're saying. I was getting the measurements confused. Quote Link to comment Share on other sites More sharing options...
pparaska Posted October 2, 2009 Share Posted October 2, 2009 Cam manufacturers have the spintron and have spent thousands of hours determining the correct spring and installed spring height and what works and doesn't work with their grind of cam. It is really kind of pointless to try to out engineer, out guess, and out theorize the cam manufacturer as to what spring rate, seat pressure and open pressure you should be using. There are guides, which is what Vizards book is about, a general guide. IMO I would use the cam kit as provided by the manufacturer and leave guesswork and theories where they belong and use tried and true solid engineering from the manufacturer. Definitely agree here - the stuff that's come out of the cam grinders in the last ten years is showing that unstable valvetrain dynamics that they THOUGHT were handled by the springs they had been using were actually giving away a bit of power before they actually hit easily noticable valve float. Lowering the linear inertia (directly related to the mass of things reciprocating) and rotary inertia of the rocker (related to the mass and how far the mass is from the fulcrum) has allowed the spring rates and seat/open forces to get lower or the max rpm go higher. Having beehive valvesprings that don't suddenly go into resonance at some rpm has helped too. The stiffness of the valvetrain parts (rockers and pushrods mostly) need to be high enough too. It's pretty enlightening to see what people have learned with spintrons and dynos using a lighter valvetrain, stiffer parts, and springs with more rate and seat/open force. Sometimes the hp gains appear hundreds of rpm below when the really bad valve float occurs. lbs is a measure of force, lb-in is a measure of rate. I think you have it right in what your reading. Stick to the manufacturers cam card and go from there. rate is actually lb/in (lbs per inch). Torque is lb-in (lbs times inches) or lb-ft. I know doc knows this - just correcting it for those that might be reading this and learning. Us anal-retentive engineers can't let that little stuff just slide by - sorry! Interestingly enough if you look at the cam card for the cam I have versus the voodoo grind pn 60104, they use the exact same spring, same installed height and same seat pressure. The GM z/28 spring was 110lb seat pressure and about 325lb open pressure at max lift of .550, works very well with a variety of hyd and solid flat tappet cams, has for years. In actuality you just want enough spring to control the valves during operation, anything in excess of that just is wasted energy and causes heat build up in the oil. Very true. Heat build up, flexing of the parts that isn't necessary (and takes away from true lift), increased where at the sliding points (cam/flat tappet interface, etc.), accelerated lowering of the actual spring rate (and therefore seat and open force). You have to balance not having so much spring force/rate that you don't cause these things needlessly, versus losing power due to noticable valve float (engine won't rev past it), and probably also losing power hundreds of rpm below that point too. Some interesting reading here: http://www.briggsracing.com/technical_talk/principals_of_valve_springs.pdf Quote Link to comment Share on other sites More sharing options...
dr_hunt Posted October 2, 2009 Share Posted October 2, 2009 (edited) rate is actually lb/in (lbs per inch). Torque is lb-in (lbs times inches) or lb-ft. I know doc knows this - just correcting it for those that might be reading this and learning. Us anal-retentive engineers can't let that little stuff just slide by - sorry! :lmao: Wouldn't expect anything less!!! Very true. Heat build up, flexing of the parts that isn't necessary (and takes away from true lift), increased where at the sliding points (cam/flat tappet interface, etc.), accelerated lowering of the actual spring rate (and therefore seat and open force). You have to balance not having so much spring force/rate that you don't cause these things needlessly, versus losing power due to noticable valve float (engine won't rev past it), and probably also losing power hundreds of rpm below that point too. Some interesting reading here: http://www.briggsracing.com/technical_talk/principals_of_valve_springs.pdf Yup, Pretty cool stuff. Oddly enough in this day and age, titanium retainers are still a good idea IMO and I'd run the same in valves if I won the lottery. If a person was to do some digging on the internet related to pushrod deflection caused by running too much spring pressure you would be amazed at what you might find. Another interesting point is rocker arm stud deflection. I run 7/16" studs on anything over .500 lift. If you delve into this area of deflection, you will find a host of problems that a little attention to parts selection can mean the difference between a winner and a looser. Edited October 2, 2009 by dr_hunt Quote Link to comment Share on other sites More sharing options...
bschiltz Posted October 13, 2009 Author Share Posted October 13, 2009 http://www.summitracing.com/parts/UEM-KB120-030/ http://www.summitracing.com/parts/UEM-9901HC-030/ http://www.summitracing.com/parts/UEM-9902HC-030/ These are three sets of pistons I've been looking at. I'm leaning towards the two valve ones, but I'm not sure which compression height to use. Quote Link to comment Share on other sites More sharing options...
dr_hunt Posted October 13, 2009 Share Posted October 13, 2009 1.561 is factory stock for a 350 with the 5.7 inch rod. The 1.565 will mean the piston is down in the hole .004 more at TDC which effects compression ratio. Quote Link to comment Share on other sites More sharing options...
pparaska Posted October 13, 2009 Share Posted October 13, 2009 1.561 is factory stock for a 350 with the 5.7 inch rod. The 1.565 will mean the piston is down in the hole .004 more at TDC which effects compression ratio. Since 1.565 is a longer distance (more distance from pin bore centerline to piston top), then it would stick above the deck .004" more than a standard 1.561" compression height 350 (3.48" stroke), 5.7" rod engine, correct? But a stock 350 with a 1.561" compression height piston would have the piston .024" down in the hole: 9.02500 - 5.7 - (3.48 / 2) - 1.56100 = 0.024 Quote Link to comment Share on other sites More sharing options...
jt1 Posted October 13, 2009 Share Posted October 13, 2009 You really need to decide which head you're going to use, iron/aluminum and chamber size being the two main factors for comp ratio, then choose your pistons to get the compression you want for what fuel you're going to run. Larger compression height puts the top of the piston higher, good for quench and higher compression. 0.004 isn't much, maybe .2 - .3 point depending. Pick fuel> pick head> pick piston> pick deck height. jt Quote Link to comment Share on other sites More sharing options...
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