turbogrill Posted May 29, 2018 Share Posted May 29, 2018 Hi, In terms of performance, what is the difference in going from a moderate (0.480" lift) to high lift (0.540") cam given that the duration is the same? Does the higher lift only make sense if your head is ported for it? From what I understand a mild clean up on the head really helps on the lower lifts but doesn't do much at higher lifts, reshaping of the ports are needed for that. Rebello has a few cams with similar duration but with different lifts. I guess the lower lifts are for "budget" builds where stock pistons and less care to the valve train is required? Quote Link to comment Share on other sites More sharing options...
theczechone Posted May 30, 2018 Share Posted May 30, 2018 Talk with Dave if you are thinking of going with his cams, he's quite helpful. As far 540 or 480 lift the difference will be negligible unless you have done quite a bit of porting. And it's a small gain for a lot of added complexity. I just got the 480 cam because i am doing an amateur port job and just learning as i go, plus less than $500 for cam regrind, lash pads, springs, and rockers resurfaced... tough to beat that. BTW this is plotted on 87mm bore 79mm stroke L28 with 10.5 static CR n42 stock flow n42 ported flow Quote Link to comment Share on other sites More sharing options...
turbogrill Posted May 31, 2018 Author Share Posted May 31, 2018 19 hours ago, theczechone said: Talk with Dave if you are thinking of going with his cams, he's quite helpful. As far 540 or 480 lift the difference will be negligible unless you have done quite a bit of porting. And it's a small gain for a lot of added complexity. I just got the 480 cam because i am doing an amateur port job and just learning as i go, plus less than $500 for cam regrind, lash pads, springs, and rockers resurfaced... tough to beat that. BTW this is plotted on 87mm bore 79mm stroke L28 with 10.5 static CR n42 stock flow n42 ported flow That's some cool graphs. How did you calculate them? Did you estimate the 0.50" lift? Quote Link to comment Share on other sites More sharing options...
JMortensen Posted May 31, 2018 Share Posted May 31, 2018 (edited) What are these graphs supposed to show? HP and torque with the .480 vs .540 cams on stock and ported heads? If that's what it's supposed to be, I have to say I don't think they're very accurate at all. My takeaway from these graphs would be that porting is a waste of money, but my personal experience and the experience of a lot of the people on this and other forums is that the L heads benefit A LOT from porting. Put in a couple grand on porting and looks like you're estimating 7 hp and 7 lb ft return. Same on the camshaft itself. If going with .060" more lift nets you 7 hp, I think the larger cam profile is leaving something to be desired. As to the original question of which cam to use, I think .480 is right in that zone where you have to do the work anyway (needs different valve springs and retainers and stem seals to prevent coil bind and prevent the retainer hitting the seal). If you're going that far, I'd spring for the bigger cam. And if those cams only have 5 hp peak difference between them, find a better larger cam. Edited May 31, 2018 by JMortensen Quote Link to comment Share on other sites More sharing options...
turbogrill Posted May 31, 2018 Author Share Posted May 31, 2018 Would the .540 cam be beneficial in with a head that only has a diy cleanup (smooth out the vale bowl) and not a extensive port? Seems like mild home porting typically improves flow at lower lifts, but over 400 the flow saturates. (Where a race port is different). Its easier to deal with 480 lift, probably no valve relifs, only outer spring, maybe stock retainer and the ford seal. Please correct me if I am wrong. Quote Link to comment Share on other sites More sharing options...
theczechone Posted May 31, 2018 Share Posted May 31, 2018 8 hours ago, JMortensen said: What are these graphs supposed to show? HP and torque with the .480 vs .540 cams on stock and ported heads? If that's what it's supposed to be, I have to say I don't think they're very accurate at all. My takeaway from these graphs would be that porting is a waste of money, but my personal experience and the experience of a lot of the people on this and other forums is that the L heads benefit A LOT from porting. Put in a couple grand on porting and looks like you're estimating 7 hp and 7 lb ft return. Same on the camshaft itself. If going with .060" more lift nets you 7 hp, I think the larger cam profile is leaving something to be desired. As to the original question of which cam to use, I think .480 is right in that zone where you have to do the work anyway (needs different valve springs and retainers and stem seals to prevent coil bind and prevent the retainer hitting the seal). If you're going that far, I'd spring for the bigger cam. And if those cams only have 5 hp peak difference between them, find a better larger cam. If you have some port flow numbers for stock and ported heads I’ll gladly update my plots. But this is the numbers I was able to find. keep in mind that larger cam will make less torque but peak will happen at higher engine speed therefore generating higher horsepower. Big cams benefit from high compression ratios, 10.5 is relatively low. So unless you’re changing other components the net benefit of a larger cam is low and kills drivability. Quote Link to comment Share on other sites More sharing options...
Leon Posted June 1, 2018 Share Posted June 1, 2018 7 hours ago, turbogrill said: Would the .540 cam be beneficial in with a head that only has a diy cleanup (smooth out the vale bowl) and not a extensive port? Seems like mild home porting typically improves flow at lower lifts, but over 400 the flow saturates. (Where a race port is different). Its easier to deal with 480 lift, probably no valve relifs, only outer spring, maybe stock retainer and the ford seal. Please correct me if I am wrong. Put me down for using the bigger lift cam. Max lift isn't one of many aspects of cam design. Holding duration constant, you will have a more aggressive ramp with the .540" cam, meaning you will achieve higher lift per crank angle. More area under the curve equals more flow due to a decreased flow restriction. Porting also decreases flow restriction and has an additive effect. Not sure what you mean by the flow "saturates". I run the Isky L6 grind (270 duration/.540" lift). I use flat-top pistons, without valve reliefs, and stock retainers along with Isky springs and whatever Chevy valve stem seals Rebello uses. Quote Link to comment Share on other sites More sharing options...
madkaw Posted June 1, 2018 Share Posted June 1, 2018 13 hours ago, Leon said: Put me down for using the bigger lift cam. Max lift isn't one of many aspects of cam design. Holding duration constant, you will have a more aggressive ramp with the .540" cam, meaning you will achieve higher lift per crank angle. More area under the curve equals more flow due to a decreased flow restriction. Porting also decreases flow restriction and has an additive effect. Not sure what you mean by the flow "saturates". I run the Isky L6 grind (270 duration/.540" lift). I use flat-top pistons, without valve reliefs, and stock retainers along with Isky springs and whatever Chevy valve stem seals Rebello uses. Did you ever measure piston valve clearance with your combo Leon? Quote Link to comment Share on other sites More sharing options...
JMortensen Posted June 1, 2018 Share Posted June 1, 2018 From: i just got my e31 head from sunbelt, am putting it on tomorrow. the printout i received showed the following data: stock (head before any work) port flow: .......................intake.................exhaust .425" lift...........158.9 cfm...........110.2 cfm .525" lift...........163.5 cfm...........118.4 cfm (.525" lift never reached with the cam i had in it) final port flow: .......................intake.................exhaust .425" lift...........180.6 cfm...........129.3 cfm .525" lift...........201.6 cfm...........145.1 cfm according to sunbelt, 200cfm by their flowbench (flow pro) is 225cfm by anybody else's (super flow). the cam jim set me up with has a lift of .520, and powers from 3500 - 7200. i think the duration is around 280. this is the max lift (valve-piston clearance) you can put in a 3.1 stroker without cutting valve reliefs into the pistons (using a 2mm gasket). the stroker kit produces a positive deck height of .025". hopefully i can dyno the car this week and let you know what this puts to the ground with a 3.1 LD28. i have pics, but won't post until i have guidelines since i remember john coffey saying something about sunbelt not liking that. john coffey, my 3,4 exhaust ports do look "funny" (but why do that only to cyl 3 and 4?)and i have single springs. all in all, i'd say ~225cfm per cyl is pretty damn good for an e31...i cant wait to hear and feel it! Quote Link to comment Share on other sites More sharing options...
Leon Posted June 1, 2018 Share Posted June 1, 2018 2 hours ago, madkaw said: Did you ever measure piston valve clearance with your combo Leon? Yeah, it's in my build thread: I used the Silly Putty again for my valve-to-piston clearance and came up with approximately .080" for exhaust and (with .012" lash at valve) .100" for the intake (.010" lash at valve). Works for me. Quote Link to comment Share on other sites More sharing options...
theczechone Posted June 4, 2018 Share Posted June 4, 2018 On 6/1/2018 at 3:50 PM, JMortensen said: From: i just got my e31 head from sunbelt, am putting it on tomorrow. the printout i received showed the following data: stock (head before any work) port flow: .......................intake.................exhaust .425" lift...........158.9 cfm...........110.2 cfm .525" lift...........163.5 cfm...........118.4 cfm (.525" lift never reached with the cam i had in it) final port flow: .......................intake.................exhaust .425" lift...........180.6 cfm...........129.3 cfm .525" lift...........201.6 cfm...........145.1 cfm according to sunbelt, 200cfm by their flowbench (flow pro) is 225cfm by anybody else's (super flow). the cam jim set me up with has a lift of .520, and powers from 3500 - 7200. i think the duration is around 280. this is the max lift (valve-piston clearance) you can put in a 3.1 stroker without cutting valve reliefs into the pistons (using a 2mm gasket). the stroker kit produces a positive deck height of .025". hopefully i can dyno the car this week and let you know what this puts to the ground with a 3.1 LD28. i have pics, but won't post until i have guidelines since i remember john coffey saying something about sunbelt not liking that. john coffey, my 3,4 exhaust ports do look "funny" (but why do that only to cyl 3 and 4?)and i have single springs. all in all, i'd say ~225cfm per cyl is pretty damn good for an e31...i cant wait to hear and feel it! I would need more info than just two points and at what vacuum pressure were these flowed. would also need more cam info to define the profile. need to know crank rotation for exhaust and intake valve events. This is the flow numbers i have found and i am using Quote Link to comment Share on other sites More sharing options...
theczechone Posted June 4, 2018 Share Posted June 4, 2018 On 5/31/2018 at 8:27 AM, turbogrill said: That's some cool graphs. How did you calculate them? Did you estimate the 0.50" lift? You can generate them with DesktopDyno it's a simple math based program but it can show trends. It's not perfect but you can learn a lot about the effects of changing components on your engine. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted June 4, 2018 Share Posted June 4, 2018 (edited) Fair enough, I can see how just a peak flow wouldn't be sufficient. I think something that is fairly instructive though is zredbaron's first stroker build which IIRC has had a small cam and no porting and made something pitiful like 160 whp vs his current one with the ported head and very particular cam profile that puts out 270 whp. He's a details guy, might PM him and see if he still has the rest of the specs you need on those flow numbers. Edited June 4, 2018 by JMortensen Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.