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| Help with cam choice https://slantsix.org/forum/viewtopic.php?t=50210 |
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| Author: | Mike_64_Valiant [ Thu Nov 01, 2012 1:32 am ] |
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8.0 DCR is pretty good area to be for at sea level for regular pump gas. And at denver alt. Its probbly 7.3-7.5ish so that can still be peppy. But if you are in CO mainly and not sure if you will be back to CA why not up the DCR allittle for CO and just run higher octane if you ever find your self back in CA. |
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| Author: | robertob [ Thu Nov 01, 2012 5:51 pm ] |
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I was thinking that too.... Maybe I should aim for 8.0 at my altitude and take out timing if I move back. |
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| Author: | robertob [ Tue Nov 13, 2012 2:08 pm ] |
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I just decided to go all the way and buy the Wiseco/K1 combo. Less machining will be needed (hopefully) and therefore less opportunity for someone else to screw up. I'm going to tune for this altitude, premium gas and a shim gasket, then if I move back to CA I can get a thicker gasket and advance the cam if I need to. Now I'm thinking a DCR around 8.5-8.75 at my altitude, so intake closes 36-42 degrees ABDC (at .050 lift) using the RBR racing calculator. That was the only one I could find that has an altitude corrector. The OCG 346 cam would close (.050) at 39 degrees installed straight up, so according to the rbr calculator and building the motor 'to spec' with the Wisecos at 10.4:1 I will have a DCR at my altitude of 8.64:1. Or at sea level of 9.64:1 (yikes!). Does that sound right? |
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| Author: | 1974duster kev [ Wed Nov 14, 2012 8:17 pm ] |
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I used the erson 270 on the 108lsa with 10:1 compression worked fine on regular gas drove it everyday about a year later put a bigger cam in  I like lumpy idles though. So if you used the erson 270 on a 114lsa that would cut back on some of the overlap and probably be very mild, considering i thought the e270 108 lsa wasn't to radical at all.Kev |
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| Author: | robertob [ Fri Nov 16, 2012 8:08 am ] |
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I called OCG and asked them about the 346 cam profile working with Mopar diameter lifters. He said, "Well there is only one way to find out, isn't there?" Not confidence inspiring. I gotta see if I can get ahold of someone at Erson. Does any other company make slant-specific cams? |
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| Author: | DusterIdiot [ Fri Nov 16, 2012 5:12 pm ] |
| Post subject: | Cam sheet |
I called OCG and asked them about the 346 cam profile working with Mopar diameter lifters On the OCG cam sheet they should have recorded the lifter diameter of the cam checking lifter...All the ones I've had reground they checked with a mopar lifter (.904)...and they are on target with lash, but can go a smidge tighter or looser on the bigger cams... -D.Idiot |
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| Author: | Mike_64_Valiant [ Fri Nov 16, 2012 9:45 pm ] |
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Ok I must be missing something here. But how does the diameter of the lifter effect anything? I understand if the length or hight of the lifter changed it would make a diffrence. Am I missing something form engine building class? |
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| Author: | robertob [ Fri Nov 16, 2012 11:29 pm ] |
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A larger lifter can use an opening/closing ramp that is more aggressive than a smaller lifter. So a cam designed for a chev-diameter lifter leaves some duration or lift on the table compared to one designed around mopar lifters. |
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| Author: | emsvitil [ Fri Nov 16, 2012 11:48 pm ] |
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The greater the lifter diameter, the more aggressive the lobe opening and closing profile can be (more area under the curve, less time to fully open valve). |
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| Author: | Mroldfart2u [ Sat Nov 17, 2012 1:25 am ] |
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This diameter bidness going on in the other thread has me confused too. Its the thread about valve lash for anyone wanting to read... if you dont check all the posts daily... |
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| Author: | wjajr [ Sat Nov 17, 2012 6:02 am ] |
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Miscellaneous ramblings: Having never thought about this lifter diameter difference before now, and cogitating on it regarding crank degrees at opening and closing event; I think a wider lifter contacts ramp sooner than a thin lifter, and stays on the ramp a bit longer at the end of event than a thin one. How much difference this makes I would guess depends on slope of ramps as to of duration valve is open. The other aspect to this I’m reading between the lines is one cam profile used for several different engine makes, of all of which use different diameter lifters. Therefor a particular cam in a Chevy will have slightly different event degrees than say a Ford or Chrysler. Old cogitater |
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| Author: | DusterIdiot [ Sat Nov 17, 2012 8:49 am ] |
| Post subject: | Yep... |
Quote: The other aspect to this I’m reading between the lines is one cam profile used for several different engine makes, of all of which use different diameter lifters. Therefor a particular cam in a Chevy will have slightly different event degrees than say a Ford or Chrysler.
Welcome to Comp Cams basic lobe selections... |
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| Author: | robertob [ Sat Nov 17, 2012 10:46 pm ] |
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Anyway, what this means in practice that you can get more area under the curve (more airflow), with absolutely no downsides, if the cam is designed to take this into account. If the cam you are using is designed around a Chev .842 lifter then no benefit because the velocity will be slower than possible with the Mopar .904 lifter.[/i] |
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| Author: | Dart270 [ Sun Nov 18, 2012 4:34 am ] |
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Also keep in mind that a given motor may not respond well to faster ramps and necessarily give more power with faster ramps. The flow and intertia of the gases entering and leaving the cylinder involve many factors. The most HP recorded on a NA gas motor (and maybe alky too?) has/have used slow ramp regrind cams. My point is that agonizing a lot over this concept will at best make a minor (possibly unmeasurable) difference, and your time and effort are probably better spent elsewhere. If you are curious though, by all means think away!! Lou |
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| Author: | Charrlie_S [ Sun Nov 18, 2012 6:23 am ] |
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A couple of years ago, I spoke to a couple of cam companies, at the pri show, about having a cam ground to optimal specs for a "Mushroom" lifter. The general consensis was, it "MIGHT" give better performance the a standard .901 lifter, but would not be cost effective, except for a max effort "class type car", that does not allow rollers.. I was thinking it would be an improvement over a "regular" cam, and less expensive then a roller cam. It is not required to have a lobe "master" these days. As long as a blank is available, the more advanced cam companies, can computer design a lobe profile, and transfer that design to a computer controlled grinder. But it ultimately comes down to trial and error, in the engine. As Lou stated there are many variables. Even the diameter and length of the headers, and intake can make a huge difference, in the cam profile, and vice versa. One of the cam company reps gave me his personal number, and said if/when I was serious about this, to call him. But not untill, I had this info, complete engine data, including flow numbers, intake, and header details. Drive train info. weight, Dyno numbers with a current cam, so he would have a baseline to design around. |
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