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cam spec understanding...kind of
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Author:  mopardemon71 [ Thu Dec 27, 2007 9:35 pm ]
Post subject:  cam spec understanding...kind of
so i'm looking at my cam choices and i believe i'm going with a schneider cam. My buddy likes the split lift of .496/.501 because of the "71% rule". I believe Doc said he didn't like the split lift configuration and said he liked an equal lift. ie .496/.496 pattern lift. My buddy says that the extra lift on the exhaust side is due to poor exhaust port efficiency, and that 71 % of the intake charge is what is needed to be expelled from the cylinder to promote proper volumetric efficiency. When i asked if making the exhaust port flow better would help make more power, he said that they have spent billions of dollars and this is the best combination available for a N/A motor. Now, who wants in.............. :twisted:
Author:  Joshie225 [ Thu Dec 27, 2007 11:44 pm ]
Post subject: 
Has your friend built any slant race engines? Those that have tend to favor a little more intake duration and lift. I would only run more exhaust duration (actually open the exhaust valve sooner) for a nitrous motor. Since I'm planing on a little N2O for the 1/4, but mostly just cruising I'll be running a single pattern cam.
Author:  terrylittlejohn [ Fri Dec 28, 2007 11:39 am ]
Post subject:  cam timing
i think your friend has it backwards,on a slant you need less lift and duration on ex side to help the piston on the bottom of the power stroke before ex stroke start so it`s timing is delayed untill the next power stroke starts on the next cylinder in firing order. i am going to try a comp custom grind 278dur int/.498 lift and 264dur ex/.464 lift, this only helps on the low end performance, more torque, hp will be the same compared to a even lift cam. thats my understanding but this is my first try at it so it might be for nothing. :?
Author:  Doctor Dodge [ Fri Dec 28, 2007 7:04 pm ]
Post subject: 
Quote:
...I believe Doc said he didn't like the split lift configuration...
Just about all the custom cams I have made these days are "dual pattern" cams and most of them have more intake duration then exhaust.
DD
Author:  argentina-slantsixer [ Fri Dec 28, 2007 7:33 pm ]
Post subject: 
prior to selling my project, I contacted tom about having their hottest cam reverting the dual pattern. That was (custom cam) 294°/286° 246/242 @0.50 with .510" lift and 112° LSA with 108° ICA. This cam with tripple webbers 45/45 and 11.5 - 12:1 SCR woul have render above 300 HP wich is not bad for a N/A car. Coupled to a 3.31 to 3.54 rear end ratio and a solid bottom end, I would have been way into the 6000 rpm redline and the torque and power curves where very nice (simulation program) with maximum area below those curves. My 2 cents.
Author:  mopardemon71 [ Fri Dec 28, 2007 8:29 pm ]
Post subject: 
I wasn't bustn' on you Doc :D . Well I think that are a few diffeent ways to look at it but thee maybe some truth tomy friends ranting. I would ten to think that the exh. may open sooner in the cycle but I'll check the cam card again and se. He hs never built a slant but is no stranger to a 300 ford so he' played with inline stuff. I'll run these fact buy him and see wha he says. Thanks and later
Author:  slantzilla [ Sat Dec 29, 2007 6:21 am ]
Post subject: 
Quote:
Has your friend built any slant race engines? Those that have tend to favor a little more intake duration and lift. I would only run more exhaust duration (actually open the exhaust valve sooner) for a nitrous motor. Since I'm planing on a little N2O for the 1/4, but mostly just cruising I'll be running a single pattern cam.
My next motor will be getting a nitrous cam with a lot more exhaust duration. :D :D
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