Cam Gurus Chime In? Coming to an End Making sure on Cam for my Stroker!!!
#41
Lets think about this .........Overlap helps fill the cylinders using the exhaust pulse negative pressure. You DONT want overlap allowing the falling piston to pull exhaust gas into the cylinder. You want that big stroke to create the negative pressure in the intake ports and manifold, which will respond better to a later IVC event, which means a wider LSA.
#42
Lets think about this .........Overlap helps fill the cylinders using the exhaust pulse negative pressure. You DONT want overlap allowing the falling piston to pull exhaust gas into the cylinder. You want that big stroke to create the negative pressure in the intake ports and manifold, which will respond better to a later IVC event, which means a wider LSA.
" The current cam will make peak HP at 6100 RPM on your engine. It just doesn't have much duration and the 106 ICL will have the intake valve closing pretty early. this makes some low end TQ but will kill top end power on an engine this size. it is a good 6500-6800 RPM cam for a 355 or "maybe" a 383. It is really small for a 396/410/414, etc. The bigger stroke just wants more duration and definitely a later IVC (wider LSA with higher ICL).
Here are how the HP #'s compare at 6000, 6500 and 7000 RPM with both cams . . .
240/250 - 596-584-563 (peak at 598 HP @ 6100 RPM)
247/255 - 630-627-610 (peak at 632 HP @ 6250 RPM)
TOO MANY variables to know the EXACT RWHP or even Fly Wheel HP #'s but with all things being equal (heads, intake, TB, headers, exhaust, etc, etc) you can still expect to see the difference in HP mentioned above from a cam swap (34, 41 and 47 HP at 6000, 6500 and 7000 RPM).
A 247/255 (280/288 adv duration) .668/.668 112 LSA cam will work much better.
You will see an extra 30-35 HP from 6000-6500 RPM and over 40 HP from 6500-7000 RPM over the current cam with about 25 HP at 5500 RPM, 15 HP at 5000 RPM and around 4500 RPM. Below 4000 RPM, the Cam Motion cam will make a lil more power and be 20-25 RWTQ better in the 2500-3000 RPM range where the cam is seeing its biggest improvements over the 247/255 cam that I spec'd fpr you.
These RWHP/RWTQ comparisons are based on the lobes that you currently have and ignoring the fact that the ramp speed is VERY aggressive and will be hard on parts. If we slow the cam down to a comparable ramp speed, the Cam Motion stacks up even worse"
I called and got further info after I got the email, but now maybe you see why I was going the direction I was going with my cam, I was basing it off of the info I got from Lloyd Elliot, reguarding a 112 LSA, and later ivc point etc. I dont remember him saying things about on most motors running such short LSA having so much carbon, and sut in intakes because the intake is being filled with exhaust gasses, and it contaminating so to speak the intake charge (that is not quoted, I am just going off of memory on that stuff, because I asked him why not use a tighter LSA and that was what he told me, to some degree, and how it makes for slightly more difficult tuning, and etc...) He also told me in talking that this would keep me under the 7000 RPM shift point, and keep power from falling off after peak, ie going through traps. FWIW, his specs actually did not even give up much down low on simulator, compared to the smaller tighter Cam Motion Grind, I think at most was 22lb ft somewhere in the early 2000 area, but it did show to pull harder up top and make more power.
This is where the cam stuff is like a black box sometimes, Toby says tighter LSA Faster ICL, and so did T&L, but LE has been tried and true with LT1 cars uses a totally different method to accomplish what looks to be the same goal, with what theoretically should be a smoother running engine ie the wider LSA.
This situation is what brought this thread to life, for me. The motors I based my build on went one way, LE sent me another, and here I am in the middle.
What say you guys now!
Luckily I was able to sell my cammotions cam, the lifters together, but at one point it was looking like I should have kept it listening to all the input. Selling it did give me the opportunity to throw around running these SR lobes with HR lifters, this may be a perk of it all .
#43
Lets think about this .........Overlap helps fill the cylinders using the exhaust pulse negative pressure. You DONT want overlap allowing the falling piston to pull exhaust gas into the cylinder. You want that big stroke to create the negative pressure in the intake ports and manifold, which will respond better to a later IVC event, which means a wider LSA.
#44
Hey I actually like this Idea it seems to work well, and even at a 108 +4 it was only down (about 18/23 hp/tq respectively) slightly compared to a 244/248 using the lobes I speak of at 108 +4, and I am to probably guess that is only because of acceleration rate, and a little additional lift...
#45
THANKS TO ALL WHO HELPED IN COMING TO SOME SORT OF CONCLUSION WITH CAMSHAFTS; I HAVE DECIDED TO GO WITH LLOYD ELLIOT AND HIS LT1 KNOWLEDE, SINCE HE DID SOME WORK FOR ME ALREADY AND HAS EXPLAINED HIS REASONING FOR HIS DECISION. WE HAVE SELECTED A 247/255 AS HE SUGGESTED, WITH MID 660's lift on both intake and exhaust, and we kept the wider LSA. I am very confident in the choice and feel good about it.
I hope to get this thing put together by the next month end.
Thanks guys
I hope to get this thing put together by the next month end.
Thanks guys