Cam gurus: overlap question
02-09-2007, 09:34 PM
#21
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Originally Posted by Ragtop 99
My cam made 344 on a mustang dyno on the stock exhaust. very flat torque curve and go throttle response even at 2000 rpm.
I agree that with a good exhaust, you can run less exhaust duration. I didn't see it in your sig. Given what you just described, a 214/220 111 109 would be something to consider. I don't know how fast the LPE lobe ramps are, but they probably aren't as fast an the combo of an XFI/Xer, so that will help idle a bit too. Doing it on a 112 LSA would bring it down to -7 overlap and ensure a clean tune.
I agree that with a good exhaust, you can run less exhaust duration. I didn't see it in your sig. Given what you just described, a 214/220 111 109 would be something to consider. I don't know how fast the LPE lobe ramps are, but they probably aren't as fast an the combo of an XFI/Xer, so that will help idle a bit too. Doing it on a 112 LSA would bring it down to -7 overlap and ensure a clean tune.
Just so you know the rest of the setup Im at 10.5:1 scr heads are stock milled, 5 angle job, bigger valves and unshrouding 2.0 on the intake, 918 springs currently have 32k miles on em not sure I want to push the lift.
Your saying the more aggressive lobes help with overlap?
02-10-2007, 01:44 AM
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Hmmmmm, I called a local tuner today, and he seemed to think that there would be no problem getting my car to run fine with my cam and a stock stall. I'll prolly just go for it, and hope for the best. (By the way, when I say stock stall, i'll have a built trans before the cam swap, with a tougher converter as well, it'll just be the stock stall speed.)
02-10-2007, 02:14 AM
#23
Originally Posted by 09CPTN
Hmmmmm, I called a local tuner today, and he seemed to think that there would be no problem getting my car to run fine with my cam and a stock stall. I'll prolly just go for it, and hope for the best. (By the way, when I say stock stall, i'll have a built trans before the cam swap, with a tougher converter as well, it'll just be the stock stall speed.)
02-10-2007, 08:13 AM
#24
The faster lobes such as the XFI have less overlap at .006 This allows you run a couple degrees overlap more on the faster lobes and still achieve the same idle quality as the slower XE lobe. It is not a huge gain, but an extra 1* or 2* of overlap seems important given that you have tuning issues.
With the 10.5 CR, a IVC = 36 will be about as early as you need to go if you go with the faster ramps of an XFI. I think you'll be surprised that the 214/220 111 109 or a 214/220 112 110 would both really pull hard down low. I'd even think about going 214/220 111 111. You still gain down low and the cam will carry well up top. If you order the cam with no advance, you can install it with an adjustible chain. If you still need more power down low, you can advance it 2* after having tried it for a couple weeks.
My last thought is that with a 218/220 112 109 (XFI/Xer) you'll pick up enough down low and have a strong midrange. This is -5 overlap and that may be enough reduction to cure your tuning issues.
With the 10.5 CR, a IVC = 36 will be about as early as you need to go if you go with the faster ramps of an XFI. I think you'll be surprised that the 214/220 111 109 or a 214/220 112 110 would both really pull hard down low. I'd even think about going 214/220 111 111. You still gain down low and the cam will carry well up top. If you order the cam with no advance, you can install it with an adjustible chain. If you still need more power down low, you can advance it 2* after having tried it for a couple weeks.
My last thought is that with a 218/220 112 109 (XFI/Xer) you'll pick up enough down low and have a strong midrange. This is -5 overlap and that may be enough reduction to cure your tuning issues.
02-10-2007, 08:36 PM
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Originally Posted by Ragtop 99
The faster lobes such as the XFI have less overlap at .006 This allows you run a couple degrees overlap more on the faster lobes and still achieve the same idle quality as the slower XE lobe. It is not a huge gain, but an extra 1* or 2* of overlap seems important given that you have tuning issues.
With the 10.5 CR, a IVC = 36 will be about as early as you need to go if you go with the faster ramps of an XFI. I think you'll be surprised that the 214/220 111 109 or a 214/220 112 110 would both really pull hard down low. I'd even think about going 214/220 111 111. You still gain down low and the cam will carry well up top. If you order the cam with no advance, you can install it with an adjustible chain. If you still need more power down low, you can advance it 2* after having tried it for a couple weeks.
My last thought is that with a 218/220 112 109 (XFI/Xer) you'll pick up enough down low and have a strong midrange. This is -5 overlap and that may be enough reduction to cure your tuning issues.
With the 10.5 CR, a IVC = 36 will be about as early as you need to go if you go with the faster ramps of an XFI. I think you'll be surprised that the 214/220 111 109 or a 214/220 112 110 would both really pull hard down low. I'd even think about going 214/220 111 111. You still gain down low and the cam will carry well up top. If you order the cam with no advance, you can install it with an adjustible chain. If you still need more power down low, you can advance it 2* after having tried it for a couple weeks.
My last thought is that with a 218/220 112 109 (XFI/Xer) you'll pick up enough down low and have a strong midrange. This is -5 overlap and that may be enough reduction to cure your tuning issues.
