The Big Guns are an interesting story. The stage 4 SUM-8709R1 is designed to be the biggest cam that fits without fly-cutting. This worked out pretty well and we released the SUM-8721R1 Saturn Stage 5 for LS7's a few years ago.

SUM-8721R1 is 247/255 114 + 5 and what I used in my TFS 260 headed LS7. It had the typical dip at 3500 caused by the back pressure of my "pretty good" '02 C5Z's factory Titanium cat back exhaust. Simply dropping the back section picked up 30 whp and 20 tq. Not just at peak either - the gains were sizeable from bottom to top. This shows exhaust flow isn't like a magic "cap", but rather a small straw you are forced to breathe through all the time. The 23 degrees of overlap is just too much for the exhaust system I want to use 95% of the time. My "fix" was Summit Vacuum operated cut-outs, but it got us thinking that's just not a reality for 90% of folks who previously accepted this dip as part of running a big cam.

So what's the fix? We brought out the Pro LS Big Guns!

For Reference, Saturn Stage 5 SUM-8721R1 has an Intake closing of 52.5 abdc., Intake opening is 14.5 btdc, Exhaust opening is 66.5 bbdc and Exhaust closing is 8.5 atdc.
Big Gun 1 SUM-8729R1 is a 10 I/O, 50 I/C, 65 E/O, 3 E/C for 13 degrees of overlap. (240/247 115.5 LSA + 5.5 Adv. .625/.605)
Big Gun 2 SUM-8730R1 is a 11 I/O, 51 I/C, 67 E/O, 4 E/C for 15 degrees of overlap. (242/251 116 + 6, .625/.605)
Big Gun 3 SUM-8731R1 is a 14 I/O, 53 I/C, 71 E/O, 4 E/C for 18 degrees of overlap. (247/255 117 + 7 .625/.605)
Big Gun 4 SUM-8732R1 is a 17 I/O, 55 I/C, 72 E/O, 4 E/C for 21 degrees of overlap. (251/255 117 + 7.5 .625/.605)

Intake closing points start at 50 and work up to 55 degrees (for guys with short runner intakes wanting more power around 7500). The biggest 8732R1 is four degrees bigger in duration than 8721R1 yet has four degrees less overlap. 8731R1 actually uses the same lobes as 8721R1, but we clock them differently to remove seven degrees of overlap.

You'll notice the overlap is biased in favor of earlier intake opening vs. later exhaust closing. (This can be spotted in the large LSA and equally large Advance numbers). This is because the intake valve that's opened the most at TDC on the intake stroke is flowing a LOT more air everywhere else on the piston's down stroke. Remember it only has atmospheric pressure to work with these cams. Most of the exhaust is removed on blowdown in those 65-72 degrees bbdc before the exhaust stroke even occurs. The little pressure that is left at tdc. overlap is just unburnable garbage, and you don't want it polluting your intake runner with reversion. This overlap bias would be more conventional like SUM-8721R1 if we were using open headers; but with a full exhaust-the ability to take advantage of wave tuning is nil.

Note we're giving you guys precise valve events along with the logic behind it. No other cam company does this and you may ask yourself "why"? Simply put, the quality of our Made in the USA cams can't be beat and the performance and value is clear. We don't need to make them "mysterious" to sell more cams....at least not yet
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