Summitracing

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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02EBC5Z06

iTrader: (1)

Nice Job Brian!! Love the detail. Now it'll be a matter of whose C5 is on the road sooner

Bob570

Very interesting. I appreciate seeing some of the thought process that goes into these cams.

Double06

iTrader: (1)

I see when you click on details the lifts above are for 1.7x ratio rockers the 1.80s add another .040 to the lift. Nice details.

Summitracing

Thank you, yes we put the 1.8 ratios in the description to make it handy for the Ls7 guys.

G Atsma

I agree! Interesting to see such high LSA's and advance numbers, but they all make sense when you figure the events in.
PLUS these cams should be a bit more civilized compared to others of similar duration and lift specs.

Ryans99ls1

iTrader: (16)

Those are some really nice grinds. Well done!

I think number 2 would satisfy a ton of your average guys that just want a cammed car that sounds good and is fun to rip on. Grinds 3 and 4 are going to lay down some healthy numbers with nice heads and modified aftermarket intakes out there now.

A lot of shops could easily buy these and slap their own label on the box..

conexion914

iTrader: (5)

@Summitracing , do you have any input on using one of the Big Gun cams in a bracket race only scenario?

Specs for the combo so far are as follows:
Gen 3 6.0, 4.005"
Gen 4 rods
Stock crank
Mahle PowerPak flat tops
0821 heads that I'll mill and have a valve job done on and plan to run a thinner gasket depending on measurements
LS3 intake manifold
Long tube headers 1 7/8" or 2" with bullet mufflers
1.80 power glide
5000-5200 8" converter
4.88 rear gear
28x9 drag radial

Thanks in advance for all that you do for us LS guys!

Summitracing

We'd like to make a recommendation but have some questions first.

What's the vehicle?

How much does it weigh race ready with driver?

Are you doing 1/8 or 1/4 mile?

conexion914

iTrader: (5)

@Summitracing It's a 99 Camaro that I'd guess will weigh ~3400 with driver after I account for the iron block versus aluminum that's in it now. I plan to race only 1/8 mile, but if a taller tire lets me get through the 1/4 I may try it out, but primary use and concern is 1/8 mile footbrake bracket racing.

Forgot to mention fuel is e85.

68Formula

Full exhaust or just mufflers @ the collectors? Nitrous?

conexion914

iTrader: (5)

Just mufflers at the collectors. No nitrous at the moment or in the current plans, but if I did it would be a lot and be used high up in the RPM range near the finish line to make a quick position change.

68Formula

Be interested in what Summit says, but I think if you have the valve clearance (and at least 11:5 compression) probably the SUM-8729R1 is the largest. However if clearance is an issue or < 11.5:1 then the SUM-8711. In either case, the LS3 is a great factory intake, but really limits the rest of your bracket-only combination.

conexion914

iTrader: (5)

Thanks for your help. I'm hoping to get compression over 11 or as close to it as I can. Pistons have generous valve reliefs from what I can tell. I have a SUM-8708r1 in my LS1 currently that I could pull and re-use. I've considered a single plane several times and have no issues cutting to make one fit if it would be worthwhile which I'm sure may want something different as far camshaft selection goes.

Summitracing

Thanks for answering our questions. If using the stock LS3 manifold the SUM-8709R1 would be a good fit for this combo and goals. Specs on it are .625/.605, 238/246, 113+3 with 16* of overlap. It's the ultimate cam for use with the factory intake. With the Mahle Powerpak pistons, you'll be good on PTV without milling. It sounds like you're already going to check PTV and proceed from there as far as milling and or thinner head gaskets to get compression up. Pair it with the Trickflow double platinum .660" lift duals with Ti retainers and it'll be happy out to 7,000+.

You'll want some stout pushrods to keep the valvetrain stable. We typically see a 7.425" pushrod used with the 8709R1. Things can vary so we always recommend measuring for pushrod length before purchasing pushrods. If you don't already have a pushrod length checker we offer the Trickflow TFS-9501. For excellent stability and strength check out our 11/32" HDR pushrods with a .120" wall. These have 25% less stress and 28% less deflection than a typical 5/16" x .080" wall Chromoly pushrod.

For a max-effort approach, we could see the stage 5 SUM-8721R1 "Saturn Stage 5" being used here. Specs on it are .625/.615, 247/255, 114+2 with 24* of overlap. This would be where we'd set the barrier for the combo without having more cubes or aftermarket heads. Certainly, check PTV. You should be able to mill and go to a thinner gasket to bump compression but check first and verify how much you can go. You'll have more than enough gear and converter for it. The limiting factor as @68Formula pointed out would be the intake. This would be a combo where we would recommend something like the Holley Hi-Ram or BTR Trinity. The Holley Hi-ram would obviously take cutting, BTR claims the Trinity fits in 4th gens. We'd even like to see one of those intakes with the 8709R1 for this combo and goals. Go with the same Trickflow spring pack and some Summit 11/32 HDR pushrods after measuring for pushrod length.

You're going to be in the 7,500+ rpm range territory here. Shaft rockers, better lifters, and better bolts for the rods should all be considered. A note on the bolts. Re-sizing of the rods and oversized bearings may be required.

Let us know if we can be of any further assistance.

conexion914

iTrader: (5)

That's a lot of great information that I will definitely take into consideration. I forgot to mention that I have ARP rod bolts for the gen 4 rods as well as their main studs and head bolts. I have the 8708R1 currently in my LS1 that's coming out and have looked at the 8709R1 many times. Would you say that link bar lifters and shaft rockers are a must with the 8709R1, or are those more for taking the max effort route with the 8721R1?

Thank you for your help and time, @Summitracing !

Summitracing

No problem and it's awesome that you already have those goodies from ARP! Link bar lifters or shaft rockers aren't a must with the 8709R1. Go with the dual spring pack and pushrods we previously recommended and the valvetrain will be happy out past 7,000.

Che70velle

iTrader: (6)

Brian, any talk of releasing a solid roller lineup for the old school guys looking to party?

Summitracing

We could. I have no doubt they would be great BUT most everyone is going to want something 1 degree and .005 different than anything we put on the shelf It's hard building any sort of consensus so then it becomes a matter of doing a range starting in the high 240's to maybe low 270's. This could be done pretty easily but then the question is lift. What heads and spring packs? .700 lift, .800, .900 etc. etc. Thoughts?

Che70velle

iTrader: (6)

No doubt your right. You would have to be in the custom cam business to cover every setup out there, which you guys aren’t. You’d end up having to shelf 30-40 grinds to cover everyone’s desires more than likely. What I do know is that I see a LOT of high 250 intake/ high 260 exhaust solids being used in the LS world…which after lash isn’t considered a big camshaft.
I was merely wondering if the solid idea had ever been tossed around the water cooler over there.