Summitracing

Thanks for your feedback. We'll get some samples and see what we find. We'll try to dig up some comparable parts and compare hardness and finish on those as well.

Summitracing

Hello all, we pulled random samples off our shelf and checked piston to valve clearance on the largest three of the latest Summit Pro LS cams. We used a box stock LS3 with little run time because it has true flat tops and the large intake valve diameters (compared to cathedral ports). This particular engine has .128 in. intake valve-drop, .007 in. positive deck, a .054 head gasket and we used checking springs for this test. We tested from TDC to 20 degrees in 2 degree increments, but the closest points were at 8 degrees I&E on all three cams. Generally we recommend for .060 intake clearance and .090 in. exhaust, but you'll see others run a little less or a little more..

Our Stage 3 LS3 cam (SUM-8710 230/242 113 +3 .625/.605) had .081 in. intake and .103 in. exhaust clearance.
Our Stage 4 LS3 cam (SUM-8711 234/247 113 +3.5 .625/.605) had .076 in. intake and .096 in. exhaust clearance.
We have another Stage 4 cam (SUM-8709 237/246 113 + 3 .625/.605) that's a little larger even yet and is primarily considered a Cathedral port cam, but will work well on a Rectangle port engine as well. It measures .061 in. on the intake and .092 in. on the exhaust. This is tight and we wouldn't recommend any head milling at all.

We wanted to share this with you to give you an idea of how much the heads could be milled. Keep in mind, we ALWAYS recommend checking piston to valve clearance before milling heads and final installation. Valve drop varies between heads and this is with a new timing chain, These particular cams happen to have a 110 ICL and thats where they ended up going in with a standard GM timing gears.

Sebambam

I am happy to see summit pullung off good LS CAMS.
I had good experience with summit sbc solid cams in the past.
i wonder if any of your pro ls cams have been CA smog tested? None of the cams seem to pass just by the specs.
on the other hand what woukd be your suggestion
to a LS1 (stock) with longtubes?
(valvetrain spring upgrade for sure)

And LS1 with ls6 top end and cnc ported 235 cfm ls6 heads. Longtubes

as nasty as possible for a street car!!
WILD IDLE BRUTE POWER MIX.

car is a manual C5.

98CayenneT/A

Currently running the Summit bushing trunnion and it is definitely a nice set.

Summitracing

Yes, none have been smog tested and aren't for legal for sale or use in Pollution controlled vehicles. Summit Racing has been actively working on C.a.r.b. approved projects though -so stay tuned. I don't know that such a cam would ever be described as a WILD IDLE BRUTE POWER MIX though

Alex_olds

Great read!!

Sebambam

is there any of your cams that you recommend for my setup?
Ls1 with ls6 top end and longtubes.
Looking for a agressive sounding and performing street cam

Summitracing

If your engine and drivetrain were swapped into a non-pollution controlled vehicle BUT you're still a very environmentally conscious individual...the answer gets a little easier in theory.

Idle and part throttle response are mostly a function of intake opening (half the overlap equation). It's a little more important than the exhaust valve closing part. This is because Idle vacuum will be highly negative and exhaust pipe pressure will be slightly positive. Flow wants to go the wrong way (at idle and part throttle especially). At WOT, the pressure differential is much closer and why overlap becomes a positive thing.

The way a lot of sleeper cams work is to close the the exhaust valve before tdc. You still get the benefits of later intake closing and slightly earlier opening...which are the most important events.

Where else will you see this happening? Turbo cams! Especially single turbo cams (for similar but more critical reasons). Our SUM-8706 Stage 2 turbo cam would be an example of this (2 degrees of overlap is pretty minimal with valve timing events similar to a Sloppy stage 2 cam). It's a little on the large side though because the intake is opening at 4btdc.

Although we are working on our own lineup, Summit Racing equipment carries a number of great turbo cams from Cam Motion, Comp, Howard's and others that are single pattern or reverse split. About the easiest thing to do would be to do a search on Gen. 3/4 turbo cams and limit your intake duration to 220 and below with wider lobe separation numbers. I hope this is helpful.

V8 Supra Builder

iTrader: (37)

I saw your SUM-8712 when looking for a fairly mild cam for my 5.3 LM 4 swap going into my Durango. I saw where you are coming out with a higher lift version SUM-8719. It is not on your site. Do you have an ETA for that cam, will it be the same price, and do you think it would be worthwhile in my setup? Details:
1998 Durango, about 5K pounds. 4x4, 3.92 gear sets, 4L80 trans, stock stall converter.
2004 LM4 aluminum block 5.3L Gen 3 V8, stock 862 heads (can change springs if needed, it looks like the 8712 does not require that).
LS2 intake (for height/clearance) and generic 96mm throttle body.
1&3/4 long tube headers, 3" single exhaust.

Smog is not an issue where I am.

Summitracing

Thank you for your interest. The SUM-8719 Stage One High-Lift LS Vortec Truck Swap cam will be available for sale roughly Oct. 10 with shipments going to our Ohio, Georgia, Texas, and Nevada locations for immediate pickup. It would be perfect for what you're doing and will make a ton of additional power for the money. It has the same cam timing as the drop-in SUM-8712 at 209/217 112 + 1. I/C 36, I/O -6, E/C -4, E/O 42 and it nets -10 deg. overlap. We designed the lobe profile for compatibility with durable LS6 springs and it has .550 lift. As much as the lift helps, the LS6 springs will extend the rev range to match the cam timing. Power goes up as expected, but the ability to make strong power to 6500 adds a bunch of power under the curve and extends it out for better overall acceleration. It is priced at $259.99 like the SUM-8712 stage one drop-in cam. Once again, Made in the USA with USA steel on a Landis 3LB with a CBN diamond grinding wheel for outstanding lobe quality. It was important for us to release the part number and specs a bit early just in case someone bought a SUM-8712, but would have preferred the extra lift.

G Atsma

Going by your numbers, overlap actually works out to -11 degrees.
209 + 217= 426 which divided by 2 is 213.
112 LSA x 2 = 224.
213 - 224 = -11 degrees.
Sound right to you?

Summitracing

You sir, have brought up one of the many exciting challenges of creating a cam line. To be the engine, we must think like the engine.... and it only understands individual valve events. It's kind of primal and doesn't care about human concepts like Duration, LSA, Centerlines or Advance. So our first step was to determine the individual valve events we wanted and let the Duration/LSA/Advance/ICL/ECL/Overlap numbers fall where they may.

What do those numbers look like on a cam card? As much as we hate rounding, we left the numbers in full one degree increments instead of .25 or .5 degree numbers. In the case of the SUM-8712 and SUM-8719, the numbers are IVO -6, IVC 36, EVO 42, EVC -4. If we enter those numbers into a calculator, it might tell you it's a 210/218 112 +1 instead of 209/217 112+1. Why is that?

The cam lobe designer doesn't like to round much either to get their lobe dynamics right. Frankly we'd rather have them get the lobe right than split mathematical hairs so they have a window. IVO between -5.5 to -6.25, IVC between 35.5 to 36.25, EVO between 41.5 to 42.25, and EVC between -3.5 to -4.25. Looking at both lows or both highs on the IVO/IVC and EVO/EVC would tell us we have 210/218 lobes. In reality they were both skewed between the closer of the two points resulting in a 209.25/217.25 cam with 10.5 degrees of overlap. We've labeled it a 209/217 duration as it's closer to reality than compromise and call it a 210/218. Stacking these rounding errors helps explain why Duration/LSA/Advance/Overlap numbers get skewed in a hurry and it's best just to think of them as concepts.

Another thing to mention is the lobes are asymmetrical. If we used the physical centerlines to degree a cam, the individual events will be slightly off. Although professional engine builders may measure it CL's, many will make their final adjustment by setting the intake closing event where they want it....as it's the most important of the four.

I hope this was helpful. Doing this can make a persons head hurt, but that's why we're trending toward individual events to give the greatest level of accuracy. Be the engine. Think.....like the engine.

G Atsma

Oh OK, I got in trouble because of the way the numbers got rounded. Thanks for clarifying!

V8 Supra Builder

iTrader: (37)

Thanks for the reply. I can wait for the high-lift version since my project is still underway.

Mike Morris

iTrader: (55)

I hope you are not using Comp to machine your cams. Good luck with your line. The specs look great!

Summitracing

Thank you for the compliment Mike. We can't disclose our vendors, be we added a link to the manufacturing article at the beginning of the thread. The cams are ground on a Landis 3LB with a Diamond wheel. With the resulting lobe quality, they require just a very very light polishing to get to finished state, so we're not disturbing the lobe itself.

G Atsma

You don't have to disclose who IS grinding your cams, but you CAN say who is NOT. And by saying Comp is NOT grinding your cams will have a lot of guys around here breathing a lot easier...

Summitracing

Only so many people grinding cams in the USA, so we can neither confirm nor deny. The graph at the end of the manufacturers article showing the Pro LS vs. average is easily confirmed though and should set people at ease.

G Atsma

TSP, Cam Motion, Comp... and Isky. Maybe a few others....

wannafbody

iTrader: (2)

I recently talked to an engine builder who worked for a major manufacturer race team. He was a big fan of Comp cams. He was somewhat suspicious about the quality of another cam manufacturer. I'm not saying his opinion is correct in either case but it was interesting to talk to him.

I've seen cases where someone had a problem and the manufacturer stood behind their product and fixed the issue. I think that would be the case with Summit.