OP,

That's a good way to get a ballpark idea of seat-to-seat duration, but we'd be a little hesitant to rely on a general rule for adding a set number to the @0.050" duration.

• Seat-to-seat duration is the actual point where the valve just starts to open and fully closes.
• Advertised duration is measured at a small lift point like 0.004", 0.006", or 0.010", which varies by manufacturer.
• @.050" duration is a standardized measurement across the industry, making it the best way to compare cams.

That said, we do look at advertised duration when calculating DCR, since it helps gauge cylinder pressure, octane requirements, and gives an idea of ramp rate. But beyond that, we focus more on @.050" duration for comparisons since it removes inconsistencies between manufacturers.

Also, the manufacturing article that @1FastBrick linked to is exactly what we’d point to for insight into our Pro LS camshafts. Our Pro LS cams are 100% made in the USA from 5150 steel cores, and the article gives a great breakdown of how they're designed and manufactured for precision and durability.

If you're open to going to .600"+ springs we'd seriously look at our SUM-8728R1 for this combo and goals. We mentioned it in posts 6 and 8.

Here's an example idle video of the 8728R1 in an L33 (5.3) application.

We appreciate the discussion. It's always interesting to dig into how these cams behave in real-world applications!

 

Thats a truck i rebuilt a LM7 5.3 for.
Its a Stock 5.3 freshened up with just this cam and springs.
https://cammotion.com/in-stock-ready...208-214-110-4/
https://cammotion.com/valve-spring-k...ve-spring-set/

That video was still on the stock tune, It was the first fire up and i couldnt send him the video over text so i uploaded it and sent him a link. (andriod to Iphone issues)

Truck has cats and dual 1.75" straight pipes out the back. And 3.42s/35" tires .
Its much better running than his old stock worn out L33 was so improvements.
The cam is just enough he can hear it at idle and he was happy.

 

Yes sir, fully aware of what all the cam specifications mean. The calculator I use needs seat to seat duration to figure a dynamic stroke, displacement, and compression ratio. Also figures overlap. And since I'm not building a max effort et motor or anything and it's all just for comparison, it's all fun and games. I saw what I wanted to see and chose the 8719R1. Was never going to install a cam with more than 209 degrees intake duration @ .050".

So cam and springs are on the way from summit. Making slow but steady progress otherwise.

Have a buddy straight piping my headpipes. Trying to decide if I want/need a pair of shorty headers right now.

Awesome thanks for posting.

 

OP,

Sounds like an awesome build coming together! We appreciate your order and can’t wait to hear how the 8719R1 performs for you. The straight-piped headpipes will free up some HP. Shorty headers could be a nice touch too, depending on your setup. Keep us posted, and thanks for choosing Summit Racing!

 

Little bits of time here and there, it's so close...

 

FYI, Don't leave that type of tape on there too long. It breaks down and won't come off in 1 piece.

 

@Summitracing @1FastBrick

It's alive. Triggered a P0342 and a P0343. Both disappeared. Now keeping a P0341. Two different new cmp sensors have been in the block.

The pcm in the truck had some mild tuning in it from before all of this with the stock engine, but not sure if other specific settings must be tweaked as part of the cam swap.

Is there a known issue and fix?

 

CKP variation learn appears to have resolved the P034x DTC's. Put a few miles on it today.

Vitals all good. Nothing leaking.
Threw a P0300 earlier, but idling little while ago misfire counters were all zero.
Drives out very smooth, very nice.
Trailblazer converter is tighter than i thought it would be.
Needs engine and trans tuning optimized.
Haven't let it rip yet but will soon.

Last time this truck drove (except to load onto trailer knocking like crazy) was 12/31/24. Recapping the changes since then...

120k mi donor L59 refreshed/resealed and cammed/springed
8719R1 cam, LS6 springs, hardened pushrods
Rebuilt/beefed up 4L60E
TB converter
Cat delete
Video

 

That's awesome 👍. Great job!

 

Thank you. This was a big deal for me never been inside a gen III engine before. Main takeaways... easier than old school sbc and weird to work on an engine with metric tools.

But i spoke too soon, still getting cmp sensor codes.