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C6 Corvette ZR1 & Z06General info about GM’s Corvette Supercar, LS9 Corvette Technical Info, Performance Upgrades, Suspension Setup for Street or Track
The max coil bind distance that I use is .100". I like to see between .080" - .060". If you call PAC, and talk to Chris, he will most likely suggest the same. No way would I go more than .100", unless I was looking to loft the valves.
Doesn't Katech use the 1511ml with their 501 cam?
If you are using OEM rockers and valves, 120 seat load is enough.
They do, and I'm shocked the 1511s can control an LSL lobe in this application. If it works on LSLs, I can't see why they couldn't control the LXL/HUC lobes on the BTR cam.
They do, and I'm shocked the 1511s can control an LSL lobe in this application. If it works on LSLs, I can't see why they couldn't control the LXL/HUC lobes on the BTR cam.
Isn't the lift of the K501 more than the BTR 3? Like .660 lift I think..
I talked to BTR and of course they recommend their .660 Duals, but the guy that I talked to didn't seem to know much about it other than what his computer told him.
Putting together everything for my cam swap here next month! I am going BTR Stage 3, when I did my heads last year I used PSI 1511ML springs to keep the valvetrain as light as I could, So my question is can I use those springs...?
That's the exact combo I used in my previous setup. I chose that cam because I think BTR did a great job selecting the Comp profiles that put less strain on the (somewhat troubled) LS7 valve train.
I actually upgraded the pushrods to heaviear Comp .135" wall items (weight 99 g vs. OEM 68 g) to reduce flex and raise their nominal frequency and still had plenty of spring force reserve left. Hard limiter was at 7400 rpm, power curve was flawless (within 2% between 6000...7200 rpm) and during some clutch trouble the engine saw 7600 rpm without any signs of contact in the pistons. I did several standing mile events with that setup and never had a single issue with the valve train.
I had both the stock LS7 cam and BTR stage3 measured in CamDoctor equivalent, measured the springs, measured the component weights, got the intake rocker inertia from 3D model, took the worst case effect of the other forces (static and dynamic pressure over the valve + lifter plunger force) into account.
I calculated the force curves for the oem setup @7100 rpm (oem hard limiter) to see how much spring force reserve there is in the oem setup. I also compared to Katech Sprintron results where the first signs of instability started to show up for another benchmark point. Naturally the effect of nominal frequencies for the whole system is another story, this exercise was just to confirm the dimensioning for the basic dynamic loading.
This is what oem intake side looks like (existing forces on the cam lobe):
Spring could support 17..18% higher forces from the valve train @7100 rpm. Valve float could be expected at around 7850 rpm.
This is how the three different aftermarket springs behave on the intake side with BTR stg3 cam and 99 g Comp pushrod setup @7400 rpm:
Springs could support higher forces from the valve train as follows:
- BTR Platinum 48%
- LS1511 33%
- LS1515 52%
However, more is not always better, but in order to keep this post short I'll stop here.
Last edited by barum; 07-08-2018 at 08:10 AM.
Reason: Attached images instead of hosted images
That's the exact combo I used in my previous setup. I chose that cam because I think BTR did a great job selecting the Comp profiles that put less strain on the (somewhat troubled) LS7 valve train.
I actually upgraded the pushrods to heaviear Comp .135" wall items (weight 99 g vs. OEM 68 g) to reduce flex and raise their nominal frequency and still had plenty of spring force reserve left. Hard limiter was at 7400 rpm, power curve was flawless (within 2% between 6000...7200 rpm) and during some clutch trouble the engine saw 7600 rpm without any signs of contact in the pistons. I did several standing mile events with that setup and never had a single issue with the valve train.
I had both the stock LS7 cam and BTR stage3 measured in CamDoctor equivalent, measured the springs, measured the component weights, got the intake rocker inertia from 3D model, took the worst case effect of the other forces (static and dynamic pressure over the valve + lifter plunger force) into account.
I calculated the force curves for the oem setup @7100 rpm (oem hard limiter) to see how much spring force reserve there is in the oem setup. I also compared to Katech Sprintron results where the first signs of instability started to show up for another benchmark point. Naturally the effect of nominal frequencies for the whole system is another story, this exercise was just to confirm the dimensioning for the basic dynamic loading.
This is what oem intake side looks like (existing forces on the cam lobe):
Spring could support 17..18% higher forces from the valve train @7100 rpm. Valve float could be expected at around 7850 rpm.
This is how the three different aftermarket springs behave on the intake side with BTR stg3 cam and 99 g Comp pushrod setup @7400 rpm:
Springs could support higher forces from the valve train as follows:
- BTR Platinum 49%
- LS1511 34%
- LS1515 54%
However, more is not always better, but in order to keep this post short I'll stop here.
That's great info! I ended up going with the BTR .660 duals, but had I known this I may have just kept the 1511's. Thank you for putting that all together and hopefully it can help others if they happen to be in the same situation!
I'm curious how you did that? CMM? Can you do the same for other rocker arms?
I think it was done manually. I'll be training my own 3D CAD skills, but typical aftermarket roller rockers (LS7 T&D/Comp for example) seem to be relatively easy to model to get the inertia.
More important thing is that the relative effect of the rocker inertia is low. Here are relative average "masses" for intake OEM valve train components in the BTR stg3 + Comp Cams pushrod case:
If the rocker inertia would be double, the spring force reserves (as listed at the end of my previous post) would drop by about 10..11 percentage points.
@7400 rpm the oem rocker inertia converts to ~68 lb peak force (on the cam lobe) during the opening/closing ramps, but more importantly, ~38 lb force in the area which is most critical for spring dimensioning.
For the record, should the oem retainer be replaced by the Katech titanium item, the maximum (theoretical) rpm raises by ~100 rpm.
As a side note, PSI LS1511ML springs are really quality items, here are the measurements after 8000 miles:
Last edited by barum; 07-08-2018 at 08:09 AM.
Reason: Attached images instead of hosted images
Ok, here's a quick sketch of the roller rocker shown above with some features from the LS7 version:
It has 150% higher inertia compared to LS7 oem item, even though the rotating mass is only 30% higher.
Each part contributes to that as follows:
- Adjuster bolt 10.7%
- Adjuster nut 4.7%
- Roll 27.3%
- Roll axle 18.2%
- Aluminum body 39.0%
The force reserves with same BTR stg3 + comp pushrod setup @7400 rpm using this roller rocker would be
- BTR Platinum 31%
- LS1511 18%
- LS1515 35%
Last edited by barum; 07-08-2018 at 08:10 AM.
Reason: Attached images instead of hosted images
02-24-2017, 01:05 PM
Good stuff in here...
