05-01-2024, 08:55 AM | #43 | ||
GPI Sales Consultant
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An aftermarket manifold and throttle body would no doubt add some additional power from 5500rpm on up, probably adding 15-20 at the peak to get you closer to that 550whp goal. It would also help stand the power after the peak up a little better. That would be my next move on this combination - assuming you're not ready to yank the cam out for something else. I don't think the fuel octane is a major contributing factor here - 93 octane might pick up a small single digit HP gain, and E85 might pick it up 10-15whp, but this is not a high compression setup that should be extremely octane limited. An engine is the sum of it's parts, and in this case the combination is not highly optimized. It's definitely up power over stock, but would take a little more sorting out in terms of parts selections to really deliver your goals. I think with the right camshaft, and a matched intake manifold with 103, you could stand to pick up another 40-50whp pretty easily, along with a broader power curve AND substantially improved driveability. That's not to say run out and make changes, it's already a big gain in power, so I'd go live with it for a while and revisit after the season if you're not happy with it. We're always here at GPI if you decide you want to talk cam options down the road. As far as the lifter preload - it's not going to change the power output in any meaningful way. The lifter pretty well does it's job no matter where in it's preload window it is. Obviously, if it's bottomed out, it's gonna hold the valves open and the engine won't run, and if there is lash (zero preload) it's gonna make a LOT of noise. Outside of that, it's gonna do it's job whether it's at .030" of preload or .130" of preload. Taken a level deeper, the higher preload actually has the benefit of reducing the potential for squish in the lifter body - you can't give up travel that you don't have. That's the concept behind a short travel lifter, it may only have .030" of preload, but then it's only got another .025" of travel left in the body, not much room to squish that cushion of oil (which likely has at least a small degree of air mixed in it that can "squish"). In practice, for a road race application like you have, I would want to minimize preload to somewhere around the minimum piston to valve clearance you have. The idea being that if you do get the valve-train unloaded in an over-rev and the lifter pumps up, you don't have more preload than you do PTVC as to avoid contact. I don't know if you've got a PTVC measurement, but I'd assume it's probably tight with that much overlap, and so a minimized preload would be appropriate on a stick car that does road course work. Just some stuff to think on. Here's some driveability on my setup for comparison. Moderate power NA setups don't have to be miserable to live with when cruising around. https://youtu.be/YLuDiMwtx4E?si=LMhZziHhc69fOutg
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GPI Max Package 2.0: Brodix BR7 heads/GPI porting, MAX3 cam, ST2116LSR, BSR Max Lift rockers, LS7 LSXR with 103mm TB, Vararam OTR, Mcleod RXT, G-Force/Strange 9" IRS setup with 4.63 gear. 551whp, 11.1@124mph.
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05-01-2024, 10:57 PM | #44 | ||||
Drives: Chevrolet Camaro Z28 (2015) Join Date: Feb 2023
Location: Washington state
Posts: 124
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first of all: thank you for the post. I really appreciate your comment and I know you already told me in advance, and to be fair I am glad you were right. It demonstrates your competence in the subject.
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I am ignorant so I might be completely wrong here. Quote:
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2015 Red Z/28. Seattle area |
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05-02-2024, 01:11 PM | #45 | |
GPI Sales Consultant
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IMO, too much preload would be if you're using more than 75% of the lifters total travel. An OEM lifter has right about .200" of travel, so it sounds like your on the "high, but ok" side of that. I wouldn't expect any additional wear as a result. I do think you have an excellent case for working towards a minimized preload for the safety factor on over-rev. Keep us updated - I'm sure the extra power is going to be a blast on the track.
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GPI Max Package 2.0: Brodix BR7 heads/GPI porting, MAX3 cam, ST2116LSR, BSR Max Lift rockers, LS7 LSXR with 103mm TB, Vararam OTR, Mcleod RXT, G-Force/Strange 9" IRS setup with 4.63 gear. 551whp, 11.1@124mph.
Got a question about a GPI product? Feel free to shoot me a message! |
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05-02-2024, 06:18 PM | #46 |
Drives: 62 Chevy II, 63 F100, 16 2500 LTZ Join Date: Oct 2023
Location: Wetumpka
Posts: 8
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Posting because I also have a Texas Speed cam in my car, put in by previous owner. It's smaller than yours at 234/246, .635 X .635 and 115LSA +3 lift, LS7 rockers, TSP .660 dual spring kit and Comp LS Rocker Trunion upgrade kit. Mine has the MSD Atomic Air Force 103mm intake and Nick Williams 102mm throttle body, Bosch 52lb fuel injector set and MSD spark plug wires. It also has Dynatech 2" headers with straight pipes and full 3" exhaust with a Dynatech cat back. BTW, my car still has the stock LS7 heads and just flipped over 10K miles
I just had it dyno tuned on Monday since the mods were done 8+ years ago in Wisconsin and I live in Alabama. I could tell the car was running rich on the original Wisconsin dyno tune, and was hard to drive as it wanted to quit when taking off in first gear, making it a real safety hazard when pulling into oncoming traffic. Anyway, that got resolved by leaning it out some and increasing the idle a little. I'd post a video of the last dynotune run but the file's too big to save from my phone to my desktop. I'll try and open facebook on my phone and see if it will let me post that way. Anyway, I'll post the dynosheet if I can figure out how, but max power was 574 & max torque was 529... |
05-02-2024, 06:36 PM | #47 |
Drives: 62 Chevy II, 63 F100, 16 2500 LTZ Join Date: Oct 2023
Location: Wetumpka
Posts: 8
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05-02-2024, 06:39 PM | #48 |
Drives: 62 Chevy II, 63 F100, 16 2500 LTZ Join Date: Oct 2023
Location: Wetumpka
Posts: 8
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Link to dynosheet
https://www.facebook.com/photo.php?f...9251229&type=3
The baseline pull was the original Wisconsin tune, not the stock tune. I gained 23 rwhp and 22 rwt over the Wisconsin tune and gained a lot of drivability. And by the way, my tuner said the LS7's get a little better dyno numbers in a Z06 vs Z28 because of the Z28's taller rear gear (3.91 vs 3.42)... Last edited by BamaGearSlama; 05-02-2024 at 06:51 PM. |
05-18-2024, 11:10 PM | #49 |
Drives: Chevrolet Camaro Z28 (2015) Join Date: Feb 2023
Location: Washington state
Posts: 124
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my tuner found a dyno session for a Z06 with exactly same cam (and original LS7 heads) and he did 540whp... so 0.3 more than me. I guess that's what this cam does.
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2015 Red Z/28. Seattle area |
05-18-2024, 11:17 PM | #50 |
Drives: Chevrolet Camaro Z28 (2015) Join Date: Feb 2023
Location: Washington state
Posts: 124
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here's a flyby on the track
before my car you hear a couple other cars (didn't check which ones but I think there was a Cayman and a M3)... then the sky opens to let the mighty LS7 scream. https://youtube.com/shorts/8vcrLYPgE_4
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2015 Red Z/28. Seattle area |
05-25-2024, 03:44 PM | #51 |
Drives: Chevrolet Camaro Z28 (2015) Join Date: Feb 2023
Location: Washington state
Posts: 124
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I don't have much updates. I've been on the track once since I put the cam and I ruined a tire in about 10 minutes, so I had to cancel the track day.
What I can say is that the car is fast (not sure about faster, but for sure the z/28 is fast) to the point that I had an entire session in my instructor Porsche GT4 and I was totally underwhelmed by the power . It is supposed to have 400hp but it really felt "slow". clearly lap times were much better because of slick tires, light car and racing suspensions... but power-wise it was nothing special
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2015 Red Z/28. Seattle area |
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