[Redlinez]

I'm no cam expert, but could it have anything to do with ground in advance?

[PRAY]

Originally Posted by Redlinez

I'm no cam expert, but could it have anything to do with ground in advance?

Everything adds up but usually when you go with smaller cams overlap will carry the day. I have these like cams in LS2's and 3's and they carry much higher. It is just really weird how the hp curve takes a crap so early. Just trying to narrow things down a bit.

[Redlinez]

Is it leaning out any up there? I've heard of some cylinder heads "stalling" at certain rpms. I think you mentioned valve float as well.

[KingLT1]

Originally Posted by PRAY

Everything adds up but usually when you go with smaller cams overlap will carry the day. I have these like cams in LS2's and 3's and they carry much higher. It is just really weird how the hp curve takes a crap so early. Just trying to narrow things down a bit.

Do you think it might have something to do with VVT?

[slick3]

Floating the valves? Have you tried a heavier weight oil? Not sure if its a wives tale or not.

[DFW1LE]

I wonder how much you could shift power to a higher RPM by retarding a few degrees and how that might affect area under the curve?

[PRAY]

I just spec'd a new cam for my car to push a couple limits. We will see what happens.

Widening lobe sep, retarding the cam and other things will help the top end.

I haven't tried heavier oil. But I am thinking oil pressure has some to do with the issues I am seeing. How exactly I haven't put my finger on yet.

My heads flow very well with no stalling till .650". Not sure if that is what you meant.

[Redlinez]

Yep. I'm just winging things I heard many years ago, I'm by no means super knowledgeable about it. Look forward to seeing the results. I plan to finally make a track visit to Rockingham the 24th.

[JaxChris]

Sorry, my brain is going to wander on this, but I hope it is helpful to the conversation at large that this question is opening the door to.

With a phaser limiter installed, I don't think there is enough retard range left to push above 6800rpm and usually power will peak 400-500rpm before that.

A LS3 which had stock phasing of 52 degrees could not go over 7000rpm when a 22 degree limiter was installed. The Gen V LT1 achieved power using a wider phasing range of 60 degrees. When that is limited to 20 degrees, it brings the max RPM down to just under 6800rpm.

A valvetrain upgrade and new pistons would be advised to clear the top and bottom of the valves when rolling past 7000rpm. If you want above that, a lighter/balanced rotating assembly is needed to raise the inertia limit. If going above 7500rpm, then you would want to look at de-stroking the motor to shorten the cycle time. At that point you'll be good for very close to 8000rpm. You'll be giving up a chunk of peak torque, but you'll have the ability to push well over 700rwhp NA and your top speed will be increased to supercar levels (which is unsafe with the SS Camaro's Cd and leading edge aero -- that speed should be reserved for the Corvette, which can actually handle it).

This is why euro-exotics have more cylinders at smaller strokes to drive power and rpm range higher, to achieve higher top speeds. Larger displacement will create more power within the same, smaller rpm band which makes too much power too fast. With the displacement and rpm range of the SBC design, you can't run any street tires above 500ft/lb to the wheels in NA without it being a smokey mess. After that, you really have to look at going to progressive boost to provide high end only supplement that eases in. That is why ProCharger is actually the best drag solution for large american V8's.

The Mustang Coyote 5.0 is very different from the SBC, well beyond the DOHC vs OHV debate. Ford opted to take the european approach to power by limiting the cycle time of the rotating assembly. This allows for a lighter assembly and spec'd valvetrain on those motors to go up to 9500rpm. The problem with smaller displacement in that situation is that they need boost to compress the intake so that enough air and fuel makes it into the chamber to continue increasing power all the way up to that limit. But their valvetrain is definitely more secure than ours being that they are DOHC -- though 4 cams is more expensive than 1 and timing is even more critical for them.

So yea, this is why all I want from my Camaro is a modest NA kit that provides 600hp/500tq to the wheels, without the added weight of boost/meth/etc. The car is already so damn good, that is all you need (along with the right handling touches) to put it on the level of cars 3-5 times its price. And that is why I always like to jab Pray to stay NA, because his work is more important than all the shops on here turning out the same boosted builds that are frankly unsafe in any situation off of a drag strip. I don't want a torque "shelf" on the dyno graph, I want to see an actual curve so that power comes in at a controllable pace on the street and the track.

No racer here wants 600+tq from 2500rpm, because exiting a corner under throttle would be insane. Give the 1LE a power bump and watch it beat the ZL1 'ring speed. Give it ride height adjustment and more aero and watch it beat the ZL1 1LE too.

I still want the 10R90 as an option on the SS 1LE for 2019, because I can't do clutches anymore.

[KingLT1]

LS3 never had VVT...and it has been spun over 7k many times. You must be talking about the L99.

[boostednut]

Originally Posted by PRAY

I just spec'd a new cam for my car to push a couple limits. We will see what happens.

Widening lobe sep, retarding the cam and other things will help the top end.

I haven't tried heavier oil. But I am thinking oil pressure has some to do with the issues I am seeing. How exactly I haven't put my finger on yet.

My heads flow very well with no stalling till .650". Not sure if that is what you meant.

What kinds of runner lengths have you tried? I would try that next in conjunction with a different cam. Get as short as you can go on there, maybe even itb with a snouted airbox for the maf. Have the oem DBW TB plugged in on the side so it will run. If a super short runner still gives you the same issues, the problem is definitely in the heads.

I don't know much about the dimensions/angles of these heads but I wonder if changing port angles will help. I feel like I haven't seen much in the ways of re castings that have more aggressive port geometry. I feel like that would be really helpful on a DI engine.

[PRAY]

The L99 cars spin just fine as well. There seems to have been a Phaser redesign for the LT1 cars from the L99 cars that doesn't work as well. I am running 0* phaser limiters now anyway so VVT is basically a moot point now.

I was talking with James Goertz last night about this issue in a round about way. The MSD has a 7" runner. I have maximized mine in every way possible. The stock GM manifolds runner number 1 and 7 are 7" as well. The rest of the runners are around 11". He was saying that it will probably take something in the 5" runner range to spin to 7,500 or so. There would be a significant loss to in low and mid range tq though. But he was saying that a 7" runner would still do very well on a 376" motor. You could still make good mid range with a strong top end. It could come down to a plenum volume issue with the MSD. I have a feeling had they designed it like the LS7 offering we could have seen a better product. For the Camaro there is still a lot of space under the hood that wasn't utilized. So it appears that it could be a cam spec issue or possible an IM volume issue with the MSD even though they got the runner length correct.

Here is my thought about valve float or something like that. If you notice on the LT1's your oil pressure shoots up to around 80psi or higher by around 5K at WOT. In my logs the engine starts to get noisy around 6,500and is in full revolt by 6,800 and at that point shows a max effort of KR. I get a 10* spike right at 6,800 and there doesn't seem to be anything I can do about it. So either the valve springs are collapsing the lifters and getting noisy or the oil pressure is overcoming the hydraulics in the lifter and going solid. Either way, something is going on in the engine that is causing major issues. Until I can keep the motor happy and quiet up top I don't think it is going to pull to my desired rpm levels.

[boostednut]

Originally Posted by PRAY

The L99 cars spin just fine as well. There seems to have been a Phaser redesign for the LT1 cars from the L99 cars that doesn't work as well. I am running 0* phaser limiters now anyway so VVT is basically a moot point now.

I was talking with James Goertz last night about this issue in a round about way. The MSD has a 7" runner. I have maximized mine in every way possible. The stock GM manifolds runner number 1 and 7 are 7" as well. The rest of the runners are around 11". He was saying that it will probably take something in the 5" runner range to spin to 7,500 or so. There would be a significant loss to in low and mid range tq though. But he was saying that a 7" runner would still do very well on a 376" motor. You could still make good mid range with a strong top end. It could come down to a plenum volume issue with the MSD. I have a feeling had they designed it like the LS7 offering we could have seen a better product. For the Camaro there is still a lot of space under the hood that wasn't utilized. So it appears that it could be a cam spec issue or possible an IM volume issue with the MSD even though they got the runner length correct.

Here is my thought about valve float or something like that. If you notice on the LT1's your oil pressure shoots up to around 80psi or higher by around 5K at WOT. In my logs the engine starts to get noisy around 6,500and is in full revolt by 6,800 and at that point shows a max effort of KR. I get a 10* spike right at 6,800 and there doesn't seem to be anything I can do about it. So either the valve springs are collapsing the lifters and getting noisy or the oil pressure is overcoming the hydraulics in the lifter and going solid. Either way, something is going on in the engine that is causing major issues. Until I can keep the motor happy and quiet up top I don't think it is going to pull to my desired rpm levels.

I really feel like there's something going on with your manifold. On all the little import motors having the right runner length and plenum volume is pretty critical otherwise the car just flattens out up top. Might still need valvetrain upgrades because pushrod but still.

I don't have any first hand experience with pushrod motors but aren't the ls7 hydraulics able to handle some extra RPM? How different are they from the lt1? Also aren't there some kind of issues at high rpm with the cam timing? Do you have a phaser limiter installed? GPI has some talk about high rpm issues. I don't know the specifics of your setup so just asking to learn

When retarding timing at the top of the RPM range, we noticed a frequent variation between our desired cam position and the actual. Sometimes it would even retard timing when not commanded to at all.

Next, we found that this behavior was becoming more and more exaggerated as the oil temps reached higher levels. This was leading to 8-10 degrees of timing retard, and power falling off at the top end after several pulls – which is obviously undesirable (you certainly don’t want each run of the night to be slower than the previous!).

We had successfully found the problem, but this was only the start.

It was time to build a new Cam Phaser Limiter Kit…

This was leading to 8-10 degrees of timing retard, and power falling off at the top end after several pulls – which is obviously undesirable (you certainly don’t want each run of the night to be slower than the previous!).
.

[PRAY]

Originally Posted by boostednut

I really feel like there's something going on with your manifold. On all the little import motors having the right runner length and plenum volume is pretty critical otherwise the car just flattens out up top. Might still need valvetrain upgrades because pushrod but still.

I don't have any first hand experience with pushrod motors but aren't the ls7 hydraulics able to handle some extra RPM? How different are they from the lt1? Also aren't there some kind of issues at high rpm with the cam timing? Do you have a phaser limiter installed? GPI has some talk about high rpm issues. I don't know the specifics of your setup so just asking to learn

The LS7's should be good. That is what I run in all of my cam kits. But I would think that any hydraulic lifter can eventually be over come by valve spring pressure.

I have a 4* degree phaser limiter in my car and the rest of the cam kits now come with a 0* phaser limiter. Interestingly enough. My cam retards a couple degrees non commanded. But the 0* shows the same fall off.

Something is getting noisy in there and causing the knock sensors to go nuts. That is happening on both motors.