Any chance its running out of fuel on the top end?

Use holley to find efi tuners https://www.holley.com/local_speed_shops/ Just put in your state and pick EFI dealers.

Here is my build
https://www.thirdgen.org/forums/ltx-...6-carnage.html

 

It was mentioned but never heard if you've done a compression test.

 

I think I have enough fuel. Injectors are at only 50% duty cycle. If the pump were struggling then I suspect the injector duty cycle would sky rocket trying to supply the target fuel.

No, I've never done a compression test. I did a "cold engine" cylinder leak-down test once and it was good. Never did the "hot engine" test.

 

Might not be a bad idea...

 

Even a straight pipe presents a restriction. Make it 10' long, add about 360° worth of bends and stick a muffler full of baffles on the end and I think it would add up to plenty of restriction.
And that's part of the problem with the 3rd gen platform. The OEM single pipe, single muffler configuration is difficult to manage once the HP goes up. 1000 CFM for 500 CHP isn't easy to come by. Start reducing that flow value and you start to limit the power potential.
Yes, this guy or that guy makes a kajillion horsepower through his mufflers but maybe A) he has 2 kajillion worth of CFM or B) he'd make 1.5 kajillion HP with a better exhaust.
I'll be clear and state that I'm not saying that this is Qwik's problem. It could be any number of things. Pulling timing was a interesting thought. Cam timing too although I think the latter would produce a different dyno graph. Maybe it's valve springs?
But in almost any of these cars, the single exhaust with high horsepower is always suspect. Even little horsepower guys suffer.

 

I don't see you exhaust holding back a lot of hidden HP with your crazy low end torque the cam must be advanced to much.

 

I doubt the 50 HP that is suspected of being AWOL. Then again that's only 10%. A small number when you put it in that context.

 

Yeah, a lot of things to chase down. Even the chain can stretch and cause you fits.
Has the reluctor wheel ever been touched?
I thinks this is where you ask someone who does this all day/every day to troubleshoot. They've likely seen all the scenarios.

 

I don't think anything is broken or malfunctioning. Keep in mind it still hauls the mail.

I'm chasing ideas related to tuning, parts mismatch, and cam install.... in that particular order.

 

Got on another dyno and ran a baseline;
then removed muffler but kept the exhaust pipes;
and then ran open headers with 2-foot extensions.

Removing muffler picked up a small bit of power but all the scenarios died out at the same rpm. In fact, it lost a lot of mid-range torque without exhaust and accelerated noticeably slower.

Ignore all the vertical lines on the chart. That is from the dyno strip chart continuing to log during deceleration after one of the runs. The remote control didn't turn off the log after the run.

I am guessing that everything is pointing at the engine combo itself.

 

What timing set are you running? I was just at the dyno shop yesterday and he was telling me about a guy that was there with a LS swap car wanting a tune so they ran it and it was a total dog then the car owner tells them he put in a adjustable timing set so they take the cover off and he had it retard like 5 degrees they fixed it for him and then it ran perfect.

 

Exactly. Next step is to look at how the cam is installed.

 

Just quit messing around. Na motors are junk. Boost that bitch!
its the best of both worlds. Don't have to build a crazy motor when u boost it!!

 

I'm with you on the combination and/or the variables in the assembly itself. The latter being cam timing, the former being the general pile of parts and how they compliment one another.
That said...

You can't add some arbitrary length to the collector and expect anything but an arbitrary result. The difference between the best HP/TQ numbers and worst HP/TQ numbers is as little as 9" in the difference. It could well be that you picked the worst. Witness this PipeMax screen shot and examine the collector length analysis near the bottom of the shot.
In fact, I'll go out on a limb and say that you analyzed what was needed regarding collector length, you would see a significant increase in power and torque. I realize though that's not likely to happen at this point. (My previous offer still stands)
But I'll repeat, I'm not saying that your woes are the result of an under performing exhaust. My opening statement illustrates my agreement with your assessment. But I think you'll find that, once you've zeroed in whatever is ailing your engine, there will be room for improvement from the headers back.

 

The extensions were simply to keep fresh air off the O2 sensors.

If the exhaust was a cork in the system it would have shown up. Quick and dirty, that's all I was going for.

 

Fair enough. Although the extensions might have made things worse.
It'll be interesting to see what you discover.

 

Ya, I was hoping it was exhaust..... easy fix.

The thought of digging in to the engine again just about makes me face palm. I want a break from the "project" side of this car.

 

I guess I am in control of that, aren't I? Car runs fine whether I touch it or not.

 

True enough.
I'm always trying to keep it in the context of a being a hobby. Many months go by, something or other is in pieces (yet again) and I pay little to no attention to it. Then there are times when the car is running great (like now) and I'll take it apart for an "improvement" (possibly this weekend). And there it might sit again...
It's a struggle!
Right now though, the Camaro is actually my daily driver while I try and access what the hell is wrong with my Tahoe. I'll tell you, the car is far easier to work on than that truck.

 

Well, guys, I just bought an LS7 so..... I guess this is the first post of my new build thread.

Cool thing is there is no pressure because the car is still a driver until I'm ready to swap power plants.

 

As in a crate GMPP LS7?

 

As in low miles used. It is a pull-out from a well-known, reputable race shop where the customer wants an LSx-based stroker or something like that. Unusually good deal that I couldn't pass up. Some things stayed with the car but nothing that mattered to me.

 

I go away for a little bit and you wreck your car and are now swapping engines again

Nice score on the LS7. Does it have any work done to it or is it stock? I think there's an issue with the valve springs (exhaust?) failing even on stock engines. May want to look into it, just passing info.

Are you still going to use the Holley system?

 

Ya, it is stock as far as I know. Sending the heads off to be decked, ported, and get new valve guides installed (resolution to the exhaust valve falling issue). Unless I'm lucky enough that the previous owner already did it! We'll see after it arrives.

An LS7 short block goes for good money so I'm also looking in to option of using that to fund a re-sleeved LS3 short block. However, I see that ERL closed that side of the business and don't know where to go for something like that.

Yes, keeping the Holley HP EFI. As far as I can tell it looks pretty straight forward to change from 24x to 58x timing system. Shouldn't take more than a weekend to do the entire swap if I get my ducks in order ahead of time.

 

Not sure if you aware but the holley hp has a 2 step feature built into it in the rev limiter section be great for the 1/4 launches.

 

Ya, I know. I bought a spare brake/cruise switch to rig it up on the clutch pedal. Never installed it though because a two-step is only useful if you can launch. My car won't launch.

 

What? so now LS7? damn! can't wait to see what you do with it!

 

Tried to take the car to the body shop for repairs but had to turn around and barely made it back to my garage. Something is wrong and the engine is running like crap. Some of the datalogs are corrupt and crash the HP EFI software. The one datalog that will open has time gaps in the data.

I'll tell ya, it's been one thing or another the last few months.

 

I know the feeling all too well.
Mine is nothing more than a body shop (!) and some exhaust work won't fix though (this time).
I hope you get to bottom of whatever glitch there is and are back to the swap soon.

 

LS7 arrived and is hanging on the engine stand. 90 hours on the clock with only 4% - 6% leak down on each cylinder.

 

Package deal with the front struts? LoL

 

Nice find. You get all the dry sump components too?

So much for the "break from the project". We all look forward to it 😉

 

No, it came just as you see in the picture below. I am converting to wet sump.

I got the engine from Phoenix Performance. They do some serious road track car builds. In this case they are swapping for an LSx engine and kept the things still needed for the Z06 car. Pretty much the only things missing are the things I was going to change anyway, or things I was going to re-use from my current engine.

It wouldn't surprise me if the original owner already did cylinder head upgrades. I just need to figure out how to visually identify if that is so.

 

I ended up rewiring my alternator today because I have had a lot of issues with the alternator turning off intermittently. I thought it was repeated alternator failures, but after 3 alternators, and about to trade in for the 4th under warranty, I finally had to be honest with myself and admit there was something wrong with my wiring.

I had previously run the alternator excitation circuit through the "SERVICE ENGINE SOON" light bulb in my dash, Post #312, https://www.thirdgen.org/forums/ltx-...ml#post5965540

Although this seemed like a slick idea, I have found that this method is not reliable. The alternator is turning off intermittently and I traced the problem to a poor connection at the dash gage pod, where the green printed circuit board mates to the electrical connector. It's just a flaky design prone to problems so I had to abandon that method and come up with a better idea.

First, I moved the accessory wire from the alternator L-terminal to the F-terminal. This allowed me to wire the alternator differently, without the need for a bulky external resistor. The wire is now run directly to a 12V switched source with a 5A fuse. (I used an extra circuit in my underhood fuse center.) No more flaky connections, no more 50 Ohm resistor, simple to troubleshoot, and alternator is now working again.




Note: Link to methodology if you choose to still use the alternator L-terminal, Post #162, https://www.thirdgen.org/forums/ltx-...ml#post5816939

 

Ya, I'll be selling the engine after it comes out of the car.

 

I had this exact issue. You're saying instead of putting a resistor in line with the L terminal, I can just cut the L terminal wire and leave the F terminal connected and all will be fine? I have L and F connected.

Thank you

 

I am trying to understand why your going to replace this engine with the LS7, when it seems to me you may have wiring issues? From reviewing some of the past posts, they lead me to believe you may have some weak or missing ground connections, or bad connections leading to intermittent circuit continuity conditions. I haven't gone back through your complete thread, but have you added ground straps between the engine block and chassis? Assuming nothing has been grounded to the intake manifold, as that too can cause continuity problems to ground as well.

Now with the added low voltage possibilities from the alternator not providing sufficient output, this in another concern that can lead to intermittent operation of the fuel injection system and data logs. Low voltage conditions will impact the voltage sensing circuits of the engine controls providing incorrect feedback, which the system will interput and adjust accordingly.

You have done a fabulous job on building and installing this 427, I would hate to see you have the same issues with the LS7...

 

Not necessarily, depends on the reason why your alternator is misbehaving. Also depends what kind of alternator you have and the requirements of wiring the regulator so it functions properly. Don't quote this as absolute truth, but as far as I can tell the LS1 Camaro got the crummy Remy CS130D alternator; Corvettes got a Valeo brand alternator (I don't know the model name); and trucks/SUV's got a more rugged Remy AD230 type alternator and maybe even the AD244 in some cases. The requirements to operate the alternator might not be the same between each type.

I can only speak to the CS130D alternator that I have. Remy provided multiple accessory terminals (the strip of 4 pins in the plug) to meet various requirements of different car makers.

* F-terminal. Think of this as the "field terminal". I think it is strictly for purpose of turning on the alternator. It might have some other function of which I am not aware. This is connected to a 12V switched source (only active with key on).

* L-terminal. Think of this as the "lamp terminal". It is dual function, it can turn on the alternator but also indicate if the alternator is ON/OFF. If the alternator is OFF, then the L-terminal acts as a ground path. If the alternator is ON, then the L-terminal raises to system voltage.

In general, regardless of alternator model, a terminal labeled as F, I, D+ should be able to turn on the alternator. The requirements of maximum current limit may vary by manufacturer (how much resistor you need in the circuit). This is why I don't know how to answer your question. Also, an L-terminal is usually just a lamp driver and can't turn on an alternator. The CS130D kind of breaks form that way. It probably should have been labeled an I-terminal instead of an L-terminal.

There is no standard between manufactures for the labels and definitions of accessory terminals. Europe, Japan, and US do their own thing. I'm sure you can see why this topic matter drives so much confusion on the forums. Gobs of misinformation out there. And I just hope I'm not contributing more to that misinformation.

If you have a Remy brand alternator (CS130D or AD-230/244) then your best bet is to call the Remy technical support center and ask your questions. Better than some stranger on a car forum.

Remy light duty tech support: 800-854-0076

 

Appreciate your help. I think it was just a combination of alternator and a failed wide-band O2 sensor. I turned off the O2 sensor in the software and car runs a lot better.

I'm going LS7 because I want to upgrade to large bore (4.125"). It makes a huge difference. I'm not going to reveal details yet but I will say this one word -- "Mamofied".

 

And for someone who didn't already know the name Tony Mamo, I was surprised when DuckDuckGo returned several responses.

 

My sbc is "Mamofied"

 

 

Did you notice an improvement in regards to charging and/or voltage output from the alt?

I have been battling what I consider a low output from my alt ever since I did the swap. I can barely hit 13v with it. I am used to something closer to 14v.

Just curious if this wiring change improved the alt's output.

 

Excessive resistance in the charging circuit, whether on the plus side or the ground side, will cause system voltage to drop.

You can see what voltage the alternator is charging at by measuring voltage between alternator B+ terminal and alternator frame. Differences between that and what you measure at battery are due to voltage losses in your wiring.

 

Jaysz28, I made an illustration that might help. If you already know this stuff then just ignore me.

Let's say the alternator charges at 14 Volt. There are voltage losses in the supply and ground circuits, due to electrical resistance of items in the circuit. The localized voltage across battery is lower than 14 Volt produced by the alternator.
So you can see how losses in your wiring/connections can cause battery voltage to read low. This is why I suggest you measure actual voltage produced by alternator, and then compare that to voltage elsewhere in the system. No point chasing an alternator "problem" if the alternator is doing its job. Might just be the wiring instead.

 

I appreciate the info. I have never used the alt case as my ground reference when checking voltage at the B+ terminal. I will do that tonight after work.

I have added ground straps, upgraded the positive and negative cables and am running a 4 gauge battery cable from the alt to the battery. Next upgrade is welding cable I have sitting on the bench. Just no time to do the work.

again, thank you very much for the advice!

 

Your positive side sounds good. Can't do any better than a run of cable directly from alternator to battery. If the alternator is charging at adequate voltage, then I might put more focus on your ground wiring.

Make sure any ring terminal connections are clean and metal to metal (not painted or greasy surfaces). The ring terminal should be in direct contact with whatever metal object it is attached. Any bolt or screw is there just to clamp things together. (Bolt threads are not the primary ground path.)

 

I have checked ground continuity through out the system and have also checked voltage at the battery and the b+ terminal. They have always been consistent.

Based on what you posted earlier, I may not have a true idea of the alt's output since I never used the alt case as a ground when measuring the B+ terminal. I very likely have a ground circuit problem that is not showing itself when I check the ground circuit for resistance.

 

The resistance is probably too low to measure with a handheld multimeter. Probably have to do this by comparing voltage readings, which you can measure.

 

Wait, wut? Tony Mamo is lurking around here somewhere?