Hey all,

Long-time forum member but been absent for quite some time - Just haven't had an applicable toy for several years. BUT, just picked up a new one that has been a dream for the past 11 years. Paid a pretty penny for it, as it's had a ton of high-quality work done to it and is unquestionably a show quality truck. However, I have some concerns about the power this thing is putting down... Here's the scoop on the powertrain.

-It's got a Gen IV LS iron block (assuming L96) with LS3 heads and a Texas Speed cam (specs unknown) along with a Delmo Speed "DELS Kit" that consists of a Holley 4150 4 bbl carb style mid-rise intake, Holley Fuel Rails, throttle body adapter (running a factory L96 truck TB I believe), etc. to make it look more old school, Speed Engineering exhaust manifolds, and a GM ECU with a MAP sensor (not MAF).
-Transmission is a 4L80E with Raybestos red clutch pack, and a 2,200 stall.
-Rear end is a QP Ford 9" with 3.70 gears

The previous owner that did all of the work (and provided boat loads of documentation for everything) also had a dyno sheet that showed it puts down 390 rwhp and 358 rwtq. However, even though it fires right up and runs quite well, the thing does not feel like it's making that kind of power... At least in the lower to mid RPM range.

When I go WOT from a standstill, it hardly spins the tires, and feels pretty sluggish until about 4,500 RPM, where it seems to wake up and pull pretty hard to 6,500 RPM. For example, just today, I used the Dakota Digital gauges 0-60 function to see what it would do, and I only managed a 6.3 second result. But, it went 60-90 in probably 3-3.5 seconds... Once it's in that upper RPM range, it doesn't feel bad.

Additionally, I've noticed, if I punch it while cruising at, say, 50mph, and kicks down into 2nd, it'll kinda "hang" at about 4,000 RPM for a good second+ before it continues climbing to redline...

Now, I do feel like the truck is running rather rich based on both the gas mileage (about 8-10mpg around town) and how strong the fuel smell is when it runs, and just from it sitting in the garage. It's potent!

So, I'm looking to the tenured LS swap folks for some advice/insights... Could what I'm experiencing be the result of running too rich? Could that cause my low-to-mid range power to suffer this much...? Are the conditions I'm describing indicative of this condition, or could it be something else?

I love this truck and am extremely excited about it but this situation has definitely put a bit of a damper on my excitement. Your feedback would be greatly, greatly appreciated!

Few pics of the truck attached. It's a beaut! Now I just need it to drive like it has an LS swap...

 

Nice truck....

A couple of thoughts sounds like your cam is designed to operate in the upper rpm range, not the lower range....it would be helpful if you could get the cam specs from the PO or maybe Texas Speed has the record of what they sold him.

You might need more stall for your converter. Changing the converter is the easier option than changing the cam.

T,

 

The no cam spec is going to be a downfall, these gurus are going to want to know that.
but nice truck, id pull the swap out mine to put in a truck like that.

 

Sadly, the docs for the engine say nothing about the cam other than "VCM Cam"... Which I'm just now seeing - That's not a Texas Speed Cam. And I've never heard of VCM before (looks like they're Australian ) Hmmm... I did ask the seller if he had the specs anywhere but he didn't. Clearly he didn't even know what kind of cam was in the dang engine...

 

I looked up VCM, and they are Aussie. They list a few different cams. See if you can get a part #. from the builder

 

Call the people who did the work, they should have that on file i would think

 

Yeah, sadly, the place that built the engine is no longer in business…🤦‍♂️

 

Someone from another forum suggested I grab a bluetooth OBDII scan tool, and a copy of torque pro, so I can scan to see if I'm running open loop and see what my AFR and fuel trims look like. Gonna try that out and, if it's running as rich as it seems/smells, I've got a shop in town that does dyno tuning that I'll take it to.

 

A real tuner is also going to want to know your cam specs, sounds like its time to do a cam upgrade.

 

I’m honestly considering pulling it, selling it, and swapping in a new LS that I know the specs on… Like a GM Performance LS3/525hp crate motor.

 

A tuner can help with the fueling etc, but not going to do much for your power band issue, no tune can fix that. The statement you made about no MAF tells me you are probably running speed density; they can be tricky to tune and get them right. Just make sure they do a driveability tune, so it has good street manners. A dyno is a great tool in the right application, but you are not trying to wring the last amount of available HP out of it.

The 525 will definitely be a good choice and will wake that truck up considerably. I'm partial to the 495 HP with the hot cam and a 3200 stall. Good street manners, nice lope and great low end...

T,

 

Yeah, it’s running MAP/speed density. And I bought it at sea level where it was dyno tuned, then brought it up to 3,700’ elevation where I live… May explain at least part of the issue. That said, I’d be happy if it just had a linear feeling power band.

Appreciate the feedback on the LS3 crate options. Have you tested/driven both the 525 and 495 iterations? My knee jerk is, of course, to go with the most powerful option but if the 495 provides better seat of the pants feel and drivability, I could definitely be swayed.

My ultimate goal is for the truck to be a fun driver, and canyon carver that I could take to some autocross events and maybe even a road course event or two. It has CPP front BBK and rear discs, full RideTech StrongArms, 4-Link, front MuscleBar and currently air suspension but I’m switching to coilovers and adding the rear MuscleBar. Just need an engine that agrees with this use case.

 

My original 5.3 i had in my single cab made 373 to tire and went mid 13's in the quarter. If it were me id switch the cam and torque convertor and take it to a good tuner. Man when you take it to a good tuner you will be surprised how much they can help you. A good tuner will tell you what is limiting you and what needs to be changed. Unless your just sold on putting a motor in it, I wouldn't tho, thats spending alot of extra money on something that can more then likely be salvageable with the right knowledge and help.

 

I appreciate this feedback. I think the reason I’m considering the LS3 is that I can handle that swap over a weekend myself, swap the torque converter while the engine’s out, then sell my current engine. All in, I imagine that’ll cost me around $6k after selling my engine. If I were to pay someone to swap the cam and torque converter, I’d bet I’d be close to the same figure with shop labor on that cam swap.

But it might be worth spending the $1k to have it professionally dyno tuned, particularly since it was last tuned at 3,600’ lower elevation and there’s no MAF helping compensate for the air density delta.

 

sounds like you have your mind made up, id just make sure i leave room for error. Something unexpected always comes up and I would definitely have it professionally tuned. Thats a must.

 

Never tested the 525. I have installed 3 or 4 of the 495's. For almost 2K more on the 525, don't see the value added for 30HP. You won't notice the difference in the truck, but you will notice a lack of traction....lol

T,

 

A question about changing to the 495 HP LS.
Would you keep the stock 495 intake and TB? If you did you would go back to mass air instead of speed density? Would that mean your current engine harness needs to be replaced?
Because I'm cheap it would be easy to pull the front grille, radiator and radiator support to replace the cam with a smaller one on your current engine? Some where around 220I/225E?
I'm kind of in the boat you are with my 80 Camaro with a LS3/4L60E swap. Mass air tune. Runs great but either too small of converter (2800 stall) or to big of cam 225I/230E.
It pushes against the brakes at a stop sign.
I'm leaning towards a 3200-3600 stall converter from either Yank or Circle. I don't have a lift. Local shop will R&R the converter for $600.

 

Im with this guy, id pull the cam and convertor. That can easily be done in a weekend as well and for much less money. Hell you could go with a simple FI setup for that kind of money. Or put it on holley and be able to have plenty of the guys here help you with the tune.

 

echoing the other posts - single plane intake, rec port heads, big cam, this combination is definitely a recipe for poor low end torque (and good top end power). combine that with your 2200 stall and i'm sure that thing feels like a dog down low.

its a system, heads, cam, intake, converter, all these things need to be well matched to get the result that you want.

in principle an L96 should be a great starting point for power, maybe just call tony mamo and have him spec you heads and a cam that's more appropriate for what you want. And then, call up a converter company and they can help you match a converter to your combination and goals.

 

So, in all honesty, I don't quite have the mechanical aptitude to handle a cam swap on my own. I'm sure I could figure it out but I know that, while not "simple", it would be easier to swap one LS for another, and then know exactly what's in my engine, and that it's a true 0 mile new crate motor. That said, like I mentioned before, I'm considering having this thing re-tuned by my local dyno shop that tunes a lot of LS swaps for a local builder. It's clearly running rich, given that I've had it missfire a few times when going WOT under load, it has that flat spot around 4,000 rpm, and emits such a strong fuel odor. If this guy can make the powerband feel more linear, I think I'd be happy.

If that doesn't do the trick, then I may take the leap and snag a new LS3 crate motor. The other thing I don't love, though I know it's common for rarely driven LS swaps (1,600 miles over 5 years) it does seep a drop of oil or two from around the rear main after a long drive. Pretty sure most of the seals are pretty well dried up from lack of use. And if I'm ever going to put in the work to change something like that, I'm just going to drop a new engine in the same swoop.