LS Swapped C10 Power Issues
 

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...

Re: LS Swapped C10 Power Issues
 

Gorgeous truck and it could be any number of things but it is likely tune related. I would find a reputable shop in your area that specializes in ecm tuning and knows GM factory ecms and software (likely HP tuners) well and have them go through it. A good tuner can look at the tune in the truck and see issues and then make corrections while street tuning but may want to fine tune on the dyno. It may have been tuned by an amateur that got to a dyno number and said good enough but left a lot on the table as far as drivability.

Re: LS Swapped C10 Power Issues
 

Thanks! I’ve got a tuner in town that seems like he knows what he’s doing - Been around for a while and had solid reviews. Just hoping I don’t blow about $1,000 trying to improve things and get nowhere! 🤞

Re: LS Swapped C10 Power Issues
 

Before you go to a tuner I'd scan it for any stored fault codes and check to see what the fuel trims and real time O2 traces look like.

If you aren't setup to scan the computer, all you need is a bluetooth OBD2 dongle, a phone and a copy of torque pro. Not counting the phone that is less than a 1/4 tank of gas. And an hour on youtube will teach you what to do/look for.

It sounds to me like it might be running open loop, which could explain both performance and smell. I can clearly see the wire on your left O2 is connected, but can't spot the right side wire.....

Re: LS Swapped C10 Power Issues
 

OP said 'GM'

Re: LS Swapped C10 Power Issues
 

yeah, there is stuff on the engine that I am not familiar with but its got coil packs and injectors in the heads fed by rails so I am assuming the GM ECU is same as what you find on an LS truck from factory. setup for MAP instead of MAF which does seem a bit odd. I am assuming it is basically an LS engine dressed for a party.

Re: LS Swapped C10 Power Issues
 

I unfortunately don't know exactly which ECU this is, but here's a photo of it if that's helpful. As for the DELS Kit, here's more info on it: https://delmospeed.com/products/dels3-kit-for-ls3

It's running MAP because I don't believe there's really any way to run a MAF with this setup. Considering swapping this setup out for a Holley Sheetmetal intake and 92mm TB with a MAF instead of running MAP.

Re: LS Swapped C10 Power Issues
 

Forgot to add the photo of the ECU... Just edited my previous post.

Re: LS Swapped C10 Power Issues
 

agreed, HPTuners is a must for tuning and making any changes related to LS swaps. The cost is miniscule on the scale of this truck. There is a learning curve.

torque pro lets you see real time data, reset codes. its cheap and useful but not a tuning tool. 10 minutes with it would either give me a good idea what is wrong here or send me tail between my legs to my son for his HPTuners chops

I guess this truck is MAP simply because there is no where to hide a MAF in that intake setup.

Re: LS Swapped C10 Power Issues
 

2010 and up GM ECU

Re: LS Swapped C10 Power Issues
 

I've played around with tuning software in the past with a couple of cars - Not my bag at all! I'd rather scan to see what's going on then take it to someone who is a pro in the field, and can throw it on a dyno to really hone it in.

Re: LS Swapped C10 Power Issues
 

Far from a expert on LS swaps but as said above since no mass air it has to be speed density.
I would contact the folks at LS1tech.com for some help.
As I understand a lot of the Holley LS EFI is speed density.
There is a guy on LS1tech.com goes by Andrew that he can tune via the internet. Has a really good rep.
Oh and the truck looks great.

Re: LS Swapped C10 Power Issues
 

I am going to assume it must have a pretty mild cam with only a 2200 converter in it...or maybe it doesn't have enough converter, which is part of the problem?

As stated, I would start with a tuner and go fro there. I know in both my truck and car, neither one of them really wake up until 3500, but I have pretty big cams in both. The truck will still spin the tires off the line, but when it hits 3k and above, it is like a totally different vehicle!

Re: LS Swapped C10 Power Issues
 

This is what I was thinking.

Re: LS Swapped C10 Power Issues
 

a TBI or a TPI ecm won't run an LS

Re: LS Swapped C10 Power Issues
 

Interested in the outcome. That is one beautiful truck! I hope you get that LS feeling soon!

Re: LS Swapped C10 Power Issues
 

A few more thoughts.
In regards to the converter. When you pull up to a stop light does the engine kind of lug and/or push against the brakes? Typically that means you need a smaller cam or higher stall converter. On my LS builds that I run a smallest cam I run a 3200 Yank or Circle billet converter. Both drive like a stocker until you floor it.
Would it be possible to find the PO/builder name and contact Texas Speed about the cam details?
And this is totally a WAG but I seem to remember that mounting a stock GM TB directly to the four barrel intake is not a good idea. Bad air distribution? Maybe a good tuner can make it work?

Re: LS Swapped C10 Power Issues
 

ok but he did state it was an LS platform.

Re: LS Swapped C10 Power Issues
 

Beautiful Truck. I’ll be following this one.

Re: LS Swapped C10 Power Issues
 

i agree with what has been said already.. the converter is most likely on the small side.. but also a tune is always going to get it to be more awake so to say.. beautiful truck

Re: LS Swapped C10 Power Issues
 

First, beautiful truck, exhaust could be a little nicer, but still a gem!!

Second, you need to work with a reputable tuner and see what's going on with the tune. It could have just been tuned for a dyno number. Not knowing what the cam specs are makes things a little more difficult, but not impossible.
Do not do a sheet metal intake! They are cheesy, make weird noises, and just not great. I'd lean towards a retune and ditching the DELMO for a legit 4150 TB like this, or similar. If you wanted to be sure on the cam specs you could pull the timing cover and verify the part number.