Increasing low end torque on 5.7 vortec

matttahoe53

Active Member
Joined
Nov 13, 2011
Location
Pittsboro
I recently put on headers and a brand-new exhaust system on my 99 Chevy Tahoe. I'm looking at my next mods to increase low end torque from basically idle to 3500 RPM. I'm going to put in a cam and probably new heads, my question is how difficult is this because I've gotten some quotes from a couple of shops and they have been really high and I think I might be a will to do it myself? Any direction on the mods or shop recommendations would be greatly appreciated.
 
1. 98% of the cams out there will not increase low end torque over the stock cam, the ones that will won't add enough to make it worth it.

2. You already have decent heads for a SBC, better heads will be $$.

3. Heads and a decent cam are going to put you over the $1k mark easily, before paying someone to install, by then you are equal to what it would cost to put a LS in there, a 5.3 will do everything you want it to for less than building the 5.7.

In the meantime, the cheapest bang for the buck thing you can do for that 5.7 is to have it tuned. I don't mean a programmer, but actually have the PCM tuned, there are several shops in the area with the capabilities, or BlackBear Performance does mail order PCM tunes, they have done tons of them and have a database of what works. Also, you mentioned you did headers and exhaust, what is that setup? Incorrectly setup it could be hurting you more than helping you.
 
1. These are the cams I am considering.

http://m.summitracing.com/parts/crn-109811
http://www.summitracing.com/parts/cca-08-409-8/overview/make/chevrolet
http://m.summitracing.com/parts/cca-08-525-8

2. If I change the heads this is what I would do:

http://m.summitracing.com/parts/edl-60979

3. I realize the cost of the parts that I want to do and am weighing the option of swapping in a 383. I am trying to get an idea of what a reasonable labor cost for putting a cam in versus whether or not I should do it myself.

The headers I put in are thorley tri y's with 2.5 inch pipe and magnaflow mufflers. This really helped up the truck from about 2000 RPMs on up what I'm looking for is from idle to about 3000 RPMs. The truck is not a dog before that it's just it's a noticeable kick in above 2000 RPMs and I would like a little more throttle response before that. I plan on getting a tune after I have this work completed on the truck.

This is the place I'm considering do you know anyone with experience with these guys?
http://www.carolinaautomasters.com/
 
1. None of those cams will give you a bang for the buck, I haven't run the numbers completely, but looking at those you will have near stock to a little lost bottom end, and maybe gain 10-15hp on the top.

2. Those heads are a nice alternative to Vortec heads if upgrading a non-vortec, but not really worth it for an already vortec engine. The CC, and valves are the same size as stock vortecs, the only advantages are CNC'd (Which edelbrocks stock CNC isn't all that fantastic when compared to a custom job by a reputable shop), and aluminum vs stock iron.

3. Good choice with the tri-y's, they are great headers to retain low end torque while opening up the top, I am curious about your exhaust setup though, did you do true duals or did you retain some sort of crossover? If no crossover that can hurt you as well.

I have never heard of carolina auto masters, I know PCM4less in Mooresville knows their way around the L31s.

But at this point still, you could be into a 5.3 or even a 6.0 LS truck engine for less. All total, not counting my fuel cell, I have under $1000 in my 5.3, harness, pcm, mounts, etc to get it running.

What are your intentions for the Tahoe? And what is your current setup drivetrain, wheel tire, weight, usage etc? There are other ways of recouping low end through mechanical advantage that may be more beneficial.
 
The exhaust is true duels I wanted a crossover pipe but they forgot to put it in. I told them I would drive it and if I felt like it needed it I would bring it back so they can put one in. The problem is there isn't a good spot to put a crossover pipe in till around the rear driveshaft and by that point I'm not sure if it would be worth putting in. The truck is a two door Tahoe which is why there isn't as much room underneath. I'm not sure that the exhaust set up is necessarily the reason for there not being as much throttle response below 2000 RPMs it could just be the larger tires. My goal really is to get the kind of punch I get above 2000 RPMs down lower because the pull I get now is great and I just want it to start sooner.

A 6.0 would be awesome I saw someone on here was parting out their 2500 suburban I don't have the skills myself to do the swap and would have to pay somebody to do it.
 
Crossover pipe needs to be at a specific location to maximize its usefullness. Spraypaint your pipes on both sides and crank the engine. The spot that dries the fastest is the hottest part of the pipe. That is where the crossover needs to be.
 
383 stroker would probably get you the extra torque you are looking for.
 
Put a blower on it.
 
Ride in a cammed 6.0 LS and you'll be sold :D Well worth it! If you look on Craigslist, there's a guy in Goldsboro selling a 5.3 with all the accessories, computer, and harness for 800 bucks. That's pretty cheap.

On a more useful note, you may need some lower gears.
 
Ok I have decided on two options.

1. Cam, rockers, and dyno tune on my existing engine. I don't necessarily want to throw the baby out with the bathwater with my current engine as it is brand-new and only has about 15,000 miles on it. In hindsight I would've never put this engine in but that was a couple years ago and I just wasn't thinking clearly at the time.

2. I have an opportunity to buy a completely built up 383 that was intended to do exactly what I want the price is $4000. My concern is if it will kill my gas mileage or not. On a positive note with the 383 I think I can swap the engine in myself since it's already built.

As fun as it would be and probably the easiest option I don't think I'm going to with a supercharger just because I'm not convinced it will be the most reliable. The current gears on my truck are 3.73. I am happy with this set up I don't really want to go higher because the truck is driven on the highway. The tires on the truck are 33 inch I don't have any immediate plans to go any larger. If I did go larger I wouldn't go any bigger than 35 inch. This truck is primarily a weekend toy/long distance vacation vehicle. We can load a lot of stuff into the back no problem and my wife prefers to ride in the taller truck with more room as opposed to my little saab. I known LS engine swap is done all the time but I would like to keep the truck somewhat set up the way it was designed and intended. If the swap to the 6.0 and it's transmission are as easy as swapping in anything else I might be inclined to do it but I just don't know that much about the swap. I don't think the 5.3 would be worth it in my case just because the engine I currently have is pretty fresh and I don't think it would make that much of a difference to swap it out.
 
I'm no expert, but I don't think option 1 is going to increase power much between idle and 3,500 rpm. I believe a stroker definitely will though. I have no idea on how a 383 will be on mpg.
 
matttahoe53 said:
Ok I have decided on two options.

1. Cam, rockers, No, won't give you your desired results and dyno tune Yes on my existing engine. I don't necessarily want to throw the baby out with the bathwater with my current engine as it is brand-new and only has about 15,000 miles on it. In hindsight I would've never put this engine in but that was a couple years ago and I just wasn't thinking clearly at the time.

2. I have an opportunity to buy a completely built up 383 that was intended to do exactly what I want the price is $4000. My concern is if it will kill my gas mileage or not. On a positive note with the 383 I think I can swap the engine in myself since it's already built.

Would be a waste of money, a LS swap would be 1/4 the cost, and much easier to tune. The 383 will be finicky to tune with the spider injector L31 setup. 383 power will be likely close to or a little less than a stock tuned 6.0 would get you.

As fun as it would be and probably the easiest option I don't think I'm going to with a supercharger just because I'm not convinced it will be the most reliable. The current gears on my truck are 3.73. I am happy with this set up I don't really want to go higher because the truck is driven on the highway. The tires on the truck are 33 inch I don't have any immediate plans to go any larger. If I did go larger I wouldn't go any bigger than 35 inch. This truck is primarily a weekend toy/long distance vacation vehicle. We can load a lot of stuff into the back no problem and my wife prefers to ride in the taller truck with more room as opposed to my little saab. I known LS engine swap is done all the time but I would like to keep the truck somewhat set up the way it was designed and intended. If the swap to the 6.0 and it's transmission are as easy as swapping in anything else I might be inclined to do it but I just don't know that much about the swap. I don't think the 5.3 would be worth it in my case just because the engine I currently have is pretty fresh and I don't think it would make that much of a difference to swap it out.
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The LS swap is easy, and really not much more work than the 383 swap would be. Just adapting some fuel lines, the L31 fuel system should be able to support a stock LS, if you have a few nights to dedicate to it the harness is really easy (but tedious) to trim down, or you can get a harness online. It will bolt up right to your existing transmission, you will just need the spacer for the flexplate. As far as the 5.3, it will be a night and day change over your 5.7, especially on the top end, although the 5.7 does have it a little better down low, a slightly looser converter (trailblazer converter) will more than compensate for that.
 
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