The scenario...

You own a 2003 LS (4-door) Blazer. You have Positraction and 3.43 gears.

You are set to race (at a track) against a 2000 Mustang GT in one month. A lot is riding on this race (straight up 1/4 mile).

Here are the stats:
You weigh 200 lbs, your friend weighs 130 lbs.

Blazer: 190 hp, 250 ft-lbs torque, curb weight: 3792 lbs., 4-speed automatic
Mustang GT: 260 hp, 302 ft-lbs torque, curb weight: 3242 lbs., 5-speed manual (driver is a decent shifter)

The question is not who will win. The question would be if you had $2000 to work with and one month, could you build a Blazer that could beat the stock Mustang GT?

If not, what's the fastest you could get it with that amount of money and what, specifically, would you do to get there?

 

Well, to do this reliably... I don't know if I have an answer that will allow you to win. A well tuned nitrous setup could get your close, but the upper intake plenum scares me when it comes to back fires. One single backfire will shatter the upper intake plenum. To get you close, you'd have to atleast go with a 100hp shot wet (nitrous and fuel), but again, I have to caution you on the proper use of Nitrous. It is VERY easy to run lean and blow your motor with Nitrous.

If you could get into the engine. A cam, rockers, ported heads, headers, and possibly higher compression pistons. Don't think this would fit within your budget, but I'd do EVERYTHING listed from this HOT ROT article - 3/4 350 - 4.3L Engine Buildup. Their outcome was 301hp and 312ftlbs. Now I know that the buildup was on an older engine, but the same still applies with the newer engines, but the newer engines have better flowing heads. But I still don't think that would be enough to knock off the GT.

 

Nice link, you think that could be done for under $2000?

What do you think about a new axle ratio? Would 4.10 gears do the trick?

 

Ok I read that article and I took this to be the basic outline of the upgrades done to the engine:

1) Pistons: Speed Pro LW2256-F-060
2) Piston Rings: Sealed Power R9902-060
3) Tri-metal Bearings: Sealed Power 6-1020CP
4) Head gaskets: Fel-Pro with 0.041 compressed thickness
5) Oil pump: Sealed Power 224-43469V
6) Oil pickup: Sealed Power 224-14263
7) Oil pump driveshaft: Sealed Power 224-6146E
8) Balancer: Pioneer 872021
9) Cam: Comp Cams 280HR with 224/224 duration at 0.050, 0.525 lift, and a 110-degree lobe-separation angle (Cam Kit K09-430-8)
10) Valve springs: Comp Cams 987
11) Rockers: Comp Cams 1318-12
12) Ignition: MSD even-fire 8597, MSD 8.5mm Heli-Core wires and a Digital-7 ignition box
13) Modify a Milodon 350 windage tray to fit a V-6
14) Modify Milodon 190,000-psi rod bolts for a 350 application

What I want to know is which of these things could be spared if I only wanted, say, 250 hp as opposed to the 300 they got? Which items are for durability or necessity (supporting parts/modifications) and which are the actual power-producing parts of the build?

 

No, I don't think it can be done for $2k.

The problem with 4.10s is that the 4.3L would seriously run out of breath once you got moving. You would get the jump off the line, but the GT would run you down and pass you before the 1/8th and possibly sooner.

The problem with this comparo is that the GT weighs 550lbs less, has 70hp more (+ more torque), and has a more efficient drivetrain (manual vs auto) so he's getting more power to the ground. So now if we use the old approximation that -100lbs = +10hp = -0.10sec in the 1/4 mile, you'd lose by .55sec on weight alone. Now taking a 15% drivetrain loss for the GT (which is HIGH), he's putting down 221whp and a 23% drivetrain loss for your auto makes your whp at ~146whp, he's putting down ~75hp more to the ground so there's another 0.75 seconds faster for a grand total of 1.3seconds faster (a very conservative estimate). So on paper inorder to match him, you'd need to drop 1300 lbs or gain 130hp.

These numbers are for conversation sake only and shouldn't be taken as fact. The +10hp/-100lbs/-0.10s is just a gross approximation. The thing that isn't taken into account is the drag difference between the GT and the Blazer.

You can also do any combination of weightloss (free) and hp upgrades to achieve your goal. So take out EVERYTHING that is not necessary. Drop the spare, remove all but the drivers seat, take out everything that isn't bolted down as well as most things that are, run with an 1/8th tank of fuel, etc. Anything to reduce the weight of the vehicle.

 

What is necessary for doing just the cam work? How much power could I get from the cam alone?

For $2000 could I do enough to the engine, on top of completely gutting my blazer, to beat the GT?

 

With a cam, you should do new lifters. To take full advantage of a new cam with a grind to give more top end, you should change your rev limit and shift points. To reliably do this without valve float, you should replace the springs with higher load springs. Also if available, you could throw on a set of higher ratio rocker arms. The springs will be the cheapest thing, followed by the cam, then the lifters and rockers. By contacting Comp Cams directly, they should be able to tell you what will work with your engine. They know a lot more than they have on their site and they would be able to tell you what to expect out of their products. I have always found Comp Cams to be very honest when you contact them directly and have never been disappointed with any of their products.

*EDIT* - more directly to your question, basically the front and top of the engine needs to be opened up. The lower intake, timing cover and all other components that need to be removed to gain access to both of them needs to be taken off (including the distributor). The reason why I recommended new lifters is because I don't know if the newer 4.3Ls use roller lifters. If they do, then you could get away without it, but they will limit the spring rate of the valve springs because too stiff of a spring could collapse the lifter.

Any more questions, just ask.

 

Is this something you could generally trust a shop to do? I don't think i could do this type of work on my own... With the install and parts, what do you think that would run me? What kind of power increase could I expect?

 

For that, you'd have to source a cam. You can call Comp Cams tech line and they could do you a custom grind to your specifications or set you up with a custom grind based off what you are looking to get. Your limitations are going to be the flow of the stock intake/heads/exhaust and the compression of the engine. Getting a cam can move your power around.

And yes, any trustworthy shop will be able to perform the work (do not take it to a dealership!), but that is going to eat up a quarter of your budget (if not more) in labor.

If you want the best bang for the buck and want to make it a close race, then I hate to say it, but a viable option would be nitrous. Do as much weight reduction as you can and put it on the bottle, but save some extra money to have a professional tune it. I don't know how the computer is going to like going on the giggle gas, but I don't see many other alternatives within your budget.

*EDIT* - But again, use nitrous with EXTREME CAUTION! I have never liked nitrous simply because people use it incorrectly and do stupid things. When tuned/used correctly, it is very reliable, but not always very consistent.

Good luck

 

How hard is it to do yourself?