Beat increase of torque for $1000

[andrewpclayton]

I’ve been fantasizing about what I’m going to do to my 1969 GMC C1500 5.7 350.. what suggestions and recommendations do you all have to most efficiently and effectively add low end torque for $1000 or maybe a bit more?

[Warrens69GMC]

I'll start. First we need to know your current-

Engine and mileage (any modifications?) 2 or 4 barrell?
Transmission
Reargear ratio
Tire outside diameter

Expeced rpm for gain 0-1800, 1000-2400, etc etc

[mike16]

change your rear end ratio.

complete rear axle, drum to drum for 80 dollars at a las vegas pick a part

water injection

cam and lifters

[Mike C]

Torque is multiplied unlike horsepower, so a lower rear gear (larger number) certainly makes it seem more powerful. But will increase RPM at all road speeds.

First thing to do is a tune-up. This can make a huge difference if things are out of whack. I'd convert to a large cap HEI. But next: Free flowing exhaust, performance camshaft and lifters-keep your .050 duration at 210 or less, performance intake manifold.

[davepl]

On top of the motor, this cost me under $1500 total in various eBay parts. Made 1200 ft-lb and it wasn't done yet! Now getting it all to fit can be a problem...

But in all seriousness, an overdrive transmission with a steeper first gear, like a 200-4R or TH700, can be nice. And it allows you to add even more gear in the rear end (but not in your budget) at a later date because you have overdrive.

[MARKDTN]

Tuned-Port Fuel injection conversion. Lots of low-end torque. Fits your current bottom end and uses current accessories. It could be done for under $1000 and be like driving a new engine. Parts available at any parts store in the USA. The following was written about 14 years ago, so prices are different but the install is still valid. TPI units are cheap now. Unless you know the injectors are worthy, I would replace them with Bosch remans that will stand ethanol fuel. The Multec ones especially are time bombs with ethanol fuel.

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You have a unit
First you have to determine whether you want mass air flow or speed density. Speed-density is easier on space issues. Mass-air flow is easier to make engine changes without PROM changes. If you are technically proficient enough to make a Camaro harness work they can be bought for $100 or less. I have been told that you can also use a 3.1 Corsica or Cavailier harness with a little work, it uses the same 7730 Speed-Density ECM. Aftermarket harnesses range from about $300 for Painless to $500 for Howell or Ebay. Howell makes a great harness, I highly recommend them. I also have a Fuel Injection Specialties (FIS) harness and it is OK. The ECM can be had used for $10-50. A good external fuel pump will cost at least $100. I use an 88 Ford Truck external pump, $114 from CarQuest, made in Texas by Airtech. I used a TBI S10 Blazer fuel tank with a TPI pump. An aftermarket PROM with VATS and Emissions codes removed will be $100-200 depending on source and complexity. You will have to add an oxygen sensor to your exhaust, $20 for the sensor, $5 for the weld-in bung, and say $25 for an exhaust shop to weld it in if you can’t. Some harnesses use VSS and some do not. An auxiliary VSS sensor is around $75. To install a TPI I say figure at least $800 plus the TPI unit and whatever repairs are necessary to bring it up to useable status. I put TPI/700R4 in a '72 C10 (Howell harness) and an 83 K20 Pickup (FIS harness) and I love it. Starts good, great torque, good fuel mileage, easy to swap onto stock engines (although both of mine are complete engines out of 90/91 ‘Vettes).

Differences in years
All Corvette TPI intake manifolds work with the older (through 86) iron heads and the factory aluminum heads through 91. F-body TPI intakes use the upright center bolts on 87-92 and thus fit all 87-95 iron heads (non LT1). Either can be swapped to fit the other with some drilling. F-body has the fuel lines come out on the drivers side and has a central port for EGR. Corvette has fuel lines that come out on the passenger side and has an external port for EGR. Corvette fuel rails fit F-body intakes and vise-versa. The runners are all the same through the years, but the LH runner has a hole for a 9th injector in the 85-88 runners. This can be plugged off if you get a nice LH runner and don’t want the 9th injector or decide to run speed-density. The plenums all physically interchange, but 90-92 have an extra vacuum port for the MAP sensor used with the speed-density computers and wiring. 89 is an odd year, it is mass-air flow but without the 9th injector. 89 up throttle bodies can be used on all years, but a 85-88 throttle body requires a ½” hole be drilled in the front of a 89-92 Plenum for idle air. 89-92 Throttle bodies have a bit more desirable cable attachment. The cable attaches around a circular linkage which has a smoother actuation than the straight linkage on the 85-88. The Corvettes have an aluminum plenum extension over the distributor, the F-body extensions are plastic. The Corvettes use an HEI coil-in-cap distributor for 85-91 (Delco 1103680). 85-86 F-body also used a big-cap distributor. 87-92 F-Body used a small cap distributor with an external coil (Delco 1103479). This same distributor is used in the 87-95 5.0/5.7/7.4 TBI injected trucks. The F-body intake gets it's exhaust for EGR from the center passages in the heads like most SB Chevys. A Corvette intake gets it's EGR exhaust from the RH exhaust manifold/header through a flex-tube to an opening near the distributor-no center passages in the intake. If you are required to keep EGR and you have a Corvette intake, I recommend getting the C4 exhaust manifolds. They are like mini-headers, and have a 2 1/2" outlet.

As far as a throttle cable to use, you must use a cable from the type car your throttle body came from if you want to have a chance of not cutting it. Again, 85-88 use a straight pull, while 89-92 have a circular attachment for more smooth actuation and so the inner cable is longer. On my 83 truck I used a TPI F-Body cable and it was OK, but I had to coil it up into a loop in the engine compartment because the housing was so long. I also TPI'd a 72 Chevy truck and used a 90 350 TBI truck cable for it. It was 1/2" short outside if anything, but I was pretty pleased with it all told-I didn't have to shorten it. In all vehicles I've done you need a die grinder to square the firewall hole off a bit. All vehicles I've done used the late throttle-body.

Why to get it
If all you want is around 300 hp there is no reason to spend a pile of money on a crate motor. The basic $1200 4-bolt Goodwrench 350 with an aluminum intake and a Holley will put out power in that neighborhood. Chevy High Performance (I think) did a series of articles with one of those a few years back and with decent exhaust should get you in that range.

I would look into a TPI. They start immediately in winter, have great vacuum, and will get great mileage.

[RedRider]

Headers are always a win-win.

[RustyBucket]

Check Craigslist for a low mileage 454/400 turbo combo from a junk motorhome. I see 'em pretty often.

[MARKDTN]

Originally Posted by RedRider

Headers are always a win-win.

By themselves not so much-in fact they might even hurt. With a thoughtful configured package of compatible parts, yes.