Project Black Magic

This has to be one of my most like projects from customers and the inspiration for my number 2 and 3 recommended SBC engines on the recommended menu.

I liked the vortec motor in my Camaro that I have decided to rebuild it and improve upon it. This is a 94 4.3L 5spd truck with 3.42 gears in it.  The goal of this project is to pull 285hp and 300lbs of torque at the rear wheels.  I also want this truck to get around 17mpg city and 22hwy with about 19mpg combined driving which is pretty much what I get with the 4.3L motor in it now well never got the 22 but city and overall are about right.  How do I plan on getting that kind of power and that kind of gas mileage well its the reason I chose a 5spd truck. The gearing for this 5spd is  4.01, 2.32, 1.40, 1:1, .73 which is much lower gearing than the 3.06, 1.63, 1, .70 gearing of the 700R4.  I plan on swapping out the 3.42 gears with a set of wimpy 2.73 gears which will put the 5spds first 4 gears pretty close to the 4 gears of the 700r4 with 3.42 gears and give me the 5th as cruise only gear. Its not like the truck will be superfast at the track anyway as the 5spd trans is hard to shift fast enough to be competitive but the tall gearing should actually help it out at the track.  I am hoping for a high 13     second time slip from this truck.  Which the truck did accomplish although that did kill that transmission.

I didn’t find the Lunati 20080660 cam that I recommend on engine option 2 until years after this project was done.

1. First I am using a 99 Vortec 350 from a van and making a  few upgrades. I am keeping the stock 9:3:1 compression ratio as I am going to be running 87 octane in this thing most of the time.

2. I did some work to the heads while they were off and I machined just enough off the heads to give them a nice flat surface as the stock machining isn’t that smooth.  I also had .050″ machined off the valve guides so I could safely run more than the .480″ lift max of the stock heads.  I also had the pressed in rocker arm studs pinned so they wouldn’t pull out with the higher lift I will be running.  I had the intake ports just cleaned up and did some porting to the exhaust ports and had 1.6″ valves installed.  For valve springs, I installed CM614 1.26″ o.d. 110lbs @ 1.800″, 325lbs @ 1.200″ springs from

2. On the cam, I ran a nice mild comp cams 8-304-8 roller cam which gave me a really nice powerband in the truck and met my gas mileage and power goals. Its specs are 210/220 duration @ .050″, .500/.510″ lift with 1.5 rockers and on a 114 lobe separation angle to keep the computer happy and achieve the great gas mileage this combo gets.

3. Needing more fuel leads me to the next alteration. I now carry a AC Delco 155lph EP381 pump which is more than sufficient for any TBI application and is only $90 shipped through my ebay store.  While I ran 80lb/hr 454 injectors at 18psi of fuel pressure, I have learned that I can run that engine with 350 injectors at that 18psi of fuel pressure or 454 injectors at stock 12-13psi of pressure.   I now have a custom chip kit with spring, fuel pump and custom chip in my ebay store as these Vortec TBI setups are VERY popular.

4. Can’t have fuel and not enough air. On my truck I am using a bored 46mm throttle body that did for this project.

5. Exhaust.  This has been the biggest issue with this truck from day 1. I have been working on this project for a year and fighting drivability issues and it took someone stealing the cat off the truck to find the problem. Stock OEM Y pipes are CRAP. Since I didnt’ want to change my catback setup on the truck (I would have if I had known what a substantial difference the Y pipe change was going to make) I had my local muffler shop bend me some 2.5″ pipes from the stainless  steel truck headers (which have worked out great by the way) that I got off ebay for $150 to a flowmaster 2:1 collector summit racing part number Y250300 and into a ebay 3″ Thunderbolt cat as I don’t like the smell of exhaust fumes on vehicles with no cats.  I will post both dyno sheets with the stock Y pipe configuration and the flowmaster.  Both used the same aftermarket cat and there was 40hp/50lbs of rear wheel power numbers from just that Y pipe change.

6. Intake. I tried the intake and thought that was my problem and changed to the edelbrock 7116 intake with Holley 17-45 adapter.  I now recommend the edelbrock 2716 for a little cleaner look or a 27164 for a pretty look.

7. I have owned a 5spd truck before  and so I know how worthless the 1st gear is with a 3.42 in a 2wd drive truck.

8.  For the air cleaner I used a 14X3″ open element air cleaner assembly.

9. Suspension. I dropped the truck 3″ in the front with DJM control arms and a customer donated some 4″ drop springs for the rear of this truck.

Here are my Dyno results.  The Top Chart is the final dyno numbers which is 292hp and 355lbs of torque at the rear wheels and that is running on 87 octane. Using a VERY conservative 15% drivetrain loss which is what the stick shift Camaro guys use. (I think the larger flywheel, bigger longer driveshaft and such used on trucks will guzzle more power but to be fair we are using the 15% number.) That would be 344hp and 418lbs of torque at the flywheel on 87 octane.  For some reason you can’t see the torque line hardly at all but that cam and head combo had that motor pulling most of that torque as low as 2500 rpms.  The dyno at the bottom is with the stock Y pipe just so you can see why its so important for everything to be able to support the motor your going to put in your truck or car. This engine would be a great motor in a Camaro as well. This motor wasn’t that expensive to build and The horsepower numbers are right in line with a LS1 car but the torque numbers far surpass an LS1 motor.

Also, just for reference a bone stock 210hp 350 automatic truck will pull about 150hp and 250lbs of torque at the rear wheels and that dyno chart is under the plum crazy project.  I haven’t had a stock 350 5spd truck to dyno to see what the difference is.

The dyno numbers below are with the stock crappy Y pipe setup and I even had 93 octane fuel trying to get better numbers.  You can see how much smoother the graph is above vs the 9.0 earthquake below.