Plum Crazy TBI

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I built this project primarily to show that you can NOT make big power using the poor flowing TBI heads.  Nothing can be done to those heads to improve their flow numbers enough to justify the work done to them.  Here is the pitiful flow data for those heads.

193 casting TBI head flow data

Valve Lift—-Flow———Flow

Compared to the Vortec head flow data

Vortec heads.

Valve Lift—-Flow———Flow

Everyone asks just how much power can be made with stock 193 casting TBI heads and so I am set out to see just what kind of power numbers can be made reasonable without hurting fuel economy at all and hopefully improving the gas mileage some as gas sure isn’t getting any cheaper.

The nice thing about this project is it can be done in stages for those with little or no budget.

1. First thing I am going to change is that blasted stock fuel pump.  I hate those things so I am going to use one of my pumps that I use in all my TBI projects and available in my ebay store.  Pump is MORE than sufficient for any TBI motor. Well actually the thermostat was the first thing as I had to change that on the truck when I bought it.

2. Next is the exhaust, stock crap has to go and I am going to steal the whole setup off the black magic truck. I may be embarking on a new project on that truck so I am going to steal its stainless shorty headers and the Y pipe I had made with the flowmaster Y collector which has been working out well with many of my customers as well as my truck and just your average cat back setup.  While this won’t give me a huge gain on the stock TBI motor when we go changing out the other parts this exhaust should really shine. Exhaust is also the most expensive mod your likely to make to your truck so do it right the first time.

*** Remember your exhaust is only as good as its worst flowing piece ***

I get a lot of customers who tell me they have good exhaust to find they are still running that stock Y pipe which killed my black magic power numbers and so make sure you check out all my projects to see how important getting everything setup properly can be.

3. I am just going to go with the traditional 14″ X 3″ open elementsummit racing air filter.  Part number Sum-239441 for $45.  A cold air intake might be nice but its not cheap for true cold air.

4. I had bore a throttle body to 47mm for this project and as usual they did beautiful work.  I can’t brag on their work enough.  They have done a couple of throttle bodies for my projects and they all performed flawless.

5. Intake and cam.  I put these together as I am sure not going to pull this intake off twice.  For cam, I am going to use an inexpensive Sealed power CS1105R which I got off ebay for $115 shipped and includes lifters and timing set for that price. With 209/216 duration @ .050″, .435″/.455″ on a 112 lobe separation angle, this cam has a really nice powerband to go along with those 193 TBI heads as running a lot of duration with these heads is pointless. Customers have reported that finding that CS1105R cam to be difficult and most customers copying this project use a comp cams CL12-256-4 or a smidge milder Melling MTC1 cam.  For the intake, I went with the mild edelbrock 3704 intake which is has recently got pretty expensive currently. I bought mine  used for nearly half new cost on ebay and took it to my local machine shop and paid them $40 to machine it out to 47mm to match my throttle body.  If you cant find a cheap used one then my recommendation is just to use the stock intake as the total power output of this engine package just doesn’t justify that cost.

6. I originally put my 18psi fuel pressure spring in the stock fuel pressure regulator because I didn’t know how much power this combo would actually make. After datalogging this project and finishing up on the dyno, it looks like the motor should only need about 12-13psi of fuel pressure on the 350 injectors to feed this motor but the fuel pump should still be upgraded to maintain that fuel pressure under heavy throttle.

7. I will also change the valve spring while the intake and cam is being swapped out as this motor should peak around 5200rpms and that is just too high to rev stock TBI valve springs.  Just a stock cheap set of Z28 springs will do.  Don’t want to spend a lot of money on those heads.

8. Underdrive crank pulley to squeeze me another 5-10hp from this engine and hopefully increase the fuel efficiency a tad as well.

9. I am also going to convert this truck to the 3 wire heated 02 sensor for the best fuel economy.

10. I am going to use a pair of electric fans instead of the stock fan setup to try and unleash a couple horses but more importantly to improve gas mileage.  I have now created a electric fan page under my recommended TBI menu as this is a VERY important modification.

Parts list so far

Fuel pump $100
AC Delco 170 stat $12
Stainless headers $150
Flowmaster Y pipe $50
Flowmonster Cat $50
Dynomax Cat Back $260
Summit Air filter $45
47mm throttle body $230
Cam, Lifters, Timing chain/gears $115
Valve Springs $26
Edelbrock 3704 intake $242
18psi fuel pressure spring $17
Underdrive crank pulley $50
3 wire heated 02 sensor conversion $60
Machine shop boring the edelbrock intake $40
Twin 14″ electric fans $60
relay for fans $6
fan switch for elect fans $44
Shipping gaskets and MISC. $100
Stage 2 chip $200
TOTAL $2027

When you add all this up, it sounds pretty steep doesn’t it. Especially not knowing what the outcome will be. After this project you will know exactly what the outcome will be so there will be less risk on your investment. This is the first project with a break down of all the costs involved and almost all this stuff has to be done to support a bigger build as well as the better heads to get bigger power numbers. But when you go looking at the price of the newer trucks this project will begin to look better and the thing about this project is you can easily build in stages and is a good backbone for even more power.


Well if you ever wondered what a bone stock truck would dyno well here it is. With Stock chip the thing only pulled 141hp and 210lbs of torque (on 87 octane gas with 170 degree thermostat).  Typically we would deduct 20% for drivetrain loss which would be about 180hp and 265lbs at the flywheel.  Strangely enough if i use 33% for my drivetrain loss it comes really close to the factory 210hp/300lb of torque numbers but GM may have used 91 octane gas or better to get the original power claims.  While I was on the dyno I decided to test some chips and so I tested a “Leading Brand” I would post the manufacturer but I am afraid of a lawsuit since it did so poorly and my HOT chip.  I tried the Stage 2 chip as well but it only pulled about 1.5hp more than the HOT chip which wasn’t worth cluttering my sheet with.  I didn’t expect the stage 2 chip to really even do that well since the motor is running on 87 octane gas. But I did manage to gain 12hp and 20lbs of torque which is a decent percentage gain on a stock truck with 87 octane fuel, much better than the other chip manufacturer did with 87 octane.


FINAL DYNO numbers:

As you can see it didn’t pull big power at the rear wheels.  Big surprise there NOT.  While we are going to calculate on a 20% drivetrain loss the important thing to look at is the base numbers vs the new numbers. 60 rwhp gain is a very noticable improvement. However we could easily gain that much more rwhp if we had changed the heads too but this project is to show what stock heads can make.  Giving that 20% drivetrain loss that comes out 250hp and 320lbs of torque at the flywheel on 87 octane fuel an no trickery to try and pull artificially higher numbers. Engine pulled strong to 4600 rpms and started dropping off slightly by 5000rpms and stock started dropping off at 4300rpms so we didn’t shift the trucks powerband that much and driveability is very nice and gas mileage seems to run exactly where I wanted at 17city and 20-21 on the hwy from this 2wd std cab shortbed 3.42 geared truck.  Now are 60rwhp gain over bone stock turns out to be a 75hp at the flywheel gain which is what I would expect from all those bolt ons and a mild cam with stage 2 chip.  While I was running 18psi of fuel pressure on the 350 injectors, by looking at the logs this motor would run just fine on about 14-15psi of fuel pressure but we are right at the point where the fuel pump should be upgraded to a better pump.