|Tweek's summer tweek....|
Author: Rick Metcalf AKA Tweek
Yeah, he's back. Has this been a long, hot summer, or what? At least the A/C in the full size GM trucks is a real ice cube maker! How about just thinking about this modification until it cools off outside a bit. This one might take a while to finish, and
Yeah, he's back. Has this been a long, hot summer, or what? At least the A/C in the full size GM trucks is a real ice cube maker! How about just thinking about this modification until it cools off outside a bit. This one might take a while to finish, and of course it is for the 90 model, but you can also make this work on the 91 and up if you want. Hey, look, the 90 model needs lots of help!
Let's talk throttle bodys here. In fact let's not fart around. Let's talk four (4) barrel throttle bodys. Everyone knows the sound of that old Quadrajet 4 barrel when you tip those massive secondarys open. When you have a big-block under the old Q-jet, the sound waves coming out of that gas mixer can be sweet!
Common knowledge is that anything that you do that would effect the sonic signature of the engine also effects the power and efficiency of that engine. Louder isn't always better, but it is an indication that you have made a change in the tuning and operation of the engine. Not just volume of sound, mind you, but the tone of the sound as well.
Some good and bad examples are: Glass packs: Loud and usually pitiful for power production. Headers: Probably the best dollar per horsepower investment you can make. Both these things change the sound of the engine and also directly effect the power production capability as well. Every performance mod will change the sound of an engine. Imagine going from a 2 barrel throttle body to a 900 CFM Holley 4 barrel one. Sound different? You bet! Better horsepower? Read on.
Let me mention this one's not for beginners. You need a good working knowledge of engine and injection repair techniques.
1. Open hood. (Instructions are in your owners manual) Just act like you are showing a Ford Lightning owner what a real engine looks like!
2. You did let the pressure down on the fuel injection didn't you? Unplug the fuel pump relay and start the engine and allow it to idle until it cuts off.
3. Remove the factory throttle body and all associated plumbing. Unplug all the electrical connectors, and remove the water lines to the unit. Remove the fuel lines slowly, wearing safety glasses to avoid fuel spray if there is some residual pressure in the system.
4. Do not throw out the throttle body. It is rare. Only the 454's use it. Sell it as a core to one of the re-builders, or sell it to a friend that has the 350 engine truck as an upgrade.
5. (91 and up model) This is where it gets expensive for you guys. Install your new 4 barrel intake manifold. The 90 model has a Q-jet manifold under the throttle body, so skip this step.
6. Install the Howell spacer plate. This adapts the square flange Holley throttle body to the Q-jet, or spread-bore flange intake and also has the required vacuum ports in it. It comes with a diagram of the vacuum line hook up, so I'll skip that part.
7. Re-work the factory fuel lines to adapt to the new throttle body. Careful bending and some pipe adapters should be adequate.
8. Install the new unit, do not over torque. This will warp the throttle body and cause the throttle plates to bind. Look on the bright side, it will only get a chance to do this once if you mess this step up. A big-block will turn 6000 RPM.....once. Hook up the fuel lines, and all vacuum lines as shown on the chart.
9. Install the new throttle cable, working from under the dash. You will need to adapt the bracket to hold the cable on the throttle body end.
10. You will want to close off the unused water lines that were hooked to the old throttle body. You can just loop the line back, hooking the outlet to the inlet, or use some plugs to cap the lines.
11. Go buy a GM double return spring set. Install this so that you get full return to idle. Test this with the motor off. Duh.
12. Grind off the tabs inside the production air cleaner so it will fit on the Holley TB. The lid should fit if you hammer the center down a tiny bit to allow the stud to be exposed. Use a block of wood to preserve the painted finish. Watch the vent line to the rocker cover. Check to insure the linkage to the TB does not bind.
13. Ya gotta adapt the two connector system to the single connector required by the Holley TB. Open up the ribbed wiring cover on the right side over the rocker cover. Find the two twisted pairs of wires there colored blue, green, red, and white. Cut these four wires ahead of the MAP bracket about 8" from the rear of the rocker cover. Strip and connect the vehicle wires to the new harness for the Holley. Blue to blue, green to green. then connect red to pink (either one) and white to pink. Butt splices work great here. Tape everything up nice and use tie-wraps to hold the new wires in place. Hook up the new connector to the Holley. Tape the four pin IAC connector up, it is no longer needed.
14. Inside the truck, remove the glove box liner. The engine computer is behind the glovebox near the firewall. I know you already disconnected the battery, didn't you? What? Who cares if the radio looses the pre-set stations!
15. Unplug and remove the computer and remove the small access door. Using a small screwdriver, unlatch the eprom cover, and remove the eprom from the computer.
16. Install the custom programmed Howell chip and re-install all that crap you took out. The chip will only go in one way, you will have to look at the old one, and orient the new one the same way. Be careful not to damage the chip, its pins, or the computer.
The fun part:
17. Start this puppy up! Let the fuel pump run for a few seconds to pre-fill the new TB. It should run if you did everything right. If it starts, let it idle for a bit to smooth out and purge the air out of the system. Check immediately for any fuel leaks and correct them. Also, look over the wiring and fuel lines to insure that they are not where exhaust heat will melt them.
18. All emissions equipment remains operational. The only function lost is the IAC or Idle Air Control. The computer can not control your idle speed because the passages for this unit are not in the Holley TB. After warm up, set the curb idle to about 8-900 RPM. This should let the engine idle even in gear with the A/C on.
19. Just like some of the other tweaks presented here, the computer requires some reprogramming time. It will take a while of everyday driving to get the data fields full of the normal operating parameters. This adaptive learning usually is almost complete after about 20 start and drive operations.
20. Here is an odd note to add. Because there is no longer heated (power robbing) water flowing through the throttle body you can experience icing. Air gets cold when you expand it. Use an air nozzle from an air compressor. The air nozzle will get cold with use. When you flow air into the engine, the vacuum under the throttle plate 'expands' the air as it flows in. This will cause cooling of the throttle plates and the surrounding metal components. In certain temperature and humidity conditions, ice will form rapidly in the throttle bores. 30-40 degrees outside air temperature and high humidity will cause this. The ice can completely block the bores, or hold the throttle open. Be aware of this and if the idle is suddenly erratic on a day like described, just allow a longer warm up time to correct this problem. As soon as the engine warms up, this problem disappears.
21. Another note. You can adjust your fuel pressure on the new TB. 11 PSI is the setting the prom was written for, but up to 13 PSI should be available from the factory fuel pump mounted in the tank. Use caution here, monitoring any changes using an OTC analyzer looking at O2 sensor data while operating at full throttle. Too much fuel is just as detrimental to power production as too little. Also, this mod usually passes inspection if they just sniff and stick. The visual should pass as long as you do a clean factory like install. How many of those inspection geeks have ever seen a 454SS anyway? Oh yeah, the Holley is not progressive. All four barrels open up at once. Talk about punch! Still it is very driveable with the modified linkage as supplied by Howell.
Now, when you mat the throttle on this big-block, you are gonna hear that big ass moan from under the hood. You know when you hear that new sonic signature that you really did do something good for making horsepower, and bad for Ford owners in your neighborhood!
Here is a post-script for the article from one of the web site readers:
Cool article on the throttle body swap! As I read it, I thought of a couple things that I wanted to pass along based on some hard lessons learned:
1) The Holley/Howell throttle bodies can be ordered from Howell with an IAC motor that plugs into the factory connector, giving you the same idle control that the SS came with from the factory. Also, the throttle body can be ordered with drilled "ported" vacuum connections for the EGR line (S port) and the CAN line (A port) in addition to the other normal vacuum ports. This retains all of the factory emissions control strategy, and will help a person to pass some of the more sophisticated state emissions tests.
2) An easy way to tell whether the MEMCAL has been installed correctly in the PCM, and contains valid codeset, is to watch the SERVICE ENGINE SOON light as you key on. Make sure the ignition is off for at least twenty seconds. Turn the key to the run position without starting the engine and watch the SES light. It should illuminate, then go out, then illuminate again and stay illuminated. This is called a SES light bounce. If you do not get a bounce then something is wrong and damage could result. If you try to start/run the engine when a proper SES light bounce is not present, then the computer will default to backup fuel and spark mode because it cannot execute a valid computer program. This can happen if the MEMCAL is in backwards, or not seated, or contains a faulty program, or if the PCM has been damaged electrically.
3) You DO NOT want to ever run the Holley/Howell in backup mode, or you will damage the cylinder bores with excess fuel. Backup fuel mode is factory calibrated for two 75 pound per hour injectors. The four Holley injectors deliver 80 pounds per hour of fuel each, which is in total a little over twice too much fuel for the engine. Backup fuel is usually around 12:1 or richer from the factory, and at twice the fuel delivery rate, you will be trying to run at 6:1 or richer!
4) Forget trying to get more fuel flow through the Holley injectors via increased fuel pressure. When the Holley injectors are "paired" and driven by the factory PCM, they will only tolerate 15-16psig fuel pressure, with a fully charged battery and a good alternator. At 18-20psig under the same conditions, the injectors intermittently shut-down or stop flowing completely. Still, at 15-16psig, you will have enough fuel delivery for just about 600 Hp.
Hope this helps a little. With other program and hardware mods the Howell/Holley throttle body is an excellent foundation for substantial horsepower and "fun factor" improvements.
Walt Sherwin firstname.lastname@example.org
Here is the contact information for:
Howell Engine Developments
24356 Sorrentino Ct.
Clinton Township, MI 48035