NOOB to TBI ... not so great with tech

[tigger4x]

Greetings TBI techies ... Although I'm just getting my feet wet in your world I am already convinced this mod is one I want for my '74 -10 with 401/TH400/QT. I apologize upfront for any of my misconceptions, misinterpretations and ramblings as I stumble along. Like most I am a budgeter and therefore am willing to take some time to find the deals and want to get it right the first time.


Question One ~ I've seen a lot of mention about programming, cabling and the like. Will I need any of this once the TBI has been installed? If it isn't then I'm hoping I can get some help from someone who already has these items. And if I ever sold my truck it'd be good to know as I like to be forthcoming with the buyer regarding mods I've done.

Question Two ~ I've seen a lot of threads that address the 360 but not the 401. Is there anything different between the two displacements in getting a "junk yard" TBI system functioning at peak efficiency?

Question Three ~ Does changing out the intake, cam, lifters or anything have an affect on the TBI system? I have an Edelbrock Performer and have been looking at upgrading the cam and lifters. I sometimes tow a trailer and am considering a slide-in camper; hence the RV type cam/lifter kit.

Question Four ~ The dizzy is the original with a pointless unit mod; they both look like they've seen better days. I've been thinking that I could benefit from an HEI unit versus a newer/rebuilt stock dizzy. Would this be a good match for the TBI or is there a better way to go?

Question Five ~ The age old question ... Assuming that everything stays the same from what I have now to a TBI system what kind of gains can I expect to see beyond easier start up and compensation for temp, elevation, etc. Any realistic gains in MPG? At 9-10 getting a couple more would be sweet.



Thanks for your time and patience!


I'm located in Camarillo, CA 93010

[Renodemona]

I have an Edelbrock performer on mine, works just fine. I have a 2-wire HEI dizzy. Works great, but of course means no timing control from the ECM. If you're replacing the dizzy anyway, might want to get an 8-pin setup (covered in some other builds). You don't -need- timing control, but if you're replacing parts anyway its not any harder to set up. I didn't do it because I had this nice new awesome HEI that was working Ah Mah Zing and I didn't want to dump it I haven't programmed anything on mine, just had a buddy read out some codes when I was having troubles. If you keep the stock programming, it works just fine. If you want to optimize the system for your needs you will want to get some stuff. I don't know what specific stuff you'll want though as I don't plan on changing anything right now. So I think I addressed 2 of your five questions? Good luck! It's fun once you get to start messing around with it. Hardest part is taking apart a running engine but it's not too bad.

[tgreese]

Greetings TBI techies ... Although I'm just getting my feet wet in your world I am already convinced this mod is one I want for my '74 -10 with 401/TH400/QT. I apologize upfront for any of my misconceptions, misinterpretations and ramblings as I stumble along. Like most I am a budgeter and therefore am willing to take some time to find the deals and want to get it right the first time.


Question One ~ I've seen a lot of mention about programming, cabling and the like. Will I need any of this once the TBI has been installed? If it isn't then I'm hoping I can get some help from someone who already has these items. And if I ever sold my truck it'd be good to know as I like to be forthcoming with the buyer regarding mods I've done.

There's parts, and there's programming. Installing the parts is separate from the programming. You can install all the parts and it won't be optimal until you program the parts for the engine. Think of the programming as tuning the system for the specific engine.

If you buy from a third party that claims that the system is programmed to your engine, then you should be able to bolt on the parts and have the tuning be near optimal. How well that works depends on the vendor and how much they are willing to do to optimize the system to your engine.

Question Two ~ I've seen a lot of threads that address the 360 but not the 401. Is there anything different between the two displacements in getting a "junk yard" TBI system functioning at peak efficiency?

At a minimum, the programming will be different for a 401 vs a 360. A system set up for a 360 should work on a 401, but it will not be optimal.

Question Three ~ Does changing out the intake, cam, lifters or anything have an affect on the TBI system? I have an Edelbrock Performer and have been looking at upgrading the cam and lifters. I sometimes tow a trailer and am considering a slide-in camper; hence the RV type cam/lifter kit.

Yes, everything you change about the engine from stock changes the programming.

Question Four ~ The dizzy is the original with a pointless unit mod; they both look like they've seen better days. I've been thinking that I could benefit from an HEI unit versus a newer/rebuilt stock dizzy. Would this be a good match for the TBI or is there a better way to go?

Pointless unit mod? You mean the Duraspark? I don't see any advantage to the HEI over the Duraspark. Do you want the computer to control spark advance? Most do. Howell sells a system without spark control, and it's basically an electronic carburetor. But theses system have the capability to control spark advance as well.

Question Five ~ The age old question ... Assuming that everything stays the same from what I have now to a TBI system what kind of gains can I expect to see beyond easier start up and compensation for temp, elevation, etc. Any realistic gains in MPG? At 9-10 getting a couple more would be sweet.

"Should" is the operational term. You "should" be getting better than 9-10 mpg with a carburetor. You "should" be able to do somewhat better than a carburetor with fuel injection, esp. with spark control.

You could blast all that away easily with spirited driving...

[tgreese]

Ok, it's a '74 - that means it has a Delco points distributor and was converted with the Pertronix kit or similar.

There are lots of ways you can go with this. The HEI is one option, though I would be reluctant considering all the horror stories about the aftermarket HEI distributors.

The Pertronix basically takes over the job of the points, and switches the coil on and off, just like the points. Not sure how you would adapt that to work with the TBI computer.

I would probably convert the Delco distributor to make a variable reluctance (VR) trigger like this http://www.junkyardgenius.com/jeep/cj502.html or substitute a Duraspark distributor from a '78 or later. Then I'd use the external GM ignition module http://www.megamanual.com/ms2/GM_7pinHEI.htm In both cases you'd have to pin the distributor to disable the mechanical and vacuum advance so the TBI computer could control the advance.

[243]

An easy route for me was buy a Motorcraft distributor from Oreilly and tack weld the advance.

Big cap adapter and cap.

There are plenty of tuners available but the stock GM 4.3 BIN had my 258 running okay with quite a bit of assistance from Bill Hamilton. Although I want to get into programming I decided the fastest route was to order a custom chip from Bill and pay him back for some of the free help I received. The new chip runs much better than the original GM 4.3 BIN.

BTW, my 79 Waggie with a 401/TH400/QT 30x10.50's (forgot the diff ratio) was darned consistent, 10 mpg.

If you are lucky, I would guess 12-13 *if* the engine is in good shape and your driving habits don't change.

In my case, I would probably get 8 mpg with TBI