shelbyt.67
Weirdo
Gotcha, my bad
350 Vortec to TBI conversion
- Thread starter Edahall
- Start date
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Wagonbacker9
One string banjo. Maybe 2
Takes a little more work, but I don't think there is anything stopping you from swapping the guts of the trans, and the longblock into the tahoe. IMO it'd be worth the effort to not take a quantum leap backward in technology.
by all means, it is your truck and you can do what you want with it. But one thing you do have to look at is that the motor that you have now is tunable and you will be lossing that with the tbi swap, along with some fuel millage (depending on gears) you will also be lossing the nice scanable obdII, which for me would be that biggest thing, well that and that the tbi still has the head gasket issues (which was one of your points earlier)
First, let's get a few misconceptions out of the way:
3. As a professional mechanic, I've had at least as many or perhaps more issues out of TBI equipped GM vehicles than Vortec equipped. The manifold gaskets were an issue, but mostly due to a poor initial design combined with the switch to Dex-Cool (which caused similar issues across GM's entire line, not just with the Vortecs) and improper torquing of manifold bolts on the assembly line. New design gaskets, torqued properly, with something other than the Red Death in the cooling system work flawlessly. Vortec heads can and do crack, and it is because of the thinness of the castings. TBI heads do as well, also due to thin spots (usually between the valve seats and around the exhaust), just not as frequently. The CSFI is an improvement over TBI in nearly every way possible. It is a pain in the ass to work on, but it is more efficient, faster (processor wise), more accurate, and easier to diagnose (via OBDII) than the TBI setup. It is more complex, true, but cost wise is comparable. Consider that it costs about 380 dollars to upgrade from the CSFI spider to the ACDelco MPFI spider. Rebuilding a TBI will cost you 160 each for the injectors (new ACDelco, not cheapies) plus another 20 for the gasket kit, plus some more if you want to get a new regulator spring, etc. All told, for ACDelco, the costs of rebuilding the systems are close enough to be a moot point, during which (of course) the inherent flaws in the injection spider are corrected with the upgrade, negating that point as well.
4. True, but only because of torque management, which was introduced to prevent the more powerful, more torquey Vortec engine from completely obliterating the woefully inadequate 4L60E and causing GM more warranty grief. With a 4L60E built to handle what a stock Vortec can dish out and torque management removed, the "seat of the pants" feel and pulling power change quite a bit.
5. This isn't an advantage. Sure, there are more injectors to fail, which would be more money to spend if they failed, but consider this: If an injector poppet fails, you drive home on seven cylinders. I've never shut down one injector on a TBI setup to see how it runs, but I doubt it's much better than an engine running on seven cylinders, and imagine that with half the fuel flow, it's probably a lot worse.
6. This is true of the later modular fuel pump assemblies, not the pump itself. Using the '96 model pump hanger with the replaceable pump cures a lot of the short pump life issues (better cooling) as well as the high cost of replacement. A quick visit to RA shows a 28 dollar difference between the two types using Delphi pumps, which I would hardly call a considerable cost difference. Since you're willing to retrofit the drivetrain, I figure that a drop in fuel pump hanger (minus a harness change) wouldn't be a big deal, and negates any benefits of a TBI pump setup.
All told, the only arguments you make that have merit are 1 and 2. Your Vortec engine is destroyed, you have a low mileage drivetrain out of an older vehicle, and you have to desire to swap it.
Your biggest problem is going to be wiring, plain and simple. You will, of course, need the TBI PCM to run the engine and trans. Splicing the harnesses so that you have adequate signal to all of the gauges shouldn't be difficult, as long as you're good with a wiring diagram. I think the VSS signals were the same, so your speedo should work off the 94 speed sensor. The TBI engine should bolt in the same as the Vortec, though you may have to rework the Y pipe to fit the TBI manifolds. I think that the output shafts on the two 4L60E's will be the same, so the driveshaft should work without issue. Your next hurdle, after wiring, is fuel delivery. Splicing the fuel lines shouldn't be too much of an issue, and I think you can continue to run the Vortec pump with the TBI engine (it will just bypass a lot more fuel). I think the accessories from the Vortec motor will bolt on to the TBI motor, so AC, power steering, alternator, cooling fan, etc should be in the same spot. You may need to change to a CS144 alternator to work with the TBI PCM, though I think you can rig a CS130D to function. I'm thinking of all this on the fly, as I've never seen nor heard of anybody wishing to do this. I'll post more up if I think of anything, but I think that's the bulk of it.
Wait, so when the pump goes in my 98 again I can swap in a 96 unit instead????
Wagonbacker9
One string banjo. Maybe 2
Yes...
Well, I oversimplified it. You would have to make an adapter to go from the 3.125" diameter of the '96 tank sending to the 4.125" '98 tank hole. All that needs to be is a ring of sheetmetal attached to the sender to make it fit the larger hole. You can weld it, though it is a bit thin for that. I prefer sheetmetal screws or pop rivets and fuel resistant sealant (Loctite makes good one). On the later trucks and SUV's the wiring harness is different, and the '96 sender will be missing the fuel vapor pressure sensor for the EVAP system. You can drill a hole and mount it, or have it tuned out and leave it off. You also need the metal, screw on lines, which RA sells in kit form for 63 bucks. Option B is buy the complete Spectra tank, sender, pump, and strap kit for a '96 for 250 (same price as ACDelco fuel pump assembly for a '98) plus an extra 63 for the lines (includes a new fuel filter) and a fuel vapor pressure sensor (you CAN use the one off of the old pump if you're cheap) and for about $100 more than a new pump assembly you can have a new tank, new sender, new pump, and new fuel lines. All that, and your replacement pumps are about sixty bucks for an ACDelco unit.
Side note: One of the major points of failure of the modular pumps (besides heat) comes from the socks (yes, there are two, one on the pump and one on the outside of the housing) stopping up with debris from the plastic tank disintegrating. The proof is finding them BLACK after a few months' running. You can clean the tank, and be somewhat successful, but ultimately it will corrode some more and put more black crap in your pump socks and kill another $250 pump assembly. The solution is to replace the tank, either with an identical new one, or one of the older steel tanks using the above method. Your choice.
Side note: One of the major points of failure of the modular pumps (besides heat) comes from the socks (yes, there are two, one on the pump and one on the outside of the housing) stopping up with debris from the plastic tank disintegrating. The proof is finding them BLACK after a few months' running. You can clean the tank, and be somewhat successful, but ultimately it will corrode some more and put more black crap in your pump socks and kill another $250 pump assembly. The solution is to replace the tank, either with an identical new one, or one of the older steel tanks using the above method. Your choice.
I will choose option B then. Thanks for the info an sry for the derail OP....
Hardly a derail, dude. Just made me slap my head and give a mighty "D'oh!" when I realized what I wrote. The OP could probably use the extra detail for the swap anyway
.Edahall
Newbie
Would this be the smarter way to go? Would the Vortec intake bolt up to the heads on the TBI engine? Would I swap the transmission valve body?
By the way, I'm not exactly sure what killed the original engine. The only thing I know for sure is that it exploded during start up and that it broke the 2 rods on the front 2 cylinders. I suspect that the engine hydrolocked during start-up. I originally thought that the intake manifold gasket was to blame but it had been replaced earlier. So maybe the heads were the culprit? I checked them carefully but could not find anything wrong with them.
