How to Put a Vortec Motor in a TBI Truck

[Kens1990K2500]

Only if the existing TBI distributor is no longer serviceable. They do have problems with the magnet near the pickup coil cracking. The pickup coil itself, the gear at the bottom, and the module are readily replaceable. Better to have a "good used" Delco distributor than a brand-new Communist Chinese knockoff.

I replaced my distributor with a new (American made) one from Davis Unified Ignition and am pleased with the quality and how the truck runs. Was originally going to rebuild my original, but it was too far corroded.

 

[FourEightZero]

The purpose is to heat the plenum during cold-starts and cold weather, keeping the intake nice 'n' toasty so that the fuel vaporizes nicely.

Hey Schurkey,

I'm currently having trouble with stumbling at cold start and snapping open to WOT from a dead stop. Engine feels/sounds great outside of these two scenarios.

I'm working with Dave @ Old School EFI to get the tune up to ***** (engine is modded- vortec heads/dual plane intake, everything else TBI)

Anywho.. I'm suspecting that I may have a fuel vaporization issue at idle/stop when when I snap the throttle open. AFR jumps up to 18 for about a second (the tweaks Dave has been doing has lessened this) then it drops, engine kicks in, and acceleration is smooth and strong.

Also, I will be encountering winters below freezing. This engine does not like running cold.

One more thing I've noticed during all the datalog runs: The stumble seems to go away after the engine heat soaks a bit.

Is it possible that I'm getting fuel condensation on the floor of the plenum? Been thinking about running the heater core bypass through the crossover underneath the plenum if this issue cannot be tuned out. The other car guys I know are advising against heating up the intake for obvious reasons.

 

[Schurkey]

Exhaust heat works way better. Faster, hotter. But that's pretty-much not an option with Vortec heads--one of their downfalls.

Hot water would be better than nothing. The TBI intake manifold essentially uses both hot coolant and exhaust.

If the engine runs better when heat-soaked, I think that's telling you that the manifold is too cold for appropriate vaporization. You could always plumb in a ball-valve to shut the hot coolant off.

 

[PlayingWithTBI]

AFR jumps up to 18 for about a second (the tweaks Dave has been doing has lessened this) then it drops, engine kicks in, and acceleration is smooth and strong.

I'm curious, is Dave w adding to your AE table to give it some more fuel when you stomp on it?

 

[FourEightZero]

I'm curious, is Dave w adding to your AE table to give it some more fuel when you stomp on it?

Yeah, he's adjusted that as well as SA and VE. Small tweaks every time and it's getting better, but we're not quite there yet.

 

[PlayingWithTBI]

Small tweaks every time and it's getting better, but we're not quite there yet.

He's great with these, you'll get there

 

[FourEightZero]

Exhaust heat works way better. Faster, hotter. But that's pretty-much not an option with Vortec heads--one of their downfalls.

Hot water would be better than nothing. The TBI intake manifold essentially uses both hot coolant and exhaust.

If the engine runs better when heat-soaked, I think that's telling you that the manifold is too cold for appropriate vaporization. You could always plumb in a ball-valve to shut the hot coolant off.

I thought you guys might like to see this.

Same tune. Same highway onramp on the way back to the house. Before and after I plumbed in the intake plenum heating circuit.

Red line is the AFR. Lean spike is almost completely gone!

Thanks Schurkey!

 

[NicoF]

"Can I swap a Vortec motor in place of my TBI motor and does it just bolt in place?"

Yes, you can swap a Vortec motor in place of a TBI motor, but no, it doesn't bolt in place. So, what does it take?

Head and Intake Differences:
The Vortec manifold has eight bolts, two on each corner, drilled vertically, higher on the head, versus the TBI intake that has two in each corner, drilled perpendicular to the mounting surface, and an additional two in the middle of each side. You would need to drill and tap holes to physically mount a TBI manifold to Vortec heads, and that doesn't fix the problem of covering the intake ports. You might get away with using the Vortec mounting holes to "clamp" the outer edge of the TBI intake, but I'm not stupid or desperate enough to do it. The Vortec intake bolts are significantly smaller, and you'll be putting them in shear as well as tension.

View media item 32351Pic: Note the differences in bolt holes.

The Vortec intake manifold has taller ports, and the TBI manifold doesn't cover the openings. Some people have proposed welding to build up the top outer edge of the TBI port and then porting the inside to match the Vortec port, but that's a lot of welding on an aluminum intake. Good luck with that. If you're sane, you'll want a Vortec-specific intake.

View media item 32352Pic: Intake sitting with TBI head on the left, Vortec head on the right. Note the gap at the top of the intake port and the bolt holes above the manifold mounting surface

The Vortec heads are missing the coolant bypass hole that the TBI and earlier heads have. Without a coolant bypass circuit you will get weird overheating events.

View media item 32348Pic: Note the bypass hole in the TBI head at left, missing on the Vortec head at right.

The exhaust gas crossover port through the intake manifold is blocked off on Vortec heads.

The valve covers on Vortec heads have a narrower PCV baffle. It's almost unnoticeable, but if you switch to aluminum roller rockers, the Vortec valve cover will sometimes fit when TBIs won't.

The missing center holes preclude the ability to mount the engine controls on the passenger side of the intake. I relocated mine to the valve cover. I mounted my coil off the back, driver's side of the intake. It has long enough leads to put it anywhere out of the way.

The TBI intake gaskets often have a piece for blocking off the rear coolant passage through the intake. Some intakes have a rear coolant passage, some don't. I don't use the coolant block off in the gasket. If my intake has a coolant passage, the coolant will flow. If it doesn't, the coolant won't flow. Simple as that.

Block Differences:
The big difference in blocks has already been mentioned - the coolant bypass. TBI water pumps have an internal coolant bypass built into the pump, block, and heads. The Vortecs changed to an external coolant bypass that runs from an extra port on the water pump to the intake manifold. If you put Vortec heads and a Vortec block in a TBI and want to keep the internal coolant bypass, you will need to drill a hole in the front of the passenger head, drill a hole in the block and run the TBI water pump. I suggest also drilling the rear of the driver's head to prevent future problems if you swap them around.

If you use the Vortec water pump on a TBI block you must plug the coolant bypass port on the block. The port in the block is between sizes for a standard bolt thread, so I tapped mine metric (M10x1.5) and found a bolt that would thread in it. I cut the head off the bolt, put a slot in it for a flathead screwdriver, put some RTV on it, and threaded it in until it was flush.

View media item 32347Pic: Note the untapped coolant bypass hole below the water pump bolt hole.

The fuel pump lever hole is likely undrilled on all the Vortecs, and is usually undrilled on TBI blocks. It's immaterial for most of us.

All Vortecs have roller provisions. TBIs likely don't, but there are exceptions. Having the provisions means upgrading to a roller cam pretty cheaply. Without the provisions you have to buy higher-dollar retrofit roller lifters if you want a roller cam.

The Vortecs have plastic "Do Not Re-Use" timing covers that are missing two bolts from the traditional timing covers. Most people don't have any problems with leaks from leaving those bolts out when swapping between timing covers. You can re-use the Vortec timing covers. Just be sure and put a dab of silicone in the corners.

The Vortec timing cover has a hole for the crank sensor. You'll want to plug that hole or use a TBI cover on a TBI motor.

View media item 32349Pic: Note the missing bolt holes and the crank sensor hole.

The balancer is shorter on a Vortec than a TBI, to fit the reluctor wheel for the crank sensor between the lower timing gear and the balancer. Note that if you keep the reluctor wheel you cannot use the TBI timing cover. You can't use the Vortec balancer without the reluctor wheel.

View media item 32350Pic: Note the reluctor wheel, stacked with the balancer in the timing cover. The reluctor wheel does not fit inside the lower lip on the TBI cover.

As stated earlier, the Vortec water pump has extra coolant ports for the coolant bypass. The extra port should be routed directly to a threaded nipple on the intake manifold's front coolant crossover. There's a nice hole in the accessory bracket to make this easy.

View media item 32317Pic: Note the coolant pipe on the right side of the Vortec water pump. This needs to go to the intake manifold's coolant port. The left side coolant pipe goes to the heater. On a TBI motor the intake manifold coolant port goes directly to the heater.

Once you swap to an aftermarket intake manifold, the serpentine belt support brackets don't fit. You'll be engineering your own solutions. If you have a welder, chopping the brackets and re-welding them to fit is your best option.

Intake swaps
GM Performance Parts' TBI manifold for Vortec heads is $540! Expensive, but this is a bolt on solution for guys who need EGR and don't want to fabricate.

Summit's cheapest aftermarket Vortec manifold for a carbed application is $160 and a TBI adapter is $35 and up. The $35 adapter is simply a 1/4" steel place with bolt holes. The TBI bores are wider than a square bore, so part of your TBI bore will be shrouded by the edges of the intake manifold. If you use a spread bore intake the shrouding is minimal. The true TBI to carb adapters run about $160 and add an inch of space.

View media item 32353Pic: Note how the sides of the square bore on the left jut into the TBI's airflow. The spread bore on the right does not. I didn't have a square bore manifold handy, so both pics are the TBI adapter laid over my square-to-spread bore adapter.

Most aftermarket intakes do not have EGR provisions. There may be an external way to do it, but I have no experience with it.

The brake booster port on a TBI manifold is at the front driver's side of the throttle body. My aftermarket intake had it on the right rear. I put the brake booster tube in my vise, bent and unbent it, and rerouted the hose. You might have to be creative.

The throttle and TV cable are critical! If you get the GMPP manifold, it's likely a bolt-on affair. With any aftermarket intake you're probably going to have to tweak the mounting to keep your TV cable aligned and properly tensioned. There is plenty of advice out there for adjusting your TV cable, but remember that if you get it wrong, you can quickly trash your transmission. You also want to ensure your throttle plates close and open fully, without undue tension when you floor it.

Wow that was amazing super helpful definitely seems like a project that might take more than I thought. But thank you so much for that information that covered just about anything I could think of

 

[NicoF]

Ok well now that I have all I need to know about switching them over how hard would it be to swap the tbi in as it sits…. Pretty much what is the bare minimum I would need to do to get that tbi in

 

[Schurkey]

Ok well now that I have all I need to know about switching them over how hard would it be to swap the tbi in as it sits…. Pretty much what is the bare minimum I would need to do to get that tbi in

Putting the TBI onto a Vortec long-block?

Either the hyper-expensive TBI/Vortec intake manifold from GM, or a Vortec carburetor manifold, with a TBI-to-4-barrel adapter plate.

EGR will be difficult, or impossible. The TBI/Vortec intake manifold has provision for EGR, but it has to be plumbed into the exhaust manifold or headers externally, since GM wasn't bright enough to put an exhaust crossover passage in the Vortec heads. Some (most?) of the Vortec-carburetor intake manifolds won't have EGR provisions at all.

Most TBIs hang the MAP sensor, EGR solenoid, and EST module off of a bracket below and to the right of the TBI unit. Aftermarket manifolds usually don't have a provision for that. They also may or may not have provisions to bolt the alternator brace or A/C compressor brace to the intake.

The Vortec cylinder heads make adapting the throttle/cruise control/transmission TV cable bracket to the left rear of the intake manifold somewhat challenging.

Front accessory drive may/may not align with the water pump pulley, depending on what water pump/pulley you have.