How to Put a Vortec Motor in a TBI Truck

[Majoraslayer]

Has anyone here happened to actually try drilling the bypass into the Vortec heads alongside running the GMPP intake? I don't know if the bypass passage circuit usually flows through any parts of the factory TBI intake, or just through the heads and block until the thermostat opens. The GMPP intake is provisioned to connect the bypass hose from the Vortec water pump, so if any part of the bypass circuit is supposed to flow through the intake it's unclear if that intake will even allow it.

Edit: nevermind, I answered my own question. If I understand right, those bypass holes should just flow a little coolant throughout all of the system into a point past the thermostat. I got so caught up in working out what goes where I over-complicated it for myself and overlooked the obvious lol

 

[Tim W]

For what its worth i have a vortec block, and vortec heads in my 94. I still run the TBI h20 pump, but have a 180° acdelco thermostat. I do not have any holes drilled in my block or heads. I do however, have the coolant bypass hole in my H20 pump blocked off.

I have the heater hose plummed into my intake manifold near the thermostat housing.

I live in Houston Texas and and in the summer with the ac going, i may see 190ish on my engine temp. I do not have any wierd temp spikes.

Iv thought about changing over to a vortec h20 pump or drilling the holes, but if its not broke i should just leave well enough alone.

Furthermore, my truck is not my daily so Im not sure if thaf has anything to do w it.

 

[Majoraslayer]

Has anyone here happened to actually try drilling the bypass into the Vortec heads alongside running the GMPP intake? I don't know if the bypass passage circuit usually flows through any parts of the factory TBI intake, or just through the heads and block until the thermostat opens. The GMPP intake is provisioned to connect the bypass hose from the Vortec water pump, so if any part of the bypass circuit is supposed to flow through the intake it's unclear if that intake will even allow it.

Edit: nevermind, I answered my own question. If I understand right, those bypass holes should just flow a little coolant throughout all of the system into a point past the thermostat. I got so caught up in working out what goes where I over-complicated it for myself and overlooked the obvious lol

I remembered where I actually meant to go with this question. There are front and rear holes undrilled on both Vortec heads. Reading through this thread, my understanding is that the bypass circuit on a TBI block runs through an extra small hole connected to the water pump in the front of the block. Coolant flows a small amount from the water pump into that hole, up through a passage in the block to the bypass hole in the front of the passenger side head, allowing that smaller flow of coolant into the cooling circuit even when the thermostat is closed.

The heads are symmetrical, so this bypass hole present in the front of the passenger head is equally present at the rear of that head. Does that rear hole on the passenger side (and front on the driver side) have any crucial function? It's only mentioned here to drill the front passenger hole and the rear driver hole (in case you ever swap the heads around) but I was wondering if the other holes are important for anything as well and might need to be drilled. The head gaskets do seem to be provisioned for them.

 

[Schurkey]

my understanding is that the bypass circuit on a TBI block runs through an extra small hole connected to the water pump in the front of the block. Coolant flows a small amount from the water pump into that hole, up through a passage in the block to the bypass hole in the front of the passenger side head, allowing that smaller flow of coolant into the cooling circuit even when the thermostat is closed.

Backwards.

The water pump forces coolant into the block through the big holes cast into the water pump and block. The coolant gets pushed through the right-side bank of cylinders, eventually up into the head through a heap of small holes in the block, head gasket, and cylinder head. The bypass allows a small proportion of that coolant to go back down to the block, and into the suction side of the water pump via a double-drilled (one section downward at an angle through head, head gasket, and block, and another section horizontal to the water pump gasket face) hole in the various parts.

The heads are symmetrical, so this bypass hole present in the front of the passenger head is equally present at the rear of that head. Does that rear hole on the passenger side (and front on the driver side) have any crucial function?

Not that I'm aware of. I always though it a compromise that the left bank had no coolant bypass aside from what might occur through the intake manifold crossover to the right cylinder head...but nobody consulted my Mom's eggs when this engine was being developed.

 

[Majoraslayer]

Just out of curiosity, has anyone done this swap and measured their power gains? The factory 5.7 Vortec setup is rated at about 255 HP while TBI is rated at around 210 HP. I would guess with no other improvements one might expect ~30 HP gains since the Vortec intake probably accounts for part of that difference, with the main selling point of this swap being that the better flowing heads opens up more effective potential from other mods. That's just a guess though, I'd like to hear from anyone who's done the swap and actually tested it.

 

[Erik the Awful]

The hard part is going to be finding someone who's done the swap and didn't upgrade the cam at the same time. Just as hard is going to be finding someone who's engine didn't need rebuilding before the swap.

 

[Majoraslayer]

The hard part is going to be finding someone who's done the swap and didn't upgrade the cam at the same time. Just as hard is going to be finding someone who's engine didn't need rebuilding before the swap.

That's very true. I'd document it myself, but like you said I'm also upgrading the cam to a Summit 8800. I also already had an exhaust upgrade. As much as I've seen everyone on the internet talk about the terrible flow of TBI heads though, I would be curious to see some side-by-side performance comparisons on head swaps alone.

 

[L31MaxExpress]

Just out of curiosity, has anyone done this swap and measured their power gains? The factory 5.7 Vortec setup is rated at about 255 HP while TBI is rated at around 210 HP. I would guess with no other improvements one might expect ~30 HP gains since the Vortec intake probably accounts for part of that difference, with the main selling point of this swap being that the better flowing heads opens up more effective potential from other mods. That's just a guess though, I'd like to hear from anyone who's done the swap and actually tested it.

About 15 hp peak to peak. Up around 5,500 above peak it was closer to 30. Tq loss from off-idle until nearly 4,500 rpm. That was swapping Vortecs on a TBI crate engine that had low mileage using the GM TBI manifold. Truck had the stock cam, 1.6 rockers, headers and decent exhaust. A lot of the vortecs added power is the intake manifold, multipoint injection, roller cam and better dual cat exhaust system.

 

[badfnz]

I'm going to be swapping a crate L31 into my '88 K5 to replace my current TBI motor. I'll be using the correct GM TBI to Vortec intake manifold. I'm still a little confused on whether or not I'll need a Vortec water pump and fan. Will the TBI WP work fine but the Vortec WP might provide better cooling? Or is the Vortec WP absolutely necessary no matter what?

Also, there seems to be confusion by me and others on the proper throttle cable bracket to use. Edelbrock 8031 was linked in this thread, but Edelbrock themselves say 8032 is required for any Vortec manifold, however the reviews say 8032 doesn't work at all. 8030 and 8036 also look like options. Anyone know which one will work best for the Vortec/700R4 combo?

Last question (for now), I know I need a melonized distro gear to work with the roller cam in the Vortec. From research, it looks like I need GM 19052845, which is discontinued. Is there another gear that will fit a .428 shaft?

 

[Schurkey]

I'm going to be swapping a crate L31 into my '88 K5 to replace my current TBI motor. I'll be using the correct GM TBI to Vortec intake manifold.

How do you plan to get the EGR to work?

I'm still a little confused on whether or not I'll need a Vortec water pump and fan. Will the TBI WP work fine but the Vortec WP might provide better cooling? Or is the Vortec WP absolutely necessary no matter what?

Both are reverse-rotation. The big deal will be belt alignment.

The next deal will be the cooling system bypass arrangement, which MIGHT be handled by the heater core if there's no heater control valve. Far as I know, only the SUVs with rear HVAC used a heater control valve.

I know I need a melonized distro gear to work with the roller cam in the Vortec. From research, it looks like I need GM 19052845, which is discontinued. Is there another gear that will fit a .428 shaft?

All the small-shaft-diameter GM gears are melonized--TBI and Vortec.

I learned that when I bought my TBI crate engine from Pace. Called 'em up after receiving it wanting to know how to get a melonized gear...and the parts department told me I already had one from the TBI engine I took out.