How to Put a Vortec Motor in a TBI Truck

[Erik the Awful]

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?

The Vortec heads aren't drilled for the coolant bypass. Some guys say they've had no problem, but I was getting temperature spikes. I used the TBI water pump. The difficulty with the Vortec pump is routing the bypass hoses through the TBI accessory brackets.

 

[badfnz]

The Vortec heads aren't drilled for the coolant bypass. Some guys say they've had no problem, but I was getting temperature spikes. I used the TBI water pump. The difficulty with the Vortec pump is routing the bypass hoses through the TBI accessory brackets.

So did you drill the heads so you could use the TBI pump?

 

[badfnz]

How do you plan to get the EGR to work?


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.


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.

I will be purchasing a vortec style EGR tube and vortec exhaust manifolds for the EGR.

Are you sure all the gears are melonized? I read only the roller cam engines had these.

 

[Schurkey]

All I know is what the parts department of Pace told me when I bought my crate engine, ~Y2K.

 

[Schurkey]

So did you drill the heads so you could use the TBI pump

Drilling the heads is needed on a TBI block, which would already have the double-drilling for the coolant bypass back to the water pump gasket surface. Most Vortec blocks don't have that drilling, so drilling the head(s) doesn't matter until the block also gets drilled.

 

[L31MaxExpress]

I have used a Vortec pump with the Vortec accessories and a TBI pump with TBI accessories. Stepping back nearly 20 years ago, used the V-belt pump with V-belt accessories prior to that. I have not hooked the external bypass up on any of them unless it has a Vortec pump. When I use an older pump setup for internal bypass I drill the RH head for the bypass. I have yet to run across a Vortec block without the bypass passageways drilled from GM, but I do know they exist. The TBI era stuff has constant bypass through the heater core and I always drill 2 x 1/8" holes in my thermostats. The latest budget L31 build I did a write up on, has the Vortec pump, I plumbed up the external bypass. It warms up quickly and runs a very consistent temperature, despite having a double bypass and drilled thermostat. I say double bypass because the heater control valve is open unless the A/C is in recirculate on the 1987 G20 van I set it up in. The van was setup factory without a heater control valve and I added a 70s style valve and connected it to the vacuum line running to the recirculation door. When you move the a/c controls to recirculate, vacuum shuts the heater valve.

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[rebelyell]

A couple other differences between L31 motor and its sibling sbc:

1) mexican 880 blocks' cylinder liners are markedly shorter than previous blocks; although L31 motor production has been moved from mexico to springfield MO USA a few years back, I dunno if that or other dimensions have changed. Moved on heels of NAFTA ending - USMCA beginning.
1a) That shorter liner length is not an issue with stock OE motors with their 3.48 stroke & thinner metric ringpaks ... but attention should be paid if/when stroke is lengthened etc; whenever ringpak may become closer to bottom than is OE (put a cheap stroker crank in with cheap pistons with wide dump truck rings too & ringpak will get that much closer to bottom of liner).

2) OE L31 have another coolant bypass issue I've not seen addressed in THIS thread. In an OE L31, there is a dedicated bypass hose between top of wp and front of lower intake manifold (not unlike BBC) AND that lower intake actually has a machined seat inside casting (Not like BBC) about 2 to 2 1/2 inches below water neck flange. That seat is for the Different-type t'stat L31 uses which has a moving Disk valve attached to Bottom of OE t'stat. That disk (and its seat) work in tandem to control coolant moving between manifold and top of wp. Take a peek inside OE L31 lower manifold, same for OE T'stat; you'll see.
(2a) I'm not saying they don't exist, but I've Never seen an Aftermarket Vortec L31 intake manifold that has a cast-in or machined seat to accommodate that L31 T'stat's Disk (even though manifold may have a threaded female port for a bypass hose.)

 

[Erik the Awful]

So did you drill the heads so you could use the TBI pump?

Drilling the heads is needed on a TBI block, which would already have the double-drilling for the coolant bypass back to the water pump gasket surface.

I have Vortec heads on an 880 TBI block in WCJr. I did not know about the bypass when I built the engine; it was my first SBC build, so it's not drilled. That's why I switched back to the Vortec water pump.

That seat is for the Different-type t'stat L31 uses which has a moving Disk valve attached to Bottom of OE t'stat.

That sounds like the big block Caddy thermostat. If you run a normal thermostat in its place you get overheating.

Checking RockAuto... Yup. Same style, but apparently different size.

Vortec - https://www.rockauto.com/en/moreinfo.php?pk=3952968&cc=1353327&pt=2200&jsn=1056
Caddy - https://www.rockauto.com/en/moreinfo.php?pk=4483863&cc=1409374&pt=2200&jsn=1227

I learn something new every day!

 

[Majoraslayer]

I've not seen this directly addressed yet, how does Vortec compression stack up against TBI compression?

Specifically the reason I ask is that I see different starter part numbers listed for my '88 TBI truck than the later Vortec trucks. Reading another thread on here, I saw that high-torque mini starters (and a slightly larger "medium size" starter) were used in some of the later TBI trucks and carried over to most of the Vortec trucks. If one were to have an early starter, would it be wise to plan on upgrading to a higher torque starter to handle Vortec compression, or is the compression pretty much the same between the two?

 

[Schurkey]

Not much different in terms of how difficult the engine is to crank over.

Should be a piece o' cake compared to a 11+ to one 427 or 454, or any version of 496 or bigger, including the 8.1L