[robz71lm7]

I'm helping my father out with a project on his truck. It's a '91 TBI 350 that to keep a long story short my sister borrowed it and ran the engine out of oil. Under my advice he bought a brand new GM '96-'00 350 Vortec longblock. We also bought the pricey GM aluminum TBI to vortec intake manifold. My father wants to keep EGR for whatever reason so we got the expensive intake.

Before someone asks the truck has a fresh pro-built 700R4 and he also doesn't want the headache of an LSX swap.

Thermostat
As I can see the vortecs have no bypass built-in and you either run a line from the front of the intake below the thermostat to the water pump or drill the thermostat. Is one preferred? Or would 3, 3/16" holes in the thermostat be good enough? Also where on the fuel pump do you tap in? The old fuel pump only has a plug on the back. Also can I get by with a TBI era water pump? I need a new water pump either way and the vortec pump has two nipples on it. Are they for the heater core and bypass? On the '91 the heater core goes straight to the radiator.


Tuning and Fuel
The truck will be stock in the immediate future with a cold air intake, high flow cat, thermostat, and catback being the only mods. We're using '96 exhaust manifolds to allow for EGR. We'll probably upgrade to a heated O2 sensor. Would a fresh fuel pump, adjustable fuel pressure regulator, and stock tbi down to the injectors work for a 250 HP vortec 350?

I was planning on using TBIChips to burn a chip for the truck...any other recommendations?

Distributor
Is a new factory replacement style '91 distributor good for the factory vortec roller cam or does the gear need to be changed? He bought a Jeg's branded external coil complete HEI distributor.
http://www.jegs.com/i/JEGS+Performance+Pro.../40006/10002/-1


I'm trying to keep everything as simple as possible as reliability and ease of maintenance is the #1 concern. I went with the new vortec because I trust it more than the local rebuilds and the swirl port heads are dead after 2500 rpm's if that. The truck is used primarily to tow his boat.

[1meanZ]

I'm helping my father out with a project on his truck. It's a '91 TBI 350 that to keep a long story short my sister borrowed it and ran the engine out of oil. Under my advice he bought a brand new GM '96-'00 350 Vortec longblock. We also bought the pricey GM aluminum TBI to vortec intake manifold. My father wants to keep EGR for whatever reason so we got the expensive intake.

Thermostat
As I can see the vortecs have no bypass built-in and you either run a line from the front of the intake below the thermostat to the water pump or drill the thermostat. Is one preferred? Or would 3, 3/16" holes in the thermostat be good enough? Also where on the fuel pump do you tap in? The old fuel pump only has a plug on the back. Also can I get by with a TBI era water pump? I need a new water pump either way and the vortec pump has two nipples on it. Are they for the heater core and bypass? On the '91 the heater core goes straight to the radiator.

I honestly don't follow you in your description of the "bypass". I'm dumb and need more details. If I were you I'd run the TBI water pump, it is reverse rotation and will match all the other accessories. If you're running a TBI water pump and a TBI intake, I'm not sure how you're missing anything as far as the cooling system is concerned.

I also don't follow your question on the fuel pump. The fuel pump is in the tank, are you trying to tap into the lines for a gage or something?

Tuning and Fuel
The truck will be stock in the immediate future with a cold air intake, high flow cat, thermostat, and catback being the only mods. We're using '96 exhaust manifolds to allow for EGR. We'll probably upgrade to a heated O2 sensor. Would a fresh fuel pump, adjustable fuel pressure regulator, and stock tbi down to the injectors work for a 250 HP vortec 350?

I was planning on using TBIChips to burn a chip for the truck...any other recommendations?

I would strongly recommend a fresh fuel pump for a TPI F-body application, the stock pump is barely enough for a stock L05. Adjustable regulator is a good idea as the stock regulators tend to vary wildly in the pressure they are set at. There are mods you can do to the stock throttle body to make it adjustable. There are also lots of free mods you can do the the stock TB to improve the flow, they are called "ultimate TBI mods" More info on the TB mods can be found on the TBI board at thirdgen.org, or fullsizechevy.com. I highly recommend thirdgen.org over FSC.... Stock injectors should do the job for you at your level with a little more fuel pressure, I'd try to get a set of shorty headers on the truck if at all possible, the stock manifolds really aren't that great. If you don't want to invest in the equipment to tune it yourself, TBIchips.com is the best place I know of, but I'll be honest, mail order tunes aren't worth a damn. Your combo will be fairly common, so he may have a tune that is great, but be careful and make damn sure that it's not lean or detonating. The last thing you want is a lean tune with too much timing pulling a boat around.

Distributor
Is a new factory replacement style '91 distributor good for the factory vortec roller cam or does the gear need to be changed? He bought a Jeg's branded external coil complete HEI distributor.
http://www.jegs.com/i/JEGS+Performance+Pro.../40006/10002/-1


I'm trying to keep everything as simple as possible as reliability and ease of maintenance is the #1 concern. I went with the new vortec because I trust it more than the local rebuilds and the swirl port heads are dead after 2500 rpm's if that. The truck is used primarily to tow his boat.

I'm concerned that the 91 style dizzy will have the wrong gear for a roller cam. You need to go with a melonized gear from GM. http://www.summitracing.com/parts/ACF-10456413/

[robz71lm7]

I honestly don't follow you in your description of the "bypass". I'm dumb and need more details. If I were you I'd run the TBI water pump, it is reverse rotation and will match all the other accessories. If you're running a TBI water pump and a TBI intake, I'm not sure how you're missing anything as far as the cooling system is concerned.

I also don't follow your question on the fuel pump. The fuel pump is in the tank, are you trying to tap into the lines for a gage or something?

I found out the answer. Anyways in a traditional SBC on the passenger side of the block there is a small hole below a larger discharge hole for the water pump to feed the block. The smaller hole actually runs up and does a 90* turn and comes out the deck around cyl #2 and into the head. This allows even temperature distribution in the block and heads while the thermostat is closed and eliminates hot spots. Although all blocks have this hole, vortec heads do not have a hole cast into them so it dead heads. People either drill the thermostat or they tap into the small hole in the vortec conversion manifolds that's below the thermostat and run the bypass external. Vortec headed engines all run an external bypass whereas the old TBI and TPI and older SBC's run an internal bypass. Both the GM and Edelbrock conversion intake have a 3/8" NPT hole in the front of the manifold coming out at the horizontal for this purpose.


Phil, thanks for the info on the water pump! I'm either going to run a vortec water pump and tee into it's suction port or run to the suction side of the radiator. These TBI pumps have zero ports as the heater core ties into the radiator.


Anyways for anyone curious I contacted Brian at TBIChips and the stock 350 TBI will flow enough air for a Vortec 350, but it needs more fuel flow. I just need to upgrade to a '96+ fuel pump and different fuel pressure regulator spring to boost the pressure and I can use the stock injectors with his tuning.