IPB

Welcome Guest ( Log In | Register )

 Forum Rules 
Northern Tool + EquipmentUnbalanced EngineeringHotpart.comFRRAX MerchandiseEastwood
 
Reply to this topicStart new topic
> Vortec head thermostat bypass, fuel, and tuning questions, TBI 350, vortec longblock swap
robz71lm7
post Jan 15 2011, 03:50 PM
Post #1


Veteran Member
*****

Group: Moderators
Posts: 2,615
Joined: 25-December 03
From: Louisville, KY
Member No.: 40



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.
Go to the top of the page
 
+Quote Post
1meanZ
post Jan 16 2011, 02:30 PM
Post #2


Mullet club chairman
**

Group: Advanced Members
Posts: 776
Joined: 25-March 06
From: South Bend IN
Member No.: 1,135



QUOTE (robz71lm7 @ Jan 15 2011, 10:50 AM) *
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?

QUOTE (robz71lm7 @ Jan 15 2011, 10:50 AM) *
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.

QUOTE (robz71lm7 @ Jan 15 2011, 10:50 AM) *
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/
Go to the top of the page
 
+Quote Post
pknowles
post Jan 17 2011, 07:26 PM
Post #3


Experienced Member
***

Group: Advanced Members
Posts: 1,425
Joined: 12-February 04
From: Huntingtown, MD
Member No.: 193



Rob,

I just went out to look a my truck, there most currently are coolant bypass hoses. One goes through the heater core and another hose goes straight back to the water pump.

If you plan on using the old TBI unit, I don't see why you couldn't use the TBI fuel pump especially if you are using the TBI ECU. I have no idea if the stock TBI unit can keep up with the increased airflow of the vortec.

I had to replace my stock distributor gear 1.5 years ago, but decided to replace the whole plastic distributor because it was about time. When I was looking for just the gear, several forums said to use a melonized gear with the stock vortec roller cam. I used what was on the replacement distributor since it was a stock replacement.
Go to the top of the page
 
+Quote Post
robz71lm7
post Jan 20 2011, 07:02 PM
Post #4


Veteran Member
*****

Group: Moderators
Posts: 2,615
Joined: 25-December 03
From: Louisville, KY
Member No.: 40



QUOTE (1meanZ @ Jan 16 2011, 09:30 AM) *
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.
Go to the top of the page
 
+Quote Post
1meanZ
post Jan 23 2011, 01:50 PM
Post #5


Mullet club chairman
**

Group: Advanced Members
Posts: 776
Joined: 25-March 06
From: South Bend IN
Member No.: 1,135



make sure that the rotation of the TBI water pump is the same as the Vortec pump. The TBI pump is reverse rotation (counter clockwise I believe) so if you're going to use the TBI accessory drives make sure that the Vortec water pump is supposed to spin CC as well...

When adjusting your fuel pressure make sure you get it dialed to where Brian recommends it. Fuel pressure will have a huge effect on injector flowrate, and he can't get you a good tune if he doesn't know exactly what your FP is.

It has been well documented that the 350 TB will flow enough for your needs, but I'd still port it and do the "ultimate TBI mods" found on thirdgen.org or fullsizechevy.com
Go to the top of the page
 
+Quote Post

Reply to this topicStart new topic
1 User(s) are reading this topic (1 Guests and 0 Anonymous Users)
0 Members:

 



Lo-Fi Version Time is now: 16th April 2014 - 09:56 PM