350 TBI Newbie, First Truck, need help

[jared6180]

Hi,

This is my first truck, a 91 GMC Sierra 1500 SLE, Regular Cab, shortbed with the step side bed.

The truck has a 5.7L 350 TBI, and I am wanting to pump it up to 400hp. Where do I begin with this project? I thought about just buying a crate motor, but would it be less expensive to pull the motor I have and build it? The motor has been babied the last 10 years because my grandfather owned it, and put only 40k miles on it! I know the truck is solid, and has been VERY WELL maintained.

I was also wondering if you guys could provide me with some specs on the truck. I am talking about stock hp/trq #s, tranny ratios(700r4 I think), and also the rear gear ratio.

I saw some people on a camaro forum talking about pulling the rear differential because they are weak, and installing a Ford 8.8 diff instead. Id this something I will have to worry about with the truck?

Thanks for the help ahead of time, I am sure I will have a ton more questions later.

Thanks,
Jared

[YenkoST]

Stock 350 TBI engien has 210 hp and 300 ft lbs of torque. The camaro's have 7.5" 10 bolts. We have 8.5" 10 bolts....a bit stronger...I'm running more than 400hp in my truck and it has lasted. You probably have a 3.08 rear-end gear. I would step it up to a 3.73 or 4.10...your pick(just depends if you do hwy driving or not), tranny ratios for a 700r4 adn yes you do have a 700r4 is 3.06, 1.63, 1.00, .70 and then you have the lockup of your converter.

If you want 400hp, you have some options...first and foremost, you need every bolt-on part you can think of, headers, exhaust, high flow cat, electric fans, etc. If you want to stay TBI, you need a cam/heads/supercharger, cam/heads/nitrous, larger displacement engine like a 383/cam/heads/nitrous, or there is tons of options out there.

A crate engine would be a good start for a project but either way you go, you need a custom tune(chip) for the engine package once you build it or buy it. If you build your own engines, its cheaper to build your own but if you don't, crate engines are almost always cheaper. You can buy a 350 with 330hp for about $2500 from GM and then add a supercharger or nitrous to finish the job.

[jared6180]

Well I was thinking about going carbed. I am going to talk to my mechanic in the morning to see about rebuilding the bottom end with 9.5 compression pistons, and then adding that edelbrock H/C/I package and a 650 or 800cfm carb.

Getting dual exhaust out the back in the morning, not sure what mufflers to use. they have flowmaster, magnaflow, and aerochamber, and a flowmaster knowckoff in stock.

[YenkoST]

Flowmasters sound good but flow like crap...with your duals, I would add an X-pipe and use magnaflow or hooker aerochambers personally.

Well, since you are going carb, we have a lot of options as well. If you are going to rebuild the engine, I would get your compression close to 10:1 and not over..throw on some vortec heads, a 218/224 hyd. roller cam, and an Edlebrock Air-gap manifold, and a 750cfm carb max. 800 is just too big for a 350. That will net you about 375hp.

[jared6180]

man, these things sound ALOT cheaper to work on then my Mustangs or Grand Prix GTPs!!! I guess that might be why so many people build the 350, I have been looking at some prices of different parts, and heads are around 40-50% of some mustang heads...WOW!!!:eek:

I was thinking about the next year or so putting a blower on, any suggestions?

[jared6180]

I was just over on the latemodel resto site, and they are selling a TBI conversion kitfor $1539, will I need something like this to run carbed on my truck? My goal is at least 400hp, and here is the page I am looking at...
http://www.latemodelrestoration.com/products/ctbiconv.aspx

Thanks,
Jared

[jared6180]

Alright, I think maybe I should go with Vortec Heads, and a Weiand 142/144 Series supercharger kit, and a 750 CFM carb...450hp???

[Chevyman247]

No...that TBI conversion is not what you need. All you really need is to make a custom fuel line with an adjustable regulator set to 5-7 psi for the carb(the TBI unit has about 11-13 psi.) You can use the intake fuel pump...just get the regulator. You need to keep the computer to run the gauges and lockup the torque converter for your tranny. You'll probably have to pickup a TV cable and accelerator pedal cable that will work with a carb.

If your not going to tow with this thing, why don't you go with the vortec heads(matching springs for the cam, etc), air-gap manifold, 750cfm carb, and a Procharger carb supercharger. I would go a little more split for the cam...something like a 214/222 or 218/230 would do nicely. Keep the compression to about 9.5:1 max and with an intercooler, that will be about 10-12 psi friendly.


I have done carb conversion, and I cut the rubber fuel line (down by the tranny) and used barbs to clamp more hose to it to go to the fuel regulator, you need a return regulator or you will burn up your fuel pump.

heres a pic of my regulator setup.
http://img.photobucket.com/albums/v383/xbox/DSC00175.jpg
http://img.photobucket.com/albums/v383/xbox/DSC00165.jpg

and you dont need the computer, the first thing I did was tear that sob outta there!
and my guages still work, you need a TQ lock up kit for your tranny to lock up in 4th gear while crusing. you dont have to keep your lock up but you will lose 1-2mpg.
you need you order a bracket that bolts on your carb from holley that will hold you TV and throttle cable. you can reuse your cables. and last you need to run an ignition hot 12V to the gray wire on the fuel pump relay, its located on the left of the engine compartmant. any questions about tbi to carb conversion you can just pm me.

[YenkoST]

No...that TBI conversion is not what you need. All you really need is to make a custom fuel line with an adjustable regulator set to 5-7 psi for the carb(the TBI unit has about 11-13 psi.) You can use the intake fuel pump...just get the regulator. You need to keep the computer to run the gauges and lockup the torque converter for your tranny. You'll probably have to pickup a TV cable and accelerator pedal cable that will work with a carb.

If your not going to tow with this thing, why don't you go with the vortec heads(matching springs for the cam, etc), air-gap manifold, 750cfm carb, and a Procharger carb supercharger. I would go a little more split for the cam...something like a 214/222 or 218/230 would do nicely. Keep the compression to about 9.5:1 max and with an intercooler, that will be about 10-12 psi friendly.

[jared6180]

I doubt I will be towing anything. Is the procharger a centri blower for the carbed intake? I will have to do more research on different blowers I guess.

As far as cam goes I want something with a little bit of lope to it that will provide good poser and driveability.

Jared

[YenkoST]

I have done carb conversion, and I cut the rubber fuel line (down by the tranny) and used barbs to clamp more hose to it to go to the fuel regulator, you need a return regulator or you will burn up your fuel pump.

heres a pic of my regulator setup.
http://img.photobucket.com/albums/v383/xbox/DSC00175.jpg
http://img.photobucket.com/albums/v383/xbox/DSC00165.jpg

and you dont need the computer, the first thing I did was tear that sob outta there!
and my guages still work, you need a TQ lock up kit for your tranny to lock up in 4th gear while crusing. you dont have to keep your lock up but you will lose 1-2mpg.
you need you order a bracket that bolts on your carb from holley that will hold you TV and throttle cable. you can reuse your cables. and last you need to run an ignition hot 12V to the gray wire on the fuel pump relay, its located on the left of the engine compartmant. any questions about tbi to carb conversion you can just pm me.
True but if you keep the computer then you save money and don't have to worry about running more wires just the get the lockup working again.

[90C350]

You will need to keep the lockup converter working if you have a 700r4, or you will burn up your tranny unless you have had other mods done to it already. Once the converter is locked up it will run all of the tranny fluid through the cooler. If it does not lock up it will not fully cool the fluid and lead to early failour. I would keep the Tbi and learn to mod and tune you ecm for your engine combo. Its cheap and easy and will still get you good HP if your engine combo is decent.

[cancritter]

ld never go back to carbs

[Chevy1500z71]

your moter sounds like its in great shape for ading lots of parts to but keep in mind its a 2 bolt main and a crate engine will be a 4 bolt.

[jared6180]

Iam new to this, please explain the difference, and how to compensate when I get the crate motor.

[Chevy1500z71]

well its as simple as 2 bolt s weeker than 4 bolt. im not sure exectly how much a 2bolt can suport but im sure it would hold 400hp.

[Fast305]

well its as simple as 2 bolt s weeker than 4 bolt. im not sure exectly how much a 2bolt can suport but im sure it would hold 400hp.

Actually, I will take a factory 2-bolt main block over a factory 4-bolt main, WHEN aftermarket splayed 4-bolt main caps are used.

[Chevyman247]

True but if you keep the computer then you save money and don't have to worry about running more wires just the get the lockup working again.

If you keep the computer and not take it out for carb conversion it will not still operate torque converter lock up. If you go carb you need the kit. Either way you still need a lock up kit for carb convert.