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5.7 Throttle body in a 68

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5.7 Throttle body in a 68

New User | Posts: 2 | Joined: 11/13
Posted: 11/04/13
03:07 PM

I was wondering who would know what motor mounts were used in the 68 C-10 throttle body conversion.Did they use the factory exhaust manifolds from the 88-94 chevy motor. Or did they use headders? I would like to run the factory manifolds, if possible  

wayne712222 wayne712222
New User | Posts: 37 | Joined: 10/13
Posted: 11/05/13
04:04 AM

a few things.. and i have helped a bunch of members from the various magazine forums with the issues that crop up on these swaps...

and people LOVE These when they are DONE...

first..  before you install the throttle body engine..  

What year is it...  92/93 up use computer shifted automatic transmissions without a Throttle valve cable.. some come with a 4L80E..

do you have the complete throttle body harness that goes all the way thru the firewall.. or an aftermarket TBI harness..

and if you have the bucks... you can.. before you swap in the engine.. swap on a set of VORTEC heads and a VORTEC TBI intake thats available both from GM and various manifold manufacturers...

you will want to spend some time over at the JAGS THAT RUN Site.. they have been doing these swaps for a while..

please verify.. that before you install the motor..  that when you open the throttle part way open. that there is NO PLAY between the throttle shaft and the throttle body shaft bore.. this is an ISSUE on many GM carbs and TBI.. Even the TPI motors..  what happens is the wear.. allows the throttle shaft to close to different angles each time.. that freaks out the computer as it never knows when you actually have your foot off the throttle.. so it does not revert to idle fuel trims and idle air control settings.. so it can either stall as you return to idle.. or stay running fast and rich....

ALL electronic fuel injected motors need an OXYGEN SENSOR installed .. these are feedback.. they control the air fuel ratio by looking at the oxygen sensor..

if you install the stock exhaust.. the have a hole for the oxygen sensor..

there are a few TBI applications where the oxygen sensors are in the downpipe..

if you install headers....  you will not only need an oxygen sensor bung.. you will need a 3 wire oxygen sensor from a 94/95 chevy truck application.. so it will be a heated oxygen sensor..  this allows you to install it farther downstream.. like into the side of the collectors... most muffler shops can perform this..

you can also get a 2 inch thick block that bolts into the collector flange..  this has an oxygen sensor bung in it.  

having a scan tool.. not just a code reader will be a big help in getting these running perfect... these can be purchased used sometimes..  you have to be careful.. as not all OBD1 scan tools. that are also OBD2.. will read more than codes..

i have a post over at corvettefever on which scan tools for C4 corvettes..

you will also find... that if you run factory exhaust manifolds.. that you can get a factory y pipe.. from parts stores that sell exhaust components.. or the junk yards.. so you have factory downpipes and flanges .. makes for a quieter better sealed installation..

lastly.  it does not matter which transmission you install... but you will NEED a Vehicle speed signal... this is fairly easy.. but sometimes NOT cheep..  this will be either a pair of pulses or 4 pulses each turn of the speedometer cable..

why.. the computer looks at the vehicle speed to know that you are moving to adjust the timing and the air fuel ratio..  so you get the best fuel economy out of it..

if you run across a 9C1 throttle body from a junk police car.. 89 to 95.. some of those might still have the increased flow fuel injector that come in handy for 383 stroker installations.. as the 5.7 will be too lean in a stroker during open loop...

i drop in this forum almost every night..

talking about this.. will really save you some time later on..

there are also several articles in the MANY magazines here..  on installing the TBI motors.. most of the current rage is to pick up a 6.0 or 6.2 LS motor.. toss the carb intake and ignition control on it.. swap a cam.. and make an easy 500 horsepower..  its just not as inexpensive as the TBI swap..  and a lot of people are also installing the fuel injection system..

keep this thread running.. so just reply here.. with your questions..

welcome to the forums..

oh.. and i know these systems inside and out. and went to GM training on these systems..  

New User | Posts: 2 | Joined: 11/13
Posted: 11/05/13
11:16 AM

Thank you for the reply. Wow that's allot of info. The great thing about it is that I have an open canvas (not a huge open pocketbook)and have no problem spending what it takes to make it right.
I'm going to use a 1994 TBI set up on a GM performance crate engine with a howell wiring harness. I will be running a 700R4 tranny. along with the vehicle speed sensor attached. But it sounds like I should take the time to explore other options. I am going to stick with this basic platform. My ultimate goal is to just have a great running 68 C-10. It's not ever going to be a race truck, but would like to get as much power but not sacrifice driveability. Any further suggestions on this would be very helpful.  

wayne712222 wayne712222
New User | Posts: 37 | Joined: 10/13
Posted: 11/07/13
07:47 AM

that will work...

you do have most of it..

if i were you.. i would shop around and invest in a used scan tool..

probably an OTC monitor extended... or extended monitor..  an early genisis.. or a snap on brick..

you will probably be very happy with that..

you did not say which performance engine... they make a bunch of different ones..

i assisted in almost that exact truck install with a forum member last year.. over at either car craft or probably superchevy forums..

TBI throttle body and injector information

These injectors are rated at the pressure used by the factory, about 13 PSI

Application Throttle bore size Injector color code Flow rate Part #

2.8l v6 1-3/8" Black/White 35 lb/hr GM 5235430 *RPD

4.3L 1-13/16" Yellow/Blue 45 lb/hr GM 5235203 *RPD

5.0L 1-13/16" Green/White 40 lb/hr GM 5235279 *RPD

5.7L pickup 1-13/16" Orange/Black 55 lb/hr GM 5235206 *RPD

5.7L Cop Car 1-13/16" Yellow/Brown 65 lb/hr 17084327-ACR

Late big block pickup 2" Blue/Black 80 lb/hr GM 1708430 *RPD

big block pickup 2" Dark Red/Dark Blue 90 lb/hr GM 5235231 *RPD  

wayne712222 wayne712222
New User | Posts: 37 | Joined: 10/13
Posted: 11/07/13
07:49 AM

please.. check the 2 links above..  lots of stuff covered...

so many ways to go..