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Off Road Carbs

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fire4j15

Registered User
Location
Springville
Tacoma, What TBI set-up should I run on a motor with 320hp and 400lbs of torque. it also has the hot-cam installed in the motor from GM Performance Parts. Any help in the right direction would be great. So are you running a big block TBI or small block TBI with a bigger throttle body? Thanks
 
7

78mitsu

Registered User
the BBC throttle body and injector assembly will fit with slight modification to the adapter plate (sanding wheel on a die grinder and about 2 minutes) open it up just a hair because the butterflies are just a little bigger. get an aftermarket adjustable fuel pressure regulator for the throttle body. ~$75.00 up the fuel pressure to about 14 and you can run 350 hp. If it stumbles off idle you need to trim out your tps 5kO pot for testing and a couple resistors, It'll increase timing and fuel mixture to clean up the idle and flatten out the fuel curve. -but it shouldn't be needed if you're running an oxygen sensor.
 
anvil

anvil

Registered User
Location
Idaho Falls
78mitsu are you using 90 or 80 lb injectors? How does it run below 1000 RPM? I picked up a TBI computer at a junk yard about a year ago, but decided to stick with my carb after reading about problems tuning the lower RPM range. It sounds like I should reconsider.
 
88 Runner SAS

88 Runner SAS

Saving Money For Parts
Location
Monticello
A couple years ago (5)I started building my 80 GMC for crawling, (before the offroad carbs hit big) I bought a Edelbrock 600cfm Performer that flooded climbing steep, i put in the spring loaded needle and seat kit, and messed with jets a few times, and never had a problem again took it to moab a few times. Then I dumped too much money in it and acquired my 88 runner. Just telling my experience with the Edelbrock.
 
7

78mitsu

Registered User
anvil said:
78mitsu are you using 90 or 80 lb injectors? How does it run below 1000 RPM? I picked up a TBI computer at a junk yard about a year ago, but decided to stick with my carb after reading about problems tuning the lower RPM range. It sounds like I should reconsider.
Click to expand...

If everything is hooked up right, once the computer reaches normal operating temperatures and starts using the o2 sensor input, it will modulate the mixture to stoic- by adjusting the timing and fuel volumes. most of the problems you hear about are cause by people deviating from a 110-115* cam centerline or cams that cause the engine have really bad vacuum. The fuel pressure is dependent on vacuum to control the pressure 2.5" manifold vacuum decreases pressure by 1psi, which in turn lowers the volume of fuel delivered.
 
BCGPER

BCGPER

Starting Another Thread
Location
Sunny Arizona
Wow, my hat's off to 78 here.

Stoichiometric is the optimum air fuel ratio for a normally aspirated engine, and probably never used here on RME before. A cheap tempory fix is easy, but it does have down sides.

A motorcraft 2100 series carb cant be beat offroad. You can find them for $25 or less. Rebuild kit is around $28. Offroad mods to it will run you around $1. After that you'll be able to lay it on it's side, and it'll just keep on trucking.

Downside is, you WILL lose power.

The more desireable 2100's are found on AMC 360's, or Ferds 351, 352, or 360 line.

78mitsu said:
If everything is hooked up right, once the computer reaches normal operating temperatures and starts using the o2 sensor input, it will modulate the mixture to stoic- by adjusting the timing and fuel volumes. most of the problems you hear about are cause by people deviating from a 110-115* cam centerline or cams that cause the engine have really bad vacuum. The fuel pressure is dependent on vacuum to control the pressure 2.5" manifold vacuum decreases pressure by 1psi, which in turn lowers the volume of fuel delivered.
Click to expand...
 
F

fire4j15

Registered User
Location
Springville
Hey Guys, thanks for all the good info. How much is a new Q-Jet carb set up for off road driving? Can it handle 330hp. Thanks again guys. Fire4j15
 
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