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Old 06-07-2001, 10:18 AM   #1
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carburetor vs. throttle body on crate motor

I have a dying 1988 350cid with a throttle body and 195K miles. I have been looking into crate motors from either GM or Jasper. I'm looking at either a stock replacement or a small step up to 300hp and 380lbs torque. I've heard conflicting ideas about my throttle body computer working on a crate motor that's not stock. Some say the stock computer will not handle the larger motor even if you change the chip because it's not made to handle the vacuum readings, etc. Others have told me that they have seen throttle body units work fine on larger engines and a chip change will work and if anything is affected, it's only the upper RPM ranges, 5K, that I'd not be using anyway. I want to keep my throttle body because of the problems carbs have on the trails. I don't want to put the extra money into a slightly larger engine if the throttle body isn't going to work. What do you guys think?

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Old 06-07-2001, 10:55 AM   #2
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Re: carburetor vs. throttle body on crate motor

I've been researching pretty much the same thing. The key is knowing what your air to fuel ratio is. You can get a chip burned to deal with it but it might not be right the first time around. If you can provide whoever does the chip burn with the technical info on what you have they can pretty much determine what needs to be done. Try the following for chip burn info. The guys at these places are very familiar with manipulating what you need done.


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Old 06-07-2001, 11:18 AM   #3
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Re: carburetor vs. throttle body on crate motor

Ideally the stock 350 TBI unit itself probably won't quite be up to the task of 300 hp for air flow and injector concers... but you can swap on a 454 TBI or a Turbo city unit w/ larger injectors... and burn a new chip. Cam would be the major concern because of vacuum mostly, but for a 4x4 application you want torque. Overlap on the came also comes into play... I'd recomend one of Comp Cams or Crower's computer cams.

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Old 06-07-2001, 12:01 PM   #4
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Re: carburetor vs. throttle body on crate motor

The computer reads the vacuum via the Manifold Absolute Pressure sensor. So any change to the cam or any other part of the engine can be compensated for via programming the chip. At least until you reach the limits of how much fuel the injectors can provide. Then you have to step up to larger injectors. You don't need the entire throttle body from a 454, those injectors will fit your existing throttle body.

A chip that's properly programmed for your particular engine will make it run perfectly.

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Old 06-08-2001, 09:09 AM   #5
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Re: carburetor vs. throttle body on crate motor

Thanks for the thoughts.

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Old 06-08-2001, 03:25 PM   #6
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Re: carburetor vs. throttle body on crate motor

Just food for thought... I'm buying a 330hp crate locally from GM (see http://www.paceparts.com/ for details) this site has all the specs and a cool picture of it.
I'm putting it in my 85 to replace my totally tired 305.
Mine was already de computerized when I bought it about 4 months ago. The guy that owned it before me put an Edelbrock intake and a Edelbrock EPS carb on it.
I can't wait to get the 330hp under the hood, should be
a fun ride...eh


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