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Tbi To Carb Conversion / 454ss


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#1 454 4-Eva

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Posted 21 September 2007 - 08:18 AM

Wanting to do a TBI to Carb Conversion. I need some info from anyone that has tackled this feat on a 1990 454SS or a truck that would have a similar application. I am also wanting to upgrade camshafts and need to know what type of cam comes stock in the '90 454SS as well as headers. This may show how uninformed i am when it come to the Chevy Big Blocks, but does anyone know what generation BB came in the '90 454SS. Also if anyone knows how the fuel delivery system will have to be modified and can tell me i am willing to listen or rather read. I am trying do do my research before tearing in to my truck, so any and all help is appreciated. Thanks in advance to everyone...


:crackup:

#2 redvett

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Posted 21 September 2007 - 05:43 PM

You must be a glutton for punishment. Going from TBI to Carb will ruin your drive abilitylet alone fuel economy. You didn't post what state you live in but most don't allow back dating. I would suggest you go to SPI like i did on my 572 90 SS454. Edelbrock makes a good system.

#3 Nytemare

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Posted 21 September 2007 - 06:53 PM

your going to need an adjustable fuel pressure regulator, to adjust the flow rate and pressure to the carb.

your going to need to disconnect the ECM and get an MSD ignition. Basiclly, you are converting your entire engine back to a basic big block.

with the carb you are going to lose some power, your going to have electrical gremlins galore, and you'll be continually screwing with things like idle and Air/Fuel ratios.

Don't get me wrong, I love carbs, But they're an outdated technology, and only good if your making massive amounts of power.

Your TBI will make way more power and be more reliable than a carb ever will. Your stock TBI flows 90lbs/hr/injector at 12psi. With 750 CFM. This is enough flow to power a 450hp big block. Your truck is like 255 stock. So your safe to make another 200hp before you out grow this unit.

I would get a set of new injectors and rebuild the TBI if I were you. those 18y/o injectors probably leak like a sieve now.

GM part # - 1704304 Red/blue top injectors.
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so you expected something that weights 5000 pounds and has aerodynamics of a piano to get what?


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#4 BryanH

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Posted 21 September 2007 - 08:38 PM

Top fuel dragsters use fuel injection. Its just mechanical (NHRA rulebook says no computers). Carbs are an old tech and some people are used to working with them (namely the performance guys who have been in the industry FOREVER are used to it). But there are many names in the racing industry that are more than comfortable with EFI (since this is a GM forum.... think Lingenfelter vette). TBI isn't the greatest system in the world but with a bit of service you'll be up to great drivability with a lot less tweaking than you would converting to carb. There are still people selling performance chips for them as well.
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#5 ss454trk

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Posted 29 September 2007 - 03:51 PM

http://www.454ss.com/