Alternative Port EFI IntakesThis board is for tech discussions and questions about aftermarket port EFI such as the HSR, MR, SR, BBK, FIRST, etc.
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I was going to use a 454 TBI as a TB, but 750cfm vs 500.
Im pretty sure I cant use a IAC, and adverse effects from not using one?
Well, you need a TPS at min.
An IAC? well. It depends. For a street car or a manual trans you probaly want an IAC for throttle following.. For a really radical off-road car, it might not matter that much.
This is why I modified my TBI throttle body. It flows excellent, while maintaining the TPS and IAC, and it was cheap to do (under twenty dollars). I had this on a 400-SBC, then on my cousins 454-BBC, and it flowed more than enough air for both....
It's completely possible. Only difference is to add a TPS and cap off the fuel inlet. My setup doesn't even use an IAC, so it theoretically operates the same as a modded carb would. It is better/nicer to have an IAC, but not absolutely needed. I almost did this when I went to fuel injection, but the setup I'm using has less packaging issues and looks more correct.
This is why I modified my TBI throttle body. It flows excellent, while maintaining the TPS and IAC, and it was cheap to do (under twenty dollars). I had this on a 400-SBC, then on my cousins 454-BBC, and it flowed more than enough air for both....
This is very interesting. I came across the images while surfing the web. I see this is a very old post, but how has it worked out for you? Have you had it flow tested? I already have a 454 throttle body, but it looks like where you cut out had a couple passages, did that affect anything?
This is very interesting. I came across the images while surfing the web. I see this is a very old post, but how has it worked out for you? Have you had it flow tested? I already have a 454 throttle body, but it looks like where you cut out had a couple passages, did that affect anything...?
It worked very well. Never had it flow tested, but its still sitting in the garage though. The passage was epoxied shut by the throttle bores, but then re-drilled (redirected) underneath the throttle body to allow for the rear vacuum port to maintain its functionality. If you go this route, you of course do no want to grind the walls below the throttle plates, and when you make your cut, get it as straight as possible. You then use your two existing throttle plates to mock up your one piece throttle plate by measuring their distance while still bolted to the throttle shaft, and measuring your cut. Transfer that measurement to some sheet metal and make your cutout. Just keep testing it's fitment, and make the required trim where necessary until it fits the way you want it, then drill the mounting holes through it where it sits on the shaft. Once you have it the way you want it, coat it with whatever you'd like....
There are alternative twin blade TBs out there. I have one here for a Magnum Dakota 5.9 that looks serviceable. Dual 48mm blades so it should flow like a stocker TPI TB or damn near it. Also has a TPS and IAC even though the resistances work out slightly different than a TPI. I'd be tempted to find a TPS that is GM to put on it and make it work.
Check EBay for a 4 barrell Holley TBI unit. I think they came in 700 and 1000. Then remove the injectors and use unit only(remove sell injectors). Comes with IAC and TPS. Newer Holley units have sequential older not.
ps. I think my 7.4L TBI is about maxed out. 96 MAP at 1000 feet elevation.
