Do it, they are using 90mm tb's on LS motors in pickup trucks. People's general thinking is that if you put a too big of a throttle body on an engine its going to somehow lose torque down low. That theory has pretty much been disproved to me. I read about small blocks in the 400-430ci range using a tunnel ram and twin accufab 4500 flange throttle bodies that flow a combined CFM of over 4200. The motor i am thinking of as an example is Jeff McConnels SBC malibu. It is probably making 800-850 on pump gas and has eight 2 1/4" throttle blades sitting on top of the intake. It would seem like overkill, but its really not. An engine is going to use however much air that it can inhale, if you have a throttle body that is too small you are creating a restriction but i do not think that there is such a thing as too big of a throttle body, the motor will pull all the air it needs, but it will never pull too much air.
Do it, they are using 90mm tb's on LS motors in pickup trucks.
LS engines have enough intake manifold, head volume and displacement to utilize a throttle body that big. When most street intakes for the 5.0L OHV don't flow much above 800cfm, a big throttle body like that isn't going to be good for anything more than a conversation piece.
Big throttle bodies are cool, but worthless unless your lower intake and heads are capable of moving the airflow they provide.
I'd have to measure, but I don't think I could physically go any larger than a 70mm throttle body on my Explorer intake (at least not without compromising the EGR gasket sealing surface)? In my case, it really wouldn't be justifyable with GT40 heads/intake to start with, since they're not going to be able to utilize any more airflow than a 70mm would provide anyway?
3 pages about throttle bodies?
See, when you start thinking like that, you really limit yourself unintentionally. A lot of people fall into this. What you're doing is basing your whole parts selection off the weakest link in the chain, so what you end up with is a whole chain full of weak links. I'm not saying everybody needs to go out and cut and weld their Explorer intake so they can fit a 90mm TB (though, I have seen it), but just because you've got a 70mm opening on your intake doesn't mean a 70mm TB is the best and only option you have.
Something else to consider is that when you put a 800 CFM throttle body on an 800 CFM intake, your total system flow isn't 800, it's going to be less overall. It's like stacking resistors in series, every additional component adds some amount of resistance to flow. With that in mind, there's no good reason for the TB to be a significant contributor to the resistance to flow at WOT.
I dunno, that's just my thoughts, but I also have ~$2100 in my cylinder heads and I still run 13s, LOL. I'll figure it out one of these days.
What, you want us to go over to Deraillers Anonymous and talk about... What is it they talk about again?
See, when you start thinking like that, you really limit yourself unintentionally. A lot of people fall into this. What you're doing is basing your whole parts selection off the weakest link in the chain, so what you end up with is a whole chain full of weak links. I'm not saying everybody needs to go out and cut and weld their Explorer intake so they can fit a 90mm TB (though, I have seen it), but just because you've got a 70mm opening on your intake doesn't mean a 70mm TB is the best and only option you have.
Something else to consider is that when you put a 800 CFM throttle body on an 800 CFM intake, your total system flow isn't 800, it's going to be less overall. It's like stacking resistors in series, every additional component adds some amount of resistance to flow. With that in mind, there's no good reason for the TB to be a significant contributor to the resistance to flow at WOT.
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