75mm TB (split from For Sale thread)

[PCGUY112887]

Yeah but cmon lets find a way to make it work lol. I need something that will go onto a 3500 upper that doesn't cost $275.

[ryan.hess]

lol, guys are using 75mm TB's on LS1's as an upgrade...

that would be like putting a 750 carb on a 305... haha

A larger throttle body isn't like putting a larger carb on an engine. When you put a larger carb on, the airflow through the carb slows to a trickle, which plays hell on the jets. Faster airflow through a carb means better metering and better atomization of the fuel.

A throttle body doesn't have fuel flowing through it. The only difference you see with a larger throttle body is the larger progression of throttle. I.e. if you open the throttle 10%, it might be like opening the throttle 20% before you swapped the larger throttle body. So it becomes more sensitive to your foot.

The hardcore racers get around this by using independent throttle bodies. This still alows the throttle feel of small throttle bodies, but they can get away with huge throttle areas for maximum WOT performance with no penalties.

[RebelGT]

Who would put a 75mm TB on a 3400?

on a 3400 no, on a boosted lQ1, sure.

[SappySE107]

lets pit experience agaimnst experience. 70mm on a 3400 makes it near undrivable on snow and is extremely touchy on dry ground as well.

[PCGUY112887]

lets pit experience agaimnst experience. 70mm on a 3400 makes it near undrivable on snow and is extremely touchy on dry ground as well.

Is that with the upper intake ported out to 70mm as well?

My theory is just that... if the opening is only 65mm, only 65mm worth of air will get though.

[bszopi]

Good theory, but... The fact is, its letting in the air that the engine needs that much faster. What used to be 10% throttle is now more like 20% throttle. And you have 100% flow (the top end will restrict the flow of the TB) at around 70% throttle. So you have just cut your effective pedal travel (and thus pedal control) significantly.

You also have a large opening and then you have a ridge between the TB and plenum. This will mess up the flow of the air into the plenum significantly which can screw with the way the air flows into the plenum and down to the heads.

[SappySE107]

Everything was ported for the 70mm on a 3500plenum, but you can only open it so far, which is part of the whole problem I am talking about. If 70 was good, we would be making them or I would sell the adapters for them. Since I know its not a good thing to do, I won't sell that setup. I can't stop anyone and if the boosted people think they can use a 75 then I would like to see it done. I would also love to see a dyno comparison between the 65 and any larger.

[PCGUY112887]

The question still stands, if you tossed a 75mm TB on a stock 3500 opening, aside from a very touchy throttle feel would it work? (with a MAF system in particular).

I totally understand what you mean, and I love your 65mm TB... but I just can't afford it and I don't know what else I could turn to for a cheap TB that would be 65mm or greater.

[sharkey]

ford 4.6l throttle body. its 65mm. brad (treez24) is running one on his hybrid with 3500 manifold, but his stand alone uses a fast idle valve. im not sure about what you would do with the iac motor, ive seen adaptors to run a gm iac on a ford throttle body.

[ryan.hess]

im not sure about what you would do with the iac motor, ive seen adaptors to run a gm iac on a ford throttle body.

ewww!

j/k..

[bszopi]

GM IAC adapter for Ford TB : http://60degreev6.com/gallery/browseimages.php?c=17

[PCGUY112887]

Sweet, where could I get one?

And umm... how exactelly does it work? I see the typical GM IAC hookup, and a compression fitting... some sort of hose go between the Ford TB and the fitting on the adapter?

Does the adapter sold here work with the Ford TB? Everything else hookup the same? And most important... the 4.6L you mean is the one from like mustangs correct?

Thanks.

[bszopi]

Although none of the attachments seem to work, here is the thread from when I originally designed that adapter. I'm sure Marty would be willing to make another one if you really wanted.

http://60degreev6.com/showthread.php?t=29285&page=2&highlight=ford+adapter

[ryan.hess]

I recognize the amount of work put into that... but damn it's ugly. Needs some more CNC machine time to make it less of a block.

[bszopi]

That was probably 15 minutes on a drill press... Function not form.