I am interested to know the stock TB sizes for these motors. Does Ford have a FRPP part for upgrades?

Thanks for the info,
Birdman

 

I measured mine a few months ago and I think I remember it being a 65mm throttle body. the new 99 mustang went up to a 70mm TB and of course, better heads.

Chris

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98 SC 4.6L stepside, Gibson headers, Gibson single exhaust, superchip, Intake mods, Piaa's, high end audio stuff.

 

I'm not sure if FRPP has any larger throttlebodies, but I'm pretty sure Edelbrock does, both for the single and twin models.



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Yes Edelbrock makes a upgrade throttle body.It is a 70mm-part#3871.I have a question myself about the effects of replacing your throttle body with a larger one.If your engine is bone dry stock will it hurt you to use a larger one? Can or will it cause off idle sputter?Can it cause your spark plugs to either burn up or foul out? Or will it make a good performance difference?THANKS

 

Engines make more power by improving volumetric efficiency. A larger throttle body, along with allowance for the mating pieces, should improve the VE of the motor since air entering the motor is less restricted. The computer controls on your car should be able to detect and utilize the improvement and no negative impact would be put on the system.

Sounds like the 65mm TB is stock. 70mm should help especially when you have aftermarket exhaust setup.

Birdman

 

Well, I'd have to disagree with that... a throttlebody will only help get more air into your engine if the throttlebody itself is the bottleneck in the intake system... and ordinarily your vehicle isn't going to come stock from the factory with a bottlenecking throttlebody. Sure you might pick up 2hp or so, but don't plan on feeling anything. You'd be better off putting your money towards something else.



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I agree somewhat, the question by F150LowDown was "are there any negative effects". No is the answer. Engine designers at all major car companies have one large problem, most cars/trucks are driven by regular people who have certain demands, not necessarily performance. Look at the restrictions in the intake tubes. Resonators and all to quench engine noise. Why size a TB any bigger than you have to? Cost is important too. If the same part can be used across all platforms, economies of scale are gained.

On a stock configured engine a larger TB will gain you little, that I agree. Upstream restriction will be the first problem. But as soon as you start putting intake tubes and K&N filters, Cat-Backs, you start to shift the limiting factors around.

The TB as well as the MAF and all those items are big enough to support some major horsepower. There are Mustangs running these sized parts but make 400-500 HP. Why, they are cammed and ported and the motor pumps better. So velocities are higher. But I don't suspect anyone here is going to go that far just yet. I have seen 2 or 3 N/A 4.6L SOHCs making well over 300 hp at a cost approaching $5000. Cams alone are $800.

Sorry so long, the TB is marginal on a stock motor, but once you start doing mods it will be more influential.

Birdman