70 or 75 mm throttlebody?

well it all depends on what engine.. and how built it is.. i mean if your running a stock 5.0l.. its useless to run 75mm tb.. but if it is a 306 with alum heads, cam, intake.. and a blower then yeah i can see putting a 75mm on it.. but you also got to realize what manifold your running.. if it is stock.. you might a 75mm is bigger then the tb opening on the manifold.. so..

TB size thoughts...

65 MM TB for a 302-306 N/A street strip.

70 MM TB for forced induction on a 302-306 or a N/A 327-347 street/strip

75 MM TB for a forced induction 327 or any 347 full race application.

The logic is that small TB works to keep intake velocity up which helps street performance & quick throttle response.

jrichker said:

TB size thoughts...

65 MM TB for a 302-306 N/A street strip.

70 MM TB for forced induction on a 302-306 or a N/A 327-347 street/strip

75 MM TB for a forced induction 327 or any 347 full race application.

The logic is that small TB works to keep intake velocity up which helps street performance & quick throttle response.

Click to expand...

yeah, thats about the best way to put it!

Just remember that a 75mm TB flows nearly 2 times the amount of air a 302 can even think of using. I would say that big of a TB is a waste on a 302 block (stroker)...whether it be a h/c/i 302 or stroked 302.

www.accufabracing.com has the charts of how much air flow the engines at a certain cubic inch can breathe in.

That is at 100% volumetric effiency which very few engines have....so they more than likely won't even flow that much.

The "bigger" the blade...the more goosier the throttle will feel.

A 70mm TB, preferably from Accufab would flow plenty for a N/A 302 based engine, even stroked.

I don't have horsepower charts, but I have heard the 65mm TB flows around the 400hp range...but I believe it is higher than that from what I have seen.

A 75mm TB is a waste of room in my opinion.

Most get it to go with the crowd, when they can't even get close to using it all.

5spd GT said:

A 70mm TB, preferably from Accufab would flow plenty for a N/A 302 based engine, even stroked.

I don't have horsepower charts, but I have heard the 65mm TB flows around the 400hp range...but I believe it is higher than that from what I have seen.

A 75mm TB is a waste of room in my opinion.

Most get it to go with the crowd, when they can't even get close to using it all.

Click to expand...

Im running a Professional Products 65mm TB, I think anything more for a N/A setup is just overkill