hey guys ! How do I tell if my BBK throttle bodies are for 85-88 or 89-92?

 

Does it have three openings at the rear gasket surface, or just two (the throttle bores)?

Early TPIs used a third opening for idle air/ EGR gasses. Later TPIs had only the two throttle openings.

 

also how to tell is by how the throttle cable attatches. Both attach a little different

 

I think this may work on both?

 

Intersting thread. Does anyone know of the impact of removing the large walls behind the TB (i.e. the obstructions just in front of the EGR ports in the floor of the plenum)? For flow? For distribution of exhaust gases through the intake (e.g. cylinder to cylinder distribution)? Has anyone ever done this and tested the plenum on a flow bench?

The TB below with the ports off to the side of each bore looks like it will work with either the old style or newer style plenums.

 

Hi

I just finished modifying my plenum. I did remove the humps behind the throttle bores and smoothed out the transition on the sides. I had the plenum welded up on both sides right behind the throttle body flange so I could smooth things out without grinding to the outside of the plenum. I also fully siamesed my plenum ports fully from port one to port four on both sides to match my modified SLP runners.

I also enlarged the bores to match my 52MM throttle body. I read just recently where someone said they picked up about 5-10hp with this mod alone. I also heavily modified my SLP runners and will be taking the car to the dyno this Saturday to see what HP changes there are if any. Made 283RWHP before the mods with a 700R4 transmission. We shall see. Allen

 

1989GTATransAm,

Good for you! Please keep us posted on your results.

 

Like this?



Check this:

Plenum Porting.pdf

 

Nice, here's one of my plenums....