OK, this is probably a stupid question, BUT, If you put a 52mm or 58mm TB on a TPI 350, I guess youve got to port the two openings in the plenum that match up to the TB openings to get any advantage right? What about the bevel that is on these openings? The diameter towards the interior of the plenum is slightly smaller than the diamter that matches up to the TB. Any reason for this, or bette to just port that to the same size as the TB as well?

 

I'd smooth it off a bit, but I would not open it up any larger than the throttle body bores. One of those "while you have it off the engine... mightaswells"

 

Right, exactly, thats what I thought. Just make the opening the same size as the TB bores and get rid of that bevel.

 

The holes are already 52mm so you're OK unless you get a 50mm TB.
You would then port the holes to at least that same size (58mm) of the TB. It's OK if you make the holes bigger, just as long as their at least the size of the TB opening. You want to avoid having a step there to interfer with the incoming air.

 

Yes, port the plenum holes for a 52mm or 58mm TB. Also, there are some bumps of metal sticking up into the airstream inside the plenum, cut these down also.

 

About the best you can do with a 58 is match it at the face of the plenum, and taper it in from there. The plenum isnt wide enough to enlarge it for a 58 without a fairly sharp taper into the plenum, you have to weld it if you want to transition it better.

 

Yeah I already removed the egr walls and did some other minor smoothing a while back, I was specifically asking about the tb holes on the front and the taper that is there on a stock one. I just basically removed the taper although there still is a little, and opened up the holes about 2mm on all sides to accomodate the 52mm. Just wondered about that taper tho

 

Totally useless.

 

the taper is "totally useless" or porting of the the plenum in general?

 

Both. LOL!

Nah, I cant see any reason for the taper. Its bigger than the back of the stock TB. Probably has something to do with the machining process I would guess.

 

haha, you are probably right on both accounts, but it gives us poor people who cant afford a Lingenfelter Supperram setup something to do eh?