How many MM is a stock throttle body on a 350 TPI Vette motor? Is 400 bucks worth a 58mm one from holley?

 

Same as the 305,48mm.
58mm is a waste of time and money unless you are blowen ,or real heavy on the mods,52mm's will be ok if you feel you need more,but for most mods the stock 48mm is pretty good.
don't waste your money on an Air foil either.

 

I know a friend that went slower after sticking the 58mm on. that was because it was mated to the stock intake system. Now, if you went out and got new intakes, it might be worth it.

 

i don't see how it could hurt if i got a new intake tubing and stuff...its just allowing more air in, i don't see how it could be slower....a buddy of mine told me if i get new injectors to compensate for the air coming in from the twin 58 mm throttle body , it would make a huge difference.

 

DO NOT change injectors without reprogramming the car. If you are being advised to change injectors due to an upgraded throttlebody, get advice somewhere else from now on. The stock 305 injectors will support about 350 hp and the stock 350 injectors are good for a little under 450 hp. The car will adjust by the mass air readings for the extra air (it won't be much). If it is a speed density car, it will see a change in the O2 sensor readings and try to compensate for the difference. But, injectors are not the miracle cure. These cars are "air limited" not "fuel limited".

Have fun!

 

Agreed,that is why I said 52mm is big enough. Putting a 58mm on a none pressurized TPI is like tring to stuff 10#'s of **** in a 5# bag,it won't help. You need to be putting out serious HP to need a 58mm.

 

well the twin 58 mm is only like 10 bucks more than the 52 mm...are you sure I should just go with the 52mm?

 

if you plan on sticking with tpi and dont plan on changing intake manifolds, stick with the 48 mm or waste your money on the 52 mm one. i'd rather spend the 400$ on the tb on something else, like headers, y pipe and an exhaust or something (if you dont already have it). the gains are minimal when going to a 52 mm tb to 48 mms... if you went 58 mm, you'd loose a little bit of power.

 

What do you finally want to put on for intakes?

 

well then what should I spend my money on? I got headers, i'm getting a flowmaster 40 series muffler, and redoing the whole exhaust, there is a power programmer for the computer...what do you guys suggest I should save up for? Something reseanable, not like a supercharger or anything.

 

Roller rockers, a cam (mild to avoid tuning problems), cylinder heads (the cost of that throttle body is getting towards the 1/2 way point on a set of heads). I'd throw an airfoil on it and be done with the throttle body for now. Large runners and a big mouth intake manifold. Those things will make a difference. Spend your first $20 on the "Insider Hints" book by TPIS (call Jegs). That book will be your best investment before spending any more money.

My thoughts.

 

What is a good set of heads and a cam for my application? I was looking at jegs, and there is like a million different choices. i don't really know what i'm looking for.

 

Since the TPI system is not the best for high RPM flow, you want to pick a head that flows well but is not "huge" in runner volume. I'd suggest looking at something like the Edelbrock Performer or Performer RPM heads or a set of the L31 Vortec heads and the intake from Scoggin Dickey performance parts to fit them. Either one of those set ups will increase your HP. The Edelbrock heads are aluminum and will take several pounds off of the nose of the car which is never a bad thing.

My thoughts.

 

my heads are aluminum as it is, so it won't really shed that much weight off, because it is a corvette engine. I was looking in jegs, and they have a plenum and runners for around 700 bucks...would this be worth getting?

 

The edelbrock heads will outflow your 'Vette heads (I had those heads on a motor once). But, you need to upgrade the "whole package" so, you could start with the intake and then do the heads later on. Once you upgrade the whole system, you'll see the best gains. Which intake are you looking at? I'd probably start with a set of high flow runners and an airfoil for the throttle body. Then, change the lower intake when you do the cylinder heads (you'll have it apart anyway at that time). And, get the book by TPIS. I have a copy laying here and it is a great book. After you read the book, then buy more parts.

The plenum is not real restrictive. The problem is mostly from the runners down. The runners and lower intake are where there is the most to gain. You can port the plenum to match a set of high flow siamesed runners and be just fine. I would leave the plenum alone until everything else is done and you have extra money to burn.

Roller rockers are worth some HP as well. Look at the Crane "self aligning" gold race rockers. They should fit under your valve covers.