Ok what is the size of a stock throlle body. I want to get a new one but don't know which one to get. stock with cold air and msd box, 3.73 gears new auto tran with b&M shift and high stall torque converter.

 

Stock TB size on a LT1 is 48mm. From what I've learned on this site there isn't much reason to go bigger until your cammed at the very least. Anyone else agree?

 

The stock throttlebody isn't a limitation for a mildly modified engine; you money would be better spent elsewhere.

 

I totally agree,don't waste your hard earned money.

 

On top of the already sound advice you have recieved I would add get a Transo NOT a B&M the only thing it does is make shifts harder it does not fix design flaws the way the Trango does and it could actually shorten tranny life where the Transgo stands a good chance of helping it live longer and is THE choice of all the reputable 4L60E/700R4 builders I know of.
Don't do the B&M stall either that would be crap too. If you insist on a 12" converter like that at least get it from Edge, Precision or the like or better yet get a 9.5" from one of them.

 

I would only do a bigger TB with Heads/Cam and a ported intake manifold.

 

Save your money for a cam, headers, porting etc!

 

I wouldn't change the tb unless you at least had a cam/headers. A 52mm gave me 10 rwhp on the dyno, but lost 1 lb. ft. of torque. This was only seen between 5400 and 6400. At the track, it only gave me .30 mph, and .02seconds over the 48mm setup. I'll bet an underdrive pulley, and tb airfoil would give the same results or better for less money.

 

True, the 48 mm will flow enough from what I have read.
I only went with a mono blade after, extensive head and intake (match) work, solid roller with a 630 lift and a smaller TB might have worked for me with my current setup. It is a bitch to control on the tree! It will load up with fuel if you don't rev it to 5000 when the second light come on.

Jim Orlando