T/A lt1

I just finished rebuilding my LT1 and before I rebuilt the engine due to oil pressure issues I was having the car ran great but since it was down I decided to change things around a little so I swapped cam, converter and throttle body among a couple others but these were the big changes. Well I had a 52mm and went to a 58mm BBK. The car now has alot less torque down low so I can credit the bigger cam and tighter converter for some of that but my question is that if I put my stock throttle body on am I giving up some HP with a 450-475HP engine? The LT1 is LLoyd Elliotts Heads, stock valves flow 264@600, Joe O cam 23X-24X@50 560+lift and 10.8.1 compression. Intake cleaned up, Jethot Longtubes, double roller and EWP. The car ran 11.60's@117mph@300' spinning 1.67-1.69 60's with a smaller cam, 52mm throttle body and a looser converter with the 3.42's. Now on my first trip with my new setup, no tuning yet, 11.90@114mph@2000' DA 1.73-1.75 60's but couldn't spin a tire leaving. Now I know it would run close to the old times with the same air but what kills me is all the torque it lost down low. I know it could use more gear and a little loose converter but it's setup to run n2o like it sits. LMK your opinions.

I am going to the track with the car this weekend and it needs a good computer tune and some tweaking but I will try swapping TB's at the track to see if it makes more torque with the stock 48mm. I wish I would have kept my 52mm so I could try all three. I have read thru the threads and haven't found any definate proof of a bigger T.B making a car faster. I have seen claims of more HP but never quicker ET wise.? Thanks Clint

Damon

A larger TB theoretically won't kill torque on an FI engine like how too big a carb could on an older carbureted setup. It's just an air door. It doesn't have to generate velocity like the venturis of a carb do to draw fuel through them. Some people go slower with a larger TB in place of the stocker as a bolt-on upgrade, but I would attribute that more to having the tuning thrown off slightly by the larger TB than anything else.

But, like with most things high performance, it's simple enough to "try it and see." If it works, use it. If it doesn't, put the bigger one back on.

A stock 48mm TB, I am told, will flow about 650 CFM @ 1.5" pressure drop. A 52mm would probably be around 750-800 CFM. But I don't think anybody really knows how they are flowed, under what conditions, etc, like a 4bbl carb where the flow ratings are standardized and have been for a long time.

FASTFATBOY

Well a bigger throttlebody on my old 5.0 stang affected the way it ran, but it had a stock motor.
I think the EFI stock eliminator guys have to run a stock throttlebody and they run in the 10's.

I would attribute the drop in ET to the tighter converter. A nitrous setup run NA is not gonna run like a pure NA setup.



David

OldSStroker

Why a TIGHTER (lower stall) converter with a bigger cam? What kind of stall now and previously?

Did you tell Joe O. what plans you had for the lower stall TC with the 3.42s and nitrous when he designed the cam for you?

I don't think the smaller TB will make much difference.

T/A lt1

Well I found out two things. 1. The smaller throttle body did hurt performance everywhere.
2. The n2o really works wonders. 10.84@126mph on a 1.60 60'. Couldn't spray out the hole b/c it would spin on ET streets. The DA was 3054'@3.00PM when I made my quickest pass. Later Clint