52s have been proven to help on otherwise stock LT4 cars in track results, but Nathan Plemons' results on his LT1 showed that he lost power on a highly modified motor

so who knows

 

The PRIMARY, most important requirements for a larger throttle body are:
Better flowing or ported heads (moving more cfm).
Big cam with more duration (able to utilize a larger volume of air).
High RPMs (needs a greater quantity of air).
Forced induction (positive pressure works best without restrictions).

SECONDARY, less important factors are:
Larger open plenum intake manifold (greater capacity for air).
Increased cubic inches (more cylinder filling required).
Free flowing exhaust (logical balance when improving the combustion process).

Other factors that can be assumably related to the above are your target HP goal, emphasis on racing, and quality of air.
BUT don't forget that without an appropriate increase in fuel quantity/quality, the benefits of more air/cfm are much less apparent and difficult to quantify.

This is why you see guys with high horsepower carburated 350s running a 650 cfm carb on the street and then change over to a 850 cfm (or larger) carb when they go racing. Their engine can handle a lot of air, and fuel, but their optimized race carb has crappy street manners, poor fuel economy, etc.. EFI cars have a little more flexibility in these areas, but can still suffer from similar driveability issues when trying to balance maximum output against off idle response.

 

 

I ran several back to back runs on mine as shown in signature, between a 48mm and a 52mm TB. I couldnt see where it helped at all. Now keep in mind I am still running stock injectors and when Alvin tuned it, he has the injectors set to max but I am going a little lean at the upper rpms.
I plan to put 30lb injectors in it and would like to catch Alvin when he will be in my neighborhood, or at least within 125 miles. to dyno tune it and at that point we could switch between the 48 and 52 for some dyno readings. May see a small gain there, but I dont look for much.
On the other side of the coin, Lingenfelter used the bigger TB on both his 350 and 383 engines. He must have seen something there in order to justify using them.

 

It's not just cubic inches that determines weather a bigger throttle body is necessary or not, it has more to do with how much air a given engine is able to consume, generally goes hand and hand with higher reving engines. Example, and radical "350" may need it, while a super mild "383" may not.

 

Anytime changes are made to either air or fuel -/+ the ecm must be recalibrated. Was this done ?

 

I my "test" the only change was the TB; no so much as to improve performance but to prove / disprove posts that a 58mm will make a stock/ mild 350 run worse and kill bottom end.
The MAF has a good ability to adjust for airflow variations , moreso than a SD which does need to be recalibrated when changes are made

 

I just hate it when someone does a back to back test and debuncs all the theories. Sort of takes the fun out of being a genius who needs no actual performance data.