Sorry if this is a question brought up time and time again, but I tried using the search and never got any resultsno matter what I put in the search criteria. I have a 2000 Ram 1500 with a 5.2l. I have been wondering what the stock throttle body measures up to. I am debating getting a fastman 50mm or 52mm. But if the stock throttle body is close to that size, I will just port and polish my own.

 

I am not 100% sure, but I think the stock throttle body is 46 or 47mm and wider at the top than the bottom. I have personally spoken with Dan Arkand (the fastman) and he recommends the 50mm for the 318 and the 360 for towing. When Dan modifies them he makes them a standard 50 mm all the way through, replaces the throttle plates and throttle plate shafts (his shafts are more aerodynamic as we looked at them while he was building my throttle body), and mills a lot of extra aluminum off the throttle body that affects the air flow.
Could a person do the work themselves, Yes. Would I recommend it, No. Dan does all of his work with computer controlled machining tools and the resultreflects his expertise and experience.

 

Thanks, that answers all of my throttle body questions. I am going to go with the fastman 50.

 

I have asked around and most machine shops will do it for about 150. That includes the throttle plates but not sure about a new shaft.

 

F&B and KRC both write
that the standard factory Holley throttle body
flowbenches about 600-650 cfm

My experiments indicate that a 1995 Magnum 5.9V8
shows about 1.8 inches Hg total restriction on the MAP sensor
of the combination of
throttle body and air filter system
at 4000 rpm and wide open throttle and brand new paper air filter.

A 5.2 will have less than that
and therefore benefit less with a larger bore throttle body.

For corrections when the pressure changes
the following equation is used:

{absolute pressure after/absolute pressure before} raised to exponent 1.2

As an example
say that the weather is changing where you live
and one day the weatherman says the pressure is
29.5 inches of Mercury as a stormy "Low" passes over
then the next day a clear sky "High Pressure Area" passes over
and the pressure rises to 30 inches of Mercury

{30/29.5} raised to exponent 1.2
{1.0169} raised to exponent 1.2
= 1.0204

If a larger throttle body dropped the restriction from 1.8 to 1.0
the percent horsepower gain would be:

(30-1.0/30-1.8) raised to 1.2 power
=1.03
or a 3% gain in maximum horsepower at high rpm
...very little gain at lower rpms where airflow is lower

 

I'm sorry if I'm totally missing what you've said here. Are you comparing the difference between the factory TB and fastman's 50mm, or 52mm, or are you comparing the difference between his 50mm and 52mm TBs? I did notice a positive power difference after I installed fastman's 50mm on my 5.2L engine. I would hate to think it's just my imagination...

 

It is your imagination.....or maybe not if you "noticed" a positive difference. Is the difference you noticed the relation of the throttle to the rpm of the shift points?
In my not so humble opinion, the stock throttle body flows plenty of air for any driving other than WOT or racing.
Except for a theory I concieved one day whilesitting on......... The opening of the throttle, the load on the engine and the adjustment of the transmission cable are designed to allow the tranny to downshift at a point designed for drivability. However, I wanted to increase the throttle opening/air flow in relation to tranny kickdown so I could stay in overdrive going up hills. That was my theory anyway. So, I bought a 50mm fastman TB.

 

with the holley 52mm, fuel/air mixture finally was tuned right. plus the fipk from k&n hellped too. my comp. was pumping way too much fuel into the cylynders. went from 6mpg to 12.5mpg. deffinetly worth the money.

 

i just got a 52 fastman for my truck last week. def made a difference and the qulity is amazing. def well done product

 

Dodge explains a lot about the design of their Holley built throttle body in this official US patent, where they had to 'swear under oath' that what they are saying is both true and complete:

http://www.freepatentsonline.com/490...mp;stemming=on

scroll down and read the 'background of the invention'

A lot of what Chrysler was trying to do was make the cruise control work smoothly without affecting the peak horsepower....but one effect is that when the accelerator is pressed quickly this factory throttle body brings the power on slower and smoother...whereas the bored out aftermarket throttle bodies 'jolt' on the torque at low rpms and this can felt.