I will have ported and polished heads with larger valves and cc305 cam. Any reason to go to a larger tb?

 

Stock intake? Run a 52MM. 58MM would be a waste without a proper intake for it.



http://community.webshots.com/album/33786390mmhudJ?888

 

You need a larger throttle body than the stock 48mm with that combo. If you run a 58mm with a 4L60e transmission, you'll need to do a little tweaking on the line pressure. Also, with the 58mm you'll need to port match the intake to the throttle body. If you go with the 52mm, you won't have either problem. And if you have an M6, you won't have the line pressure issue either.

I'm also not sure what's considered a "proper intake" for a 58mm TB, but maybe somebody cound find some cfm flow numbers for both, and compare them. Or have you already done this quasar?

 

By "proper" it was meaning that the stock port is too small / restrictive for a 58MM T.B. A 52MM however is OK. Sorry, don't have the CFM flows between the various T.B.'s, however I do recall seeing them someplace online. I'll post the site if I run into it again.

 

Id dont think theres any reason to change unless your running some type of forced induct. or a big stroker motor

 

Quote:

If you run a 58mm with a 4L60e transmission, you'll need to do a little tweaking on the line pressure.

Interesting... right after i installed my throttle body i bought off of a friend i noticed my transmission was shifting weird then couiple days later my tranmission went out again i just thought it was a dumb luck.

What do you mean by tweak the line pressure and how do you do it

 

The "standard" flow numbers tossed around for throttle bodies is:

48mm= ~660cfm
52mm= ~750cfm
58mm= ~1000cfm
monoblade= ~1300cfm

I'm sure there might be a little difference between brands, but that's close enough.

 

all you have to do to make your intake "proper" for a 58mm TB is, port the opening of the intake to match the 58mm TB gasket.
a dremel tool would do the trick.

jesse

 

http://users3.ev1.net/~thor10/HP-FAQ.htm

 

we have a local board member here that is or was porting stock TB to 52mm...
do a search for NOMAD

jesse

 

It only costs me $75 to have my local machine shop bore my stocker to 52mm and make new plates to fit. My brother paid a little more ($90) from a different machine shop to do the same thing, so paying $150 or more to overbore a stock throttle body sounds a little high.