There is a crossfire throttle body on ebay - I know that there is a shortage of these so if anybody is looking for one to bore out and make a 74mm...
Item # 380091078883

 

There's no shortage of 68mm TBs. They are all over for 120.00.

 

What's the maximum you can bore a stock 68mm t-body out to? (70mm?)

 

Trying to save TVT some time so he can get that 300 kit on the dyno so I will attempt to answer based on what I have previously read....

The 68mm stock TB can be bored to 74mm MAX

Please correct me if I am wrong....

 

That's the impression I was under, but when TVT said there were plenty of stock t-body's around I was wondering why they weren't being snapped up and bored out to 74mm.

 

If I understand correctly, the MB TB that TVT is using is a much more stout piece of hardware, built to handle 400-500 HP with beefier internals. I believe this is the way many were wanting to go, but I certainly would not mind a bored stock XF TB if it will hold up the same, obviously the same flow....

 

How does a TB need to be beefed up wtih internals?

 

What I mean was that if you are starting with a more stout (thicker, possibly heat treated) TB versus going with one that is designed for less power (our stock TB) and then bore out the hole, you are losing even more structural integrity. You may still be well within OEM specs once bored to 74mm, but I do not know, I was simply raising a question hopefully someone else can answer???

Would there be any significant differences between going with a stock TB bored out versus the larger MB TB???

 

Would there be any significant differences between going with a stock TB bored out versus the larger MB TB???

I don't believe there would be any performance difference (or at least noticeable) as long as they are the same bore diameter. However, you raise an interesting point about the structural integrity of the part - if this was suspension or a moving item I would be concerned, but seeing as though it doesn't really move or have many forces applied to it I wouldn't be concerned. Seeing as though both throttle bodies (68 + 74mm) will fit onto the same air intake tubes (which is before the butterfly - so the initial intake is the same size) there may just be far more material on the stock 68mm which can be machined away to make it a 74mm unit. I don't have a throttle body at hand to see how they are built up/assembled so I'm assuming the above.

If you look at the pic below posted by psuperit, the butterfly is significantly less than the inside diameter of where the air-intake assembly attaches to - reitterating my assumption above.

 

For sale stock TB out of my 04 with 20K. Lets see some offers ok!