90mm Throttle Body??

[ATXHEMI]

I have a Fastman standard bore 85mm ported TB. It is not ported on the back side. When I bought it all I had was intake and exhaust. After talking to Dan he advised not to get his performance TB as I didn't have enough mods to warrant the extra porting. Now I have BV Heads and Cam upgrade. Would it be worth the coin to upgrade to a true 90mm TB? I know I'd have to open up the intake to take advantage of this. May even go to a Vararam also.

 

[ATXHEMI]

Even being the standard bore? Would it be worth upgrading to the performance bore?

 

[charonblk07]

Don't do a 90mm, you will regret it for a couple of reasons:

1) lower flow velocity which means you'll be slower off the line BUT you will have more volume available in the upper RPM where it's more important to have volume than velocity. Less of an issue if you have a higher stall converter of course.
2) your intake manifold inlet isn't big enough to support a 90mm TB, you'll have a massive lip unless you port match the manifold. The 6.1L aluminum intake is the only oem intake that's got enough meat in it to handle the 90mm port work.
3) you will throw 'air flow too high' codes and throw the engine into limp mode unless you get a tune tweak and even then it's not a guarantee it'll get rid of them, went through it myself with Johan, not fun at all.


I would go to either the Fastman 84mm or the BBK 85mm. The Fastman will have less chance of throwing codes over the BBK but both will work well for the application.

 

[ATXHEMI]

Thanks...I plan on calling Dan Monday. He was very helpful when I ordered my TB that I have now.