i got an 87 pontiac firebird with the 2.8v6 and auto trans. and i plan to put the ford 2.9 injectors in it to give it more fuel but before i do that i want to get a larger throttle body. i know alot of people make adapter plates and port the stock intake manifold to use larger throttle body's. but i read in a few different places that throttle body spacers negatively affect torque and throttle response on mpfi engines. it is actually better the closer the throttle body is on dry type intakes like my mpfi. and an adapter plate would do the same thing as a throttle body spacer. so what i was thinking is getting a 65mm throttle body and intake manifold from a early 2000's ford explorer with the 5.0. then cut off the neck of both that intake manifold and and my stock intake manifold weld the ford throttle body and intake neck to my stock intake manifold as close as possible. that way i don't have to deal with porting the intake or making an adapter plate. anyone got any tips or suggestions. can cast aluminum be welded. i know how to weld regular aluminum but i don't know if cast aluminum is different or not. thanx

 

i got a pretty good idea how to weld cast aluminum. and i finally start work again on Monday. so maybe next weekend i should start to look for the ford explorer intake. but still have a few questions before i start to do this to my car. like what do i do about egr? from what i have been reading on rustang forums the explorer throttle body doesn't have egr. can i just leave the egr valve unhooked? would that act like an exhaust leak?

 

You can leave the EGR disconnected. But, I have four words: Block Off Plate (for under the EGR transfer tube that the valve sits on), and ILLEGAL. An inspection station pops the hood and sees the EGR valve disconnected from the intake or removed altogether, you'll fail emissions (or you should). Same thing as if you were to remove the catalytic converter. Not to mention you'd have to reprogram the ECM to get rid of the code 32. Maybe you could weld a bung on the plenum for it and run a flex pipe from a later car.

Welding aluminum is NOT easy, even for the experts (as I mentioned in your other topic). I'd get some scrap and practice before I did anything like cutting and welding the plenum. And then you have to make sure it's sealed.

 

i am thinking i'll take the manifold and hire some one to weld it. and ill have them weld on a bung for it. any one know how much that would cost?

 

Just a question. What exactly do you expect to gain from doing all this?

 

better airflow into the v6 and more power.

 

IIRC, it cost me about $15 to have the TB mounting ear on my old upper plenum welded back on and $40 (including cleaning) to have the shop weld the mounting ear and the lower part of the countershaft bearing support (with the other mounting ear on that side) welded back onto the first T5 maincase I bought (junkyard owner broke both ears off of the same side pulling it and part of the bellhousing as well... had to have him pull it because I couldn't exactly get under that 84).

 

Just like disconnecting the coolant lines to the throttle makes more power, right? How 'bout some NAWZZ stickers!

Seriously though, that's a larger throttle than the heads can even use. Why bother?

 

WTF?

Who's been smoking the good crack.

You're WAY over thinking this.

No, TB spacers on an MPFI type intake do NOT negativily effect how an engine performs, they just generally don't do anything in a positive way either.

In theory, the spacer/adaptor should do only good, because it would be increasing the plenum volume, which is in most cases a good thing. The thing is, that spacers and adaptors most often add so little volume that there is no benefit, if you're looking for a performance gain from it.

Also, as said above, stick with your stock TB.

I have had a few cases where a smaller TB has IMPROVED bottom end torque, helping with better overall acceleration. In my truck many years ago, I went from a 56mm TB to a 52mm TB and dropped 3 or 4 tenths of a second, same day, back to back passes.

Remember this:

Bigger is NOT always better.