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Throttle Bodies
The Stock throttle body is only 52mm in diameter (56mm for the 3400s and 2000+ 3100s). This is hardly enough space to suck in the air this motor needs for peak performance. This unit is 62mm in diameter, and is a much better design than the stock peice. Note that this is NOT a stock throttle body that has been modified, this is a COMPLETELY new peice machined from billet aluminum. This TB is available from The 60DegreeV6.com Store. There are ported out stock units available from several other companies, but many of them use the existing throttle plate, and thus retain the stock opening. Other companies have bored out stock units, but this only increases the opening a few millimeters.
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TB Calculations (originally done by Chris Williams, corrected by Dave (Orief) from the Pennock Fiero board)
You need to multiply it by the VE than divide it by 1.5hg's. Per the Holley book, a single barrel TB has a VE of 1. (this is assuming a round faced single barrel TB. An oval faced TB could have a higher VE by design and then would have higher CFM rating)
So as an example we'll use the stock Fiero TB.
52mm is 2.05" throttle plate has 3.3sq/in which is 462, X VE (which is 1) is 462. Divided by 1.5 = 308 CFM.
65mm=2.56" = 5.15sq/in = 480cfm
62mm=2.44" = 4.67sq/in = 435cfm
58mm=2.28" = 4.08sq/in = 381cfm
56mm=2.20" = 3.8sq/in = 354cfm
52mm=2.05" = 3.3sq/in = 308cfm
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Air Intake Options
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Intake Manifolds : Old 3100 vs New 3100/3400
Here is a side by side comparison between the old style 3100 manifold gasket (bottom) and new style 3100/3400 manifold gasket (top). As you can see, the new manifolds have much larger port sizes, allowing for improved flow. Also notice that there are only 3 mounting bolts used for the new style, whereas 6 bolts were previously used.
Here is a picture showing the newer style heater line hookup. Older style 3100 manifolds used a screw in type connection, whereas the newer style 3x00 manifolds use a push in pressure fitting.
Here is what I'd like to refer to as being the official "rabid guinnea pig". This is what happens when you use standard non-roller rockers on a new style 3x00 manifold. Due to the increased runner size, the rockers don't like to clear the manifold. This causes notching of the manifold, along with pieces of aluminum inside the block and the failure of ~4 lifters. See the rest of teh pictures for the remedy.
With alittle help from the die grinder, the area where the notches were was ground down. If you have to do this, be very careful to not remove too much material, cause you could easily ruin the manifold by going all the way through. I ground little by little, then installed the manifold and checked the clearances. It took me a couple times to get everything to fully clear.
These 2 pictures show the exact same area on the old style 3100 manifold (left) and newer style 3x00 manifold (right). You can clearly see the difference in clearances.
Ok, the above pictures are comparisons between a 1999 3400 lower manifold, a 1994 3100 lower manifold and a 2000 3x00 manifold. The biggest thing to notice is the difference in runner dimensions between the old and new style. The amount of airflow gained by the increased size is most likely the main reason for the jump in HP between the years. You may also notice that the 2000 manifold is already ground down in the area where I had to modify the 1999 manifold. This makes me think they had some issues with the design, which was then fixed in 2000.
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TB Calculations (originally done by Chris Williams, corrected by Dave (Orief) from the Pennock Fiero board)
You need to multiply it by the VE than divide it by 1.5hg's. Per the Holley book, a single barrel TB has a VE of 1. (this is assuming a round faced single barrel TB. An oval faced TB could have a higher VE by design and then would have higher CFM rating)
So as an example we'll use the stock Fiero TB.
52mm is 2.05" throttle plate has 3.3sq/in which is 462, X VE (which is 1) is 462. Divided by 1.5 = 308 CFM.
65mm=2.56" = 5.15sq/in = 480cfm
62mm=2.44" = 4.67sq/in = 435cfm
58mm=2.28" = 4.08sq/in = 381cfm
56mm=2.20" = 3.8sq/in = 354cfm
52mm=2.05" = 3.3sq/in = 308cfm
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Air Intake Options
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Intake Manifolds : Old 3100 vs New 3100/3400
Ok, the above pictures are comparisons between a 1999 3400 lower manifold, a 1994 3100 lower manifold and a 2000 3x00 manifold. The biggest thing to notice is the difference in runner dimensions between the old and new style. The amount of airflow gained by the increased size is most likely the main reason for the jump in HP between the years. You may also notice that the 2000 manifold is already ground down in the area where I had to modify the 1999 manifold. This makes me think they had some issues with the design, which was then fixed in 2000.