Here's a detailed view of the Summit non-polished
58mm throttle body.
The TB comes in a plan white box with only a Summit part number sticker. I looked everywhere to see where it was made. From the look and feel of the plastic bags that the some of the parts come wrapped in, I think it might be made in China. I've see that type before in other things that came from there. Maybe just the hardware just came from there. Who knows? Overall the TB seems to be a good product for the money $259.95 at the time of this writing. 2/13/07. Ok, it doesn't have the look of the Holley or AS&M units but the bores are machined well. The linkage is smooth and has no binding.
Putting the Summit TB together
Removing coolant/IAC cover that fits onto the bottom of the TB off the stock unit and installing it onto the Summit unit I found no issues. The same screws can be used off the stock unit as well as the screws that it came with. The TPS sensor screws that came with the unit were a 1/4" to long and I did not want to stack 4-5 washers. The original screws from the stock unit were the wrong size as well, thicker and different thread. I found that the screws from coolant/IAC cover fit. Because the screw head was small I had to add 1 washer. See the last 2 photos. My IAC counts didn't change much. Before the install with the stock TB, it was 55-58 with the motor at operating temp. Now they are 68-71.
After driving the car around for 20 min. the throttle began to stick open. In short what I found was when the car is running the throttle linkage spring is not strong enough to fully close the blades. I turned the motor off and the binding was gone. I check for binding and found none. Started the car again and the binding was there. I had to extract some extra spring material from the linkage and bend the extra piece down and over where the spring meets the TB spring stop. Now the TB snaps closed and the problem is gone. I will have to notify Summit of my findings. At this time, I did not have to do the IAC drill mod. It idles fine. All in all, it still looks like no mater aftermarket brand you buy, you still have to do some sort of modding. I am very happy so far with this purchase and I would recommend it.
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