I thought it would be a good idea to post some real world pictures of Garrett swing valves side by side to help others less knowledgeable about them more easily identify one from the other.
First of all, lets take it for granted that using a line of sight into the housing on the down pipe side and a ruler is perhaps the WORST way to determine the size of the valve. Since there are a variety of sources and stampings vary widely, trying to come up with an all inclusive list of part numbers that might be cast into the valve is also not the best option.
Below are some pictures, side by side of a 2.25" and a 2.5" Garrett T1 and T2 style swing valve. The Garrett VNT swing valve is different and not addressed in this post. The T3 swing valve MAY also be different, it is also not addressed in this post. Of course most of us already know that the T4 and T3 turbos CAME w/2.5" swing valves to begin with.
This image shows the two swing valves side by side. Visually you can easily see the one on the right is quite a bit larger. The one on the right is the 2.5" swing valve.
This image shows a line of sight measurement using a ruler and with the view being about 12" away from the valve. Notice that it appears this is a 1.5" maybe a 1 5/8" valve...wrong. Moving the frame farther away or closer will change the measurement you see.
Same optical illusion here but the ruler is on the 2.5" swing valve. Trying to measure one like this is not going to give you the actual measurement. Note that it looks like the 2.5" valve in this picture is more like a 2.25" valve...wrong. It's a 2.5" for sure
This pic shows the two swing valves side by side, also shown are the cast part numbers and other information. The valve on the LEFT is noticeably larger. The one on the left in this picture is the 2.5" valve.
This pic shows the huge difference in the down pipe flange size. On the left is a 2.25" swing valve, on the right is the 2.5" unit. It is easy to see why a new down pipe might be needed when you upgrade from one to the other.
This pic shows the measurement from the center of the down pipe flange bolt hole to the center of the other sides flange bolt hole on the 2.25" swing valve. The measurement is approximately 4 1/4". Approximately!
This pic shows the measurement from the center of the down pipe flange bolt hole to the center of the other sides flange bolt hole on the 2.5" swing valve. The measurement is approximately 4 3/4". Approximately!
I hope this help you to more easily identify your turbo Dodge Garrett swing valve parts.