I'd apppreciate you folks tolerating someone who doesn't own a GM product. That being said, I still need a little info about throttle bodies.
I'm building an EFI conversion for my hot rod. What I need to know is the outside diameter of the oval GM throttle bodies.
Can anybody with an oval TB pull the intake hose off and wrap a tape measure around the throat of the TB where the hose attaches and let me know what it measures?

What I'm working on is a 1965 Plymouth Belvedere. Kinda looks like an old Max Wedge car for those of you who might recall seeing those. I've been running a twin turbo 440 for over three years and I'm converting it to EFI. I made the mistake of using a Ferd Cobra twin 57 mm throttle body when my custom intake was made. Unfortunately, Ferd mounted it at a funky angle and ther are no 90 degree elbows for it.
It's got an oval shape that is different than the GM shape but I'm hoping the circumference is close to the GM. If so, a rubber elbow or hose might squish to fit.

Thanks bunches,
K

 

There are aftermarket ones also, the sizes I know about are 48mm, 52mm and 58mm. I think 48mm is the stock size on an LT1.

 

Those are throttle bore diameters.


A rough perimeter measurement taken from an intake elbow is ~11¾". Of note is that some people use a 4" [edit-make that 3"] diameter waste pipe rubber coupler(that you get at a home center in plumbing supply) for certain adaptations. It can be helpful to warm the coupler in some hot water to make it more pliable. Maybe this will give you some options/ideas.

 

I use the 3"x3" Fernco coupling. Its 85mm inside diameter, which makes the perimeter = 10.5" It had to be heated slightly to get it to slip over the throttle body, so 11" might be a better number.

http://cjcfo.fbody.com/members/injun...B/N2ONozzl.jpg

 

I goofed. Thinking 4" for some reason. Sorry. 3" would make more sense, since people seem to have to stretch it. I don't know what I was thinking.

 

Thanks for the responses.
I know that the LT1 and LS1 throttle bodies are too small. I'm wondering about the older TPI or other oval shaped items.
The difference between a 4" and 4.5" circumference is over an inch and you can't stretch it that far.

I've been using the fernco fittings from Home Depot on my intake tract for a few years. Their 4" fitting actually has the 4.5" inside diameter that I need because the PVC pipes are 1/4" thick and measure 4.5" on the outside.
The only step downs they have go way too small and the transition is so short that I can't cut it back to the size I need.

Does anybody have one of the older throttle bodies to look at?