dunno if this has been done before, or even worth while, but after seeing what rx7.com charges for bigger tb's, I figure I can do something similar.
Why could we not do the TB, and the remove the secondary throttle plates? Then use a brake cylinder hone and bore out the holes a little more, maybe an extra 3 or 5 mm. Then, spin a set of aluminum plates (also very easy) and mount them in, with all modifications done to the mounting bars of course. The finish coudl then be mirror polished, and measured with an inside micromeetr, and the plates made the exact same size with a normal micrometer.
If Rx7 is boring out tb's for $500 and a core, what do they ahve that we can't do?
(I am aware that swapping to a FD intake and TB would be better, but you could do the same thing to a FD throttle body).
I may try this, provided there are no huge shouts pointing towards no.
Sean Cathcart
-big on original mods...

 

Id rather run a Mustang throttle body like my friend has on his 79

 

Sure, running a 65mm-75mm single plate TB would be nice, but not free, and a little more work to hook up things like the TPS.
and where's the challenge in that?
sean

 

The FC TB has 3 x 45mm bores. That's the same cross-section area as a single 78mm bore. Even taking into account extra surface area and the extra shaft, that's a BIG hole! And it's free!

 

This is basically the single exhaust vs. dual exhaust argument.
By that theory, a twin 58 mm TB would outflow a 75 mm single plate. In EVERY flow test I have seen conducted on mustang TB's (which are EXTREMELY basic), the single 75 mm, with a smaller area, out flowed the twin 58 mm by at least 17%. I can post the test results from the flowbeanch for this one.
To say that mere area is the only thing to affect airflow is incorrect.
But this is all beyond the point. What do you guys think of boring my TB so that I have a 48 mm primary, and 50 mm secondarys? Already have a ported TB as it is, maybe some dyno test would be a good idea.... course, gotta get some more fuel first, as I can't nail it and not hit fuel cut. (I will not put on an FCD, I am gonna use my right foot as a boost controller until I can do this right). Dyno testing would suck if you can't hit WOT.
Sean Cathcart

 

the FD TB has 45mm primary and 50mm secondaries, why not bore them all so you have approx 48mm primary and 53 or 54mm secondaries to have EVEN MORE flow?

 

I'd like to see you "spin" some throttle plates.&nbsp Those things are cut at an oblique angle - not perpendicular to the flat throttle plate face...



-Ted

 

Wont the low end Throttle responce be dodgy on a single throttle? why not just go and get a std FD top inlet and fit that? What power do you want?

 

This would be the shout of no I was looking for.
Sean

 

a carbie specialist can source butterflies in the right sizes