I have the extremfi 46mm tbi, the bores on the performer tbi are 43mm. Its going on my lo3 with full exaust, free ram air intake and coustom chip.
Is it worth boring the performer tbi manifold bores to 46mm?
Id really appreciate your opinions.

 

The air will bind up.. So you might want to do something... whether you bore it out to 46mm or kind of make the manifold Throttle Bores get a V shape to get the air to flow better... and when/ if you make the V Cone shape, try to leave it a bit rough, i think that it may help with atomizing the fuel... However im unsure.. so wait till someone else posts.


Just My 2cents....

 

Personally, I would chamfer the edges of the bore and leave it. If you were going with a 50mm, I would step up to a 50mm bore in the intake though.

 

I dremmeld the bores all the way in and finished with a file.
Now it is pretty rough like the casting surface. Is that to rough? Id like to post some pics but i dont know how.

Using the stock cilinder heads, correct me if im wrong, I think the 46mm tb and the chamfered performer will not be restrictive.

 

I'd add 1.6 ratio rockers to take Full advantage of the extra Air and fuel.. I think youd want some rough edges to help with atomizing...

 

that would be the job of the plenum itself. you do not want turbulence. turbulence eats possible power.

 

I was thinking of 1.6 rockers too, from reading posts it should be worth it.
But first I need to find some more information on how to do the job cerrectly.

I dident leave any ruogh edges, its just that the hole surface isent as smoot as before.

 

Well if you got Something Fine grit and hook it to the dremel and work its way smoother.. I dunno.. Depends how how rough it actually is.. I dont think there will be any air binding..