i may not use this intake manifold, but i thought i might bore it out just incase i don't get around to building a new one before the engine is in the car.

setup on mill:



first setup the manifold so that the t/b mounting surface is flat, then indicate the port to find the center, or as close to center as you can get. the stock casting isn't perfectly round.


measurement before porting:


oem tb measurement:


replacement tb measurement:


comparision between the two... i will have to modify the replacement to add the map sensor on top. shouldn't be hard to do.



i couldn't fit a proper boring head in the limited travel of my mill, so i opted to use this small flycutter. here it is making the second cut. worked fine with the quill feed engaged.


finished dimesion (slightly larger than the tb):


as you can see the casting isn't exactly even all around so make sure you go deep enough to get all the material to make it a smooth transition.

 

I just did one yesterday made the bore 67 mm using a boring bar we set it up on a mill table horizontally. The opening is kind of egg shaped as you said.
I wish I took pics of the job like you. I will take a few of the new 67 mm opening and post them up

Nice work

 

Nice job. Is that DH Racing T body 66mm straight bore or tapered? Any welding on the manifold?

 

the tb is tapered from 74mm down to 66mm at the throttle plate. there was no welding done on the manifold, although i'm not sure why it would need it? maybe if the bore was a few mm bigger perhaps welding would be needed on the lower iacv port.

 

Nice work, great pictures
Do you have that mill at home?

 

Here is the one we did to 67 mm
That is a stock TB


The car it's going on is N/A if it were FI a little bit of a weld job maybe needed to keep the gasket from blowing out.

Don't meen to thread jack, just showing what a 67 mm bore looks like without any weld work done

 

so by weld work, i'll assume you mean on the iacv ports?

 

Yes I think with some high quality gasket material, there should be no issues with a N/A application.

 

no, that is at my shop.

i can see why welding might be required. i can also imagine it would be a real pita to weld that area. welding cast alum is never fun unless it is new.

i was surprised at how biased the plenum was to the #1 runner. half the tb port opens directly into it. this is mainly why i'd like to build a better one.