Port intake for 65mm TB

[Hard Driver]

Just got my 65 mm TB adapter today and need to port my 3400 intake manifold.I measured about 8-9 mm difference between the adapter and the intake.How far back should I grind and should it taper,don't want to ruin a manifold.

[ericjon262]

you're not going to ruin it by porting it unless you go through it. I would lay a gasket on it, and center it over the existing hole, and slowly work my way around and do a smooth even taper, and you'll be good.

[robertisaar]

abrupt transitions kill airflow. ^^ do that.

[Hard Driver]

Thanks Guys,I've done a little porting but not on any of the 3400 stuff,didn't know if there was some thin spot or other particularities of which I should be aware.

[ericjon262]

Thanks Guys,I've done a little porting but not on any of the 3400 stuff,didn't know if there was some thin spot or other particularities of which I should be aware.

the casting should be pretty thick around the TB, I wouldn't worry about it to much.

[Superdave]

You'll be fine, I would use the adapter as a guide instead of a gasket though.


When I used to do them i'd clean the TB flange and spray paint it black, bolt on the adapter plate and then scribe the line. port the opening out to that and then blend it back.

[Hard Driver]

Yeah,it appears to be fairly thick just doing my research.Superdave good point,I noticed with the adapter bolted in place the manifold appears to protrude inward a few mm more at the top rather than being centered.Fortunately the manifold appears to be a little thicker at the top which would support more grinding .

[bob442]

i blew through a intake when i attempted to do mine, about 1"in center line of the opening. coulda just been me rushing though

[Hard Driver]

Thanks bob442,I keep that in mind when I'm porting and be extra careful.I'm thinking,enlarge it full size for about the first 1/2 inch and then taper.