There are 2 differents bolts on the intake i want to block off. I dont have any bolt that screw in because they are way to big. It's a performer 400 intake. Did someone have done this before and know the size? I should bring the intake with me to a bolt shop store before installing it.

 

Lucky you didn't find anything, those holes are for pipe fittings with tapered thread, usually called NPT.
So you need pipe plugs like the Summit part number G1454N $10.99.
I think they're 3/8" NPT.
R.

 

ok thank you very much dogdays. !!!

 

The only pipe fitting I know of is for the vacuum tree in the back on passenger side. there are two regular threaded holes in the front. On is for a heat sensor and doesn't really go anywhere, I think the other is for a coil mount.

 

https://www.edelbrock.com/performer-400-intake-manifold-2171.html

 

The hole on the right front is in a heat passage and not open to the intake. The one on the left is. Both are for emmissions/ cold drive sensors. Both are standard threads.

 

Ok thanks you .

 

No need to buy the pipe plugs at Summit, you can buy these at your local hardware store. Use brass not steel. They won't cost you $11 for them either. more like a dollar or two.

 

i agree 100%. Im from Canada and it could be expensive too. Import charge .

 

The three bungs in the port passages will all be pipe thread. The two in the intake port passage look like 3/8"NPT. That right front one would be 1/2"NPT or 3/4"NPT.

 

Correction, remember to engage brain before mouth.

The two holes in the front are pipe. There is one next to the carb on left thats standard, maybe for coil mount. Right rear is pipe for vacuum tree.