Can someone tell me what size plug I need for the front of the intake manifold. I have a 305 and just picked up an edlebrock EPS intake. There are three holes, two of them to one side of the hole for the thermostat, one to the other side. The stock manifold only has the two holes that are together and not the third so I need to get a plug but I need to know what size the plug is.

 

Let me tell you how I figure these things out: Remove one and and take it to the hardware/parts store and get another one like it.

 

five7 has a good method, another is to screw a tap in it and see what fits. you can always take the shotgun approach and buy a plug or two in each size close to what it is. my guess is it's 3/8NPT but there's a chance it's 1/2 NPT and a very small chance it's 1/4 NPT. either way you can buy plugs for a couple of dollars.

 

I had some threaded pipe and I just checked it with that, it ends up it is some 1/2 and some 3/8. Thanks