[39 chev]

I am helping a friend with his 86 302 ford engine. We finally decided to give up on the fuel injection,and go with a 600 holley on a aftermarket manifold.The engine has a tube at the rear of the heads ,goes between the heads,must be part of the emission system? can this be blocked off without any harm to the engine?the engine is in a 48 ford truck,and doesnt have to pass emission testing.The holes are about 5/8 and are not threaded,what would be a good way to plug them?

[BOBCRMAN@aol.com]

Just get some correct sized soft plugs and drive them into the holes. This will take care of the air/exhaust leak you will have if you try to leave them open. They are passages for the stock air injection/emission controll.

[rodder john]

The tube you are working with is the air injection tube.If you are not using the air injection system then the tube is worthless.A soft plug won`t work to seal the cavity at the back of the head because it is threaded. This is not a pipe thread but a coarse straight thread.You can use a bolt with sealer but the best way to seal this area is with a thermactor plug made specifically for this purpose.Your local automotive machine shop will have this part.Good luck from rodderjohn.

[39 chev]

Thanks for the info guys. The holes in the 1986 heads are not threaded,but we looked at an earlier 302 that had threaded holes. I think the soft plug idea will work fine.

[xntrik]

The best way is to just tap threads and screw in a recessed head pipe plug. Its the perfect size for pipe thread. I have done it several times.

The holes are on the rear of the heads. If that soft plug comes loose, you have to pull the head off to fix it.