That's his best bet to plugging the holes. Just use the Thermactor pipe, bolt it in place and cap the center inlet over the check valve with a rubber cap from the "help" section at the parts house. The check valve lets air being pumped in, but exhaust does not come out past the valve.
What type of tap are you using? The carbon deposits are hard enough that most taps without a long lead in wont work. You need to go get a 5/8-11 taper tap, you will probably have to get it from one of the industrial supply places because most places like sears or autozone only have 5/8-11 bottoming/plug taps. Those or intermediate taps are also what you use too start tapping holes in hard materials and then if you have to go in with a plug tap afterwards.
If he's got the distanceI think he does behind the heads to the firewall, there simply isn't room to get a tap in there to start it.
I had to cut about 1/2" off of the back of the tap I used, and ground flats on it with a bench grinder so I could feed the tap in with a crecent wrench.
X2! Easiest fix for now and if it goes bad just replace it! It should buy you the time you need for very little in work or money!
