Midyear A.I.R , Air injection Reactor owners

[Christopher A.]

I have a few questions for those that are fairly certain they have the correct bolts in place. My car is a 66 427/390hp car.

Questions 1 and 2 Apply to 327 and 427 with A.I.R.

1. What is the headmark on the bolt that passes through the pump bracket? This is the bracket that bolts to the passenger side of the intake and front passenger side of the block.

2. What is the headmark on the bolt that passes through the belt tensioning bracket and top of the pump?

Questions 3 and 4 Apply only to 427 cars with A.I.R.

3. What are the headmarks on the Thermostat housing bolts?

4. Where can i buy the correct upper radiator hose for a 66 427/390hp A.I.R Vette?

5. Does anybody know the thread size of the air tube nuts where they thread into the manifolds? I haven't had time to measure them yet and i need to order some plugs to block off the holes. I am trying to diagnose some engine problems now that i have the spark plug wire issues resolved and I am going to remove the A.I.R system to see if i can pinpoint the issue. I don't want to end up chasing my tail and i think it will be much easier to locate the trouble maker with the A.I.R. system blocked off.

[Jeff S.]

Re: Midyear A.I.R , Air injection Reactor owners

Christopher

#5 ... the A.I.R. tube nuts are straight plug, not tapered pipe, in 1/2-18 threadform. Taps are difficult to find as the pitch is between UNC & UNF. Also, the hole in the manifold is 'quasi' blind, so a tap with tapered flutes bottoms out in the casting before all the threads can be chased clean. I'm not sure what is typically use to plug/block the A.I.R. holes, but suspect that 1/4-18 NPT plug would do it since it has the same pitch -- just don't overtighten & end up introducing an inadvertant taper in the female threads.

[Terry M.]

Re: Midyear A.I.R , Air injection Reactor owners

Christopher

#5 ... the A.I.R. tube nuts are straight plug, not tapered pipe, in 1/2-18 threadform. Taps are difficult to find as the pitch is between UNC & UNF. Also, the hole in the manifold is 'quasi' blind, so a tap with tapered flutes bottoms out in the casting before all the threads can be chased clean. I'm not sure what is typically use to plug/block the A.I.R. holes, but suspect that 1/4-18 NPT plug would do it since it has the same pitch -- just don't overtighten & end up introducing an inadvertant taper in the female threads.

We most often see pipe plugs in these holes, but they fit poorly and only go in a couple of threads until, as you note the female threads deform. For temporary use careful use of brass pipe plugs may be your best choice.

There are properly fitting plugs -- there are a run of 1970 big block manifolds that were drilled and tapped for AIR (probably for LS7 use) and then plugged for use on LS5s. These plugs have internal square openings and resemble the plugs that are used in the cylinder case to plug the openings used to drill oil passages. Try industrial supply houses like McMaster Carr of Granger or the like. If you can find them you might have to buy 25 or 100 of them though.

[Christopher A.]

Re: Midyear A.I.R , Air injection Reactor owners

Thanks for that info!!!!

I will just plug off the tubes at the end where the valves attach. No sense in risking stripping the threads out. I stripped one when removing a broken off piece of the original pipe and threaded fastner. The only way i could fix it was to drill it out and install a threadsert. Not a helicoil-i tried one of those initially and it did not work. Anyway, i dont want to mess another one up, that is for sure.

[Terry M.]

Re: Midyear A.I.R , Air injection Reactor owners

There are check valves at each manifold tree on C3s. I note mid-years seem to have the check valves at the diverter valve end of the hose, but that ought to still work if:
A) The check valves are still functional (and if they are not functional you definitely need to get new ones).
B) You don't run the engine too long -- the hoses might depend on cool incoming air to keep them from melting.

[Ronald L.]

Re: Midyear A.I.R , Air injection Reactor owners

On your head bolts - look in your aim for the part number and then those that have the data base can search for you for what other location had that bolt application.

On the rad hose - that 390 air hose WAS the service part and...once in a while you can find one. I might know someone with one of those too.

The JG and repro catalogs were wrong in their call out of this hose, up until late June when the part number changed to what would become the 67 model year part.

Its real clear what I am referring to, if you look at various pages of the 66 AIM, and you have the prints. Actually, the only print that seems to have disappeared is the one that calls out the blue stripe