I am refurbishing a 1979 L-82 alumininum intake manifold, number 14007378. It went out for machine shop clean-up yesterday. I ordered and received a new GM #14088753 thermostat housing. The new has two threaded holes; the old had only one (for the TVS/EFE switch). And suggestions as to what I use to plug the second hole? It is about 5/8" in diameter. Thanks.
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Re: 1979 Thermostat Housing-Blind Plug
Paul-----
I would use an allen head pipe plug. The size is either 3/8 or 1/2 NPT (national pipe thread). You should be able to get these in any good hardware store.
Also, the original type with just one tapped fitting originally used on your car may be available NOS from Dr. Rebuild. They're probably expensive (like most NOS pieces), but that rascal used to have some of these in stock. I don't know if he still does, or not.In Appreciation of John Hinckley -
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Re: 1979 Thermostat Housing-Blind Plug
Joe,
I checked GM parts today and that part is not available (as usual). The advice was the same as yours: check plumbing/hardware stores as the thread is a very coarse plumbing variety. I will do that.Comment
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Re: 1979 Thermostat Housing-Blind Plug
Geoffrey,
I must admit that I am a bit of a packrat. And enjoy tinkering. The blue housing that you saw on the CorvetteForum is actually in pretty fine condition. I did hit it with a wire wheel and the aluminum came up very nicely. My concern with that unit is pitting/scoring on the mating surface to the intake. About one mm in depth. Nothing that a gasket and some Permatex 2 could not handle. I suppose that I could have been more aggressive with the wire wheel or a sanding block. But I went with the new, not expecting the two holes to be present. No harm done: I get employee prices on parts. Back to the packrat, I also have the housing (one hole) that is sitting on the car now. So I have three....I may return or sell the new one.
It is my understanding that the 1979 L-48 had the two-hole housing. I have heard this from others also. It relates to the "federal" version not having an AIR pump but I do not know the details. From what I see in the 1979 GM Shop Manual, the L-82 (all had AIR) only had the TVS/EFE switch in the t-stat housing. So I believe things are in place/original.
Thanks for your comments!Comment
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Re: 1979 Thermostat Housing-Blind Plug
Geoffrey-----
You bring up a good point. I guess that I just assumed that Paul's was either beyond repair or incorrect. Most of the thermostat housings can be cleaned up and reused. Even if some moderate pitting is found in the area under the hose connection, that will usually be no problem and cannot be seen once the hose is installed. Also, if some corrosion is found on the surface which interfaces with the manifold, that surface can either be restored by milling or simply sealed using RTV.
Also, I think that you're correct about the fitting configuration on the thermostat housing. I re-read Paul's post and notice that he says that his is an L-82; I was thinking that it was an L-48. I do think that the L-82 generally used the "2 hole" thermostat housing. In this configuration, the EFE and EGR switches were located on the thermostat housing. For L-48s, the EGR switch was on the manifold.
However, I think that 1979 L-82s may have been produced both ways---that is with the EGR switch on the manifold and the EFE switch on the thermostat housing AND with both switches on the thermostat housing. In fact, as I think about it, that MAY have been the difference in the 458520 aluminum L-82 manifold and the 14007378 manifold.In Appreciation of John HinckleyComment
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Re: 1979 Thermostat Housing-Blind Plug
Joe,
The TVS/EGR is definitely on the intake. I can send you a pic if you wish.Comment
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Re: 1979 Thermostat Housing-Blind Plug
Paul-----
Yes, but is it on both the 458520 AND the 14007378?In Appreciation of John HinckleyComment
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Re: 1979 Thermostat Housing-Blind Plug
I do not know??Comment
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