Intake Manifold 5/8� Heater Hose Fitting �66 L79

[Gary B.]

The 5/8” heater hose fitting I removed from the front of the intake manifold on my ‘66 L79 has been put in my collection of parts to be cleaned up and zinc/cad replated. Invariably it takes me a long time to accumulate enough parts to justify sending things to a player. So in the meantime I want to install a repro fitting that may wind up being used for several years. The fitting in question is indicated by part #13 in this drawing from the Long Island Corvette Catalog.

DC58F347-0431-4FD4-9BF0-A1D291B27675.jpg

The next set of images shows my original heater hose fitting (which I believe is original to the car) along with two reproduction hose fittings. In the series of images, my original is always at the left. The fitting at the center is one I purchased from Corvette Central, which they say is for ‘75-‘82 with AC. I bought the CC fitting since it looked most similar to my original fitting. The fitting at the right is one I purchased from Long Island Corvette, which the LIC catalog said is the correct one for my engine. All three have 1/2” NPT on the intake manifold end, and they all accept a 5/8” heater hose on the hose end. But the repros differ in other ways.

Hose End
A787CEA4-3782-491B-8E07-E4EE6930B3BA.jpg

Intake Manifold End
DB4EBE2C-A198-419D-A0F3-314FD7221D6F.jpg



93093121-E9D3-4FDC-B2B6-F1D0F6160E6F.jpg


Lengths
015706CA-BA65-49E3-A67C-8E486AB7C2F4.jpg

The ID dimensions of the three fittings are:

ID intake manifold end; ID heater hose end
Original GM 0.46”; 0.39”

Corvette Central 0.46”; 0.31”

LIC; 0.53”; 0.53”

As you can see, the original fitting has a smaller ID on the hose end than on the intake manifold end. The Corvette Central fitting does also, but the hose end ID is 21% smaller than the original. The LIC fitting has the same ID from end to end, but it is 1.75” long, whereas my original and the Corvette Central fitting are both 1,5” long. I’d rather not use the LIC fitting since the extra length of the LIC fitting is on the pipe thread end, and it would be obvious to anyone who knows the length of the original that the LIC fitting is too long when installed.


The reduced hose end ID of the Corvette Central filing translates into a reduced flow area of 37%. My question is, does that represent a problem? It seems like it would restrict heater hose flow, and might increase the temperature of the heater core water. Just guessing about that, Or should I drill it out, which of course would remove the zinc plating and add to corrosion.

Thanks

[Mark F.]

...The reduced hose end ID of the Corvette Central filing translates into a reduced flow area of 37%. My question is, does that represent a problem? It seems like it would restrict heater hose flow, and might increase the temperature of the heater core water. Just guessing about that, Or should I drill it out, which of course would remove the zinc plating and add to corrosion. Thanks

Gary,

Seems to me the CC one is a better match - and drilling it out would be easier than re-threading the LIC all the way up to the nut flats - if that unthreaded shoulder showing when installed bothers you (plus cutting off the extra length, if that's a problem?).

As for corrosion, how much of that do you think would really be a problem if it's only in there until you get your original replated?

[Gary B.]

[Leif A.]

[Gary B.]

8BB47FF5-444D-49D0-9109-BF9DD9AEF976.jpg

[John D.]

[Gary B.]

[Gary B.]

I don't know about 1966 heater hose fitting but 63 to 65 FI etc use a restrictor hole in the center.
Try NAPA 660-1732. Only thing missing from original is the notches on the hex. I use that heating on '57 to '65 FI's although some of the early years had an adapter screwed into the baseplate and then this fitting won't work. Go right to the sales clerk with this number instead of looking at a display. John

[Gary B.]

I don't know about 1966 heater hose fitting but 63 to 65 FI etc use a restrictor hole in the center.
Try NAPA 660-1732. Only thing missing from original is the notches on the hex. I use that heating on '57 to '65 FI's although some of the early years had an adapter screwed into the baseplate and then this fitting won't work. Go right to the sales clerk with this number instead of looking at a display. John

John,

You nailed it. The Napa fitting #660-1732 is a near dead ringer for the original GM fitting. Apart from the missing notches, which no repro has. Here are photos of the Napa 660-1732 at left, original GM at center, LIC 21-13A (now sold by Zip as M-149) at right.

48E13477-752F-4F9C-AF0F-549D74397155.jpg

A2D722D7-6709-4945-B38D-BEE4BCC27D1D.jpg

[John P.]

[Gary B.]

[John D.]

[John D.]

johndegreg@aol.com
My info is on page 2 of the Restorer.

[Gary B.]

Gary, Long ago I noticed the restricted hole. Then later in life I met Robert Jorjorian and we emailed about this fitting. He said all the originals f least tthe restricted hole. Restrict water flow? IDK
I have had the ones you posted in the photos with the fat barb at the end. But never liked them as messed up the appearance of my restorations.
hahaha