VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1912-1928 1925 Radiator Cap

Today I talked to a guy in need of a radiator cap for his 1926 truck. I said I had a couple and would give him one. When I got home to look, I have two different caps and I need to know which one is correct for 1925. The Jan 1st, 1926 parts book says the cap was the same as the previous year, so I can interpret that to mean 25-26 are the same.

One cap is taller than the other with the serrations taller and the curvature of the rounded top much rounder. The height difference is a quarter inch. One is 5/8ths, the other 7/8ths. They both fit my 25 radiator and my 26 radiators. Which one is correct?

Roger

I don't know.
But I have a third type.
The cap to left is 7/8 " high and 55 mm in diameter.
The caps to the right are 1" high and 58 mm in diameter.
I am sure someone can tell us which one is correct.

Or my be all is correct, but from different manufacturing plant?

Arvid

The radiator cap on the right is the same as the one on my '28 Capitol LP truck.

Thanks Arvid for the picture. Actually, neither one of mine are identical to either of yours. My tallest cap (7/8ths) is the same, (55mm) as your smaller cap on the left, but mine looks identical to the one on the right, only (1/8th) shorter.

Roger

The cap to the right seems identical to the original cap of my 1916/490. I believe the inner diameter and screw is equal on all caps from 1916 to 1928, but some have slightly different shape outside.

:vcca:

The small cap fits the small neck radiators through 1927. The large cap fits the large neck radiator beginning with 1928 and into the 29 + radiators.

The Bakelite caps are the original caps.

Hello Ray.

All the black bakelite cap have 1 3/4 x 16 tread and fit through 1927 car and 1928 truck small radiator neck.

1928 - 29 cars have the large 2 5/8 x 18 plated Cap.
I have not seen a bakelite cap for 1928-29?

As Bluezone stated, the bakelite caps do not fit 1929 since the radiator filler neck is bigger in diameter. The correct cap for 1929 is the plated cap shown on the right of the photo, and this same cap also fits 1930 as well since the radiator filler neck is the same size as the 1929.

What Bluezone and Skip say are correct. I don't know what the center cap fits. Perhaps it is non-Chevrolet.

All the caps, other than aftermarket, for the 28, are the plated cap.

Ray - are you are saying the one on the right in the picture of two caps is not Chevrolet? That is the one that looks closer to the picture in the parts book, which shows the serrations meeting with the domed top without the extra indented upper ridge.

Roger

Actually there are three caps in the picture. I don't have the measurments of the two Bakelite caps, but assume the one on the left is for the pre 28. The one on the right appears to be the 1928 cap and ______.

There are only 2 caps in the picture with 2 caps and with that picture with 2 caps there are measurements stated.

Roger

My comments are in reference to post # 143061 which shows a picture of THREEcaps.

Thanks Ray - I'm still not coming away with a satisfying answer to my question. Arvid posted a great picture in post # 142986 and gave the dimensions for both caps, which neither matches my two caps exactly, although very close.

The cap on the right in post # 142986 looks more like the drawings in the repair manual and the picture in my parts list dated Jan 1st, 1926, which is also a drawing.

Can you look at that picture in post # 142986 and give me your opinion which one looks more like the original cap?

Roger

We are trying to mix apples and oranges.

It appears that the figures given above about the caps is the OD, which is unimportant. What we need is ID. So with the figures for the ID we find that the early cap <28 is ~43MM, and the late cap >28 is ~63MM.

To answer your question we must have the ID of the two caps.

I started with apples and someone else brought the orange, not me.

Let's stick with apples. Since the O.D dimensions Arvid gave us are smaller than the I.D. dimension of that later(orange) cap, then I have to assume that both Bakelite caps in the photo showing only 2 (apple) caps are of the smaller diameter.

If you were to assume that both caps in the picture with only 2 caps were of the smaller diameter threads, then which one, in your opinion would most likely resemble the original cap?

Roger

The one on the left is the correct cap for the <28.

The Chevrolet 4-cylinder parts book has an illustration of the cap used for 1928 and it shows the large plated cap. Also, both the 4-cylinder parts book and the 1929 6-cylinder parts book shows the same part number for the cap gasket and that the application for the gasket is the same for 1928 and 1929. If the gasket is the same for both applications then the large I.D. on both caps should be the same as well.

Thanks Ray, I will save that one for myself to use on a tour, while I'm sleeping in the motel room with my winged cap under my pillow and give the other to someone that needs one for his 1926 truck.

Roger

To help sought some of the confusion.
The 28 truck, both early and late models has the same small bakelite covered cap shown in the 1st pictures. It fits all Chev cars from the 1916 490 thought to the 1927 car and 1928 truck.
The larger plated cap shown fits 28 cars only and 29 and 30 cars and trucks. Phew!!
Chris

And all of that is true!

The '28 1 ton trucks used the smaller radiator neck and cap. However the 1/2 ton trucks used the larger neck and cap the same as the passenger. They also used a steel radiator shell of the same design as the passenger aluminum. So to say '28 trucks used the small cap is only partially true.

Chipper
I've never seen or heard of any 28 truck that had the larger radiator cap and a steel 28 car style radiator. I was under the impression that the steel surrounds for 28 were aftermarket.
Can you supply any photos or documentation as I'd be keen to see it.
Thanks
Chris

Hi Chris.
Here is pictures of 1928 car style radiator in steel.
I have this as spare parts for my aluminum radiator.
The shell is good condition , only a little surface rust and no dents.
I can plate it or paint it with aluminum if I need it.
I have never seen a copper back plate like this?

I would suspect that is a "one of" and appears to be of good quality. Would like to see the back side.