Restoring Eccentric Adjusting Bolt (3820253)

[Allen N.]

The judging guide describes the eccentric adjusting bolt as black phosphate plated. In threads on this forum, assembly 3820253 is described as having a black phosphate bolt with a natural cam. In all of the pictures I can find, the head of the bolt is grey. Does anyone have a good picture of what an original looks like? Has anyone restored this assembly with the two finishes, and how did you do it?

Thanks,
Allen

[Patrick H.]

Re: Restoring Eccentric Adjusting Bolt (3820253)

I highly suspect that the cam was installed on the bolt after it was phosphated. Having said that, I've never tried to remove the cam to see if this theory is correct.

[Joe L.]

Re: Restoring Eccentric Adjusting Bolt (3820253)

I highly suspect that the cam was installed on the bolt after it was phosphated. Having said that, I've never tried to remove the cam to see if this theory is correct.

Patrick------


The cam was installed on the bolt after the bolt was phosphate-finished. The cam is a heavy interference fit on the bolt.

[Patrick H.]

Re: Restoring Eccentric Adjusting Bolt (3820253)

Patrick------


The cam is a heavy interference fit on the bolt.

I suspect that's an understatement.

[Joe L.]

Re: Restoring Eccentric Adjusting Bolt (3820253)

Here are photos of an NOS GM #3820253 bolt/cam assembly [not for sale]:

[Allen N.]

Re: Restoring Eccentric Adjusting Bolt (3820253)

Thank you Joe.

It looks like to me that the black phosphate is only on the bottom half of the bolt. Am I wrong on that?

[Gene M.]

Re: Restoring Eccentric Adjusting Bolt (3820253)

Bolt and cam are assembled together and phosphate finished. Only the loose cam on the other side with the nut is natural.

[Allen N.]

Re: Restoring Eccentric Adjusting Bolt (3820253)

Bolt and cam are assembled together and phosphate finished. Only the loose cam on the other side with the nut is natural.

Gene, thank you for your response.

You are the first person I have heard say that the cam is not natural.

[Joe L.]

Re: Restoring Eccentric Adjusting Bolt (3820253)

Gene, thank you for your response.

You are the first person I have heard say that the cam is not natural.

Allen------

The entire bolt, including the head, is phosphate-finished. The attached cam is natural steel. The separate cam that goes on the other end is dull zinc plated.

[Gene M.]

Re: Restoring Eccentric Adjusting Bolt (3820253)

Allen------

The entire bolt, including the head, is phosphate-finished. The attached cam is natural steel. The separate cam that goes on the other end is dull zinc plated.

No, No, No, read post #8. You are speaking about replacement parts. Not the case for original build. This is for the one piece assembly in the photo shown above as used in mid year cars. I have no clue what the part numbers are.

[Joe L.]

Re: Restoring Eccentric Adjusting Bolt (3820253)

No, No, No, read post #8. You are speaking about replacement parts. Not the case for original build. This is for the one piece assembly in the photo shown above as used in mid year cars. I have no clue what the part numbers are.

Gene------


Nope; you are the one that's wrong. The bolt, cam, and separate cam are finished as I described above. This is EXACTLY how the original parts were finished on my 1969 and it's exactly how the GM #3820253 I pictured above is finished.

The same cam/bolt assembly, GM #3820253, was used for 1963-E1977 and, as far as I know, they were all finished the exact same way. I think the 1963 version was a little different in that I do not think the attached cam had the degree marks on it as all later versions did. For L1977-82, the cam/bolt became GM #458979. This assembly was entirely zinc plated. It became SERVICE for 1963-E77 when the 3820253 was discontinued.

The same separate cam, GM #3790331, was used for 1963-1982. It was always zinc plated.

[Dick W.]

Re: Restoring Eccentric Adjusting Bolt (3820253)

Gene------


Nope; you are the one that's wrong. The bolt, cam, and separate cam are finished as I described above. This is EXACTLY how the original parts were finished on my 1969 and it's exactly how the GM #3820253 I pictured above is finished.

The same cam/bolt assembly, GM #3820253, was used for 1963-E1977 and, as far as I know, they were all finished the exact same way. I think the 1963 version was a little different in that I do not think the attached cam had the degree marks on it as all later versions did. For L1977-82, the cam/bolt became GM #458979. This assembly was entirely zinc plated. It became SERVICE for 1963-E77 when the 3820253 was discontinued.

The same separate cam, GM #3790331, was used for 1963-1982. It was always zinc plated.

Agree with Joe, I have an original that was taken out of a car years ago, it matches what Joe describes

[Gene M.]

Re: Restoring Eccentric Adjusting Bolt (3820253)

[QUOTE=Joe Lucia (12484);817084]Gene------


Nope; you are the one that's wrong. The bolt, cam, and separate cam are finished as I described above. This is EXACTLY how the original parts were finished on my 1969 and it's exactly how the GM #3820253 I pictured above is finished................

I have to say the photo is a ring welded phosphates assembly used for mid year applications. Look close it is not press fit. I have no idea where you get the your ideas on this simple part. Interesting bla bla on ‘77 up and service but irreverent on original configuration. No use educating you on correct configuration, you have your mind made up.

New 68-69 manual on page 219 gives an excellent picture fig Ch 7.27 and description.

[Joe L.]

Re: Restoring Eccentric Adjusting Bolt (3820253)

[QUOTE=Gene Manno (8571);817088]

Gene------


Nope; you are the one that's wrong. The bolt, cam, and separate cam are finished as I described above. This is EXACTLY how the original parts were finished on my 1969 and it's exactly how the GM #3820253 I pictured above is finished................

I have to say the photo is a ring welded phosphates assembly used for mid year applications. Look close it is not press fit. I have no idea where you get the your ideas on this simple part. Interesting bla bla on ‘77 up and service but irreverent on original configuration. No use educating you on correct configuration, you have your mind made up.

New 68-69 manual on page 219 gives an excellent picture fig Ch 7.27 and description.

Gene------


The photo in the judging manual does not show what you claim it does. I see no evidence, whatsoever, of any weld retention of the bolt to the cam. What I do see is a cam that is obviously of a different finish than the bolt head. The cam appears like a slightly rusted, plain steel finish. The bolt head appears like a phosphate finish.

By the way, I don't need to be "educated" into an erroneous belief.

[Edward J.]

Re: Restoring Eccentric Adjusting Bolt (3820253)

I myself have taken apart the rear cam bolts on my cars 72/63 and they are splined at the at the end of bolt where the cam washer fits,it's likely pressed together.