Drum Brake Surfacing

[James W.]

I just purchased a pair of new in the box, NOS GM front brake drums for my 1964 Corvette. Since these are new, do they need to be surfaced before installation or are they ready to go right out of the box?

Any comments would be greatly appreciated.

Thanks,

James West

[Duke W.]

Re: Drum Brake Surfacing

As long as the friction surfaces are not seriously corroded, no problem using them as is. Don't be concerned about light surface rust, I believe the friction surface of drums going to parts stock were treated with a rust preventative - the evidence of which may be long gone - but clean the friction surface thorougly with a solvent such as brake cleaner or mineral spirits before you install them. After solvent cleaning you can dress off any surface rust with steel wool or Scotchbrite pads if you wish.

What are the drum part numbers (on the box) and what are the casting numbers molded into the drum? Also, do the drums have "Max Dia. 11.090" or similar verbiage molded into the casting? Any other numbers, letters, or symbols?

Same questions for the installed drums, and can you determine for sure whether your car was originally built with base brakes or J-65 metallic brakes.

Duke

[James W.]

Re: Drum Brake Surfacing

Hello Duke,

I don't have the new or old drums in front of me to look at right now, but I will get you the brake drum part number info that you asked about. As for the car being equipped with the J-65 option, the car is a plain jane 327/300 hp hardtop convertible. If the original owner was so tight that he or she deleted the soft top for the $200 or so dollar credit for a hard top only I doubt they would have put the metallic brakes on the car. I've owned it since 1980 and when I bought it as a basket case to restore and there was no evidence that it had metallic brakes.

I'll get you the p/n info tonight and thanks for the response to my question.

Thanks again,

James West

[James W.]

Re: Drum Brake Surfacing

Duke,

I compared the new NOS GM brake drums and my original from my '64. The original brake drums have casting numbers 3828671, W-15 designation and no Max. diameter designation.

The new NOS drums are part number X3828672 with a W-11 designation cast into them and no Max. diameter designation. The GM boxes they came in had a 10-68 and a 12-68 designation on the back of them. From the writing on the box, they came out stock from a small Chevrolet dealer in SW Iowa in 1975. I do not believe these are a Corvette part number, but they are identical in appearance.

Upon taking them out of the original GM boxes, the rust preservative you mentioned was still in place and the drum friction surfaces look perfect after I cleaned them with acetone.

Any advice in how to get the new NOS anti-chatter springs installed on the outside of the drums? I don't think it can be done by hand, I've tried it.

Thanks,

James West

[Duke W.]

Re: Drum Brake Surfacing

What is the part number on the boxes? The part number is different than the casting number.

It's been awhile since I swapped anti-squeak springs, but I recall that I "rolled" them off, then rolled them on the new drums. You may have to pry a bit to get them off if they are rusted to the drums.

3828671 is the OE drum number for metallic brakes. The AMA specs for '63 say the web thickness is greater for J-65 drums than base drums, which would mean a different drum, but I'm not sure if that may be an error.

Casting number X3825672 is both interesting and mysterious!

Duke

[Michael H.]

Re: Drum Brake Surfacing

James/Duke,

I'm having trouble following this one. Are you sure about the part number and casting number that you posted? I have different numbers for 63-64 drums. I can't find the 3828671 or 672 in any 63 printing of the parts book and I don't see it in any number change pages either.

The web thickness difference between drums for standard brakes and metallic brakes seems to be reality. The standard brake drum web thickness is supposed to be .109-.119 and the web thickness for drums for metallic brakes is supposed to be slightly thicker at .125-.135.

Duke, I asked you to measure the web on your known original metallic drums and you said it was .135, if I remember correctly. I've since gotten dimensions from a few people that had known original 63-64 non metallic drums and their web dim is roughly .112 for one and .116 for another.

This difference in web thickness has only to do with front drums. The rear is supposed to be the same as the dimension for std non metallic brakes.

Michael

[Duke W.]

Re: Drum Brake Surfacing

3828671 is the same my my original J-65 drum CASTING number. The part number is assigned to the final machined part, which would be on the box, but James did not state the part number on the box.

The X3828672 casting number I have previously run across.

Still need the part number on the box to move this forward.

Duke

[Michael H.]

Re: Drum Brake Surfacing

Ok, I thought he said the 3828671 was the cast number on the old drum and 3828672 was the PART number on the new one. (I assumed he meant that was the number from the box)

[James W.]

Re: Drum Brake Surfacing

Duke and Michael,

I just came in from putting the left front brake and hub assembly back together and saw your posts. I went back to the garage to verify the brake drum casting numbers, they are;

- old/original drum casting number is 3828671
- new NOS drum casting number is X3828672
- part number on each GM box is 3830166

Let me know if you need and measurements.

Thanks to the both of you for your input.

Regards,

James West

[Michael H.]

Re: Drum Brake Surfacing

Thanks James. The 3830166 would be the correct original part number for a 63-64 front with standard brakes. It was discontinued/replaced in January of 1972.

The casting number 3828672 was the number that I was curious about. Typically, this casting number is 3828671 on originals but, as Duke mentioned, he has recorded the 672 also. I wonder when/why that casting number changed? Or were there 672's used in production?

If you happen to have a micrometer handy, I would be interested in the dimension/thickness of the web or face portion of your drums, near an area between the wheel stud holes, both original and NOS. Thanks,

Michael

[James W.]

Re: Drum Brake Surfacing

Michael,

I'll get you the dimensions tonight when I get home.

Thanks,

James West

[Duke W.]

Re: Drum Brake Surfacing

No, I have not run across the "672" casting number. Also, the "X" preceeding it would indicate an "experimental" part???

The base drum part number is 3830167, but, so far I don't have a casting number for the base drum, assuming it was different.

A few of us are researching drum casting and parts numbers in hope of sorting this out, but the missing information is verification of the casting number for C2 front base drums.

Duke

[James W.]

Re: Drum Brake Surfacing

Duke,

Would you like digital pictures of both drum castings? If so please email me at jwest@oppd.com and I'll send them to you on Monday.

Thanks,

James West